Skywatcher's Almanac/ Astronomical Fact of the Week

Flash's Skywatcher's Almanac
Flash's Astronomical Fact of the Week
 

Flash's Skywatcher’s Almanac
 

Each week, Flash's Skywatcher's Almanac keeps you abreast, for the ten-day period upcoming, of significant happenings in the night sky.  The almanac lists also important anniversary dates in space history.

Visitors are invited to log on each week for an updated almanac.
 

For the ten-day period beginning June 15, 2003

June 16
 

June 17
 

June 18
 

June 19
 

June 20
 

June 21
 

June 22
 

June 24
 

Astronomical data from The Old Farmer's Almanac and Star Date magazine

Historical data from Life in Space (a Time-Life Book), Time Almanac 2003, and The World Almanac and Book of Facts 2003

Space Shuttle data from Air Force magazine and the Space Shuttle Launch site at http://science.ksc.nasa.gov

Supplemental data from the Encyclopedia Astronautica website at http://www.astronautix.com
 
 

Flash's Astronomical Fact of the Week
 

Each week, Flash's Astronomical Fact of the Week presents a brief essay on space science, space exploration, space history, and space personalities.  It is intended to encourage your study of astronomy and enhance your enjoyment of stargazing.

Visitors are invited to log on each week for a new science lesson; and to check out past essays, which are archived on this webpage.
 

For the week beginning August 25, 2002

Flash’s Astronomical Fact #149

In the aftermath of the French Revolution, France adopted a new calendar.  It was called (naturally enough) the French Revolution calendar.

New Year’s Day on the French Revolution calendar was the autumnal equinox (the first day of fall in the Northern Hemisphere).  Thus, the first day of the first month of Year I (that is, Roman numeral one) of the Republic was September 22, 1792.

Probably in keeping with the principal of equality, each of the new calendar’s twelve months had thirty days.  The thirty days were divided into three weeks of ten days each.

The months for each season purposely were given rhyming names, as follows: 

The autumn months were Vendemiaire (Vintage), Brumaire (Mist), and Frimaire (Frost).
The winter months were Nivose (Snow), Pluviose (Rain), and Ventose (Wind).
The spring months were Germinal (Seed), Floreal (Blossom), and Prairial (Meadow).
The summer months were Messidor (Harvest), Thermidor (Heat), and Fructidor (Fruits).

To keep the new calendar in synch with the solar cycle, five or six days were tacked on after the twelfth month to make for a total of 365 or 366 days (depending, of course, on whether the year was an ordinary year or a leap year).  These extra days, called collectively the Sans-culottides, were:

Jour de la Vertu (Day of Virtue).
Jour du Genie (Day of Genius).
Jour du Travail (Day of Labour).
Jour de L’opinion (Day of Reason).
Jour des Recompenses  (Day of Rewards).
Leap Day was Jour de la Revolution (Day of Revolution).

Of course, developing a new calendar is one thing; putting it into effect throughout a relatively large and relatively populous nation like France is another thing entirely.  Moreover, the leaders of the French Revolution had to give priority to overseeing the Reign of Terror and other pressing matters of state.  As a result, the French Revolution calendar did not become operative until November 24, 1793. 

So what became of the French Revolution calendar?  We will examine that question in the next edition of Flash’s Astronomical Facts.

 Source:  The French Revolution Calendar site at http://www.wundermoosen.com
 

For the week beginning August 18, 2002

Flash’s Astronomical Fact #148

As they hurtle through the atmosphere, the vast majority of meteors burn up completely due to air friction. Consequently, most meteors never reach the Earth’s surface. 

But a certain percentage of meteors do survive the fiery plunge to reach the ground.  After a meteor hits the Earth, it is called a meteorite.

As you might imagine, most meteorites are small.  But a handful of meteorites are multi-ton behemoths.

The largest meteorite in the world is located on the African continent in present-day Namibia.  It is called the Hoba Meteorite, named for the farm on which it was discovered.

The Hoba Meteorite is estimated to be between 200 million and 400 million years old, and is believed to have fallen to the Earth some 80,000 years ago.

The Hoba Meteorite weighs 66 tons.  Not only is its weight noteworthy, but so too is its shape.  Most large meteorites are shaped like a potato.  The Hoba Meteorite is cuboid in shape (like a slice of cornbread) and measures 2.95 m (9.68 ft) by 2.84 m (9.32 ft). 

The composition of the Hoba Meteorite is 82.4% iron, 16.4% nickel, and 0.76% cobalt.  The ratio of nickel to iron is unusually high.  Such an iron/nickel meteorite is called a nickel-rich ataxite.

Scientists believe that if the Hoba Meteorite had been any bigger, it would have broken up into many pieces as it plummeted through the atmosphere.  Thus, not only is the Hoba Meteorite the largest on Earth, it is unlikely that any meteorite ever found will be appreciably larger.

The Hoba Meteorite was discovered and first described by a certain J. Brit in 1920.

The Hoba Meteorite was declared a national monument in 1955, but still continued to suffer damage at the hands of vandals.

In 1985, Rossing Uranium, Ltd. donated funds to combat 
vandalism. 

In 1987, the Hoba farm donated the lands surrounding the Hoba Meteorite for educational purposes.  An education center was erected at the site the same year.

The Hoba Meteorite is on display to the public; so, if you are willing to take a trek to Namibia, you can see with your own eyes the world’s largest meteorite.

 Sources:  Voyage Through the Universe/Comets, Asteroids, and Meteorites, a Time/Life Book series, and the Hoba Meteorite site at http://www.namibweb.com
 

For the week beginning August 11, 2002

Flash’s Astronomical Fact #147

The planet Venus is the brightest object in the night sky, save for the Earth’s Moon.  Venus has a maximum apparent magnitude of –4.4, which makes it brighter than any of the other planets in our solar system, and brighter also than any of the true stars.  During its times of greatest brilliancy, Venus shines so brightly that the planet has been mistaken for such objects as orbiting satellites, approaching aircraft, and even flying saucers.

But what is it about Venus that makes it appear so bright in our night sky?

There are four principal factors that account for Venus’ brilliancy.

The first factor is reflectivity.  Venus is enveloped in clouds, the top layers of which are composed primarily of sulfuric acid.  These clouds reflect a large percentage (76%) of the sunlight that falls on them.  In fact, no other planet in the solar system reflects a greater percentage of the sunlight that falls on it than Venus.  The Earth, by comparison, reflects only 33% of the sunlight that falls on it.  Astronomers refer to this reflectivity factor as the planet’s albedo (pronounced al-bee-doh).

The second factor is size.  Venus is a planet, and therefore a relatively large body (of the nine planets, Venus is the sixth largest).  This means that its top cloud layers are relatively large in area, which means in turn that it can reflect relatively large amounts of sunlight. 

The third factor is Venus’ position in the solar system.  Venus orbits second outward from the Sun at a distance of only 107 million km (67 million miles).  Only the planet Mercury orbits closer.  As a result of this relative closeness, the planet Venus is bathed continuously in high concentrations of sunlight.

The fourth factor is the Earth’s position in the solar system.  The planet Earth orbits third outward from the Sun at 150 million km (93 million miles).  Venus can approach closer to the Earth than any other planet in the solar system.  At its closest approach, Venus lies only 43 million km (26 million miles) away.

These four factors combine to make Venus a dazzling sight in our night sky.  Small wonder that the classical civilizations named the planet for their goddess of beauty.

 Sources:  The Venus sites at http://www.seds.org and http://zebu.uorgeon.edu
 

For the week beginning August 4, 2002

Flash’s Astronomical Fact #146

In this edition of Flash’s Astronomical Facts, we will conclude our discussion of the Space Shuttle’s Payload Deployment and Retrieval System by relating a few random facts about the Remote Manipulator System (RMS), popularly known as the “robot arm”.

A special bolt is fitted to the RMS to hold it in place securely during launch.  After achieving orbit, the Space Shuttle crew releases this bolt to enable the robot arm to be put to use.  Interestingly, it is not considered necessary to re-insert the special bolt into the RMS in preparation for re-entry.

The robot arm can never endanger the Space Shuttle and her crew by making it impossible to close the cargo bay doors.  If, for any reason, the RMS cannot be folded properly so as to enable the cargo bay doors to be closed, the crew can jettison part or all of the assembly by releasing special bolts found on all three of the robot arm’s joints. 

As implied above, the RMS is not affixed permanently to the body of the Space Shuttle, but is instead removable.  And not just for the safety reason cited above.  The ability to remove the RMS means that the device need be taken along only on those missions during which it will be needed.  If a particular mission does not require the services of the PDRS, the entire system can be removed, affording a savings in weight at launch of 450 kg (994 lbs).

 Source:  The Payload Deployment and Retrieval System site at http://prime.jsc.nasa.gov
 

For the week beginning July 28, 2002

Flash’s Astronomical Fact #145

Beginning with the July 7, 2002 edition of Flash’s Astronomical Facts, we have been examining the Space Shuttle’s Payload Deployment and Retrieval System (PDRS).

The Remote Manipulator System (RMS) is the active part of the PDRS.  The RMS (or “robot arm”, as it is popularly known) has performed magnificently.  It has deployed satellites from the Space Shuttle’s cargo bay, and retrieved orbiting satellites for repair and re-deployment or for return to Earth.

But how is this amazing system operated?

The RMS is operated by not one, but two, astronauts.  By means of remote control manipulation of the shoulder joint and elbow joint of the robot arm, the first astronaut can extend the booms that constitute the upper arm and forearm of the RMS.  The end effector (grasping mechanism), which corresponds to the hand of the robot arm, is operated by yet another remote control device.

The second astronaut assists the first by operating the closed-circuit television camera mounted on the robot arm’s elbow joint.

The first operator can see what he is doing by looking at the television monitor; or by looking out of the aft flight deck payload windows or the aft overhead windows - all the while remaining safely inside the Space Shuttle’s “shirt-sleeve” environment.

We will conclude our discussion of the Space Shuttle’s Payload Deployment and Retrieval System in the next edition of Flash’s Astronomical Facts.

 Source:  The Payload Deployment and Retrieval System site at http://prime.jsc.nasa.gov
 

For the week beginning July 21, 2002

Flash’s Astronomical Fact #144

In the July 7, 2002 edition of Flash’s Astronomical Facts, we began our examination of the Space Shuttle’s Payload Deployment and Retrieval System (PDRS).  The most important part of the PDRS is its robot arm, known formally as the Remote Manipulator System (RMS).

The robot arm is aptly named, for it truly does resemble a human arm in both form and function.  The robot arm consists of two long booms that serve as the "forearm" and "upper arm".  A "shoulder joint” attaches the upper arm to the cargo bay's interior bulkhead.  An “elbow joint” attaches the upper arm to the lower arm.  A “wrist joint” attaches the lower arm to the “end effector” (grasping mechanism), which corresponds to the "hand".

The joints give the RMS six degrees of freedom (free movement):  Yaw and pitch at the shoulder; pitch at the elbow; yaw, pitch, and roll at the wrist.  These movements combine to enable the robot arm to go anywhere its length permits.

Speaking of length, the RMS has a total length of 15.32 m (50.25 ft).  Each of its booms has a maximum diameter of 38 cm (15 in).  The total PDRS has a weight of 450 kg (994 lbs).  Of that weight, the RMS alone accounts for 410 kg (905 lbs). 

Each of the booms is made of a composite material of graphite bonded with epoxy resins.  The joints are metallic, and the electronic housings are made of an aluminum alloy.

The RMS can handle a payload with a mass of up to 29,500 kg (65,000 lbs).  But significantly, the robot arm can work only in space.  It is too fragile in structure and too weak in power to operate in Earth’s gravity.

I will have more to say about the Space Shuttle’s Payload Deployment and Retrieval System in the next edition of Flash’s Astronomical Facts.

 Source:  The Payload Deployment and Retrieval System site at http://prime.jsc.nasa.gov
 

For the week beginning July 14, 2002

Flash’s Astronomical Fact #143

In the previous edition of Flash’s Astronomical Facts, we began our examination of the Space Shuttle’s Payload Deployment and Retrieval System (PDRS).  The portion of PDRS that is most familiar to the general public is the robot arm, known formally as the Remote Manipulator System (RMS).

When you see the RMS in action on television, you cannot help but notice the small Canadian flag and the word “CANADA” in big bold letters painted in red on one of the booms.  There is a very good reason why those markings are there.

The National Research Council of Canada, in association with NASA, created the RMS.  The Canadian firm of Spar Aerospace Ltd. designed, built, and tested the RMS.  Another Canadian firm, CAE Electronics Ltd., provided the electronic interfaces, servoamplifiers, and power conditioners for the robot arm.  A third Canadian firm, Dilworth, Secord, Meager & Assoc. Ltd., built the specialized “end effector” (grasping mechanism) for the RMS.

Giving the contract for the RMS to Canada was of mutual benefit to both nations.  America gained by spreading the costs of the Space Shuttle project.  Canada gained by becoming a partner in, and acquiring a stake in the success of, the Space Shuttle.

Although Canada does not have a space program comparable to that of the United States, it does recognize the importance of the high frontier and wishes to take an active part in its development. Building the RMS enabled Canadian firms to gain valuable experience in the engineering of space systems.  At the same time, it allowed Canada to contribute to the Space Shuttle project in a significant way. 

And the Canadians are committed to doing more than just manufacturing space hardware.  As of October 1, 2001, nine of the astronauts who have flown aboard the Space Shuttle have been Canadian.

I will have more to say about the Space Shuttle’s Payload Deployment and Retrieval System in the next edition of Flash’s Astronomical Facts.

 Sources:  The World Almanac and Book of Facts 2002 and The Payload Deployment and Retrieval System site at http://prime.jsc.nasa.gov
 

For the week beginning July 7, 2002

Flash’s Astronomical Fact #142

The Payload Deployment and Retrieval System (PDRS) is the formal name for the totality of devices and mechanisms that make it possible for the Space Shuttle to remove payloads from its cargo bay and deploy them into space; or to capture previously deployed objects (such as orbiting satellites) and place them into the cargo bay for repair and re-deployment or for return to Earth.

The active portion of the PDRS - and the part most familiar to the general public - is the Space Shuttle’s robot arm, known formally as the Remote Manipulator System (RMS).

The RMS has three basic functions.  One function is the deployment and retrieval of payloads, as described above. 

The second function of the RMS is to provide a work platform for a spacewalking astronaut.  This is accomplished by attaching special foot restraints to the end of the robot arm.  By placing his boots into the foot restraints, the spacewalking astronaut obtains a steady purchase.

The third function of the RMS is to effect a visual inspection of the Space Shuttle by means of its attached closed-circuit television cameras.

I will have more to say about the Space Shuttle’s Payload Deployment and Retrieval System in the next edition of Flash’s Astronomical Facts.

 Source:  The Payload Deployment and Retrieval System site at http://prime.jsc.nasa.gov
 

For the week beginning June 30, 2002

Flash’s Astronomical Fact #141

What follows is the sixth of an occasional series about flags with stars.

With Independence Day coming up on July 4, this edition of Flash’s Astronomical Facts will present another in its series of flags with stars.

In Flash’s Astronomical Facts #138 (for June 9, 2002), we examined the flag of the state of Rhode Island.  In this edition, we will examine its predecessor colonial battle flag, which had a number of similarities - and differences.

The Rhode Island battle flag was introduced in 1772.  The field of the flag was white.  The principal design element was a blue anchor.  An anchor line, also blue in color, snaked artistically around the shaft of the anchor.  Arcing above the anchor was a ribbon of blue on which the word HOPE (Rhode Island's state motto) was written in large white block letters.

The most significant design element of the Rhode Island colonial flag was the canton (union) of blue in the upper left-hand portion of the flag.  Placed in the canton were thirteen five-pointed stars (pentagrams) intended to represent the Thirteen Original Colonies.  The Rhode Island battle flag was the first to use stars in this way.  The stars were gold in color (or silver, or white, depending on which source you access). 

Even more significantly, the Rhode Island colonial flag was the first to arrange the stars within its canton in a stylized pattern.  The stars were arranged in a row of three above a row of four above two rows of three (3-4-3-3), or a pattern of three rows of three alternating with two rows of two (3-2-3-2-3) (again, depending on which source you access).  The latter pattern is significant because the same pattern later would be used on the first flag of the United States.

Rhode Islanders were among the strongest advocates of the Revolutionary cause, and got in the act early.  On June 10, 1772, Rhode Islanders took action against the British revenue cutter Gaspee.  Although the burning of the Gaspee will not be examined in detail in this essay, it is worth studying, as it was one of the first actions taken by American colonists in defiance of British authority.

 Sources:  An Album for Americans, by David H. Appel, the Gaspee site at http://www.gaspee.com, and the Flags site at http://www.anyflag.com
 

For the week beginning June 23, 2002

Flash’s Astronomical Fact #140

Way back when, manned space flight was the undertaking of only two nations:  The United States and the Soviet Union.  Consequently, the only humans in space were either Americans or Russians.

Nowadays, any nation can participate in the exploration of outer space - and without having to develop a full-fledged space program in order to do so.  The International Space Station is now in orbit, with the American Space Shuttle and the Russian Soyuz employed to ferry personnel and materiel aloft.  Thus, a country that wishes to become part of the space effort does not have to have launch facilities, space vehicles, and orbiting space stations of its own.  It need only have its best scientists apply for astronaut training.

During the first forty years of manned space flight (1961-2001), 422 individuals took at least one trip into space.  As of October 1, 2001, here is how the numbers break down by nationality:  United States, 267; Russia (both the old U.S.S.R. and the new C.I.S.), 97; Germany (West, East, and United), 11; Canada, 9; France, 8; Japan, 5; Italy, 3; two each for Bulgaria and Spain; and one each for Afghanistan, Austria, Belgium, Cuba, Czechoslovakia, Hungary, India, Mexico, Mongolia, the Netherlands, Poland, Romania, Saudi Arabia, Slovakia, Switzerland, Syria, the United Kingdom, and Vietnam.

Doubtless, astronauts from many more nations will be sent aloft in the years to come.  Stay tuned. 

 Source:  The World Almanac and Book of Facts 2002
 

For the week beginning June 16, 2002

Flash’s Astronomical Fact #139

The Zuni Indians of the southwestern region of North America have an interesting legend about the Sun, the Moon, and the seasons.

It is said that when the world was young, the sky was always dark and the Earth was always hot (that is, it was always summer).

One day, the coyote and the eagle decided to go hunting together.  In due course, they came upon the powerful Kachinas people.  From the Kachinas, the coyote and the eagle learned the reason why the sky was always dark and the Earth was always hot.  The Kachinas had captured both the Sun and the Moon, and were holding them prisoner inside of a box.  With the Sun so close to the Earth, it was no wonder that it was always summer!

The coyote and the eagle decided that they would steal the box.  They waited for the Kachinas to lie down to sleep, then made their move.

The eagle tried to carry the box by himself.  But the box proved to be too heavy for the eagle, so the coyote offered to carry it.  But unlike his brother the eagle, the coyote was curious.  The coyote opened the box, which allowed the Sun and the Moon to escape.  Both bodies rose up into the sky. 

As a consequence of the Sun ascending into the heavens, light fell upon the land, putting an end to the perpetual darkness.  But with the Sun now so far above the Earth, there was less heat upon the land.  And thus was born the season of winter.

 Source:  The Solar Legends site at http://solar-center.stanford.edu
 

For the week beginning June 9, 2002

Flash’s Astronomical Fact #138

What follows is the fifth of an occasional series about flags with stars.

With Flag Day coming up on June 14, this edition of Flash’s Astronomical Facts will examine another flag that contains stars.

One of the most star-spangled of all state flags is that of the state of Rhode Island (known fully as the State of Rhode Island and Providence Plantations).  The flag was adopted by the Rhode Island state legislature at its January 1897 Session.  This made it the third of the Original States (after New Jersey and New York (in 1896)) to officially adopt a state flag.

Although it appears to be perfectly square in shape, the official Rhode Island state flag actually has a fly (length) of five foot six inches and a hoist (height) of four foot ten inches.  The flag’s field is white.  In the middle of the white field is an anchor of gold.  Beneath the anchor is a ribbon of blue, on which the word HOPE (Rhode Island's state motto) is written in gold block letters.  Surrounding the anchor and ribbon is a circle of thirteen gold stars, one for each of the Thirteen Original Colonies.

The design elements on the Rhode Island state flag pre-date the American Revolution.  Under the authority of the Cromwellian Patent of 1643, the Providence Plantations adopted (in 1647) the anchor as the official seal of the Province.  Later, under a more liberal charter granted by King Charles II of England to the Colony of Rhode Island and Providence Plantations, the word HOPE was added above the anchor.

The circle of stars on the Rhode Island state flag is another design element that pre-dates American Independence.  Several battle flags of the American Revolution bore a circle of stars.

The flag's colors also pre-date the American Revolution.  Blue and white have long been Rhode Island's official colors (hardly surprising, being as it is a coastal state).  Blue and white have appeared on state regimental banners carried by Rhode Islanders into such conflicts as the American Revolution, the War of 1812, and the Mexican War.

As in other states, the design of the Rhode Island state flag is defined in Rhode Island statutory law; but that law contains several peculiarities.  For one thing, Rhode Island law expressly requires that the flag be trimmed with decorative yellow fringe (in most states, the use of the decorative fringe is optional).  Moreover, in most states, the pike (staff) from which the flag flies may be surmounted by any number of decorative devices (ball, star, spear, flat truck, eagle, halberd, etc.).  But Rhode Island law states that the pike must be surmounted by a spear.  Finally, the law defines even the official height of the pike (9 feet). 

I guess it can safely be said that Rhode Islanders leave nothing to chance.

 Sources:  The Rhode Island flag sites at http://www.netstate.com and http://www.state.ri.us
 

For the week beginning June 2, 2002

Flash’s Astronomical Fact #137

In the previous edition of Flash’s Astronomical Facts, we examined the metallic element beryllium.

Because beryllium is relatively scarce in the Earth’s crust and hard to extract from ore, it is a very expensive metal; far too expensive to use in everyday applications. 

However, there are certain applications for which beryllium is indispensable.  And one such specialized application played an important role in the early days of the space program.

In passing through the Earth's atmosphere, most meteors burn up completely - and long before reaching the Earth's surface - due to the heat generated by atmospheric friction.  And exactly the same fate would befall a space capsule and her crew upon re-entry – unless precautions were taken to prevent it.

That is where beryllium comes in.

Beryllium has a number of properties that made it the metal of choice to protect Mercury capsules from the heat of re-entry.  First, beryllium is very light in weight.  In fact, beryllium is the second lightest of all the metals.  And the less that something weighs, the less the amount of fuel required to send it into orbit.

Not only is beryllium light in weight, it has one of the highest melting points of all the lightweight metals.  Aluminum, for instance, melts at 660 degrees C.  By contrast, beryllium melts at a whopping 1278 degrees C!

And as if that were not enough, beryllium has one of the highest specific heats of all the metals.  A complete explanation of the concept of specific heat is beyond the scope of this essay.  But here is the practical upshot:  A substance with a high specific heat can absorb large amounts of heat while increasing in temperature only slightly.

And far from being an untested commodity, beryllium already had proved itself to be an effective and efficient absorber of heat.  Years before the beginnings of manned space flight, the U.S. Navy had used beryllium to absorb heat on selected parts of unmanned Polaris missiles.

Given all of its intrinsic qualities, coupled with its proven track record, it is little wonder that beryllium - in the form of a heat shield fitted to the underside of the spacecraft - was called upon to protect Mercury capsules from burning up during re-entry.

And protect them it did.  During re-entry, the beryllium heat shield absorbed almost all of the heat generated by atmospheric friction, leaving almost none to endanger the Mercury craft and her occupants.  This technique of protecting space capsules from the heat of re-entry is called heat sink or - more fully -beryllium heat sink.

Capsules in the successor Gemini series used a different method of protecting the spacecraft from the heat of re-entry.  But we will examine that technique in a future edition of Flash’s Astronomical Facts.

 Sources:  CRC Handbook of Chemistry and Physics, the Beryllium sites at http://www.osha-slc.gov and http://www-tech.mit.edu, and the Beryllium Heat Sink site at http://www.hq.nasa.gov
 

For the week beginning May 26, 2002

Flash’s Astronomical Fact #136

Metals are a class of chemical elements characterized by such properties as malleability, strength, and the ability to conduct heat and electricity.  Without metals, modern civilization would be impossible.

Different metals have different properties, and it is a metal's properties that determine how it is used.  Copper, for example, is an excellent conductor of electricity, and is found in everything from power generators to house wiring.  Lead is extremely dense, and is useful as a radiation shield.  Iron is incredibly strong, and can be used to build tall structures (such as the Eiffel Tower). Aluminum, light in weight, is found in everything from kitchen utensils to aircraft bodies.

The average individual is familiar with the above metals because they are relatively abundant, fairly easy to refine, and frequently encountered in the course of everyday life.

But there are other metals with which members of the general public are not as familiar.  These metals are relatively scarce, quite difficult to refine, and seldom encountered in the course of everyday life.

One such metal is beryllium.

Beryllium - the principle ores of which are beryl, phenacite, and chrysoberyl - is relatively scarce in the Earth’s crust at just six parts per million.  Moreover, the processes required to extract the metal from ore are chemically complex and can be accomplished only under high temperatures and pressures. 

As a consequence, beryllium is a relatively expensive metal.  While most refined metals sell for just pennies per kilo, pure beryllium metal retails for over $5,000 per kilo (over $2,000 per pound)!

While beryllium might be used for a number of everyday applications, less expensive metals that can serve the same purpose are used instead.

However, there are certain applications for which beryllium is indispensable.  And one such specialized application played an important role in the early days of the space program.  We will examine that aspect of beryllium in the next edition of Flash’s Astronomical Facts.

 Sources:  CRC Handbook of Chemistry and Physics, Webster's New World Dictionary, the Eiffel Tower site at http://www.tour-eiffel.fr, and the Beryllium sites at http://www.osha-slc.gov and http://www-tech.mit.edu
 

For the week beginning May 19, 2002

Flash’s Astronomical Fact #135

In April of 1959, seven men were selected to become Mercury astronauts.  But there were only six manned flights in the Mercury series.  Obviously, someone with “The Right Stuff” did not get to fly a Mercury mission.

And that someone was U. S. Air Force Captain Donald K. “Deke” Slayton.  In August of 1959, just four months after becoming one of America's charter space pioneers, Slayton underwent medical tests that revealed that he had an irregular heartbeat.  Grounded by his cardiac condition, Slayton would never fly a Mercury mission.  One can only imagine how profound must have been the depths of his disappointment. 

But hey, no need to feel too sorry for Slayton.  After getting his heart problem under control, he was selected for another mission into space - a mission that would turn out to be one of a kind. 

Slayton was chosen to be one of the three astronauts to fly the American portion of the historic Apollo/Soyuz joint mission.  Astronaut Thomas Stafford commanded Slayton and astronaut Vance Brand.  The Soviet portion consisted of cosmonaut Alexei Leonov commanding cosmonaut Valeriy Kubasov.

Besides accomplishing its scientific and diplomatic objectives, the Apollo/Soyuz joint mission must surely have compensated Slayton for whatever disappointments he might have felt at having been denied a Mercury flight .  For one thing, Slayton and his fellow astronauts shared the honor of flying the last Apollo mission (the Apollo capsule was retired from service following theApollo/Soyuzjoint mission).

But Slayton got another honor; and it was one that he did not have to share with anyone.  At the time of the Apollo/Soyuz joint mission, Slayton was 51 years of age.  This made him the oldest man (up to that time) ever to take a trip into space.

Thanks to the Apollo/Soyuz joint mission - which lasted from July 15 to July 24, 1975 - Slayton logged 217 hours and 28 minutes “out there”.  Not too bad - especially for a man who, at one time, was seemingly destined never to venture into space at all.

I will have more to say on the Apollo/Soyuz joint mission in future editions of Flash’s Astronomical Facts.

 Sources:  Time Almanac 2002, Life in Space (a Time/Life book), the Deke Slayton site at http://www.jsc.nasa.gov, and the National Aviation Hall of Fame site at http://www.nationalaviation.org
 

For the week beginning May 12, 2002

Flash’s Astronomical Fact #134

In 1985, Mexican astronaut Rodolfo Neri Vela requested that one of his favorite foods - soft flour tortillas - be included in the Space Shuttle’s food manifest as one of his optional menu items.

Unfortunately, his request could not be granted.  Way back when, NASA decided to put neither a refrigerator nor a freezer in the Space Shuttle’s galley.  This resulted in the saving of much precious weight and space.  But it meant also that only those foods that did not require refrigeration could be sent aloft aboard the Space Shuttle.

A typical Space Shuttle mission lasts seven days. Coincidentally, that is also the amount of time that it takes for soft flour tortillas stored at room temperature to begin to spoil.  Since it could not be guaranteed that soft flour tortillas would remain edible for the duration of a typical mission, soft flour tortillas were out as a food for Space Shuttle astronauts.

But that was then, this is now   Present-day Space Shuttle astronauts can have soft flour tortillas as part of their diet - because NASA food scientists put their heads together and developed a soft flour tortilla with a shelf life of six months!

This is not to say that NASA food scientists are miracle workers.  For all their efforts, they have yet to find a way to shelf-stabilize one of the world’s favorite snack foods – pizza!

 Source:  Ad Astra magazine, May/June 2002

Ad Astra magazine is a bimonthly publication of the National Space Society, an organization dedicated to the exploration and development of space.
 

For the week beginning May 5, 2002

Flash’s Astronomical Fact #133

Many aspects define the orbit of a satellite.  In the previous edition of Flash’s Astronomical Facts, we discussed the aspect of orbital altitude, or height above the surface of the Earth.  In this edition, we will discuss another aspect, called orbital inclination.

In this context, inclination refers to the tilt of the satellite’s orbit around the Earth.  This tilt, by convention, is measured in degrees relative to the Earth’s equator.

Although a satellite can be made to orbit the Earth at any inclination desired, three special orbital inclinations have proved to be the most useful.

The first of these useful orbital inclinations is the equatorial orbit.  An equatorial orbit, as the term implies, means that the satellite orbits above our planet's equator.  A satellite in equatorial orbit will have an inclination of either 0 degrees or 180 degrees, the difference being this:  If the orbit has an inclination of 0 degrees, it means that the satellite is orbiting above the equator in the prograde direction (that is, west to east, with the rotation of the Earth).  If it has an inclination of 180 degrees, it means that the satellite is orbiting above the equator in the retrograde direction (that is, east to west, against the rotation of the Earth).

Global communications satellites typically are placed in prograde equatorial orbit AND at the geosynchronous orbital altitude of 35,786 km (22,241 miles).  A communications satellite in such an orbit will stand above the same patch of the Earth at all times, thus enabling it to stay in continuous contact with its ground transmission and receiving stations.

Another useful orbital inclination is the polar orbit.  A polar orbit, as the term implies, means that the satellite passes alternately over the Earth’s north and south geographic poles. A satellite in polar orbit will have an inclination of 90 degrees. 

Weather satellites typically are placed in polar orbit AND at an orbital altitude of about 850 km (530 miles) above the Earth’s surface (a satellite orbiting our planet at such an altitude is said to be in Low Earth Orbit).

Why are weather satellites made to orbit the Earth in that way?  Certainly, the low altitude enables the satellite to take clear, close-up shots of our planet’s weather systems.  That is part of the reason.

But in addition, a polar orbit enables a single weather satellite to collect images and data from the entire surface of the Earth.  This is because a polar orbit stands at right angles to the Earth's rotation. 

While the weather satellite moves in its orbit from one pole to the other, its downward-directed cameras and sensors collect images and data from the section of the Earth directly beneath it.  At the same time, the Earth rotates on its axis from west to east.  Thus, on each successive orbit, the satellite gathers images and data from the section of the Earth just to the west of the one previous. 

The images and data are then transmitted to ground receiving stations, where meteorologists assemble the sections into a weather map.  Because the satellite gathers images and data on both sides of the Earth with each orbit, the weather map is never more than twelve hours old.

The last of these useful orbital inclinations is the heliosynchronous (a.k.a  Sun-synchronous) orbit. Literally translated from the Greek, heliosynchronous means “in time with the Sun”.  A satellite in heliosynchronous orbit maintains at all times the same angle with respect to the Sun.  A heliosynchronous orbit has an inclination of 98 degrees, which means that its orbit is near polar and in the retrograde direction. 

A heliosynchronous orbit is tricky to achieve, as it requires not only the right orbital inclination, but also the right orbital altitude and the right orbital eccentricity (that is, its orbit must be an ellipse of the proper shape).  However, it is well worth the effort, because a satellite in heliosynchronous orbit stays continuously above the lighted half of the Earth.  And since good lighting makes for good imaging, a heliosynchronous orbit is exactly where you would want to place a vital observation satellite - such as a military satellite.

 Sources:  Air Force Magazine Space Almanac 2001, and the Satellite Orbit sites at http://www.thetech.org, http://noaasis.noaa.gov, http://physics.uwstout.edu, http://octopus.gma.org,  http://scienceworld.wolfram.com, and http://eesurrey.co.uk
 

For the week beginning April 28, 2002

Flash’s Astronomical Fact #132

Hundreds of artificial (man-made) satellites revolve around the Earth.  Each satellite follows its own unique path - called its orbit – as it circles our planet. 

Many aspects define a satellite in orbit.  And one of the most significant of these aspects is its orbital altitude (that is, its height above the Earth's surface).

Those who are charged with launching satellites into orbit speak of four distinct orbital regions, as described below.

Low Earth Orbit (LEO) refers to those orbits that are closest to the Earth.  A satellite in LEO usually has an orbital altitude in the range of 250 – 300 km (150 - 180 miles) above the surface of the Earth. 

Actually, LEO can range from as little as 100 km (60 miles) to as much as 1000 km (600 miles) above the Earth's surface; but a satellite in orbit would encounter difficulties at either of these extremes.  The more the satellite's orbit drops below the optimum range described in the preceding paragraph, the greater the atmospheric drag on the satellite.  The more the satellite's orbit rises above the optimum range, the greater the disruptive effects on the satellite from the radiation of the Earth’s enveloping Van Allen belts.

Weather satellites typically are placed in LEO so that they can obtain close-up views of the Earth’s weather systems.

Geosynchronous Earth Orbit (GEO) refers to the orbit at which a satellite’s orbital velocity matches precisely the Earth’s rate of rotation.  This orbital altitude is 35,786 km (22,241 miles) above the surface of the Earth.  Geosynchronous, literally translated from the Greek, means “in time with the Earth”.  A satellite that is in GEO  - and orbiting above the Earth’s equator  - will stay above the same patch of the Earth’s surface at all times.

As noted above, LEO consists of a wide range of orbital altitudes.  But GEO consists of only a very narrow range.  Move only a short distance away (in either direction) from the orbital height of 35,786 km (22,241 miles), and the orbit no longer will be geosynchronous.

A handful of weather satellites are placed in GEO so as to get a wider overall picture of the Earth’s weather patterns. But most of the satellites that are placed in GEO are those that provide global communications.  A geosynchronous orbit allows a communications satellite to stay in continuous contact with its ground transmission and receiving stations.

Medium Earth Orbit (MEO) consists of the region between LEO and GEO.  Few satellites are placed in MEO because of the presence of the Van Allen belts, the radiation from which can play havoc with humans and electronics alike (before you ask, Apollo astronauts on their way to, or returning from, the Moon were able to pass safely through the Van Allen belts because they did so quickly).

High Earth Orbit (HEO) is anything above GEO.  Satellites in HEO usually are placed at such heights in order to investigate interplanetary phenomena, such as the solar wind.

In the next edition of Flash’s Astronomical Facts, we will examine another aspect of satellite orbits – their inclinations.

 Sources:  Air Force Magazine Space Almanac 2001, Webster’s New World Dictionary, and the Satellite Orbit sites at http://www.thetech.org, http://eesurrey.co.uk, and http://scienceworld.wolfram.com
 

For the week beginning April 21, 2002

Flash’s Astronomical Fact #131

The great German astronomer Johannes Kepler (1571-1630) determined the physical laws that govern the orbital motions of the planets.  We examined Kepler’s Third Law of Planetary Motion in Flash’s Astronomical Fact #48 (for September 17, 2000).  In this edition, we will examine Kepler’s First Law of Planetary Motion. 

By analyzing the observational data bequeathed to him by the Danish nobleman and amateur astronomer Tycho Brahe (1546-1601), Kepler found that the orbit of the planet Mars was not circular.  Rather, its orbit had the shape of a slightly flattened circle.  Such a geometric figure is called an ellipse.  Moreover, Kepler found that the Sun did not lie at the exact center of Mars’ elliptical orbit, but instead lay offset from the center at one of the ellipse’s two focal points, called foci. 

Kepler later determined that all of the planets in the Solar System have elliptical orbits – including the Earth.

This discovery brought Kepler much relief .  For years, he had been operating on the assumption that the planets have orbits that are perfectly circular.  And for years, he had been driving himself batty trying to make his circular orbit hypothesis fit the observational data.

Kepler's First Law of Planetary Motion may thus be stated as follows:  The orbits of all planets are elliptical, with the Sun located at one of the two foci of the ellipse.

Additional information:  Because the Sun lies offset from the center of a planet’s elliptical orbit, it means that there will one point - and only one point - where the planet will be farthest from the Sun.  This point is called aphelion.  Likewise, there will one point - and only one point - where the planet will be nearest to the Sun.  This point is called perihelion.

We will examine Kepler's Second Law of Planetary Motion in a future edition of Flash's Astronomical Facts.

 Source:  Cosmos by Carl Sagan 
 

For the week beginning April 14, 2002

Flash’s Astronomical Fact #130

Do you enjoy playing word games (Scrabble, Anagrams, and the like)?  Well then, here is a doozy of a word for you:  Syzygy (pronounced "ziz-uh-gee").

Syzygy is the shortest word in the English language that contains three letters ‘y’.  Syzygy comes from syzygia, meaning “yoked” or “paired”.  The word comes to us from Greek via Late Latin.

Syzygy refers to an alignment of celestial bodies, but is used almost exclusively to refer to alignments between the Sun, the Moon, and the Earth.

Originally, syzygy described an alignment where the Moon was at conjunction (that is, positioned between the Sun and the Earth).  The Moon thus had the Sun on one side and the Earth on the side opposite, hence the references to yokes and pairings.  When the Moon is at conjunction, it is at the phase called New Moon, where its lighted half faces fully away from the Earth.

Later on (and almost in defiance of its etymology), syzygy came to refer also to alignments where the Moon was at opposition (that is, positioned on the side opposite the Sun as seen from the Earth).  When the Moon is at opposition, it is at the phase called Full Moon, where its lighted half faces fully towards the Earth.

And what is the significance of syzygy?  For one thing, when the Sun, the Moon, and the Earth are at syzygy (in either of its two forms as described above), gravitational effects are at their maximum, and the highest ocean tides occur.

 Sources:  The Weird Words site at http://www.worldwidewords.org, the Tides site at http://csep10.phys.utk.edu, and Webster’s New World Dictionary
 

For the week beginning April 7, 2002

Flash’s Astronomical Fact #129

Over the course of the next several weeks, skywatchers will be treated to a rare celestial event.  Every planet in the Solar System that is visible to the unaided eye will line up the western sky immediately after sunset.  Mercury will be close to the horizon.  Just above Mercury you will find Venus.  Followed in turn by Mars, Saturn, and Jupiter.

As if that were not enough, the waxing crescent Moon will flirt with each planet in turn.  The Moon will be near Mercury on the 13th; Venus on the 14th; Mars on the 15th; Saturn on the 16th; and Jupiter on the 18th. 

And there is yet more.  On the 16th, people living in certain areas will see the Moon occult (pass in front of) Saturn.

 Sources:  The Old Farmer’s Almanac (2002 edition) and Time Almanac 2002
 

For the week beginning March 31, 2002

Flash’s Astronomical Fact #128

Triton, the largest of Neptune’s eight known natural satellites, has the distinction of having the coldest surface temperature of any object in the Solar System.  The surface temperature of Triton is -235 degrees Celsius (-391 degrees Fahrenheit).  By comparison, the coldest temperature possible - called absolute zero - occurs at -273.15 degrees C (-459.67 degrees F).

So just what is it about Triton that makes it so cold?

Simply put, Triton is cold because circumstances make it nearly impossible for the satellite either to acquire or retain heat.

For starters, Triton - which orbits some 330,000 km (205,000 miles) above Neptune’s cloud tops - receives very little heat from its mother world, which is an extremely cold body in its own right.  The mean temperature of Neptune’s cloud cover is -193 degrees C (-315 degrees F). 

In addition, Triton lies far away from the Sun.  Triton is, as I said, a moon of Neptune; and Neptune orbits the Sun at a mean distance of 4.6 billion km (3 billion miles).  The Sun, to be sure, puts out enormous amounts of radiant energy.  But the farther away from the Sun an object lies, the less of the Sun's energy it receives.  Moreover, this decrease is not linear, but in fact squared.  Thus, situated as it is near the outer edge of the Solar System, Triton receives very little of the Sun's heat and light. 

But the biggest single reason why Triton is so cold is because its surface is so bright.  And bright surfaces are reflective surfaces.  Estimates vary, but Triton reflects at least 60% to as much as 95% of the sunlight that falls on it (by comparison, the Earth reflects only about 30% of the sunlight that falls on it).  In other words, not only does Triton receive virtually no sunlight, it reflects back into space almost all of what little it does receive.

When you consider all that Triton has going against it, it is actually astounding that the satellite is as warm as it is!

 Sources:  The Triton and Neptune sites at http://www.seasky.org, the Earth Albedo site at http://eosweb.larc.nasa.gov, and Time Almanac 2002
 

For the week beginning March 24, 2002

Flash’s Astronomical Fact #127

In the study of astronomy, the word “retrograde” has two different meanings, one of which we will examine here.

If you could look down at the Solar System from a point high above the Earth’s North Geographic Pole, you would see the Earth spinning on its axis counter-clockwise.  This west-to-east motion is what causes the Sun to appear to rise in the east and set in the west.

If you were then to look down at the other planets in the Solar System, you would see that five of them – Mercury, Mars, Jupiter, Saturn, and Neptune – also have a counter-clockwise spin.  Since they have a west-to-east motion like the Earth, these five planets are said to have prograde rotation.  The word “prograde” comes from a couple of Latin roots that mean “to step forward”.

However, three planets in the Solar System – Venus, Uranus, and Pluto – have a clockwise spin.  Since their east-to-west motion is the opposite of the Earth’s west-to-east motion, these three planets are said to have retrograde rotation.  The word “retrograde” comes from a couple of Latin roots that mean “to step backward”.

The terms prograde and retrograde apply also to other planetary motions.  Looking down again at the Solar System, you would see that the Earth revolves around the Sun in a counter-clockwise direction.  So too does every other planet in the Solar System.  Therefore, all of the other planets are said to have prograde revolution.  If, hypothetically speaking, a planet revolved around the Sun in a clockwise direction, it would be said to have retrograde revolution.

And what applies to planets orbiting the Sun applies also to satellites orbiting planets.  For instance, Phoebe, one of the moons of Saturn, revolves retrograde relative to its sibling satellites and the rotation of its mother world.  This retrograde movement suggests strongly that Phoebe did not form with Saturn.  Instead, Phoebe probably was an asteroid that wandered too close to Saturn and was captured by the planet's gravity .

By the way, the word “direct” sometimes is used in place of the word “prograde”.  Astronomers use both terms.  They are equal and interchangeable.

We will examine the other meaning of the word retrograde in a future edition of Flash’s Astronomical Facts.

 Sources:  The Retrograde Rotation sites at http://www.go.ednet.ns.ca and http://www.bartleby.com, Time Almanac 2002 and Webster’s New World Dictionary
 

For the week beginning March 17, 2002

Flash’s Astronomical Fact #126

The Earth is approaching a special orbital position called the vernal equinox.  On March 20, 2002, at precisely 2:16 p.m. EST, the Sun will cross the Earth’s celestial equator from south to north.  Thus, March 20, 2002 will be the first day of spring in the Northern Hemisphere and the first day of fall in the Southern Hemisphere.

In the previous edition of Flash’s Astronomical Facts, I set the record straight regarding a myth associated with the vernal equinox; specifically, that on the first day of spring, it is possible for someone situated on the equator to stand a raw egg upright on its large end (see Flash’s Astronomical Facts #125 (for March 10, 2002) for the details).  In this edition, I will clear up another misconception about the vernal equinox.

It is popularly believed that, on the first day of spring (or the first day of fall), daytime and nighttime last exactly twelve hours each all across the globe.

Certainly, it is understandable why one would suppose that this is so.  At the equinoxes, the Earth presents its Northern and Southern Hemispheres equally to the Sun.  Moreover, the word “equinox” is Latin for “equal night” (which implies, by extension, equal day).

But, however intuitively correct this popular belief may seem, it is simply not true. 

Were you to refer to a detailed almanac (such as The Old Farmer’s Almanac, one of my best sources), you would find that the length of the day (defined as the period of time between sunrise and sunset) is closer to twelve hours on a date several days before, rather than on, the first day of spring.  A similar thing happens around the time of the autumnal equinox.  The length of the day is closer to twelve hours on a date several days after, rather than on, the first day of fall.

Why should this be?

It is the consequence of two factors, both of which are responsible – each in its own way – for making the period of daytime slightly longer than it otherwise would be.

Factor one:  The Sun is a relatively large body that lies relatively close to the Earth.  Therefore, it appears in our sky not as a pinpoint of light, but rather like a disc.  Sunrise, as defined by astronomers, does not begin when the middle of the disc appears above the horizon, but rather when the first portion of the Sun’s disc (called the leading limb) appears above the horizon. Similarly, sunset does not occur when the middle of the Sun’s disc drops below the horizon, but rather when the last portion of the Sun’s disc (called the trailing limb) drops below the horizon.

Daylight is thus extended by a few minutes at sunrise and a few minutes at sunset.

Factor two:  The Earth has an atmosphere.  The atmosphere refracts (bends) sunlight.  Sunlight appearing over the horizon is refracted by about one-half of one degree.

Thus, when we first see the Sun emerge over the horizon at sunrise, we are not seeing the Sun itself, but rather its refracted image.  The Sun is actually below the horizon.  A similar thing happens at sunset.  When we see the Sun on the horizon, we are not seeing the Sun itself, but again, its refracted image. Again, the Sun is actually below the horizon.

Refraction thus extends daylight by a couple of minutes each day.

And so, at the equinoxes, daytime and nighttime are not equal in length.  On the first day of spring (or the first day of fall), daytime lasts twelve hours plus the minutes of extended daylight resulting from factors one and two.  Nighttime lasts twelve hours minus the minutes of extended daylight resulting from factors one and two.

 Sources:  The Old Farmer’s Almanac (2002 edition) and the Astronomy site at http://scienceworld.wolfram.com
 

For the week beginning March 10, 2002

Flash’s Astronomical Fact #125

The vernal equinox is the name given to one of two points in the Earth's orbit where the plane of the Earth's celestial equator intersects the plane of the Earth's orbit.  The Earth will not attain this orbital position for another ten days. But I wanted to get a little ahead of the curve in order to refute a widely-held notion about this celestial event, which marks the first day of spring in the Northern Hemisphere.

A popular myth states that, on the day of the vernal equinox, it is possible for a person situated on the equator to stand a raw egg upright on its large end.  At the vernal equinox, the Sun lies across the Earth's equator, creating a gravitational balance so perfect as to make this feat possible - or so the believers contend. 

But this myth is exactly that - a myth.  It has no foundation in science.  It is completely untrue.

Let me be clear about what I am saying.  It is indeed possible to get an egg to stand upright; but the position of the Earth’s equator relative to the Sun has absolutely nothing to do with it.

The simple truth is, if you hold an egg upright on a level surface long enough for its fluid interior to come to rest, the egg can remain standing on its end indefinitely.  Generations of school children have put this "equinoctial egg theory" to the test in science class.  Students have managed to get an egg to stand upright at any latitude, at any time of the year (including the solstices), and even on the small end!  Moreover, some classes have claimed that after getting their eggs to stand upright, the eggs remained in that position for days, weeks, even months (although I doubt that they would want to use those same eggs to cook a congratulatory omelet).

But if this notion is so flat-out wrong, why does it persist?

Could be for a lot of reasons.  For one thing, the vernal equinox takes place around the time of Easter.  The egg and the resurrection of Jesus long have represented (each in its own way) eternal life.  The Easter connection may explain also why nothing is heard of this “upright egg” myth around the time of the autumnal equinox (the first day of fall in the Northern Hemisphere), where - once again - the plane of the Earth's celestial equator intersects the plane of the Earth's orbit.

Mostly though, I imagine that the myth persists because there is a certain delightful whimsy about the idea of the cosmos occasionally coming into a configuration that enables us lowly humans to perform seemingly impossible feats.

In any case, as long as you know and accept the truth as truth, then the misconception can do you no harm.  In fact, this is one of those cases where knowing the truth seems only to make the misconception all the more delightful.

 Sources:  The Egg and the Equinox sites at http://webs.wichita.edu, http://www.badastronomy.com, http://www.straightdope.com, http://www.usatoday.com, and http://www.clarkfoundation.org 
 

For the week beginning March 3, 2002

Flash’s Astronomical Fact #124

What follows is the first of an occasional series about series of spacecraft.

Pioneer is the designation for the first U.S. series of sophisticated interplanetary spacecraft.  The earliest Pioneer missions were conducted in association with the International Geophysical Year (IGY) of 1957-1958.

As I noted in this week’s edition of Flash’s Skywatcher’s Almanac, March 3, 1959 was the date on which Pioneer IV was launched.  Pioneer IV took the honor of being America's first successful deep-space probe.  But, as you are about to read, several earlier probes in the Pioneer series took mostly a lot of arrows.

The first attempt by the United States to launch a deep-space probe occurred on August 17, 1958.  This mission, which later would be named Pioneer 0, did not go well. 77 seconds after liftoff, the first stage exploded.

Pioneer I was launched on October 11, 1958.  Although the rocket launch was successful, the probe failed to achieve escape velocity (the speed necessary to break free of the Earth’s gravitational pull) and attained a maximum altitude of only 113,800 km (70,700 miles).  Thus, Pioneer I did not make it even one-third of the way to the Moon.  This is not to say that the mission was a complete bust, however.  Instruments aboard Pioneer I were able to determine the radial extent of the Van Allen radiation belts, make the first examinations of the Earth’s magnetic field and of interplanetary magnetic fields, and take the first measurements of the concentration of micrometeorites in interplanetary space.

The launch of Pioneer II on November 8, 1958 ended in disaster when the third and fourth stages failed to separate. Pioneer II attained a maximum altitude of only 1,600 km (1,000 miles) and logged only 12,000 km (7,500 miles).

The launch of Pioneer III on December 6, 1958 was practically a rerun of mission Pioneer I:  A successful rocket launch, followed by the failure of the probe to achieve escape velocity. Pioneer III attained a maximum altitude nearly identical to that of Pioneer I:  102,300 km (63,580 miles).  Thankfully, like Pioneer I, Pioneer III made a significant discovery that kept the mission from being a complete flop.  Specifically, it discovered that the Van Allen radiation belts consist of at least two separate bands.

Total success came with the launch of Pioneer IV.  It broke free of the Earth's gravitational field and came to within 59,500 km (37,000 miles) of the Moon.  After completing its flyby of the Moon, Pioneer IV continued on and eventually settled into orbit around the Sun.  Before radio contact was lost, the craft had logged 654,252 km (406,620 miles).  By achieving escape velocity and flying close to another world (the Moon), Pioneer IV became America’s first successful deep-space probe.

I will relate the details of later missions in the Pioneer series in future editions of Flash’s Astronomical Facts.

 Sources:  The Aeronautics and Astronautics Chronology site at http://www.hq,nasa.gov, the History of Space Exploration site at http://www.astro.keele.ac.uk, the Space FAQs site at http://www.landfield.com, and Time Almanac 2000
 

For the week beginning February 24, 2002

Flash’s Astronomical Fact #123

In the previous edition of Flash’s Astronomical Facts, I noted that the current opposition of Saturn is a close one.  This is due to the fact that the planet is nearing its closest orbital approach to the Sun, called perihelion.

But there is more.

As it happens, the current orbital geometry is such that the planet Saturn appears fairly high in the Earth’s Northern Hemisphere night sky.

Would it make difference if it were low in the sky?

As a matter of fact… yes.

When you look at a celestial object that is directly overhead, you are looking at it along a straight line through the atmosphere.  But when you look at an object that is near the horizon, you are looking at it along an angle through the atmosphere.  In other words, the higher overhead an object is, the less the amount of atmosphere through which you must look to see it.  And since the atmosphere is in constant motion, it creates turbulence that distorts the light coming from that object.  Thus - all other things being equal - the higher overhead an object is, the clearer it will be.

So, here is a summary of what I have been saying for the last few editions of Flash’s Astronomical Facts.

The rings of Saturn are now tilted in the upward direction.  In fact, right about now, Saturn’s rings are about as wide open as they ever get.

Saturn’s current opposition is a close one.  In fact, right about now, Saturn is about as close to the Earth as it ever gets.

And, as I just got through saying, Saturn is high overhead for Northern Hemisphere observers.  In fact, right about now, Saturn is about as high overhead as it ever gets.

So what does it all mean?  What it means, dear visitor, is that if ever you needed a reason to dust off your backyard telescope, this is it.  The above combination of circumstances makes this an excellent time to view the planet Saturn.  In fact, right about now, conditions for viewing Saturn are about as good as they ever get; and will not again be this good until the year 2030!  You owe it to yourself to take at least one quick look. 

After sunset, look fairly high in the west for the constellation Taurus (The Bull).  In Taurus, you will see two bright star-like objects.  The one that is twinkling will be the star Aldebaran.  The one that is shining steadily will be the planet Saturn.

 Sources:  The Saturn site at http://www.spacedaily.com, the Saturn Perihelion site at http:///rimu.orcon.net.nz, andThe Old Farmers Almanac (2002 edition) and The World Almanac and Book of Facts 2002
 

For the week beginning February 17, 2002

Flash’s Astronomical Fact #122

In the previous edition of Flash’s Astronomical Facts, I noted that the rings of the planet Saturn are now tilted in the upward direction.  In fact, right about now, Saturn’s rings are about as wide open as they ever get.

But there is more.

As I noted in Flash’s Skywatcher’s Almanac, on December 3, 2001, Saturn attained an orbital position called opposition. That is, the Earth - in its smaller, faster orbit – came between the Sun and Saturn.  Saturn was thus positioned directly opposite the Sun as seen from the Earth (hence, opposition). 

Saturn comes into opposition about once every 54 weeks, as the Earth in its orbit goes around the Sun and once again “catches up” with the far planet Saturn in its larger, slower orbit.  Skywatchers always take note of when a planet is due to come into opposition, because when a planet is at opposition, it is also at or near its closest approach to the Earth; and also at or near its greatest brilliancy.

But not all oppositions are created equal.

The orbits of the planets are not perfect circles, but instead are slightly flattened circles called ellipses.  One consequence of an elliptical orbit is that a planet’s distance from the Sun is not the same at all points in its orbit.  At one point, the planet lies closest to the Sun.  This point is called perihelion.  At another point, the planet lies farthest from the Sun.  This point is called aphelion.

Obviously, an opposition occurring at perihelion affords much better telescopic viewing than one occurring at aphelion, as the planet is closer.  And yes, the difference can be quite substantial.  When Saturn is at perihelion, it is 1,352,000,000 km (840,400,000 miles) away from the Sun.   When Saturn is at aphelion, it is 1,514,000,000 km (941,100,000 miles) away from the Sun.  A difference of 162,000,000 km or over 100,000,000 miles!

When perihelion and opposition coincide, the planet is as close to the Earth as it ever gets.  And as it happens, Saturn is approaching perihelion, which will occur on July 25, 2003.  Thus, Saturn’s current opposition is a close one.  And next year’s opposition will be closer still. 

But there is still more – as I will explain in the next edition of Flash’s Astronomical Facts.

 Sources:  The Saturn site at http://www.spacedaily.com, the Saturn Perihelion site at http://rimu.orcon.net.nz, and The Old Farmers Almanac (2002 edition) and The World Almanac and Book of Facts 2002
 

For the week beginning February 10, 2002

Flash’s Astronomical Fact #121

As I stated in the previous edition of Flash’s Astronomical Facts, the planet Earth does not rotate on its axis bolt upright relative to its orbital plane.  Rather, it has an axial tilt – or rotational inclination, to use the scientific term – of some 23.45 degrees off of the vertical. 

Because the Earth tilts on its axis, its Northern and Southern Hemispheres alternately tilt towards and then away from the Sun over the course of the planet's one-year orbit.  As a result, the Earth undergoes seasonal changes - from spring to summer to autumn to winter.

But these seasonal changes are not unique to the Earth.  Because every other planet in the solar system tilts on its axis (to one degree or another), every other planet has seasons as well.

One example is the planet Saturn.  Saturn tilts on its axis some 26.73 degrees off of the vertical relative to its orbital plane, giving it a rotational inclination almost identical to the Earth’s.  Saturn’s Northern and Southern Hemispheres alternately tilt towards and then away from the Sun, just like the Earth's.  Therefore, Saturn undergoes a progression of seasons - from spring to summer to autumn to winter - just like the Earth.  The only significant difference is that Saturn requires 29.46 Earth years to complete one orbit of the Sun.  Therefore, whereas Earth seasons last only three months, Saturnian seasons last a little over seven years.

In the case of Saturn, however, more than just the planet itself tilts.

Saturn’s majestic rings stand above that planet’s equator.  This means that when the planet tilts, the rings seem to tilt with it.  During Saturn’s Northern Hemisphere summer, the planet’s Northern Hemisphere tilts towards the Sun, and observers on Earth see the ring system tilted in the downward direction.  This is generally considered to be the most aesthetically pleasing position, at least in the opinion of textbook illustrators.

A little over seven years later (or earlier), Saturn’s Northern Hemisphere experiences autumn (or spring), and the planet faces the Sun squarely.  The rings at those times have no tilt at all, and are seen edge-on.  This causes the rings – that are very thin relative to their breadth – to all but disappear completely from view.

Currently, Saturn’s Northern Hemisphere is experiencing winter, which means that the planet’s Northern Hemisphere is tilting away from the Sun.  This means in turn that the rings are now tilting in the upward direction.  In fact, right about now, Saturn’s rings are about as fully open in the upward direction as they ever get. This may not seem significant, but as a consequence of the position of its reflective rings, Saturn currently is the fourth brightest star-like object in the night sky, outshined only by Venus, Jupiter, and Sirius (The Dog Star).

I will have more to say about Saturn in the next edition of Flash’s Astronomical Facts.

 Sources:  The Saturn site at http://www.spacedaily.com and The Old Farmers Almanac (2002 edition) and The World Almanac and Book of Facts 2002
 

For the week beginning February 3, 2002

Flash’s Astronomical Fact #120

In the previous edition of Flash’s Astronomical Facts, I noted that the Earth does not spin on its axis (the imaginary line running between the Earth’s north and south geographic poles) bolt upright relative to the Earth’s orbital plane.  Rather, the Earth’s axis tilts 23.45 degrees off of the vertical. 

Currently, the Earth’s north pole points almost directly towards the star Polaris in the constellation Ursa Minor (The Lesser Bear).  And this orientation does not change as the Earth orbits the Sun.  No matter where the Earth is in its orbit, its north pole points towards Polaris.

It is the Earth’s tilt on its axis that is responsible for the change of seasons.  In the month of June, the Earth’s Northern Hemisphere tilts towards the Sun, while the Southern Hemisphere tilts away from the Sun.  This results in the Northern Hemisphere receiving the Sun’s rays directly, while the Southern Hemisphere receives the Sun’s rays at an angle.  This makes the Northern Hemisphere warmer than the Southern Hemisphere.  Thus, in June, the Northern Hemisphere experiences summer, while the Southern Hemisphere experiences winter.

Six months hence, in December, the Earth is on the opposite side of its orbit, but its north pole is still pointing towards Polaris.  Now, the seasonal situation is reversed.  Now, it is the Earth’s Northern Hemisphere that tilts away from the Sun, while the Southern Hemisphere tilts towards the Sun.  Now, it is the Northern Hemisphere that is receiving the Sun’s rays at an angle, while the Southern Hemisphere receives the Sun’s rays directly.  Now, it is the Southern Hemisphere that is warmer than the Northern Hemisphere.  Thus, in December, the Southern Hemisphere experiences summer, while the Northern Hemisphere experiences winter.

In between those extremes, the Earth in its orbit (still pointing towards Polaris, mind you) presents both its Northern and Southern Hemispheres to the Sun squarely.  Thus, both Hemispheres receive the Sun’s rays equally, and mild weather comes to both Hemispheres.  In March, the Northern Hemisphere experiences spring, while the Southern Hemisphere experiences fall.  In September, the situation is reversed.  The Northern Hemisphere experiences fall, while the Southern Hemisphere experiences spring.

The tilting of the Earth on its axis – properly known as rotational inclination – is not unique to our world.  Every planet in the solar system has some degree of rotational inclination.  In future editions of Flash’s Astronomical Facts, we will examine the axial tilts of some of the other planets in our solar system – some of which produce interesting effects in their own right.

 Sources:  Time Almanac 2002 and The World Almanac and Book of Facts 2002
 

For the week beginning January 27, 2002

Flash’s Astronomical Fact #119

A year is the amount of time that it takes for the Earth to complete one revolution of the Sun.  The path that the Earth takes in going around the Sun is called its orbit.  The plane defined by a planet’s revolutionary path is called its orbital plane.  The Earth’s orbital plane is given a special name: The ecliptic.

At the same time that the Earth is orbiting the Sun, it also is spinning on its axis, an imaginary line running through the Earth’s north and south geographic poles.  A day is the amount of time that it takes for the Earth to complete one rotation on its axis.

As the Earth spins on its axis, it does not do so while standing bolt upright relative to the ecliptic.  Instead, the axis of the Earth is tilted some 23.45 degrees off of the vertical.  A planet’s axial tilt is called its rotational inclination.

It is the Earth’s tilt on its axis that is responsible for the seasons - as I will explain in the next edition of Flash’s Astronomical Facts.

 Sources:  The World Almanac and Book of Facts 2002 and Webster’s New World Dictionary
 

For the week beginning January 20, 2002

Flash’s Astronomical Fact #118

In the previous edition of Flash’s Astronomical Facts, we discussed the concept of the light-year:  A unit of measure defined as the distance that light travels in one year.  A light-year is equal to about 9,460,800,000,000 km (5,865,700,000,000 miles).

Smaller distances also can be defined by the speed of light, simply by using shorter units of time.

One such measure is the light-second:  The distance light travels in one second.  A photon of light travels about 300,000 km (186,000 miles) per second. 

The mean distance from the Earth to the Moon is about 384,318 km (238,855 miles).  Thus, it would take a photon of light about 1.28 seconds to travel from the Earth to the Moon. The distance from the Earth to the Moon may therefore be expressed as 1.28 light-seconds.

There is also the light-minute:  The distance light travels in one minute.  A light-minute is 60 times greater than a light-second.  A photon of light travels about 18,000,000 km (11,160,000 miles) in one minute.

The mean distance from the Earth to the Sun is about 150,000,000 km (93,000,000 miles).  Thus, the Sun is about 8.33 light-minutes from the Earth.  Expressed another way:  If the Sun were to stop shining now, the people of the Earth would not become aware of it until another eight minutes and twenty seconds had passed.

Then, there is the light-hour:  The distance light travels in one hour.  A light-hour is 60 times greater than a light-minute.  A photon of light travels about 1,080,000,000 km (669,600,000 miles) in one hour.

The mean distance from the Sun to the outermost planet, Pluto, is 5,873,000,000 km (3,649,000,000 miles).  Or, about 5.44 light-hours.

The terms light-week and light-month are almost never used, partly because of the possibility of confusion.  That is to say, is a light-week based on a calendar week or a working week?  Is a light-month based on a 30-day month or a 31-day month?  Besides, such distances are a substantial percentage of a light-year, and are better expressed that way.  A light-month would be about 0.083 of a light-year; a light-week, about 0.019 of a light-year.

 Sources:  The Light Measurement sites at http://www.howstuffworks.com, http://www.glyphweb.com, and http://www.cyburban.com and Time Almanac 2002
 

For the week beginning January 13, 2002

Flash’s Astronomical Fact #117

Using terrestrial units of measure (such as kilometers or miles) to express the vast distances between the stars results in numbers so large as to be almost beyond comprehension.  The distance to the nearest star system visible to the unaided eye (Alpha Centauri A/B) is about 41,154,000,000,000 km (25,516,000,000,000 miles).  Even if expressed in scientific notation, these numbers are simply too big and too cumbersome to handle.  And mind you, this is the distance to just the nearest visible star system.

Obviously, to give meaning to the tremendous distances between the stars (as well as to the enormous sizes of certain heavenly bodies), astronomers need a unit of measure that is truly celestial in scale.  Their unit of choice is the light-year.

Despite what you might infer from the presence in the term of the word "year", a light-year is in fact a measure of distance and not of time.  A light-year is the distance that a photon of light, moving at 300,000 km (186,000 miles) per second, travels in one year; specifically, one sidereal year of 365 days, 6 hours, 9 minutes, and 9.54 seconds mean solar time.  This works out to about 9,460,800,000,000 km (5,865,700,000,000 miles).  Thus, the distance to Alpha Centauri A/B may be expressed as 4.35 light-years.  Stated another way:  A photon of light from Alpha Centauri arriving at Earth today left that star system 4.35 years ago.

Here are some distances and sizes – expressed in light-years - of some of the better-known heavenly bodies.  The distance to the brightest star in Earth’s night sky (Sirius) is about 8.7 light-years.  Our home galaxy (The Milky Way Galaxy) is at least 100,000 light-years in diameter.  The distance to the farthest object visible to the unaided eye (The Andromeda Galaxy) is about 2,900,000 light-years.

As an exercise, dear visitor, you do the math and convert the figures in the above paragraph from light-years to kilometers and from light-years to miles.  By doing so, you will see quickly enough why astronomers prefer using light-years!

I will have more to say on this subject in the next edition of Flash's Astronomical Facts.

 Sources:  The Light-Year sites at http://www.howstuffworks.com and http://www.encyclopedia.com, the Alpha Centauri site at http://home.sunrise.ch, the Sirius site at http://antwrp.gsfc.nasa.gov, and the Milky Way Galaxy and Andromeda Galaxy site at http://seds.lpl.arizona.edu
 

For the week beginning January 6, 2002

Flash’s Astronomical Fact #116

In the previous edition of Flash’s Astronomical Facts, I noted that the Earth’s atmosphere is divided into four distinct layers according to how the temperature of the air molecules within those regions varies.  We then examined the two lowermost layers – the troposphere and the stratosphere – in detail.  In this edition, we will examine in detail the two uppermost layers.

The next layer out from the stratosphere extends from about 50 km (30 miles) to about 80 km (50 miles).  It is called the mesosphere, or “middle sphere”.  The temperature of the air molecules within this region once again decrease with altitude, dropping from about 0 degrees C at the lower reaches to about -100 degrees C at the upper reaches.  The air in the mesosphere is thinner than in the stratosphere (although, it should be noted, most meteors burn up in the mesosphere).

The next layer extends from about 80 km (50 miles) to about 600 km (360 miles).  It is called the thermosphere, or “hot sphere”.  It is aptly named, for the temperature of the air molecules once again begins to increase with altitude, rising from about -100 degrees C at the lower reaches to about 1000 - 1500 degrees C at the upper reaches.  The air is thinner than in the mesosphere, but what few atoms are present become heated to extreme temperatures as a consequence of absorbing high-energy radiation (chiefly gamma rays and X-rays) from outer space.  It should be noted that although the individual atoms are extremely hot, the air is so diffuse that there is not much in the way of total heat.

The thermosphere may be divided into two sub-layers.  The lower thermosphere sometimes is called the ionosphere or “sphere of ions” and extends from about 80 km (50 miles) to about 400 km (250 miles).  In this layer, electrons are knocked off of atoms by cosmic radiation bombardment and exist only in the form of ions.  Several subdivisions within the ionosphere  – called the D layer, E layer, and F layer - reflect select frequencies of radio waves.  The layers act something like mirrors, sending radio signals from the ground back towards the planet's surface where they can be heard beyond the horizon.

The upper thermosphere sometimes is called the exosphere or “outer sphere”.  It extends from about 400 km (250 miles) to about 600 km (360 miles).  At the upper reaches of the exosphere, the chemical composition of the atmosphere becomes indistinguishable from the chemical composition of outer space.  At that point, the Earth’s atmosphere may be said to have reached its maximum height.

Beyond the exosphere lies true outer space.

 Sources:  The Earth’s Atmosphere sites at http://newmedia.avs.uakron.edu, http://www.doc.mmu.ac.uk, http://www.jccc.net, and http://www.miami.ci.org
 

For the week beginning December 30, 2001

Flash’s Astronomical Fact #115

The envelope of air that surrounds the Earth is called the atmosphere.  The atmosphere retains and distributes heat, provides life-giving oxygen, and in other ways helps make possible life on our planet. 

But the atmosphere does not have the same composition throughout.  Its physical and chemical characteristics vary with altitude.

Scientists divide the Earth’s atmosphere into four distinct layers according to how the temperature of the air molecules within those regions varies.  How high above the Earth’s surface each layer begins varies with latitude or the overall temperature of the atmosphere.

The bottommost layer of the atmosphere is called the troposphere or “turning sphere”.  The troposphere extends from the Earth’s surface up to an average altitude of about 12 km (8 miles).  Note that I said average altitude.  As I stated above, the height of each atmospheric layer varies with latitude.  Over the poles, the troposphere extends up to about 8 km (5 miles); over the equator, up to about 16 km (10 miles). 

Within the troposphere, temperature decreases fairly steadily with altitude, beginning at an average of 15 degrees C (59 degrees F) at the planet’s surface and then dropping by about 6.5 degrees C for every 1 km elevation.  At the upper reaches of the troposphere, temperatures can drop to as low as –50 degrees C.

About 75% percent of the air molecules in the entire atmosphere are found within the troposphere.  The air within this layer is relatively dense and water vapor is plentiful; hence, almost all weather phenomena occur within the troposphere.  Indeed, the highest of the true clouds are found at the upper reaches of the troposphere.

The next layer outwards is called the stratosphere or “covering sphere”.  The stratosphere extends from an average of about 12 km (8 miles) to about 50 km (30 miles) above the Earth’s surface. The temperature of the air molecules within the stratosphere actually increases with altitude, from about –50 degrees C at the lower reaches to about 0 degrees C at the upper reaches.  This is due to the presence in the stratosphere of ozone, which absorbs high-energy ultraviolet radiation from the Sun. 

Within the stratosphere, air is more diffuse and water vapor is virtually non-existent.  As a consequence, there are no true clouds within the stratosphere.  Stratospheric winds tend to be strong, steady, and horizontal.  Jet planes, therefore, travel through this region whenever possible as it means increased fuel economy and a smoother ride. 

We will examine the two remaining atmospheric layers in the next edition of Flash’s Astronomical Facts.

 Sources:  The Earth’s Atmosphere sites at http://newmedia.avs.uakron.edu, http://www.doc.mmu.ac.uk, http://www.jccc.net, and http://www.miami.ci.org
 

For the week beginning December 23, 2001

Flash’s Astronomical Fact #114

The passing of the old year and the beginning of the new will be heralded by a number of spectacular celestial events, which I will describe in detail below.  Be sure to mark the following dates on your calendar:

December 28, 2001:  Saturn and the Moon will come into conjunction.  Conjunction is the astronomical term for when two celestial bodies reach the same celestial longitude.  During most such Moon/planet conjunctions, the Moon passes either above or below the planet.  But in the early morning hours of December 28, 2001, skywatchers in most of the continental United States will get a rare treat, as the Moon will pass directly in front of Saturn, concealing it from view.  Such an event is called an occultation.  Consult your local newspaper for the exact time when this event will occur in your area.

December 30, 2001:  Not only are we going to have a Full Moon, we are going to have a lunar eclipse.  Unfortunately, the Moon rides high this night, so our satellite world will not enter the darker, central portion of the Earth’s shadow (called the umbra).  Instead, it will enter only the lighter, outer portion of the Earth’s shadow (called the penumbra).  Hence, this eclipse will be what is called a penumbral eclipse.  Though it will not be as spectacular as a total lunar eclipse or even a partial lunar eclipse, it still will be worth watching.  The Moon will take on a dull reddish-brown color as it enters the penumbra.  The eclipse will be visible from start to finish, from Hawaii to across North America (except for the east coast, which will not see the end of the eclipse).

January 1, 2002:  The planet Jupiter will come into opposition during the very early morning hours of New Year’s Day.  Opposition is the astronomical term for when an inner planet  passes directly between the Sun and an outer planet.  In this case, Jupiter will be positioned directly opposite the Sun as seen from the Earth (hence, opposition).  When a planet is at opposition, it rises in the east at sunset, stays out all night, and sets in the west at sunrise.  Moreover, a planet at opposition is also at or near its closest approach to the Earth, as well as being at or near its greatest brilliancy.  Indeed, Jupiter will be brightest for the entire calendar year of 2002 just one hour into the New Year.  As if that were not enough, the planets Saturn and Mars will join Jupiter during the early evening hours of December 31, 2001.

What a way to say goodbye to the old year – and welcome the new.

 Sources:  The Saturn Occultation site at http://www.lunar-occultation.com and The Old Farmer’s Almanac (2001 and 2002 editions), Time Almanac 2001, and The World Almanac and Book of Facts 2002
 

For the week beginning December 16, 2001

Flash’s Astronomical Fact #113

With Christmas coming up in just a few days, this week’s edition of Flash’s Astronomical Facts will relate how the stars gave birth to a popular yuletide practice:  The placement of decorative lights on Christmas trees. 

We begin with the origin of the Christmas tree itself. 

In Europe, the evergreen tree has been used as a pagan symbol of the winter season since at least the 8th century.  Evergreen trees are aptly named because they remain ever green - even during the winter, when all other flora either are entering a period of dormancy or dying from the freezing cold.  Small wonder then that the evergreen tree came to represent also eternal life.  And eternal life in the hereafter is the reward promised to those who accept Jesus Christ as their savior.  As you can see, it all fits together.

Okay, so much for the tree.  But what about the lights?

A famous legend explains how people came to decorate their Christmas trees with lights.  The story goes that Martin Luther, the 16th century Protestant reformer, was walking home one clear winter night when he came upon an evergreen tree.  The stars in the background appeared to be attached to the edges of the tree. It created such a beautiful sight that Martin Luther wanted to replicate it.  Using some lengths of wire, he attached a number of candles to the branches of his home evergreen tree.  When he lit the candles, his tree looked like the tree he saw on his way home.

Unfortunately, there exist no historical records that substantiate that the above incident ever took place. The tale, however delightful, is almost certainly apocryphal. 

But regardless of the veracity of the legend, having an evergreen tree in the house during the Christmas season was a firmly established custom in Germany by the 1600s, although lighting the tree with candles was not a common practice until the 1700s.

Nowadays, Christmas trees are lighted by means of strings of electric light bulbs.  Not only is this far safer, the light from the electric bulbs more closely resembles the starlight that Martin Luther is supposed to have seen.

 Sources:  The Christmas Tree sites at http://www.happywomanmag.com and http://www.ultranet.com
 

For the week beginning December 9, 2001

Flash’s Astronomical Fact #112

What follows is the fourth of an occasional series about the constellations.  It is being presented in two parts, of which this is the second.

In the previous edition of Flash’s Astronomical Facts, we examined the constellations Corona Borealis (The Northern Crown) and Corona Australis (The Southern Crown).  Though both constellations are small, they are noteworthy in that the principal stars of each form patterns that are remarkably similar to each other in both size and shape.

Each of these constellations has some mythology associated with it.  Unfortunately, as a consequence of the stories being handed down largely by word of mouth, some of the details have become muddled.  Keep that caveat in mind as I relate the legends of the celestial crowns.

The myths regarding Corona Australis are neither very long nor very interesting, so let us get the Southern Crown out of the way first.  In classical mythology, Corona Australis originally was the crown of Seleme, the mother of the Greek god Dionysus.  Dionysus placed Seleme’s crown in the heavens in her honor.  But another legend suggests that the Southern Crown fell off of the head of Sagittarius (The Archer), its neighboring constellation.

The mythology of the Northern Crown is much more interesting - and much more epical.

Corona Borealis played a minor role in one of the greatest stories in classical mythology:  Theseus’ battle with the Minotaur. 

The Minotaur, a ferocious beast that was half man and half bull, was confined on the island of Crete within the Labyrinth - a maze so huge, so complex, and so baffling, that no one who entered it could ever find his way back. 

For reasons too complicated to relate in this essay, the city of Athens was obligated to pay tribute to King Minos of Crete every ninth year.  The tribute took the form of seven Athenian youths and seven Athenian maidens.  These unfortunate souls were forced to enter the Labyrinth, where they soon were eaten by the Minotaur.

When the time came for the next group of young people to be rounded up for tribute, a gallant youth named Theseus volunteered to be one of the sacrifices.  Some thought he was just being noble; in actuality, he had a plan to kill the Minotaur and put an end to King Minos' barbaric tribute.

Time out for an aside:  Theseus' ancestry is one of those "muddled details" I mentioned.  In most versions of the story, Theseus is the son of King Aegeus of Athens.  In this version - which includes the origin of Corona Borealis - Theseus is the son of Poseidon, the god of the sea.

Upon arriving in Crete, Theseus proclaimed himself to be the son of Poseidon and demanded an audience with King Minos.  Theseus and Minos made a wager of sorts.  If Theseus could kill the Minotaur barehanded, then Athens' obligation to pay tribute to Minos would be rendered null and void.  In addition, Theseus wished to be the first to enter the Labyrinth, so as to spare the other sacrifices.

Minos agreed to Theseus’ terms – on the condition that the youth first prove that he was indeed the son of Poseidon.  Minos threw his gold ring into the sea and challenged Theseus to find it and bring it back - a task that should be simple enough for someone claiming to have been fathered by the god of the sea. 

With the help of the Nereids (sea nymphs), Theseus not only recovered Minos’ ring, but also was given (either by the Nereid Thetis or the sea queen Amphitrite, accounts differ) a crown fashioned by Hephaestus, the god of the forge.  The crown was a masterful work, a half-circle of gold rosettes adorned with jewels.

When Theseus brought back the crown in addition to the ring, King Minos needed no further convincing of the veracity of Theseus’ claim.  The heroic youth would indeed be the first to enter the Labyrinth.

But while Theseus was confident that he could defeat the Minotaur mano-a-mano, he was less than sure of his ability to find his way back out of the Labyrinth.  That was when Ariadne, the daughter of King Minos, came to Theseus’ aid.  In exchange for the young man’s promise of marriage, Ariadne provided Theseus with a means by which to escape from the Labyrinth:  A ball of magic string. 

Theseus placed the ball of magic string down on the ground near the entrance to the Labyrinth.  The ball unrolled itself, leading Theseus straight to the Minotaur.  After wrestling the creature to the ground and beating it to death with his fists, Theseus escaped the Labyrinth simply by following the string back out the way he came.

King Minos honored his wager with Theseus.  The city of Athens was released from its obligation to send tribute to Minos.  Minos then gave Hephaestus’ crown to Theseus and Ariadne as a wedding present.

But the wedding was never to take place.  The couple set sail for Greece so that Theseus could present his fiancée - now wearing Hephaestus’ crown - to his family.  En route, Ariadne came down with the worst case of mal de mer in history and had to go ashore on the island of Naxos.  From this point forward, accounts differ as to the final fate of Ariadne.

One version states that a violent gust of wind sent the ship far away, stranding Ariadne on the island.  By the time Theseus was able to get back to Naxos, Ariadne had died. The goddess Aphrodite then placed Hephaestus’ crown in the heavens, where, as Corona Borealis, it would serve as an eternal tribute to a marriage that might have been.

Another version suggests that Theseus took the opportunity to abandon Ariadne on the island because she had dared to extract from him a promise of marriage.  Ariadne appealed to the supreme Greek god, Zeus, who dispatched the god Dionysus to comfort her.  Dionysus fell in love with Ariadne.  They married and had four children.  When Ariadne died, Dionysus placed Hephaestus’ crown in the heavens where, as Corona Borealis, it would honor his mortal wife throughout eternity.

Yet another version states that Dionysus already had eyes for Ariadne.  To get his rival out of the way, Dionysus gave Theseus a case of amnesia.  This resulted in Theseus sailing off without his betrothed out of forgetfulness rather than malice.  When Dionysus presented himself to Ariadne, he told her that he was a god.  She challenged him to prove his claim.  So saying, Dionysus threw Hephaestus’ crown skywards.  The jewels became stars and Corona Borealis was born.  Apparently, that was proof enough.  Ariadne accepted Dionysus’ proposal of marriage. 

Other ancient cultures developed their own mythologies about the celestial crowns.  One delightful story from North American Indian lore explains the opening in the circle of the Northern Crown this way:  Originally, Corona Borealis was a full circle, each of its stars being a beautiful fire maiden dancing in the night sky.  The gap occurred when one of the fire maidens became smitten with a handsome male warrior down here on Earth.  That fire maiden left the troupe and descended to Earth to be with him, thus leaving a hole in the choreography.  In essence, she gave up show biz for true love.

 Sources:  The Corona Borealis and Corona Australis sites at http://www.mtsn.tn.it, http://www.dibonsmith.com, 
http://einstein.stcloudstate.edu, http://chandra,harvard.edu, http://seds.lpl.arizona.edu, and Mythology by Edith Hamilton
 

For the week beginning December 2, 2001

Flash’s Astronomical Fact #111

What follows is the fourth of an occasional series about the constellations.  It is being presented in two parts, of which this is the first. 

There are eighty-eight officially recognized constellations in the heavens.  The constellations come in a variety of shapes, depicting animals (both real and fanciful), inanimate objects, and the gods and heroes of classical mythology.  Some constellations are huge, covering vast areas of the night sky.  Others are small, taking up little more than a tiny patch of the fabric of space.

One thing that can be said of the constellations is that - like snowflakes - there are no two exactly alike.

But two constellations put that assertion to the test.  The constellations to which I am referring are Corona Borealis (The Northern Crown) and Corona Australis (The Southern Crown).  Not only are these two constellations similar in both size and shape, they are depicted as representing similar objects!

The brightest stars in each constellation form an incomplete circle, suggesting not a coronet as might have been worn by a European monarch, but rather a half-wreath of laurel leaves as might have been worn by a Roman emperor.

Corona Borealis is a small northern hemisphere constellation located between the large constellations Hercules (The Strongman) and Bootes (The Herdsman).  Comparably small Corona Australis, a southern hemisphere constellation, likewise is sandwiched between two large constellations - in this case Sagittarius (The Archer) and Scorpius (The Scorpion).

Both Corona Borealis and Corona Australis have some mythology associated with them.  But we will examine that aspect of the two crowns in the next edition of Flash’s Astronomical Facts.

 Sources:  The Corona Borealis and Corona Australis sites at http://www.mtsn.tn.it
 

For the week beginning November 25, 2001

Flash’s Astronomical Fact #110

The planet Earth seems to spin on its axis exactly once every twenty-four hours, as steady as clockwork.  In actuality, the clockwork is not all that steady.  The rotation of the Earth varies slightly in the following ways:

Tidal friction is slowing down continuously the Earth’s rotation.  This variation increases th