[meteorite-list] Holmes coma bigger than sun

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Thu, 15 Nov 2007 15:30:26 -0400
Message-ID: <4f7pj3trpbbsj308m96ruqjot5memsmbf3_at_4ax.com>

http://www.networkworld.com/community/node/21947

The Sun is no longer the largest object in our solar system. The recently
visible-to-the-naked-eye Holmes comet has achieved that distinction today. The
comet has a larger gas and dust cloud known as the coma, and consequently it has
a larger diameter than the sun according to astronomers at the University of
Hawaii. Scientists don't seem to have a guess as to how big it will ultimately
become.

The Holmes coma's diameter on Nov. 9 was 869,900 miles (1.4 million kilometers),
based on measurements by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the
University of Hawaii Institute for Astronomy. The sun's diameter, stated
differently by various sources, is about 864,900 miles (1.392 million
kilometers).Holmes is still visible to the naked eye as a fuzzy star anytime
after dark, high in the northeast sky. You can find it by using this sky map.

On Monday, Nov. 19, the comet will create a unique sky watching event according
to the Web site Spaceweather.com: "The comet will glide by the star Mirfak [also
called Alpha Persei] and appear to swallow it-a sight not to be missed.

"NASA's Hubble Space Telescope has watched the bright core of Comet 17P/Holmes,
which mysteriously brightened by nearly a millionfold in a 24-hour period
beginning Oct. 23, 2007. "This amazing eruption of the comet is produced by dust
ejected from a tiny solid nucleus made of ice and rock, only 3.6 kilometers
(roughly 2.2 miles) in diameter," The Hawaiian astronomy team wrote in a press
statement. The new image from the Hawaiian observatory also shows a modest tail
forming to one side, now just a fuzzy region to the lower-right. That's caused
by the pressure of sunlight pushing on the gas and dust of the coma. But the
comet is so far away-149 million miles (240 million kilometers), or about 1.6
times the distance from Earth to the sun-that even Hubble can't resolve its
nucleus.

Comets have gotten a lot of attention this year. For example, in October NASA
said one of its satellites captured the image of a solar hurricane ripping off
the tail of a passing comet. The resulting collision saw the complete detachment
of the plasma tail of Encke's comet, which was traveling within the orbit of
Mercury, NASA said. The comet is only the second repeating, or periodic, comet
ever identified and has the shortest orbital period - about 3.3 years - of any
known comet. Halley's comet was the first.
Received on Thu 15 Nov 2007 02:30:26 PM PST