[meteorite-list] What Happened to Comet ISON?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 4 Dec 2013 15:44:48 -0800 (PST)
Message-ID: <201312042344.rB4Nim9w011115_at_zagami.jpl.nasa.gov>


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

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."

Author: Dr. Tony Phillips
Production editor: Dr. Tony Phillips
Credit: Science at NASA
Received on Wed 04 Dec 2013 06:44:48 PM PST

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