Friday, October 14, 2011

Waiting for Comet Elenin




Left Panel: Image from the STEREO H2A imager on 9 October showing Earth (bright object with long artefact spikes to the left of Centre), comet 45P/Honda-Mrkos-Pajdušáková (near centre with visible tail) and Neptune (far right), predicted position of Elenin shown as well. click to embiggen.
Right Panel: Image taken of predicted position of Elenin on 12 October. Image composed of a stack of 4 x 120 second luminance exposures in the Global-Rent-a-Scope GRAS-05 instrument (stacked in ImageJ), tracking on the predicted position of Elenin. Images taken between 20-5 minutes before astronomical twilight, but still lots of interfering Moonlight. No object appears near Elenin's predicted position (image centre), stars down to magnitude 14 visible, the spikes are imager artefacts (click to embiggen).

Well, September 27, when comet C/2010 X1 Elenin, Earth and the Sun were aligned, has come and gone without massive earthquakes (or any earthquakes at all really, there were no quakes of M 6+ around then), the Pacific Ring of Fire did not burst with with volcanic eruptions, andwell, not much of interest happened really. Just like we astronomers predicted.

Now we are waiting for Elenin's closest approach to Earth, on October 16 12:20 UT (that's about 11:20 pm in Australian Eastern daylight saving time. Elenin has been high enough above the morning horizon for scopes to pick up for a couple of days yet, however, bright Moonlight makes picking up dim objects not far above the horizon difficult.

Amateurs have been scanning the sky for any sign of the remnants of Elenin after it's disintegration, but so far no confirmed sightings. A couple of very experienced observers have reported a sighting of an object at magnitude 9-10, but many other experienced observers have found nothing down to much lower limiting magnitudes (see here and here). My images, taken with Global-Rent-a-Scope GRAS-05 instrument above, don't show anything and a magnitude 10 object should have shown up with stacking.

The last reported sighting of Elenin in STEREO was by Comet Al, in images from H2A on October 9. This was at the limit of detection, so this implies the comet remnants are around magnitude 10.5 or 11, pretty dim. My image from the STEREO H2A imager is above. I can't see anything where Elenin should be, but comet 45P/Honda-Mrkos-Pajdušákováand its tail are clearly visible, as is Neptune, so any remnant must be much dimmer than that. You can see an animation showing 45P's tail twisting in the solar wind here (warning 2 meg AVI file).

If comet Elenin hadn't disintegrated, it should have been between magnitude 6.5-7.5 by now, easily visible even under the conditions we have at the moment.

That hasn't stopped the conspiracy people though, after Elenin failed to do anything doomsdayish during it's alignment with the earth and Sun, they have no moved on to worrying about Elenin's "debris field" doing something bad at the time of closest approach. However, the remnants of Elenin will be nowhere near Earth.

So, astronomers will continue to observe , looking for Elenin. As the Moonlight wanes and the comet gets higher above the horizon, we may be able to pick up some of the debris of this comet.

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