[meteorite-list] SOHO Raises The Ante With Discovery Of Its 500th Comet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:52:14 2004
Message-ID: <200208151638.JAA17840_at_zagami.jpl.nasa.gov>

Lindsay Renick Mayer
Goddard Space Flight Center, Greenbelt, Md. August 14, 2002
lmayer_at_pop100.gsfc.nasa.gov
Phone: 301/286-5687

RELEASE: 02-127

SOHO RAISES THE ANTE WITH DISCOVERY OF 500TH COMET

Amateur astronomers worldwide placed their bets, crossed their
fingers and waited in anticipation for the ESA-NASA Solar &
Heliospheric Observatory (SOHO) spacecraft to spot its 500th
comet. Their patience was rewarded on August 12 as SOHO, a mission
actually designed to research the Sun, revealed its own type of
royal flush with comet C/2002 P3 (SOHO).

It is the 500th comet to be discovered by SOHO since it launched
on December 2, 1995, making the spacecraft by far the most
prolific comet-hunting observatory in history.

Between May 2 and May 31, using the SOHO website, 1,256 amateur
astronomers tracked SOHO's observations of comets and made
predictions about the date and time that the 500th comet would
be at perihelion (the closest approach to the Sun). Comet
C/2002 P3 (SOHO) had a perihelion time of August 12 at 12:04:48
p.m. EST.

Diane McElhiney won the sweepstakes with a prediction only one
hour and 43 minutes away from the correct time.

The website also allows comet aficionados around the world to
look at real-time SOHO data and images. Once they see what
appears to be a new comet, they seek confirmation from others
on-line. If confirmation is provided, they have accomplished a
feat that is the goal of many amateur astronomers.

More than 75 percent of the comet discoveries have come from
amateurs from Australia, Canada, China, France, Germany, Italy,
Lithuania, Russia, the United Kingdom and the United States.

"Analyzing SOHO data is a great challenge and you have to
combine many skills," said Rainer Kracht, the discoverer of
C/2002 P3 (SOHO). "But every amateur astronomer dreams of
finding a comet."

Kracht, a mathematics, physics, computer science and astronomy
teacher at the Kooperative Gesamtschule Elmshorn in Elmshorn,
Germany, has discovered 63 comets since August 2001 with the
help of SOHO data and images. An entire group of near Sun comets
that he discovered is even named after him -- the Kracht group.

C/2002 P3 (SOHO) is not only an unanticipated milestone for the
mission, but whereas most near Sun comets are of the Kreutz
family, C/2002 P3 (SOHO) is a member of a family of comets
called the Meyer group. The Meyer group is one of three new
families that have been discovered with SOHO data. A comet
family is a group of comets that originated from the same place
and follow the same path. C/2002 P3 (SOHO) has a perihelion
distance of 5.37 million km from the Sun.

"We don't yet know much about this family, or the other new
families," said Dr. Doug Biesecker, the head of SOHO's comet
discovery program stationed at NASA's Goddard Space Flight Center
and a solar physicist with L3 Com Analytics Corporation. "With
such few known members of this family, we need every additional
comet we can get."

The use of SOHO as a tool to discover comets is a byproduct of
the mission's original purpose -- to continuously monitor solar
weather and assist scientists in analyzing how the Sun functions.
The Large Angle and Spectrometric Coronagraph (LASCO), one of the
instruments on SOHO, blocks out the Sun to create an artificial
eclipse and then views the space around the Sun, looking for
outbursts of solar activity. This eclipse allows the Sun's faint
outer atmosphere (corona) to be seen and studied.

Like the corona, comets that would usually be lost in the glare
of the Sun unexpectedly come into LASCO's field of view. Almost
all of them end up vaporized in the solar atmosphere. In spite
of the fact that the SOHO Kreutz family comets tend to be only
10 meters in diameter, they are fragments of a comet that was
originally much larger, maybe 100 km in diameter. This is so
large, in fact, that it might have been visible during daylight
more than 2000 years ago.

"Though LASCO was not originally built for this purpose, no
other instrument has discovered more of these comets," said Dr.
Bernhard Fleck, ESA Project Scientist for SOHO stationed at
Goddard. "It was a wonderful surprise, of the kind we get in
science sometimes."

For more on SOHO, including links to the SOHO page and more
information about the SOHO 500 Comet Contest, visit:
     http://www.gsfc.nasa.gov/topstory/20020815comet500.html

*****

ESA Science News
http://sci.esa.int

15 Aug 2002

SOHO discovers 500th new comet

On Monday 12 August 2002, about 16.05 UT, ESA's SOHO spacecraft
spotted its 500th comet as the comet passed close to the Sun.

It seems a little strange that SOHO, designed to examine the Sun,
should turn out to be the most productive cometfinder in the
history of astronomy, and by a very wide margin. We interviewed
ESA's project scientist for SOHO, Bernhard Fleck, about that.

"Congratulations on the comets -- but what's SOHO's job supposed
to be?"

"To watch the solar weather, 24 hours a day. To find out how the
Sun works, all the way from its hot core, through its stormy
surface, to the solar wind that buffets the Earth."

"Don't all these comets ever distract you from those vital tasks?"

"Not at all. They turn up by chance in pictures we gather for
quite different reasons. An instrument called LASCO (Large Angle
and Spectrometric Coronagraph) routinely monitors a huge region
of space around the Sun, watching for its eruptions. Most of
SOHO's comets have simply flown unexpectedly into LASCO's field
of view."

"But they must mean a lot of extra work for your team, surely?"

"Again, no. Just one team member, Doug Biesecker, runs our comet
discovery programme at SOHO headquarters. But more than 75% of
the discoveries have come from amateur comet hunters around the
world. To me, that's the most exciting aspect."

"How do you involve the amateurs? "

"It's very simple. Since 1999, up-to-date SOHO-LASCO pictures
have been available to anyone on the Internet. Take a look
yourself. But it's best if you know something about the subject,
otherwise you may be misled by odd white flashes due to cosmic
rays. And remember you'll be competing with people who spend
several hours a day searching the latest images."

"Who are these people?"

"They live all over the world. Confirmed discoveries of comets
have come from Australia, Canada, China, France, Germany, Italy,
Lithuania, Russia, the United Kingdom, and the United States."

"Have any individuals done especially well?"

"The biggest tallies have come from Mike Oates in England, Rainer
Kracht in Gemany who found SOHO-500, and Xavier Leprette in
France. They went back over pictures from 1996-99 and found dozens
of comets that the professionals had overlooked. Mike Oates runs
an electroplating business in Manchester, but thanks to SOHO and
the Internet he is also the highest-scoring discoverer of comets
ever, with 136 to his name."

"Did you expect all these comets to show up, when you were
planning SOHO?"

"Not at all. They were a wonderful surprise, of the kind we get
in science sometimes. I remember the possibility being mentioned
when we were preparing the spacecraft that we might discover one
or two comets each year. We had two comet experts on the original
science team, Philippe Lamy from Marseille and Jean-Loup Bertaux
from Paris. Philippe was in charge of the design of the LASCO C2
coronagraph. Jean-Loup is responsible for the French-Finnish SWAN
instrument on SOHO, which studies the solar wind by its effects
on hydrogen atoms all across the Solar System. Jean-Loup expected
SWAN to see dense clouds of hydrogen around big comets discovered
by other people. Sure enough, it did and Comet Hale-Bopp in 1997
had the biggest cloud ever seen, 100 million kilometres wide.
But now SWAN has also discovered a couple of comets for itself."

"What was so surprising about the hundreds of SOHO-LASCO comets?
Did you learn something new?"

"Yes, we found out that comets can be both extremely large and
extremely small. Nearly all of the SOHO discoveries are what we
call sungrazers. They hit the Sun's atmosphere and disappear.
They are quite small, typically only about 10 metres in diameter.
And most of them come from the same direction in space, because
they're fragments of a really huge comet."

"How do you know that?"

"Big fragments were seen by the ancient Greeks, more than 2000
years ago. The original comet must have been enormous to create
so much debris -- probably more than 100 kilometres in diameter
and well visible even during daylight. And quite scary really,
if you think what damage a comet like that could do if it ever
hit the Earth."

"Is SOHO-500 part of that debris?"

"As a matter of fact it's not. Just this year, among the SOHO
comets, we've discovered three smaller families of near-Sun
comets, each with different orbits: the Meyer, Marsden, and
Kracht groups. Kracht's SOHO-500 belongs to Meyer's group. The
experts are busy trying to work out where these new families
came from."

"So the story isn't over yet?"

"In science, you never know what you'll discover tomorrow. That's
why we enjoy it!"

Note:

Rainer Kracht of Elmshorn in Schleswig-Holstein, Germany, spotted
a small object in an image from SOHO received via the Internet.
It has been officially confirmed as Comet 2002 P3 (SOHO). It is
the 500th comet discovered with the ESA-NASA solar spacecraft and
it made its closest approach to the Sun at 16:05 UT on Monday,
12 August 2002. Diane McElhiney won a contest run by the SOHO
science team for guessing that date and time for SOHO-500. Her
prediction was too early by only 103 minutes.

SOHO Project Scientist Bernhard Fleck received his PhD in physics
in 1991 from the University of Würzburg, Germany. In 1993 he
joined ESA's Space Science Department at ESTEC in Noordwijk, the
Netherlands, to work on the SOHO project. With the launch of SOHO
in December 1995 he moved to the SOHO operations centre at NASA's
Goddard Space Flight Center in Greenbelt, Maryland. His main
research interests include the dynamics of the solar atmosphere,
in particular, wave propagation characteristics in the
chromosphere.

USEFUL LINKS FOR THIS STORY

* SOHO home page
  http://sci.esa.int/home/soho/
* SOHO science web site
  http://sohowww.nascom.nasa.gov/
* SOHO-500 Comet Contest
  http://soho.estec.esa.nl/cometcontest/
* SOHO 500 moving gif
  http://sungrazer.nascom.nasa.gov/soho500_movie.gif
* SOHO Sungrazers
  http://sungrazer.nascom.nasa.gov/

IMAGE CAPTIONS:

[Image 1:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=14&cid=12&oid=30392&ooid=30394]
SOHO Project Scientist Bernhard Fleck received his PhD in physics
in 1991 from the University of Würzburg, Germany. In 1993 he
joined ESA's Space Science Department at ESTEC in Noordwijk, the
Netherlands, to work on the SOHO project. With the launch of SOHO
in December 1995 he moved to the SOHO operations centre at NASA's
Goddard Space Flight Center in Greenbelt, Maryland. His main
research interests include the dynamics of the solar atmosphere,
in particular, wave propagation characteristics in the
chromosphere.

[Image 2:
http://sci.esa.int/content/searchimage/searchresult.cfm?aid=14&cid=12&oid=30392&ooid=30395]
Comet C/2002 P3, also known as SOHO-500. Comet C/2002 P3 (SOHO-500)
discovered in LASCO C2 images on 12 August 2002.
Received on Thu 15 Aug 2002 12:38:56 PM PDT