The approaching Comet Elenin has triggered suspicious and fearful speculation among some observers. A contribution to this brouhaha has been the lack of images of this visitor from deep space, but at last there are images from a NASA space observatory of this oncoming comet.
On 1 August 2011 Comet Elenin (C/2010 X1) passed within just 7 million km of the STEREO-B solar observatory spacecraft. Taking advantage of this happy coincidence, the spacecraft was physically rolled to allow it to spend an hour capturing images of the little comet and its coma with its wide angle HI-2 instrument.
The STEREO spacecraft will make hour-long observations every day for the next week or longer until the comet enters its normal field of view. Then the comet can be continuously observed into September with other instruments, such as the SOHO C3 coronagraph.
Astronomers expect that the comet will become significantly brighter to STEREO-B over the next few days due to an effect called “forward-scattering” when sunlight is reflected of the dust in the comet’s coma directly towards the spacecraft . This is purely an observational artefact of STEREO-B’s position with respect to the Sun and comet and does not mean anything significant is happening to the comet itself.
The first images show Elenin to look just as you would expect a small comet to look. No tail is visible yet. It is clearly not a planet-sized body, or a brown dwarf or a red dwarf. It is exactly where it was expected to be. Hopefully this will reassure the worried that this is just another comet (like the much more interesting Comet Garradd (visible with binoculars near Pegasus).
There are now videos assembled from STEREO-B images. The first shows the comet moving across the field of view between 1 and 5 August 2011. The animation “jumps” a couple of times when the image was lost as the spacecraft rolled back to its usual orientatation.
This false colour movie is the observation from 3 August, the comet is the little moving fuzzball about a quarter of the way across from the left. Note the constellation of Orion.
The next animation was made on 6 August and it appears that the comet’s tail is developing (see image above link).
Latest news (31 August):
Comet Elenin had already been dimming, but there was worse to come, recent images show Comet Elenin is starting to become elongated, appearing as a bright smear against the blackness of space. It seems that the comet’s nucleus is breaking up. The Mayans and Hopi Elders didn’t see that coming! (Nor too, did the Electric Universe theory.)
If you are new to studying comets, this may sound dramatic but is a fairly common event (you can read about another current example at the Faulkes Telescope site).
Since the 1950s, the nucleus of a comet has been thought of as a “dirty snowball” of mainly ice with some rocky material. Recent visitations by spacecraft to some comets have suggested that some (possibly older) comets are more rock than ice. However younger comets like Comet Elenin still seem to be loose mash-ups of dust and ice, probably very loosely bound together and rather fragile. As the comet nears the Sun, solar heating drives ice to melt into vapour and escape into space, effectively removing the cement that holds the comet together. The nucleus breaks up into a series of chunks or disintegrates entirely into a blizzard of small fragments.
This development makes Elenin possibly more interesting still to astronomers for it what it could show them about the make-up of comets. Hopefully, it also marks the beginning of the disintegration of the weird doomsday cult that has grown up around this minor comet