ISON: Comet show will turn out well

The comet becomes fainter after its passage through the sun, could be broken

What's left over from ISON: a tidal structure moves away from the sun. © ESA / NASA / SOHO
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The comet ISON does not seem to have survived its sun passage intact. Shots of the comet after completing the sunniest part of his orbit show only a faintly glowing tail. Astronomers suspect that the comet might be broken apart. Whether there is still a solid core at the top of the tail is therefore questionable. The hoped-for spectacle of heaven will probably be canceled in any case.

The comet ISON completed its biggest solar approach last Thursday night. The interesting question was whether the cometary nucleus, consisting only of dust and ice, survived this close encounter. Special photographs of the SOHO solar observatory showed that ISON still had an active core during the Sun Passage, spewing gas and dust. The special camera splits the light emanating from the celestial body into its individual components. From this, researchers can deduce elements and molecules in the dust cloud of the comet.

Split tail and dwindling brightness

"Our measurements show a clear signal of the comet during the solar flyby, " says Werner Curdt from the Max Planck Institute for Solar System Research in Katlenburg-Lindau. About two hours after perihelion passage, however, there was no sign of active tail production. At first, the comet was even considered completely destroyed. Then the tail of ISON appeared again on Thursday evening in the field of vision of the solar observatory. At this time, it was unclear whether or not there was a comet nucleus at the tip of the tail.

Images taken several hours after the perihelion allowed further conclusions. "The dust tail of the comet is now divided into two parts, " reports Curdts colleague Hermann Böhnhardt. The part of the tail pointing towards the sun consists of dust particles that were released before the perihelion passage. The other part, on the other hand, apparently contains more recent material: it was emitted during the flyby, suggesting that at least part of the core still existed and was active at that time.

Recording from December 1, 2013: ISON can only be recognized as a faintly glowing cloud on the upper right edge of the picture. © NASA / ESA / SOHO

Fragments or core remnant?

On recent images, the brightness of the comet has decreased significantly. ISON seems to have stopped its dust production. This may indicate that there is no longer a solid core that could release dust. Whether the comet nucleus in the perihelion was still intact or continued on its way as a small fragment or as an ensemble of fragments, is not yet clear. According to NASA, there were initial indications that there was still a small core remnant at the tip of the tail. Other astronomers assume that only one cloud of dust is left over. display

But one thing seems clear: A big comet show will almost certainly not exist anymore. Because even if a small core is left over, ISON will not be able to produce so much tail material that it will be seen with the naked eye as hoped.

Animation of the Sun Passage of Komet ISON (NASA)

(NASA / Max Planck Institute for Solar System Research, 02.12.2013 - NPO)