[meteorite-list] NASA Investigating the Life of Comet ISON
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 2 Dec 2013 13:56:50 -0800 (PST)
NASA Investigating the Life of Comet ISON
Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, Md.
December 2, 2013
After several days of continued observations, scientists continue to work
to determine and to understand the fate of Comet ISON: There's no doubt
that the comet shrank in size considerably as it rounded the sun and there's
no doubt that something made it out on the other side to shoot back into
space. The question remains as to whether the bright spot seen moving
away from the sun was simply debris, or whether a small nucleus of the
original ball of ice was still there. Regardless, it is likely that it
is now only dust.
Comet ISON, which began its journey from the Oort Cloud some 3 million
years ago, made its closest approach to the sun on Nov. 28, 2013. The
comet was visible in instruments on NASA's Solar Terrestrial Relations
Observatory, or STEREO, and the joint European Space Agency/NASA Solar
and Heliospheric Observatory, or SOHO, via images called coronagraphs.
Coronagraphs block out the sun and a considerable distance around it,
in order to better observe the dim structures in the sun's atmosphere,
the corona. As such, there was a period of several hours when the comet
was obscured in these images, blocked from view along with the sun. During
this period of time, NASA's Solar Dynamics Observatory could not see the
comet, leading many scientists to surmise that the comet had disintegrated
completely. However, something did reappear in SOHO and STEREO coronagraphs
some time later - though it was significantly less bright.
Comet ISON is shown approaching the sun and curving away from it in this
movie containing imagery from both NASA's Solar Terrestrial Relations
Observatory and the joint ESA/NASA Solar and Heliospheric Observatory
from November 2013. ISON dims dramatically as it streams away from the
Image Credit: ESA/NASA/SOHO/STEREO/GSFC
Whether that spot of light was merely a cloud of dust that once was a
comet, or if it still had a nucleus - a small ball of its original, icy
material - intact, is still unclear. It seems likely that as of Dec. 1,
there was no nucleus left. By monitoring its changes in brightness over
time, scientists can estimate whether there's a nucleus or not, but our
best chance at knowing for sure will be if the Hubble Space Telescope
makes observations later in December 2013.
Regardless of its fate, Comet ISON did not disappoint researchers. Over
the last year, observatories around the world and in space gathered one
of the largest sets of comet observations of all time, which should provide
fodder for study for years to come. The number of space-based, ground-based,
and amateur observations were unprecedented, with twelve NASA space-based
assets observing over the past year.
For more information on Comet ISON: www.nasa.gov/ison
To download recent ISON imagery: http://svs.gsfc.nasa.gov/Gallery/CometISON.html
Received on Mon 02 Dec 2013 04:56:50 PM PST