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* Originally from baalke{at}earthlink.net (1:3634/1000) to All.
* Original dated: Wed Dec 04, 18:45


http://science.nasa.gov/science-news/science-at-nasa/2013/04dec_isonrecap/

What Happened to Comet ISON?
NASA Science News
December 4, 2013

Astronomers have long known that some comets like it hot.  Several of the
greatest comets in history have flown close to the sun, puffing themselves
up with solar heat, before they became naked-eye wonders in the night sky.

Some comets like it hot, but Comet ISON was not one of them.

The much-anticipated flyby of the sun by Comet ISON on Thanksgiving Day
2013 is over, and instead of becoming a Great Comet...

"Comet ISON fell apart," reports Karl Battams of NASA's Comet
ISON Observing Campaign. "The fading remains are now invisible to the
human eye."

At first glance this might seem like a negative result, but Battams says
"rather than mourn what we have lost, we should perhaps rejoice in
what we have gained - some of the finest data in the history of cometary
astronomy."


On the morning of Nov. 28th, expectations were high as ISON neared
perihelion, or closest approach to the sun. The icy comet already had a
riotous tail 20 times wider than the full Moon and a head bright enough to
see in the pre-dawn eye with the unaided eye. A dose of solar heat could
transform this good comet into a great one.

During the flyby, more than 32,000 people joined Battams and other solar
scientists on a Google+ Hangout. Together they watched live images from a
fleet of solar observatories including the twin STEREO probes, the Solar
Dynamics Observatory, and SOHO. As Comet ISON approached the sun it
brightened and faded again.

"That might have been the disintegration event," says Matthew
Knight of NASA's Comet ISON Observing Campaign.


Cameras onboard the Solar Dynamics Observatory followed the comet all the
way down to perihelion and saw ... nothing. 

"We weren't sure what was happening," recalls Knight.  "It
was such a roller coaster of emotions."

The researchers were surprised again when a fan-shaped cloud emerged from
the sun's atmosphere. No one knows for sure what was inside. Possibilities
include a remnant nucleus, too small for SDO to detect, or a "rubble
pile" of furiously vaporizing fragments. By the end of the day, Comet
ISON was nothing but a cloud of dust.

"It's disappointing that we didn't get a spectacular naked eye
comet," says Knight, "but in other ways I think Comet ISON was a
huge success. The way people connected with Comet ISON via social media was
phenomenal; our Comet ISON Observing Campaign website earned well over a
million hits; and I had trouble downloading images near perihelion because
NASA's servers were swamped."

"So maybe ISON was the 'Comet of the New Century,'" he says.

Battams agrees:  "The comet may be dead, but the observing campaign
was incredibly successful." Since its discovery in Sept. 2012, Comet
ISON has been observed by an armada of spacecraft, studied at wavelengths
across the electromagnetic spectrum, and photographed by thousands of
telescopes on Earth.  For months at a time, uninterrupted, someone or some
spacecraft had eyes on the comet as it fell from beyond the orbit of
Jupiter to the doorstep of the sun itself. Nothing was missed.

The two astronomers hope that the wealth of data will eventually allow them
and their colleagues to unravel the mystery of exactly what happened to
Comet ISON. 

"This has unquestionably been the most extraordinary comet that
Matthew and I, and likely many others, have ever witnessed," says
Battams. "The universe is an amazing place and it has just amazed us
again."

Credits:
Author: Dr. Tony Phillips 
Production editor: Dr. Tony Phillips 
Credit: Science{at}NASA


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