September 21, 3006 — Quiet skies, stormy skies…

September 21, 3006 — Quiet skies, stormy skies…

The past few weeks have been very unusual for SOHO comets. August was a shockingly quiet month for comets. In fact, we went from August 4th to September 2nd without a single comet discovery! That’s one of the longest "dry spells" in recent years. The spell was eventually broken by a Meyer-group comet, found in C2 images by Hua Su. That comet was our first Meyer-group comet in nearly four months — another unusually long comet-free period. And when Tony Hoffman spotted a Kreutz-group comet on September 11, so ended a 38-day period with no Kreutz-group comets — yet another very uncharacteristically long "dry" time. But as we all know, when it has been dry for such a long time you have to expect a storm sooner or later, and two days ago we got ours…

It all began with a Kreutz group comet spotted by expert SOHO/LASCO (and SOHO/SWAN) comet hunter, Rob Matson, late at night on September 17th. Shortly after discovery, SOHO entered into a reasonably long data gap that lasted into most of the next day. During these data gaps, even though we do not have "real time" contact with the spacecraft, data from the instruments is recorded on board ready for downlinking at the next time of contact. I often give advice to comet hunters at times like this to watch the spacecraft contact times and await the influx of new data. Clearly, Rob was following this advice when the data began to flow because, in the space of 42 minutes and 14 seconds, he reported another four Kreutz comets in the LASCO C3 and C2 fields of view! By the time a few other comet hunters had rejoined the hunt, Rob had already cleared up. This was the first time that five Kreutz comets were visible in C3 in less than twenty-four hours, and certainly the first time a comet hunter has found five comets in such a short period. Congratulations, Rob!

Pictured opposite are three of the five aforementioned Kreutz comets (click for a larger image). The other two (SOHO-1189 and SOHO-1191) were a little way ahead of these, so I chose these three as a nicer image. You can see a short tail on SOHO-1190, and (even though it was the brightest of the five comets) a much shorter one on SOHO-1192. SOHO-1190 had no noticeable tail at all.

The official set of SOHO comet confirmations for the past couple of weeks looks as follows:

Soho#  Date/Time of Post  Discoverer   Tel   Group  Images of..
1186  Sep02,06 12:54:52  H.Su          C2   Meyer   Sep02,06
1187  Sep11,06 15:04:09  T.Hoffman     C3   Kreutz  Sep11,06
1188  Sep18,06 03:11:18  R.Matson    C3,C2  Kreutz  Sep18,06
1189  Sep18,06 17:01:56  R.Matson    C3,C2  Kreutz  Sep18-19,06
1190  Sep18,06 17:04:52  R.Matson    C3,C2  Kreutz  Sep18-19,06
1191  Sep18,06 17:12:05  R.Matson    C3,C2  Kreutz  Sep18-19,06
1192  Sep18,06 17:44:10  R.Matson    C3,C2  Kreutz  Sep18-19,06

So, as you can see, SOHO is now up to 1,192 comet discoveries!

PS:the original text is taken from here: Latest News and Information.

September 21, 3006 — Quiet skies, stormy skies…

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