Comet Elenin ... September 26, 2011 ...

Saturday, 11 June 2011 21:30

Comet Elenin ... September 26, 2011 ... ^Featured

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From a posting on spaceobs.org...
From new observations of Comet C/2010 X1 (Elenin), the Minor Planet Center has published new orbital parameters. There has been a fundamental change; instead of a perihelion near Jupiter’s orbit, the comet will have an aphelion at Mercury’s orbit! Of course the new comet does not belong to the class of sungrazing comets, but it will be visible in images from the coronagraph installed on the space observatory SOHO.

C/2010 X1 comes within 0.03 a.u. (4.5 million km) of the Earth’s orbit, but only

~0.4 a.u. from the planet itself. The average distance from the centre of the Earth to the center of the Moon is 384,403 km.
While Comet Elenin's coma (the blurry part around the comet) is currently estimated at ~22,000Km. The actual comet  itself is estimated to be between ~2.5 and ~7 miles wide
The comet will increase its brightness; in August of 2011 it will be mag. 6-8. By the end of the month and throughout September the comet will be hidden from earthly observers in the rays of the Sun, but it will be easily visible in images from the cosmic coronagraph. At that time the comet’s brightness will be at maximum – about mag. 3-4 (although with passage so close to the Sun anything can be expected). By the way, at that time the comet will again be at the same equatorial coordinates where it was discovered in December of 2010.

Beginning in October, the comet will again become visible for observations from Earth; at that time its brightness will be magnitude 4-5, i.e. the comet will be visible to the unaided eye far from large cities. Visibility conditions from northern latitudes will be favorable – the tailed guest will climb into the northern sky. After that, C/2010 X1 will slowly become fainter and move away from the Earth. By the beginning of 2012 its brightness will be around mag. 11-12.

A list of planetary bodies showing the scale magnitudes is shown below for comparison.

1. The Sun. No surprise here. The Sun shines at magnitude -26.7. Technically, the Sun can't even be looked at without optical aid when it is at its brightest. Sunrise and sunset are the best times to view our closest star.
2. The Moon. The moon varies in brightness depending on what phase it is in. At its full phase when it is the brightest, it tops out at magnitude -12.6, and in a crescent phase it is about a -6.
3. Venus. As with all the other solar system objects, Venus varies in brightness depending on a number of factors, including how close it is to Earth and what phase it is in. Venus can shine as brightly as -4.7 and is frequently referred to as the Evening Star or the Morning Star.
4. Mars. Mars is the second closest planet to Earth after Venus, but it does not often reach its maximum magnitude of -2.9. Its reddish-orange hue helps to distinguish it from other planets.
5. Jupiter. This gas giant is often brighter than Mars and at its maximum shines almost as bright, at magnitude -2.8.
6. Mercury. Surprise! The rarely seen Mercury shines more brightly than Saturn at its best. Mercury can reach -1.9 magnitude but because of its position near the Sun, it does not get to be seen high in the night sky. Its brightness is often offset by the fact that you are viewing the planet near sunrise and sunset.
7. Saturn. Saturn, which is stunning in a telescope sporting wide rings, is also a fairly easy catch without optical aid. At magnitude 0.7 it outshines most stars.
8. Ganymede. Ganymede is the largest moon of Jupiter. Keen eyes can spot it circling Jupiter when the satellite is at its brightest, approximately 4.6 magnitude.
9. Vesta. This asteroid, which was the fourth asteroid to be discovered, can reach magnitude 5.4 at its closest approach to Earth. Because it does not have a brighter sky marker, as Ganymede has with Jupiter, it is best to watch for it a couple nights in a row to see which dim "star" in the area appears to slowly move.
10. Uranus. The seventh planet from the Sun appears at magnitude 5.5 at its best. Uranus is best picked up with the naked eye after first pinning down its location with binoculars or a telescope. It has a disk instead of a pinpoint image through an optical device and may even appear faintly bluish green.