So… What’s Up With ISON?
Yesterday sure was interesting. As the astronomical world, from scientists to journalists to enthusiasts alike, watched online in near real time as ISON came within its closest pass of the Sun — in literally ever — the comet, having spent the previous several hours brightening steadily, suddenly went dim as it traveled deep into the Sun’s outer corona. It appeared that it had fallen apart, disintegrating* into a smear of bright particles just as it began to round the Sun. Even as astronomers looked to spot a sungrazing ISON in several of NASA’s Solar Dynamics Observatory’s imaging fields, nothing was to be found, leading many to pronounce the billion-year-old icy visitor from the Oort Cloud dead on arrival.
But then, just as the Twitterverse was lamenting the loss of this year’s most famous comet, something reappeared… and even now, a full day later, they’re still not quite sure what.
As ISON watchers (myself included) monitored the SOHO site — which was repeatedly overloaded with all the hits from around the world — as well as our Twitter feeds and other blog sources, it was clear that some part of ISON had survived perihelion as a streak became visible in the upper portion of the LASCO C2 images. (Check out the video below edited by astrophotographer Babak Tafreshi.)
It didn’t appear to be a typical cometary nucleus, and some dismissed it as just the dusty remnants of ISON’s tail. Which made sense at first — until the “remnants” began to gain brightness — even beyond the vignetting expected in SOHO’s imaging area around the corona — and then even appearing to develop a fanning tail-like structure of its own.
Even now, images from SOHO’s LASCO C3 wide-angle camera are showing a bright blob with a fuzzy tail and faint debris trail in pretty much the place where a surviving comet ISON would be expected to be. Is it ISON’s original nucleus, re-heated and forming a new tail for its trip back out into deep space? Or is it a ‘mock comet’ made of a cluster of ice and rock, the remains of an ISON that got torn to bits by the Sun’s intense gravity and radiation?
Even the experts don’t know yet.
Astronomer Karl Battams of the U.S. Naval Research Lab, who was one of several researchers who had traveled to observe ISON’s perihelion from the Kitt Peak National Observatory near Tucson, wrote yesterday afternoon on the Comet ISON Observing Campaign blog:
“…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. If it is visible in the night sky, it is too soon to say how bright it will be…”
But there is undeniably something there in ISON’s orbit, be it nucleus, dust cloud, or something somewhere in the middle of the two. Meanwhile all we can do at this point is patiently wait and see what it does in the coming hours and days, with the few observatories that can successfully and safely keep watch.
“This morning we thought it was dying, and hope was lost as it faded from sight. But like an icy phoenix, it has risen from the solar corona and – for a time at least – shines once more… The universe is an amazing place and it has just amazed us again.“
– Karl Battams
For lots more information, check out this update by Emily Lakdawalla and Bruce Betts on the Planetary Society blog, read what Phil Plait the “Bad Astronomer” has to say, and stay tuned to the CIOC blog here. Also you can follow the latest news regarding everything #ISON on Twitter.
UPDATE 11/30: Well, it looks like *whatever* survived ISON’s perihelion is now dissipating, based on recent images from SOHO and STEREO instruments. Read a great recap of the last few days’ crazy-intense observations by Karl Battams here.
And as far as whether or not we’ll still be able to see ISON’s remains in the sky come next week? “Please don’t get your hopes up,” Karl says, “but we all need to keep in mind how ISON keeps surprising us.”
*Disintegration? Or fragmentation? The differences are not just semantic — read here for a more accurate description.