Comet ISON Nov. 19 update: another outburst, possible break-up

All I had to do was write about Comet ISON's fading yesterday and today news comes of another outburst and a possible breakup. Astronomer Emmanuel Jehin of the

All I had to do was write about Comet ISON's fading yesterday and today news comes of another outburst and a possible breakup. Astronomer Emmanuel Jehin of the TRAPPIST team , using a 60-cm telescope and working well into morning twilight today, recorded another uptick in activity deep within ISON's coma, that big blue bubble of gas and dust surrounding the comet's core or nucleus.

"This morning we found ISON very active again," writes Jehin. The amount of dust and gas streaming from the comet's core increased sixfold from the night before. "This looks to be the start of a new outburst linked to the active regions (seen about a week ago) as the jets are strong again today," he added.

Jets are just what they sound like - geysers formed of rapidly vaporizing ice in the comet's crust. They form when cracks develop on the surface, exposing fresh ice to the sun's heat. They also occur when solar heating vaporizes pockets of ice beneath the crust. The pressure of the expanding gas can blast a hole right through the crust and spray a mixture of ice, dust and rocky material straight out into space.


Jet material is blown back from the nucleus by the pressure of sunlight to form interesting fountain-shaped structures within the coma and long, wispy streamers in the tail. Vitaly Nevski's recent photos record these dusty blasts in beautiful detail.

Nevski was co-discover of Comet ISON along with his observing partner Artyom Novichonok. He also recently discovered another comet on his own: C/2013 V3 Nevski. Like ISON and Comet Lovejoy, it's a morning sky object and bright enough to see in a small telescope. Once the moon wanes to a crescent, I'll provide a map to help you find it.

Jehin also echoes other reports by amateur astronomers about the difficulty of tracking Comet ISON now that it's rapidly closing in on the sun. I had hoped to see it this morning but clouds thwarted the effort.

On the heels of the Jehin's news comes a report of a possible fragmentation of the comet's nucleus. Scientists from the Max Planck Institute for Solar System Research (MPS) in Germany and the Wendelstein Observatory of the Ludwig-Maximilians-University in Munich, Germany recorded the subtle wing-shaped structures within ISON's coma last weekend.

Based on previously observed behavior in other crumbling comets, they believe the wings grew when several pieces broke off the nucleus possibly during the Nov. 14 outburst. Is this the start of the comet's breakup or are these mere scraps? We should know very soon.

ISON is now only about 5 degrees high in early twilight below the star Spica. Most binoculars observers are reporting that the tail is too faint to see against the dawning sky, but the head remains visible as a small fuzzy spot with a brighter center glowing at magnitude 5.


This new outburst could see another temporary jump in the comet's brightness, so if you can check it out, please do. There are precious few days left. By Saturday Nov. 23, the comet will be next to impossible to see in twilight very close to the southeastern horizon. Unless of course another outburst causes it to brighten up to 2nd or 1st magnitude.

Around the time it rounds the sun on the 28th I'll have new maps and directions on how to see it. Once we get into December, the comet quickly climbs higher in the eastern sky during morning twilight and should become a naked eye object much easier to see than it is at present.

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