This week NASA scientists showed off new images of Jupiter and other data taken by the Hubble Space Telescope during and after the planet's head-on collision with Comet Shoemaker-Levy 9. In many ways the spots are evolving as might be expected, stretching out in longitude and gradually decreasing in contrast. But there have been surprises. For example, the comet's interactions with the Jovian magnetosphere were surprisingly strong. At one point, during impact of fragment K on July 19th, the orbiting Rosat observatory detected a burst of X-rays coming from Jupiter's *northern* hemisphere (the comet itself struck at latitude 44 deg south). Scientists believe ions in K's fireball were accelerated and propeled northward along magnetic field lines, causing a temporary auroral display at both ultraviolet and X-ray wavelengths. But the process responsible for this remains unexplained, at least for now.
Periodic Comet Machholz 2 has been undergoing some changes, say observers. The brightest of its five pieces, A, has become more diffuse, and its magnitude has faded to about 9 or 9.5. Meanwhile, component D has done just the opposite, brightening and becoming much more condensed. It's now estimated at magnitude 9 also. The following positions are for component A, given for 0 hours Universal Time and equinox 2000 coordinates. The D nucleus is located about 5 arc minutes to the north-northeast of A.
R.A. Dec. ============= Oct. 2 9h 26m +16.3 deg Oct. 4 9 31 +15.1 Oct. 6 9 36 +13.9
Saturn now looms brightly in our evening skies, and new activity has been sighted in its Equatorial Zone. Unlike the low-contrast spot reported a couple months ago, this is a bright white feature fairly prominent in amateur instruments. Ohio amateur Tom Dobbins first sighted a spot 4 arc seconds long on September 23rd at 3:16 Universal time. The spot's System I longitude is 206 degrees. You'll find Saturn situated low in the southeast among the stars of southern Aquarius as darkness falls. It's a gleaming, yellow-white beacon, the brightest point of light in that region of the sky.
While your waiting for twilight to end, take a good look low in the west. After this week you can just about kiss Venus goodbye, as it's barely above the west-southwest horizon after sunset. Jupiter is not far behind, either, setting less than 90 minutes after sunset from most locales.