U.Va. Astronomy Professor Ed Murphy Offers Notes for Backyard Astronomers

Dec. 6, 2007 — The next public night at McCormick Observatory is Friday, Dec. 7, from 7 p.m. to 9 p.m., and University of Virginia associate professor of astronomy Ed Murphy says that there will be plenty to see throughout the rest of December and in January.

Murphy provides details a variety of upcoming events in the following series of notes:

You can find a nice map of the December sky at: www.skymaps.com/skymaps/tesmn0712.pdf

Winter officially arrives at 2:08 a.m. on Dec. 22. At this time, the sun reaches its southernmost point for the year. The winter solstice has the longest night and shortest day of the year.

For the upcoming year, the Earth is closest to the sun (a phenomenon called perihelion) on Jan. 2, around 8 p.m.

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Space Shuttle Visible

The space shuttle Atlantis is scheduled to be launched on an 11-day mission to the International Space Station this Friday, Dec. 7 at 4:09 p.m.. The crew is delivering and installing a new European research module, called Columbus. One of the astrononauts, Leland Melvin, was drafted by the Dallas Cowboys and graduated from the University of Virginia with a master's degree in materials science in 1991!

The space station is in an orbit tilted by about 57 degrees with respect to the equator of the Earth. This tilt is large because the Russian facilities used to launch crew and supplies to the ISS are at a high latitude on Earth. To get the shuttle into this orbit requires that it launch up the Eastern Seaboard of the United States. Everyone on the East Coast has the chance to see the shuttle climbing to orbit. It will look like a moderately bright point of light moving from south to north (right to left) very low along the eastern horizon. This launch will be especially good because the sun will be quite low in the western sky.

McCormick Observatory Public Nights
Friday, Dec. 7, 7- 9 p.m.
Friday, Dec. 21 7- p.m.
Friday, Jan. 4, 7- 9 p.m.
Friday, Jan. 18, 7- 9 p.m.

If the shuttle does not launch Friday afternoon, there will be additional launch opportunities over the following days. Go to http://www.spaceflightnow.com to follow the events.

If the shuttle launches after dark, it is possible to see it from Charlottesville. You must first ensure that the shuttle launches. If you have cable or satellite TV, you can watch the shuttle launch live on NASA TV or some of the cable network news channels will carry it live. Otherwise, you can go to www.nasa.gov and click on the link to watch NASA TV on your computer or go to www.spaceflightnow.com and click on their "Mission Status Center" link to see a minute-by-minute update of activities.

A few minutes after the shuttle launches, head outside. You will need a clear eastern horizon with no mountains or trees blocking your view. Look low in the southeast for a moving point of light.  It will pass from right to left staying very low along the horizon.  It should blink out of view when the main engines shut off, about eight minutes after launch.  I have seen one previous shuttle launch from Charlottesville, so I know it can be done if the weather cooperates.

• • •

Mars Opposition

Every 26 months, the Earth passes Mars in our orbit around the sun. When these passes (called opposition) occur, Mars is closest to the Earth and it is the best time for viewing Mars. The Earth is rapidly overtaking Mars as I write, and will pass closest to the red planet on Dec. 18-19, 2007 at a distance of 54.91 million miles.

We are hosting a special event for the Friends of the McCormick Observatory on Friday, Dec. 14, from 10 p.m. to midnight, to let everyone see Mars at its closest, weather permitting (also see the Geminid note below). In case of inclement weather, the backup date will be Tuesday, Dec.18, from 10 p.m. to midnight. Just a few days earlier on Mars, the equinox occurs, ushering in spring in the Martian northern hemisphere and fall in the Martian southern hemisphere. Through the 26-inch telescope, we should be able to spot what is left of the northern Martian Polar Cap (the water and carbon dioxide ice that cover the pole) and dark markings on the surface of Mars. However, there were some large dust storms on Mars earlier this year, and it is possible that a planet wide dust storm could obscure our view (I will keep you updated as the date approaches).

The best oppositions of Mars occur when Mars is closest to the sun while the Earth is farthest from the sun. This results in a particularly close pass, as happened in 2003. This year, Earth is not as far from the sun and Mars is not as close to the sun, so Mars will appear much smaller than it did in 2003. The oppositions will continue to worsen
for some time. In fact, not until 2016 will Mars again appear as large as it does this year.

• • •

Geminid Meteor Shower

The annual Geminid Meteor Shower peaks on the nights of Dec. 13-14 and 14-15. The Geminids are one of the finest and most reliable showers of the year. Observers can see up to 100 meteors per hour under very dark skies.

Most meteor showers occur when the Earth passes through debris that has been shed by a comet. Comets are very dirty snowballs, consisting of water ice, methane ice, ammonia ice, and little bits of rock, dust and metal. As the comet approaches the sun and warms up, the ice sublimates (goes from a solid to a gas), thus releasing the little bits of rock and
dust trapped in the ice and forming a beautiful tail. However, the Geminids come from an asteroid, 3200 Phaethon. Asteroids are usually considered to be rocky bodies, with little or no ice, and do not sport a tail as do comets. Thus, we would not expect a significant amount of debris in their orbits. It may be that Phaethon is a dormant, or extinct, comet.

Every Dec. 7-17, the Earth passes through the debris stream behind Phaethon, whit the best nights being Dec. 13-14 or 14-15. To see the shower, go outside, lay down in a sleeping bag or in a lawn chair, face east, and look about halfway up in the sky after the moon sets (around 8:30 p.m. on the 13th and 9:40 p.m. on the 14th) The meteors will appear to stream out of the constellation of Gemini the Twins (hence the name Geminids). The Geminids are best after 10 p.m. when Gemini is high in the sky. The Earth passes through the densest part of the stream on Dec. 14 at about noon EST, so we will miss the best part of the shower this year. I would still expect to see about 20 or more meteors per hour.

Compiled and written by Edward Murphy, associate professor of astronomy and manager of the Department of Astronomy’s education and public outreach program.

For information on becoming a member of the Friends of the Leander McCormick Observatory, visit: http://www.astro.virginia.edu/public_outreach/friends.pdf