[meteorite-list] Catch Comet Machholz at Its Best

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jan 6 12:33:07 2005
Message-ID: <200501061728.JAA29535_at_zagami.jpl.nasa.gov>

http://skyandtelescope.com/observing/objects/comets/article_1423_1.asp

Catch Comet Machholz at Its Best
By Tony Flanders
Sky & Telescope
January 6, 2005

Comet Machholz, C/2004 Q2, is entering its glory days. For observers in
the Northern Hemisphere, all the circumstances are at their best in the
first half of January 2005. The Moon is conveniently approaching new
phase just as the comet shines at its brightest and makes its closest
approach to Earth. And to add to the fun, the comet is traversing one of
the best-known and best-loved areas in the night sky, passing 2? west of
the Pleiades on the night of January 7th (see "Comet Machholz in the
Evening Sky"
<http://skyandtelescope.com/observing/objects/comets/article_1396_1.asp>).

The northeastern US has been suffering from a long cloudy spell, but a
brief break on the evening of January 1st allowed many Sky & Telescope
editors to view the comet. Editor in chief Rick Fienberg spotted it from
his home within walking distance of downtown Boston using only his
eyeglasses for optical aid, but he wasn?t completely sure that he had
the right target until he viewed it through binoculars.

Observing from the Boston suburbs that same night, I found Comet
Machholz to be an easy naked-eye target, slightly brighter and
distinctly more condensed than either the Andromeda Galaxy or the Double
Cluster in Perseus. At first glance through my 7-inch reflector, the
comet seemed extremely bright but nearly featureless ? an almost stellar
nucleus surrounded by a bright coma some 10 arcminutes across. On closer
inspection, it was apparent that the coma had a fairly sharp western
edge but trailed off vaguely well beyond the 5-arcminute radius in all
other directions. And scanning the area with averted vision at 120x, I
saw faint extensions about a half-degree long to the northeast and
slightly west of south, matching the positions of the ion tail and the
dust tail, respectively. Observers under dark skies have reported that
the dust tail is fairly easy to see, extending perhaps 2?, but the ion
tail is much more elusive. To our knowledge, no visual observers have
traced the ion tail to anything like the 6? length shown in photographs.

The ion tail is carried by the solar wind, so it stretches almost
directly away from the Sun. The heavy particles of the dust tail, for
the most part, extend along the comet?s orbital path. Earth passed
through the comet's orbital plane on December 26, 2004, so we are now
seeing the dust tail from ?below? rather than ?above.? This caused the
apparent positions of the tails to flip, as shown in the photographs
above. (NASA has a Java applet
<http://neo.jpl.nasa.gov/cgi-bin/db_shm?sstr=2004+Q2&group=all> that
simulates the orbits of Comet Machholz and the planets in three
dimensions.)
Received on Thu 06 Jan 2005 12:28:29 PM PST