M
MeteorWayne
Guest
What should be the best shower of the year occurs this month.<br />Unlike most other major showers that are best observed during the predawn hours, the Geminid radiant rises before dark in the Northern Hemisphere and reaches it's highest elevation in the south around 2 AM local time. With the long winter nights, you can easily see many hundreds of meteors in one night. It also can be observed from the Southern Hemisphere, although the radiant rises later. The moon will provide little interference this year, setting before 9PM north of 45 degrees N, and later the further south you are.<br /><br /> The Geminids are the debris from what is now asteroid 3200 Phaethon, which is a de-iced comet nucleus. The perihelion is only 0.14 AU (21 million km, or 13 million miles), well inside Mercury's orbit. The resultant heating has eliminated all the gas producing ices, and in fact is enough to sinter the surface of the asteroid as well as the Geminid meteoroids.<br /><br /> The Geminids are active from the 1st to the 20th, with the peak expected this year at 1645 UT on the 14th (11:45 AM EST, 8:45 AM PST), with a dip in rates afterward, then a second lower peak about 3 hours later. Since most showers (and the Geminids are no exception) have rates that slowly rise, then fall off more rapidly after the peak, if you have only one night to observe, the best would seem the be the night/morning of December 13/14, although the nights before and after should provide a nice show as well.<br /><br /> These are fairly slow meteors (about 35 km/sec) and tend to have a different color than most other showers, since the slower speed doesn't cause as much emission from nitrogen and oxygen in the atmosphere.<br /> Another item of note is that model projections of the evolution of the meteoroids by J. Jones, and R.L. Hawkes suggest that Geminid rates will increase for the next few decades, rising from the current 120 an hour to around 190 per hour by 2050 before beginning to decline.<br /><</safety_wrapper> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>