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Post Info TOPIC: Comet C/2010 X1 (ELENIN)
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Title: Disappearance of Comet C/2010 X1 (Elenin): Gone with a Whimper, not a Bang
Author: Jing Li, David Jewitt

We examine the rise and sudden demise of comet C/2010 X1 (Elenin) on its approach to perihelion. Discovered inbound at 4.2 AU, this long-period comet was predicted to become very bright when near perihelion, at 0.48 AU on 2011 September 10. Observations starting 2011 February (heliocentric distance ~3.5 AU) indeed show the comet to brighten by about 11 magnitudes, with most of the increase occurring inside 1 AU from the Sun. The peak brightness reached mR = 6 on UT 2011 August 12.95±0.50, when at ~0.83 AU from the Sun. We find that most of the surge in brightness in mid-August resulted from dust particle forward-scattering, not from a sudden increase in the activity. A much smaller (~3 magnitudes) brightening reached a maximum on UT 2011 August 30±1 (at 0.56 AU), and reflects the true break-up of the nucleus. This second peak was matched by a change in the morphology from centrally condensed to diffuse. The estimated cross-section of the nucleus when at 1 AU inbound was ~1 km˛, corresponding to an equal-area circle of radius 0.6 km. No surviving fragments were found to a limiting red magnitude r' = 24.4, corresponding to radii lesssim40 m (red geometric albedo = 0.04 assumed). Our observations are consistent with disintegration of the nucleus into a power law size distribution of fragments with index q = 3.3±0.2 combined with the action of radiation pressure. We speculate about physical processes that might cause nucleus disruption in a comet when still 0.7 AU from the Sun. Tidal stresses and devolatilization of the nucleus by sublimation are both negligible at this distance. However, the torque caused by mass loss, even at the very low rates measured in comet Elenin, is potentially large enough to be responsible by driving the nucleus to rotational instability.

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On October 16, 2011, comet 2010 X1 (Elenin) made its closest approach to the Earth

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NASA Says Comet Elenin Gone and Should Be Forgotten

Latest indications are this relatively small comet has broken into even smaller, even less significant, chunks of dust and ice. This trail of piffling particles will remain on the same path as the original comet, completing its unexceptional swing through the inner solar system this autumn.
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Comet C/2010 X1 (Elenin) makes its closest approach (0.15 AU) on the 16th October, 2011,  @ 19:51 UT ± 00:05.



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The magnitude 10.7 comet C/2010 X1 (Elenin) will pass 0.20° from the magnitude 8.9 galaxy NGC 2903 in the constellation Leo, at 11:00 UT, 14th October, 2011.



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Comet C/2010 X1 (Elenin) is at  Perihelion (0.482 AU) on the 10th September.



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Comet Elenin Poses No Threat to Earth

Often, comets are portrayed as harbingers of gloom and doom in movies and on television, but most pose no threat to Earth. Comet Elenin, the latest comet to visit our inner solar system, is no exception. Elenin will pass about 35 million kilometres from Earth during its closest approach on Oct. 16, 2011.
Also known by its astronomical name C/2010 X1, the comet was first detected on Dec. 10, 2010 by Leonid Elenin, an observer in Lyubertsy, Russia, who made the discovery "remotely" using an observatory in New Mexico. At that time, Elenin was about 647 million kilometres from Earth. Since its discovery, Comet Elenin has - as all comets do - closed the distance to Earth's vicinity as it makes its way closer to perihelion, its closest point to the sun.
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Comet Elenin captured by STEREO/SECCHI HI-1B



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Observing Comet Elenin

As Comet Elenin passed to within just 7 million kilometres of the STEREO (Behind) spacecraft, NASA rolled the spacecraft to take a look at it (Aug. 1, 2011) with its wide angle HI-2 instrument. Though the observation lasted only a little over an hour, the fuzzy looking comet can be seen moving across a small portion of the sky. STEREO will be taking these one-hour observations every day for almost the next week or more until it enters its nominal field of view, at which time we should enjoy continuous viewing of the comet. Over time, we expect the comet to be visible in the SOHO C3 coronagraph on September 23 for six days and possibly STEREO's COR2 coronagraph as well. The closest the comet will come to Earth is 0.023 AU (Astronomical Units), or approximately 34-million kilometres, so it poses no threat to us. We will attempt to keep this page updated with the latest observations.
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Comet 2010 X1 (Elenin) will pass ~0.027 AU from the STEREO-B spacecraft on the 25th July, 2011.



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