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UPDATE NOVEMBER 30, 2013. As Comet ISON pulled away from the sun over these past couple of days, it first brightened and then faded again. It now seems unlikely we will get any good view of Comet ISON in our skies this December. Personally, I still hold some slim hope that the comet will surprise us again.
Read more about ISON’s status at this time: In ISON’s wake, a trail of questions
NOVEMBER 29, 2013. It has been … a wonderful ride. Comet ISON rounded the sun yesterday at 18:45 UTC/ 1:45 p.m. EST, and appeared to be disintegrating. Then yesterday evening the comet started appearing brighter again. Will some remnant be visible in Earth’s skies in early December, as ISON pulls away from the glare of the sun in our sky? It hardly seems likely at this point that we’ll get a very bright comet. But we might get something. And, whatever happens now, hasn’t it been great so far?
NASA Goddard’s Karl Battams has almost singlehandedly informed the world about this comet, either via his Twitter feed @SunGrazerComets or via NASA’s Comet ISON Observing Campaign website.
In the early evening of November 28, he posted these words: We’re calling it … you heard it here first … we believe some small part of ISON’s nucleus has survived.
EarthSky blogger Shireen Gonzaga contributed the following movie of ISON as the comet rounded the sun. She made the movie from SOHO LASCO C3 images. In it, you can clearly see that ISON appears fainter just after it emerges from perihelion – closest point to the sun – and then brightens again as it pulls away from the sun. Thank you, Shireen!
Download File
Late at night on November 28, Battams gave details in his blog:
As the comet plunged through the solar atmosphere, and failed to put on a show in the SDO images, we understandably concluded that ISON had succumbed to its passage and died a fiery death. Except it didn’t. Well, maybe…
After perihelion, a very faint smudge of dust appeared in the the LASCO C2 images along ISON’s orbit. This surprised us a little, but we have seen puffs of dust from sungrazer tails, so it didn’t surprise us enormously and didn’t change our diagnosis. We watched and waited for that dust trail to fade away. Except it didn’t.
Now, in the latest LASCO C3 images, we are seeing something beginning to gradually brighten up again. One could almost be forgiven for thinking that there’s a comet in the images!
… Right now, here’s our working hypothesis:
As Comet ISON plunged towards to the sun, it began to fall apart, losing not giant fragments but at least a lot of reasonably sized chunks. There’s evidence of very large dust in the form of that long thin tail we saw in the LASCO C2 images. Then, as ISON plunged through the corona, it continued to fall apart and vaporize, and lost its coma and tail completely just like Lovejoy did in 2011.
… Then, what emerged from the sun was a small but perhaps somewhat coherent nucleus, that has resumed emitting dust and gas for at least the time being. In essence, the tail is growing back, as Lovejoy’s did.
So while our theory certainly has holes, right now it does appear that a least some small fraction of ISON has remained in one piece and is actively releasing material. We have no idea how big this nucleus is, if there is indeed one.
If there is a nucleus, it is still too soon to tell how long it will survive.
If it does survive for more than a few days, it is too soon to tell if the comet will be visible in the night sky.
2013年11月30日 23点11分
1
Read more about ISON’s status at this time: In ISON’s wake, a trail of questions
NOVEMBER 29, 2013. It has been … a wonderful ride. Comet ISON rounded the sun yesterday at 18:45 UTC/ 1:45 p.m. EST, and appeared to be disintegrating. Then yesterday evening the comet started appearing brighter again. Will some remnant be visible in Earth’s skies in early December, as ISON pulls away from the glare of the sun in our sky? It hardly seems likely at this point that we’ll get a very bright comet. But we might get something. And, whatever happens now, hasn’t it been great so far?
NASA Goddard’s Karl Battams has almost singlehandedly informed the world about this comet, either via his Twitter feed @SunGrazerComets or via NASA’s Comet ISON Observing Campaign website.
In the early evening of November 28, he posted these words: We’re calling it … you heard it here first … we believe some small part of ISON’s nucleus has survived.
EarthSky blogger Shireen Gonzaga contributed the following movie of ISON as the comet rounded the sun. She made the movie from SOHO LASCO C3 images. In it, you can clearly see that ISON appears fainter just after it emerges from perihelion – closest point to the sun – and then brightens again as it pulls away from the sun. Thank you, Shireen!
Download File
Late at night on November 28, Battams gave details in his blog:
As the comet plunged through the solar atmosphere, and failed to put on a show in the SDO images, we understandably concluded that ISON had succumbed to its passage and died a fiery death. Except it didn’t. Well, maybe…
After perihelion, a very faint smudge of dust appeared in the the LASCO C2 images along ISON’s orbit. This surprised us a little, but we have seen puffs of dust from sungrazer tails, so it didn’t surprise us enormously and didn’t change our diagnosis. We watched and waited for that dust trail to fade away. Except it didn’t.
Now, in the latest LASCO C3 images, we are seeing something beginning to gradually brighten up again. One could almost be forgiven for thinking that there’s a comet in the images!
… Right now, here’s our working hypothesis:
As Comet ISON plunged towards to the sun, it began to fall apart, losing not giant fragments but at least a lot of reasonably sized chunks. There’s evidence of very large dust in the form of that long thin tail we saw in the LASCO C2 images. Then, as ISON plunged through the corona, it continued to fall apart and vaporize, and lost its coma and tail completely just like Lovejoy did in 2011.
… Then, what emerged from the sun was a small but perhaps somewhat coherent nucleus, that has resumed emitting dust and gas for at least the time being. In essence, the tail is growing back, as Lovejoy’s did.
So while our theory certainly has holes, right now it does appear that a least some small fraction of ISON has remained in one piece and is actively releasing material. We have no idea how big this nucleus is, if there is indeed one.
If there is a nucleus, it is still too soon to tell how long it will survive.
If it does survive for more than a few days, it is too soon to tell if the comet will be visible in the night sky.