The first radio observations of comet Elenin

NRAO

American radio astronomers report that did not detect any water coming from any remains of comet Elenin. Amy Lovell observed it for 7 hours on Sept 7 using the Green Bank Telescope (it is not yet in the Arecibo declination window) and did not detect any OH line above the noise level of 2.4 mJy. This puts a limit of a few times 10molecules/second on the gas production rate, which is about 100 times less than earlier predictions. This data may confirm disintegration proccess in comet’s nucleus which stareted on mid August. The next radio observations may be carry out on October by Arecibo radio observatory, of course if we will see comet Elenin on images from SOHO spacecraft.

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Countdown to perihelion

Perihelion passed.

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Comet Elenin – the final prospect

L. Elenin

As many readers already know, Comet Elenin has begun the irreversible process of breaking up. We spoke earlier about the probablility of such an outcome, but I considered it less than 50%. On the graph at left you can see a selection of ten comets that approach the Sun closer than 0.5 a.u. The red line shows the boundary, to the left of which, derived from J. Bortle’s formula, is the safe zone, but to the right is the zone of disintegration. The yellow color shows Comet Elenin, with absolute magnitude obtained by visual observations, and the blue is from JPL-NASA data. As we see, Bortle’s formula, all-in-all, doesn’t work too badly. Although there is a bright exception – the green triangle belongs to the unique comet 96P/Machholtz, about which I will speak next time.

Now it is absolutely clear that the comet’s drop in brightness, first noted by Michael Mattiazzo on Aug. 20th, was not coincidental – the decay process had already begun, and over the course of the next several days the comet changed greatly. Its pseudo-nucleus became diffuse and extended, and later vanished completely. On images from Sept. 1st in the comet’s coma there was no condensation visible, and that meant the comet had already broken up into fairly small pieces, with a maximum size of not more than a hundred meters.

Such a breakup of small comets passing near the Sun is not rare, and in that is nothing surprising. I note that this is a breakup, not an explosion. All the pieces continue to move on the comet’s trajectory. The large fragments are likely to continue to disintegrate into smaller ones. It is possible that in October when the comet moves into the morning sky, we will no longer be able to see what once was Comet Elenin. It is possible that something will be visible to large earth-based telescopes. The breakup of a long-period comet fairly close to the Earth (on a Solar System scale) is a rather rare event. During such a breakup we can see the interior of the comet to better understand its construction and composition.

Overall, the most scientifically interesting thing is the breakup scenario, but unfortunately right now the comet is not visible to the largest telescopes or even the Hubble Space Telescope because of its close angular distance from the Sun (small elongation). On the other hand, amateur astronomers, awaiting this comet which might have been visible to the unaided eye, will now not see it, at least visually in their telescopes and binoculars.

We will wait for Sept. 23rd when the comet is due to appear in the field of view of the SOHO space coronagraph. Any result will tell us what we can expect at the beginning of October when the comet once again should appear in the pre-dawn sky. We will wait. The end of this story is near…

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The first Jovian trojan has been discovered at the ISON-NM observatory

Calvin College

August 23, at our observatory, the first Jovian trojan was discovered, receiving the designation 2011 QJ9. After the appearance of this object on the NEO Confirmation Page, and after refinement of its orbit on Aug 24, it became possible to link these observations to observations obtained on Aug 28 by the American survey Pan-STARRS. After that, the observation arc immediately rose to nearly a month.

Earlier we were able to recover two Greeks and now we have discovered a new rarer object. The total number of Greeks (3176) is twice that of the Trojans (1700). 2011 QJ9 is a rather large object, with a diameter on the order of 5.5 km, although for this family of asteroids, it is a very small object. The largest Trojan is over 100 km in diameter.

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CME 0036: three days before collsion with comet Elenin

Coronal mass ejections, which will collide with comet Elenin three days later. This images taken by coronagraphs COR2, which installed on the STEREO spacecrafts.

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