SOHO/Near-Sun Comet News and Views
This newslog will focus on sungrazing and near-sun
comets, as well as any comets observed in the SOHO (Solar and
Heliospheric Observatory) LASCO coronagraph images, though I will also
include important news items of general interest regarding comets.
November 22, 2006
I'm sorry that it's been so long since I last updated these
pages. Shortly after my previous report I had to have Windows
reinstalled on my machine, which wrote over my old applications,
including the Web design program I'd been using (Arachnophilia). I had
been hoping to switch programs as Arachnophilia is quite primitive
(even with it, I do most of the coding myself by hand) and tried a
couple of new ones, but couldn't find one with which I could make good
tables, and then I became too busy to experiment. For the moment, I'm
back with Arachnophilia--If anyone knows of a good, freeware or
inexpensive Web design program, please let me know. I will try to keep
these pages updated more regularly.
With Karl's latest round of confirmations, the SOHO comet count is up
to 1225. The most spectacular SOHO comet found in the past couple of
months was a very bright Kreutz, one of the brightest ever seen in
SOHO. I found a double Kreutz on November 20 UT, and a Meyer comet a
month ago; most of the other comets found lately have been single
Kreutz comets, mainly in C2. The Stereo/SECCHI mission was launched,
and Karl says that eveerything is going well with it; we'll probably
see the first images from it in January.
September 26, 2006
For nearly a month, up until last week, SOHO went through a
that drastically reduced SOHO's image coverage. Between August 4 and
September 18, only two SOHO comets were found, a Meyer-group comet by
Hua Su on September 2, and a C3 Kreutz by me on September 11. I found
the C3 Kreutz after a gap in images; it was obvious, even though still
near the edge of the C3 field, so it had the potential to become
brilliant. Unfortunately, it was only visible in seven images after
which there was a long data gap, so we'll never know how bright it got.
On September 18, Rob Matson found an amazing five realtime SOHO comets,
all visible in both C2 and C3. This included one close pair, and
another pair in which one comet followed the other by a few hours. (I
actually reported the trailing member of the second pair in C3,
thinking it was a new comet, but it turned out that Rob had already
reported it in C2, thinking it was the entry of the leading member of
the pair, which he had already reported in C3.) An amazing day for SOHO
comets, and for Rob.
August 17, 2006
Rob Matson, co-discoverer of Comet 2006 M4 (SWAN), was the
first to detect the comet in C3. The comet is still very faint (it's
amazing that Rob was able to detect it), but it should brighten in the
August 12, 2006
Comet 2006 M4 (SWAN), discovered nearly a month ago in SOHO's
SWAN images by Rob Matson and Michael Mattiazzo, should be in the C3
field by now (at the extreme lower left), but it hasn't been reported,
so it is presumably still too faint. Hopefully that will change as the
comet approaches perihelion; it will remain in the C3 field for more
than two weeks, finally exiting to the upper right around August 28. It
will pass through C2 from August 19-23, but due to SOHO being in the
middle of a keyhole period, image coverage may be greatly curtailed.
Karl Battams has prepared finder charts for both C3 and C2.
(See his news page for August 1).
On August 9, Karl posted confirmations for six SOHO Kreutz comets. This
included the first SOHO comet by Shihong Yuan of China (a nice object
visible in both C3 and C2, the only C2-visible comet of the current
confirmations) and the first 3(!) SOHO comets for Arkadiusz Kubczak of
Poland, includiing the 100th SOHO Kreutz comet (SOHO-1185)! The two
other comets in this batch were found by Hua Su, who also--since my
last update--found a companion to the bright Kreutz he found on July
25--both components were visible in C2 as well as C3.
Among the asteroid namings in the Minor Planet Circulars of August 6
was one for an object of particular significance to me, a main-belt
asteroid about 2km in diameter with the name 112900 Tonyhoffman. Many
thanks to Rob Matson for this great honor. Rob found the minor planet
in NEAT images from Mt. Palomar taken in 2002. Here is an orbital diagram.
The asteroid is currently near opposition in Capricornus and is about
magnitude 20. This would seem to be the 7th asteroid named for a SOHO
comet discoverer; others include 4730 Xingmingzhou, 73491 Robmatson,
68946 Mikeoates, 51983 Honig, 52005 Maik, and 35461 Mazzucato.
July 25, 2006
Today, Hua Su became the fourth SOHO hunter to find 100
comets by finding a C3 Kreutz comet, less than two years after his
first discovery. His latest was found well away from the sun and has
the potential to become rather bright. Hua has found five C3 comets in
the past two weeks; his discovery of July 23 was also visible in C2
July 23, 2006
Today, Hua Su found a Kreutz comet in C3. Hua also found C3
comets on July 20 and 21; neither of them were visible in C2. Hua's
latest comets brings him to 99 by my count; one more and he will join
Rainer Kracht, Michael Oates, and Xavier Leprette as the only people to
have found 100 SOHO comets. The twin STEREO solar observatories are now
scheduled for launch in late August and should be fully operational
(and presumably discovering comets) a month or two after that.
According to Karl Battams, though, many if not most of the near-Sun
comets will continue to be found in SOHO images; although STEREO is
more sensitive and has a wider field of view, its images will be posted
once a day while SOHO's will still be released in real time.
July 19, 2006
Today, Karl Battams confirmed five SOHO comets that I
mentioned in my last report, bringing the total to 1,174. It includes
the SWAN comet, but not the C2 Kreutz comet that I found on July 14. It
was only visible in 3 positions, so it becomes an X/comet.
Karl also mentioned (in the Yahoo Sohohunter group) that the launch
date of NASA's STEREO mission has been pushed back to no earlier than
August 20. STEREO will consist of twin solar observatories, one
positioned ahead of the Earth and the other behind it, taking images at
the same time to create 3D pictures of the solar corona, CMEs--and
comets. Its detectors will be more sensitive than SOHO's, and the field
of view wider, but the images will only be made available once a day en masse, so it's likely that SOHO will still find its share of near-Sun comets.
July 17, 2006
Rob Matson and Michael Mattiazzo have co-discovered a comet
in images from SOHO's SWAN (Solar Wind Anisotropies) instrument. At
just 12th magnitude, C/2006 M4 SWAN is just barely visible in SWAN
images. It was confirmed by Rob McNaught and other ground-based
observers, and a prediscovery image of it was found by Terry Lovejoy.
According to the orbit published in an MPEC on July 15, it will reach
opposition on September 28. It should brighten to about 8th magnitude
in September and October when it will be well placed in the evening sky
for Northern Hemisphere observers. It should be visible in LASCO C3
from about August 11 to August 28, and in C2 between August 18 and
August 23. We're looking forward to a good show.
The past week has seen several Kreutz comets. Steve Farmer found a
faint C3 Kreutz comet on July 11 that was nonetheless visible in C2. On
July 13, Hua Su found a C3 Kreutz. On July 14, I found a faint C2
Kreutz, though I can only make it out in 3 positions, so it probably
won't be confirmable unless it's visible in C3. On July 14, Wentao Xu
found a moderately bright C3 Kreutz that was also well seen in C2. And
on July 17, I found a faint, slightly elongated C3 Kreutz--it is my
75th SOHO comet (unless I get credit for the July 14 C2 Kreutz).
July 10, 2006
Sorry for the delay in updating; I'd been traveling quite a
bit over the past couple of weeks. Several new comets, all C2 Kreutz
have been found since my last update. On June 19 I found an obvious
(though not bright) and fairly condensed Kreutz comet in delayed C2
images. Hua Su found one on June 22, and two on June 27, one of which
was a co-discovery with Tao Chen, who reported it 6 seconds earlier. It
has been two weeks since any SOHO comets have been found.
On June 27, Brian Marsden and I were presented with a popular writing
award from the solar physics division of the American Astronomical
Society for the article we co-wrote on SOHO comets that appeared in the
August 2005 issue of Sky and Telescope. It is one of two awards that are
presented each year by the solar physics division for articles that
help popularize some aspect of solar or heliospheric study. Brian and
his wife drove up from Massachusetts, and I drove up from New York, to
accept the awards at the solar physics division's annual meeting in
Durham, New Hampshire.
June 10, 2006
Since LASCO came out of safe mode three days ago after SOHO
was flipped, three new SOHO comets have been found, all quite faint C2
Kreutz comets. Hua Su found an especially faint one on June 8. Guoyou
Sun found another, also in images of June 8, then I found another one
today in delayed images. I would like to dedicate this discovery to my
mother, who died unexpectedly three weeks ago, a day after suffering a
massive stroke. Thanks to me, she probably observed more comets than
many astronomers, and she was always impressed by the things I was able
to find and intrigued by what I'd tell her about the latest advances in
astronomy. She was a great lover of nature.
June 2, 2006
I'm sorry, I missed one congratulation in my previous post:
to John Sachs, for passing the 50-comet mark. Gouyou Sun found his 4th
SOHO comet in C2 on June 2. Karl confirmed 10 more comets, including
many of those mentioned below and also a non-group from December 1999.
May 25, 2006
Several congratulations are in order: to Gouyou Sun, for
finding his first three SOHO comets(!), to Luciano Cane, for finding
his first, and to Rob Matson, for passing the 50-comet milestone. Karl
Battams confirmed 10 more comets on May 23, including two by Rob Matson
(two more since then has brought his total to 51), four by Hua Su
(including a faint C3 non-group comet visible above Venus in nine
images from May 22), one by Wentao Xu, one by Bo Zhou, Luciano Cane's
find and the first of Gouyou Sun's three comets. One of Hua Su's and
one of Rob Matson's Kreutz comets were visible in C3 as well as C2; the
rest were C2 only. Since then, in addition to the other comet I mention
above, Tao Chen found a C2 Kreutz.
Funding for the SOHO mission
has been extended until 2009.
By that time it should be one of a fleet of solar observatories, including Japan's Solar-B, ESA's Proba-2,
and NASA's STEREO and Solar Dynamics Orbiter.
May 13, 2006
Yesterday, Karl Battams confirmed eight comets, all found
between May 8 and 11--the spring "comet storm" season for C2 Kreutz
discoveries is in full swing. Karl found a C3 Kreutz comet in delayed
images on May 8 that got bright and was well seen in C2 as well. Also
on that day, Hua Su found a Meyer comet tracking almost vertically to
the left of the Sun in C2. Rob Matson and John Sachs also jointly found
a C2 Kreutz that day; they reported it 16 seconds apart. Another joint
C2 Kreutz discovery was made on May 10; Hua Su and Tao Chen reported
the comet just two seconds apart! That same day, I reported a double
comet, two small, round, relatively faint Kreutz comets, the fainter
one closely trailing its slightly brighter companion. On May 11, I
found another C2 Kreutz, small, round, and diffuse, with just a hint of
a tail. Half a day later, John Sachs found a similar C2 object.
This recent active period for SOHO discoveries was preceded by a more
than a month of relative quiet. Since my last report, Hungarian amateur
Adam Ambrus found his first SOHO comet, a Kreutz that was well seen in
C3 and later in C2. On April 28, Hua Su and John Sachs reported a C3
Kreutz 20 seconds apart; it was also seen in C2. The other comets found
during that period were all C2-only Kreutz objects, four by Hua Su, one
by Karl Battams, and one by me.
April 15, 2006
Yesterday, John Sachs reported a C2 Kreutz comet; Hua Su also
reported it less than a minute later. It was moderately bright and had
a short tail. Early on the morning of April 11, I found a C2 Kreutz
comet; it was faint, round, small, and diffuse. The LASCO site is down
for the weekend; I don't see any new images on the Nascom site, either.
March 31, 2006
Two days ago, Karl Battams confirmed five comets; my recent
Marsden and Meyer finds, plus an archive Kreutz from June 1998 found by
Rainer Kracht, a faint C2 Kreutz found by Rob Matson on March 28, and a
bright Kreutz found by Hua Su on the morning of March 29 when still
very near the edge of the C3 field. (though bright, it remained largely
stellar in appearance in C3 and showed a faint, narrow tail in C2.)
New MPECS have been published, for 6 Kreutz plus 1 Meyer from January,
plus the two recent Marsden comets. The orbit of C/2006 A5 (SOHO), or
SOHO-1087, the very bright Kreutz comet that was visible in SOHO in
early January (see its image at the top of this page) is of particular
interest as its published perihelion distance (0.0043 AU) is smaller
than the Sun's radius (0.00465 AU), meaning that if the orbital
elements are correct, the comet was on a collision course with the sun,
though it seemingly vaporized shortly before impact. The comet, still
bright as it entered the C2 field and trailing a narrow, straight tail
that eventually stretched across the entire field, faded rapidly as at
approached the Sun at more than 700,000 km/hr,until finally it was all
tail, with no discernable head. The last data point used to calculate
the orbit was only about 80 minutes before perihelion. Only about 6
SOHO comets have had published orbits that indicate they might be
sunstrikers; however, Brian Marsden has emphasized that there is a lot
of uncertainty in the orbits due to their short observational arcs and
the relatively low resolutions of the SOHO coronagraphs (11 arc-seconds
in C2 and nearly an arc-minute in C3), and it's likely that some comets
with published sunstriker orbits weren't sunstrikers, and vice-versa.
SOHO-1087, however, was observed in about 60 positions, so its orbit is
perhaps more accurate than many of the others. Karl Battams also
reported that SOHO-1087's peak recorded brightness was between
magnitudes 0 and -1 when it was around 11.5 solar radii from the Sun.
It became even brighter, and peaked at around 10 solar radii from the
Sun, but its brightness couldn't be measured due to a software bug;
Karl thinks it peaked at around magnitude -1.5. There may have been
five or six SOHO Kreutz comets that reached a similar or greater
March 26, 2006
I found an apparent Marsden comet in the early UT hours today
(last night, New York time). It was visible in 6 images, the first 4
separated from the final 2 by an hour's gap. It will be interesting to
see if this comet and the one found by Rob Matson can be shown to be
returns of Marsden comets seen in February 2000, but there may not be
March 22, 2006
Tonight I reported what appears to be a Meyer comet, cutting
across the upper left corner of the C2 field. It's only visible in four
images so far, after which there's a gap-- hopefully the remaining
images will come up later.
Today, Karl Battams announced eight new confirmations, bringing the
SOHO count up to 1116. These included the recent comets found by me (on
March 15, Michele Mazzucato, Rob Matson, and Hua Su, plus four more
archival discoveries from 1997-98 by Rainer Kracht: two Kreutz
(including a C2 Kreutz that was relatively bright), a Meyer, and a
small, stellar-looking C2 non-group comet.
March 21, 2006
This morning, Michele T. Mazzucato reported a faint C3 Kreutz
comet, a small splotch just out from the left edge of the pylon.
Congratulations are in order, as this is Michele's first SOHO comet.
March 16, 2006
Yesterday, Rob Matson found a very faint Marsden comet in C3,
climbing almost vertically to the left of the Sun, in images from the
early hours UT of March 15. (Because of image gaps, the only available
C3 images showing the comet are between 0218 and 0842 UT on March 15.)
It's possible that it is also seen exiting the top of the C2 field in
images of 0048 and 0100 UT; hopefully the earlier images will become
available at some point.
March 15, 2006
At long last, I have updated all the totals of comets that
Karl has confirmed. The official count is up to SOHO-1106, with two yet
to be confirmed; I found one of them tonight, the first C2-only Kreutz,
it would seem, of the year. One of Rainer's archive comets was a Meyer,
as was a realtime discovery by Hua Su.
January 10, 2006
Yesterday, I found a faint and condensed (stellar-looking) C3
comet, visible intermittantly in about 8 images before I reported it.
It came on an unusually high arc from the left; I suspect it may have
been Subgroup II. It was visible in more than 20 C3 images, but
apparently not in C2. This is presumably SOHO-1088.
SOHO-1087 is being featured as the
Pick of the Week
on the SOHO Web site.
January 5, 2006
Yesterday's C3 comet got very bright as it neared the sun,
and its tail grew to be over a degree in length. It was well seen in
C2, too, with a straight and narrow tail that ultimately extended from
the edge of the C2 field to the occulting disk. This will be SOHO-1087.
January 4, 2006
Last night, I found a C3 Kreutz comet after an image gap, in
images from early January 4, UT. Though near the edge of the field, it
was obvious, small and condensed. It quickly brightened as it climbed
towards the Sun, to the left of the Sagittarius Milk Dipper, which is
visible in C3. Today it has gotten very bright, with a tail of about
1/2 degree in length.
January 3, 2006
Yesterday, Rob Matson found the first SOHO comet of 2006, a
faint C3 Kreutz that was also visible in a few C2 images. Karl Battams
confirmed it, along with three archival Kracht comets from December
5-6, 1996 (including the two aforementioned bright ones) and three
archival C2 Marsden comets from January 29, 1997, all found by Rainer
For 2005, Hua Su led all SOHO hunters with an extraordinary 55 realtime
comets ( + 1 archival find). The year's 7 new SOHO comet discoverers
were all Chinese, Yuan-Tseng Tsai (who discovered a very bright Kreutz
at the beginning of 2005) from Taiwan and the others from mainland
China: Chong Liang, Jinao Zhang, Tao Chen, Quanzhi Ye, Wentao Xu, and
JianGao Ruan. The latter two discovered their first comets within 5
minutes of each other, the two components of a "twin" pair of C3
comets. In addition, two SWAN comets were discovered, C/2005 P3 (SWAN),
found by Hirohisa Sato, Masayuki Suzuki, Michael Mattiazzo, Michael
Jäger, and Vladimir Bezugly and C/2005 T4 (SWAN), found by Michael
Mattiazzo and Rob Matson. Both SWAN comets were briefly visible in the
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