9月10号晚上,我发现了一颗非同寻常的SOHO彗星!

http://www.nasa.gov/mission_pages/soho/soho_periodic_comet.html

SOHO Mission Discovers Rare Comet
Stuart Clark
European Space Agency
September 26,2007

The Solar and Heliospheric Observatory (SOHO) has discovered a rare
periodic comet. SOHO has already discovered more than 1,350 comets
during its mission, but this is the first time one of its discoveries
officially has been designated periodic.

Many of the comets SOHO has discovered are believed to be periodic,
meaning they follow their orbits around the sun more than twice and have
orbital periods of less than 200 years. Thousands of comets have been
seen by astronomers, but only around 190 are classified as periodic. The
most famous periodic comet is Halley's Comet, which returns every 76
years. It most recently passed close to the sun in 1986.

SOHO's new find has a much smaller orbit than Halley's Comet. It takes
the comet approximately four years to travel once around the sun. It was
first seen in September 1999 and then again in September 2003. In 2005,
German PhD student Sebastian Hoenig realized that the two comets were so
similar in orbit that they might actually be the same object. To test
his theory, he calculated a combined orbit for the comet and
consequently predicted that it would return on Sept. 11, 2007. Hoenig's
prediction proved to be extremely accurate -- the comet reappeared in
SOHO's Large Angle and Spectrometric Coronagraph camera right on
schedule and has now been given the official designation of P/2007 R5
(SOHO). Credit for the original discovery and recovery of the object
goes to Terry Lovejoy (Australia, 1999), Kazimieras Cernis (Lithuania,
2003) and Bo Zhou (China, 2007).

A puzzling aspect to P/2007 R5 (SOHO) is that it does not look exactly
like a comet. It has no visible tail or coma of dust and gas, as is
traditionally associated with the phenomena. Initially, this led some
scientists to wonder if the object was actually an asteroid, a chunk of
space-rock, rather than a chunk of space-ice. However, P/2007 R5 (SOHO)
did exhibit some characteristics consistent with a comet. As scientists
watched the object pass close to the sun, drawing to within 4.9 million
miles, or around 5% of the distance between the Earth and the sun, they
saw it brighten by a factor of around a million, which is common
behavior for a comet.

"It is quite possibly an extinct comet nucleus of some kind," says Karl
Battams of the Naval Research Laboratory, Washington, who runs SOHO's
comet discovery program. Extinct comets have expelled most of their
volatile ices and retain little to form a tail or coma. They are
theorized to be common objects among the celestial bodies orbiting close
to the sun.

This comet faded as quickly as it brightened, and soon became too faint
for SOHO's instruments to see. Estimates show that P/2007 R5 (SOHO) is
probably only 100 to 200 yards in diameter. Given how small and faint
this object is, and how close it still is to the sun, it is an extremely
difficult target for observers on Earth to pick out in the sky.

Now we know for certain that P/2007 R5 (SOHO) is there, astronomers will
be watching closely for it during its next return in September 2011.

SOHO is a cooperative project between the European Space Agency and NASA.

Stuart Clark
European Space Agency

************************
http://tech.groups.yahoo.com/group/comets-ml/message/12751

Sep 28 2007 17:00:55

Confirmations *** TO Sep 27 2007 13:09:27 ONLY ***:
Soho#  Date/Time of Post  Discoverer    Tel   Group  Images of..
==========================================
xc62  Aug29,07 10:37:16  B.Zhou         C3   Kreutz  Aug29,07
1352  Aug31,07 23:10:08  H.Su           C2   Kreutz  Sep01,07
1353  Sep08,07 10:33:22  H.Su         C3,C2  Kreutz  Sep08,07
1354  Sep09,07 19:09:34  B.Zhou         C3   Kreutz  Sep09-10,07
1355  Sep13,07 09:46:25  B.Zhou         C3   Kreutz  Sep13,07
1356  Sep17,07 09:15:06  A.Kubczak      C2   Meyer   Sep14-15,07
1357  Sep17,07 10:39:12  B.Zhou         C3   Kreutz  Sep16,07
1358  Sep24,07 08:58:42  M.Uchina     C3,C2  Kreutz  Sep23-24,07
1359  Sep26,07 14:52:00  R.Matson     C3,C2  Kreutz  Sep26-28,07
--
And, of course, we also have
SOHO-85=661 Sep10,07 18:10:41 B.Zhou  C2,C3 KrachtII Sep10-12,07 !!
--
Note that Bo's object from Aug29 has to go as an x-comet. The positions
do not line up with Hua's C2 Kreutz. In addition, it is not visible in
HI-1B (which it definitely should be) or COR2 (which is likely for an
object as bright as that should have been). So it can be an x-comet for
now.
--
Going back to P/2007 R5... I have two choices regarding SOHO numbers. I
can either vacate the SOHO-661 spot for the next archvie Kreutz to be
reported, or I can just stick with SOHO-85=661 and leave it at that.
(Note that I am NOT willing to reduce the SOHO comet number of comets
662 through 1359!). I think I will probably vacate 661 and give discovery
credit on the web page to Terry, Kazimieras and Bo. That sound OK to
everyone?
~~KB

October 11, 2007 -- Predicting revolutions...

Once again, SOHO comets have made headlines with the recent announcement of SOHO's first officially periodic comet, P/2007 R5! This discovery was due to the brain power of the highly succesful SOHO comet hunter Sebastian Hoenig, who first proposed that SOHO comets C/1999 R1 and C/2003 R5 were actually the same object, and Terry Lovejoy (Australia), Kazimieras Cernis (Lithuania) and Bo Zhou (China), who found the comet in our data at each of its respective apparitions in 1999, 2003 and 2007. Huge congratulations are due to all involved!

     This image (click for larger version) shows P/2007 R5 at each of its three observed perihelion passages in 1999, 2003 and 2007. You may note that the size, shape, brightness and location of the comet in each image is remarkably similar -- as expected, of course!

So this leads us to the question of just how many of SOHO's comet discoveries are actually periodic objects? Well, we know that the Kreutz comets are technically periodic but as we have never knowingly seen the same Kreutz comet twice (their orbital period is at least several centuries), we can't call them periodic. A more positive link is made amongst the Marsden and Kracht group comets. Here, we are quite confident that they are all related to 96P Machholz, and we even have some possible linkages between individual objects seen approximate five years apart in SOHO data. Admittedly, some of these linkages are made at a stretch but some also look quite compelling. (Maik Meyer has a good summary on his website of Kracht and Marsden comets and some of the proposed linkages.)

Recently, inspired by Sebastian's work, Rainer Kracht -- the reigning champion SOHO comet hunter! -- has been looking for new potential linkages within the Kracht group (guess who that group is named after...), and has made some very tentative predictions about possible returns of some of the Kracht objects next year (2008).

Rainer has been kind enough to share this work with us, and so with his permission, here is a list of his predictions for Kracht group comets next year:

Designation                   Possible return date:
C/2002 N2  (SOHO-501)    2008 Feb 12/13
C/2002 Q8  (SOHO-504)    2008 May 12/13
C/2002 Q10 (SOHO-505)    2008 May 16
C/2002 S4  (SOHO-519)    2008 Jun 28
C/2002 S5  (SOHO-520)    2008 Jun 30
C/2002 S7  (SOHO-522)    2008 Jul 03/04
C/2002 S11 (SOHO-526)    2008 Jul 22/23

Rainer used the free SOLEX program to calculate the orbits, making sure to incorporate gravitational influences of planets and, of course, the Sun, on the comets. Full documentation of Rainer's work can be found on his website. It should be noted clearly that these are simply rough predictions based on the limited observations we have of these objects and some basic assumptions about their orbits and behavior. As Rainer notes, "Some of them could be already too faint at their return in 2008 to be found again in the SOHO LASCO images. Some of them could fragment further with unknown consequences on their perihelion times.". We will have to wait until 2008 to find out for sure, but based on our current knowledge, it seems certainly seems likely that we should see a return of at least some Kracht group comets next year.

*********************
http://ares.nrl.navy.mil/sungrazer/index.php?p=latest_news

congratulations! for your hard work

November 2, 2007
--------------------------

I'm sorry it's been so long since I last updated these pages. I've made all the comet totals current. Of course, the big cometary news is the enormous outburst of Comet 17P/Holmes, which on and just prior to October 24 increased in brightness within a matter of days (if not hours) by nearly a millionfold  to become an easy naked-eye object in Perseus--it's been holding steady for the past week at about magnitude 2.2, and has emitted two expanding, concentric shells, the outer of gas and the inner of dust.

The big SOHO comet news in recent months was the return of SOHO's first official periodic comet, P/2007 R5, on September 10-11. The return of this comet, which is closely related to SOHO another comet (C/2002 R5), had been predicted by Sebastian F. Hönig. The comet was found by Bo Zhou, and it reached perihelion within about 4 hours of the predicted time! It had previously reached perihelion on September 5, 1999 and September 8, 2003, and had been found on those returns by Terry Lovejoy and Kazimieras Cernis, respectively.
*********************
http://home.earthlink.net/~tonyhoffman/SOHOnews.htm