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The Universe This Week - December 12 - December 18, 2005.


Ten Years Since The Revolution at Amazon.

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Credit: Roger Warner.
Credit: Roger Warner.

It's "mid-time of night and the stars in their orbits shone pale through the light of the brighter cold Moon." But, be sure to take the time to "gaze for awhile on her cold smile"! There will be a brief opportunity this week to hide from that light to catch the Geminid meteor shower, as well as plenty of time to check out bright planets, stars and clusters. So turn your eyes to the skies, because...

Here's what's up!

Monday, December 12 - Let's hope observers in Eastern Siberia had the chance to catch the Moon occulting Mars!

Be sure to at least take binoculars out tonight and have a look at the cold and beautiful Moon. Trace its wonderful bright ray systems - such as those that extend from Tycho, Copernicus and Kepler. There is no astronomical target out there able to compete with the details you'll find on the lunar surface!

Tuesday, December 13 - Set the alarm for 4:30 a.m. and bundle up to watch for your one good chance at the Geminid meter shower!

Today in 1920, the first stellar diameter was measured by Francis Pease with an interferometer at Mt. Wilson. His target? Betelgeuse! Tonight let's defy the Moon and have a look at the giant star as we look towards the northeastern corner of Orion.

One of the largest known stars, the Hobbits called it "Borgil" - but in the ancient world the Arabs knew this star as "Beit Alguese." Its bright variability was first noticed by Sir William Herschel in 1836, and followed through its near 6 year cycle of erratic changes. During the phases of expansion and contraction, at smallest Betelgeuse still exceeds the diameter of Earth's orbit around our own Sun. For all of its size, you might think Betelgeuse to be massive - but it's not. Although it exceeds Sol by 160 million times in volume, it has only about 20 times more physical mass!

Enjoy its red photons tonight...

Wednesday, December 14 - Today is a very busy day in the history of astronomy. Tycho Brahe was born in 1546. Brahe was a Danish pre-telescopic Astronomer who established the first modern observatory in 1582 and gave Kepler his first job in the field. In 1962, Mariner 2 made a flyby of Venus and became the first successful interplanetary probe. And, in 1972, the last humans (so far) to have been on the lunar surface returned to Earth on this date. Eugene Cernan left the final bootprint at Taurus-Littrow and called it the "end of the beginning."

Tonight will be one of the most hauntingly beautiful and mysterious displays of celestial fireworks all year - the Geminid meteor shower. First noted in 1862 by Robert P. Greg in England, and B. V. Marsh and Prof. Alex C. Twining of the United States in independent studies, the annual appearance of the Geminid stream was weak, producing no more than a few per hour, but it has grown in intensity during the last century and a half. By 1877 Astronomers were realizing that a new annual shower was occurring with an hourly rate of about 14. At the turn of the century it had increased to an average of over 20, and by the 1930s to from 40 to 70 per hour. Only eight years ago observers recorded an outstanding 110 per hour during a moonless night... But this time we're not so fortunate.

So why are the Geminids such a mystery? Most meteor showers are historic, documented and recorded for hundred of years, and we know them as being cometary debris. When Astronomers first began looking for the Geminids' parent comet, they found none. After decades of searching, it wasn't until October 11, 1983 that Simon Green and John K. Davies, using data from NASA's Infrared Astronomical Satellite, detected an orbital object which the next night was confirmed by Charles Kowal to match the Geminid meteoroid stream. But this was no comet, it was an asteroid.

Originally designated as 1983 TB, but later renamed 3200 Phaethon, this apparently rocky solar system member has a highly elliptical orbit that places it within 0.15 AU of the Sun about every year and half. But asteroids can't fragment like a Comet - or can they? The original hypothesis was that since Phaethon's orbit passes through the asteroid belt, it may have collided with other asteroids, creating rocky debris. This sounded good, but the more we studied the more we realized the meteoroid "path" occurred when Phaethon neared the Sun. So now our asteroid is behaving like a comet, yet it doesn't develop a tail.

So what exactly is this "thing?" Well, we do know that 3200 Phaethon orbits like a comet, yet has the spectral signature of an asteroid. By studying photographs of the meteor showers, scientists have determined that the meteors are more dense than cometary material but not as dense as asteroid fragments. This leads us to believe that Phaethon is probably an extinct Comet that has gathered a thick layer of interplanetary dust during its travels, yet retains the ice-like nucleus. Until we are able to take physical samples of this "mystery," we may never fully understand what Phaethon is, but we can fully appreciate the annual display it produces!

Thanks to the wide path of the stream, folks the world over get an opportunity to enjoy the show. The traditional peak time is tonight - as soon as the constellation of Gemini appears around mid-evening - and it lasts through tomorrow morning. The radiant for the shower is right around bright star Castor, but meteors can originate from many points in the sky. From around 2:00 a.m. until dawn (when our local sky window is aimed directly into the stream) it is possible that we can see about one "shooting star" every 30 seconds, but the Moon will significantly decrease the number of fainter meteors. The most successful of observing nights are ones where you are comfortable, so be sure to use a reclining chair or pad the ground while looking up. Best of luck spotting one of the incredible and mysterious Geminids!

Thursday, December 15 - Heads up for Australia and New Zealand! On this universal date, the Moon will occult bright star Beta Tauri. Please check with IOTA for times in your location. Clear skies, mates!

Today in 1970, Soviet Venera 7 performed a first as it made a successful soft landing on Venus and went into the history books as the first object to land on another planet.

Tonight why not take a few minutes after sunset to land your eyes on Venus? Even if you don't use a telescope, you can't miss its ultra-bright appearance to the southwest in the northern hemisphere. If you use a telescope - Power up! Can you tell what percentage of the planet is shadowed? Follow it to month's end when it will only be 6% illuminated, because it will be a year and a half before we see it like that again!

Friday, December 16 - Today we celebrate the birth of the working-class hero astronomer, Edward Emerson (E.E.) Barnard, Born into hardship in 1857 in Nashville, Tennessee, he was home schooled and began work at age 9 as a photographer. His first telescope was made from a cardboard tube and discarded parts. Continuing to self-educate, he purchased his first telescope and supported himself through awards from Comet discoveries. His reputation as an outstanding observer brought him a Fellowship to Vanderbilt College and eventually to the doors of Lick and Yerkes Observatory where his photographic and observational skills became unsurpassed.

While we most commonly recognize Barnard's discoveries of dark nebulae, did you know that he also did extensive work on objects that we can easily observe? The hauntingly nebulosity in the Pleiades belongs to Barnard, as well as a companion star in the Trapezium. Take a look at the Andromeda Galaxy while you're out tonight - despite the Moon. While Edward Holden took credit for much of Barnard's work, his ability to photograph this Galaxy with second-hand equipment, and to discover comets in the same way, helped pave the way into a new era of observing.

Saturday, December 17 - Before the Moon rises tonight, let's turn our attention towards a very beautiful and lesser known open cluster - NGC 663. You'll find it about one fingerwidth northeast of Delta Cassiopeiae...

This magnificent tornado-shaped collection of stars will be quite noticeable in binoculars and will resolve out more than a dozen members to a small telescope. Larger Telescopes will fully resolve this magnitude 7 cluster and reveal color amongst its many stars.

For southern hemisphere observers, look a little more than a fistwidth southeast of Canopus for the incredible NGC 2516. Visible to the unaided eye, this cluster should be spectacular in binoculars or a small telescope! Look for a red star in its center...

Sunday, December 18 - With the later rise of the Moon tonight, take the time to do a quick tour of the skies with binoculars. It would be a great time to try to spot M33 - the "Pinwheel Galaxy" - about three fingerwidths southeast of Beta Andromedae.

If you're still around when the Moon rises, be sure to take a look at the Mare Crisium area. The terminator will show just how much of a curve we view this feature on!

Until next week, ask for the Moon but keep reaching for the stars! light speed... Tammy Plotner


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