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Last updated on April 17, 2014 at 17:30 EDT

Comet ISON Needs To Make Up Its Mind

November 18, 2013
Image Caption: This new view of Comet C/2012 S1 (ISON) was taken with the TRAPPIST national telescope at ESO's La Silla Observatory on the morning of Friday 15 November 2013. Comet ISON was first spotted in our skies in September 2012, and will make its closest approach to the Sun in late November 2013. Credit: TRAPPIST/E. Jehin/ESO
[ Watch the Video: ISON Keeps Giving Us The Run-Around ]

Alan McStravick for redOrbit.com – Your Universe Online

I’ve been nerding out for most of the year, since Comet ISON first came on my radar, so to speak. Back in February, I wrote a piece for redOrbit detailing the discovery of a comet so magnificent that its show was going to be the stuff of legend.

And then in July, redOrbit’s Brett Smith tried to rain on my astral parade when he reported on the diminished expectations for ISON within the scientific community. But a mere two months later, in a redOrbit exclusive, Karl Battams walked back the gloomy prediction for the fate of ISON, stating that the rumors of its impending demise had been greatly exaggerated. He also claimed its designation as ‘Comet of the Century’ was mostly hype driven by the media, not professional scientists.

First, it was on. Then it was possibly off. Then we were assured it was definitely on. And then last Wednesday, scientists with the Max Planck Institute for Solar System Research (MPI) and the Astronomical Institute at Ludwig Maximillian University (LMU) witnessed something potentially disheartening for all amateur stargazers. They saw that Comet ISON, currently visible in the eastern predawn sky, has wings.

These wings, according to a post written on the International Astronomical Union’s Comets and Asteroids Facebook page, suggest the nucleus of ISON is breaking apart.

“The coma wings suggest the presence of two or more sub-nuclei with individual expanding atmospheres in the overall cometary coma and may indicate nucleus splitting in the comet,” they said.

The European Southern Observatory’s La Silla facility houses the Transiting Planets and Planetesimals Small Telescope (TRAPPIST). TRAPPIST has been keeping its keen eye on ISON since mid-October. Everything seemed normal until the first day of this month, when an outburst was observed, in effect doubling the amount of gas being emitted by the comet. Last Wednesday, another giant outburst was reported. This event has increased the comet’s activity by a factor of ten.

Responsible for these outbursts is the intense heat of the Sun which causes ice contained in the nucleus of ISON to sublimate, throwing off excess amounts of both dust and gas. With ISON’s closest approach to the Sun in 10 days, it is expected that far more ice will sublimate. But, if the MPI and LMU scientists are to be believed, it is far more likely the nucleus will break down into several small fragments, once and for all dashing our chances of witnessing a wondrous winter event.

Battams, however, retains his optimism that ISON will survive its solar encounter and present us with an impressive show. He claims fragmentation is but one possibility resultant from the appearance of wings on ISON.

He cites the symmetrical appearance of the wings as negating, almost assuredly, the theory of fragmentation. This is because a comet nucleus breakup is usually an asymmetrical event. He believes the wings might actually be dust emission from jets contained in ISONs nucleus that had already been spotted. Another theory for the wings might be that it is actually a solar wind ion tail structure brought about by ISONs having come into contact with high solar winds, in a coronal mass ejection for example.

“If the comet has fragmented, we should see some dramatic changes in the next few days,” Battams said. “Typically we expect a large increase in brightness followed then by a dramatic decrease in the comet’s brightness in these situations.

“If instead jets are the cause, we expect the ‘wings’ to persist and grow. If the behavior is driven by the solar wind then we should see continual changes as the solar wind changes.”

So for those of you who, like me, have been marking the passing days until I could experience ISON with my unaided eyes, keep your fingers crossed that it survives its perihelion with the Sun. If it does, the first few weeks of next month will make this a December to remember.


Source: Alan McStravick for redOrbit.com - Your Universe Online