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(meteorobs) "Headlines": Reasons for outburst of Comet C/2001 A2 (LINEAR)
This appeared on a local Club email list today. It is not attributed, so
I have no way of knowing where it came from, or who to credit. Still, it
seemed of interest to our 'meteorobs' list.
Clear skies all!
Lew Gramer <owner-meteorobs@jovian.com>
------- Forwarded Message
From: Robert Laverdiere <spaceshotbob@mediaonedot net>
Subject: (NSAAC) Headline
Date: Thu, 12 Apr 2001 18:10:56 -0400
Headlines
Last Updated: 10 April 2001
As reported on this page at the beginning of the month, C/2001 A2 (LINEAR)
had an unexpected brightening from about 12.0 to 7.5 magnitude with the
majority of the increase coming in a 36 hour period from March 29.5 UT to
March 31.0 UT. It is obvious now that this increase in brightness is not a
short-lived event although the comet has faded about a magnitude from its
peak. [It is possible that some of this fading is due to interference from
the moon.]
There has been speculation as to what has caused this brightening. When a
brightening like this first occurs, it is possible that it is an outburst, a
sudden release of dust and gas from a vent. This is usually an isolated
event (although such outbursts can occur more than once during an
apparition). The brightness of the coma increases rapidly and a disk of
material is seen speading from the nucleus. The light curve thus far
suggests that this isn't the case. The event is lasting longer than one
would typically expect from this scenario.
Some have called this a "turn-on" event referring to the time/distance at
which water ice becomes the primary volatile fueling the comet's brightness
increase. Some periodic comets show rapid increases in brightness when this
happens. However, the timing is wrong for a water turn-on event. The comet
is too close to the Sun.
Another type of "turn-on" might occur if a major vent or vents on the comets
nucleus were suddenly exposed to sunlight. Having been on the nightside of
the nucleus, the vent would have been inactive. Now because of precession of
the nucleus, the active area is exposed and significantly increasing the
dust and gas production of the comet.
Another possibility is, of course, the break-up of the comet's nucleus.
We don't know at this point whether the brightening will continue or the
comet will fade to pre-outburst magnitude. If the nucleus did break-up, we
should see some evidence of it in the future. It is important that this
comet be monitored both visually and with CCDs. CSM.
------- End of Forwarded Message
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