Dear All

Given that we are all getting very excited about reaching a certain milestone, I wanted to post a couple of comments about recent reports, and in particular about the non-group and Marsden comets over the past few days.

First, I will begin by noting that I was unable to confirm Masanori's report from March 10, 2024. I saw something there for a few points but it disappeared very quickly. There was also nothing visible in HI-1, and all the recent Kreutz have been in that field of view. So that supports my conclusion that this was not a real comet, but instead just well-placed noise.

Now on to slightly more confusing matters...

Jiangao recently made two C3 non-group comet reports, the first on March 22, then a second on March 23. These are certainly real comets.

Then Hanjie reported two Marsden group comets in C2, the first report on March 23, and then this morning (March 25). Both are also real comets. But I can tell you, for certain, that Hanjie's first report is the same comet as Jiangao's first comet. The below image demonstrates it quite clearly. I was able to visually follow the comet in C3 all the way to the C2 field of view, so there is no doubt here.

This is a type of plot we call "height-time", which plots the apparent distance of the comet from the Sun ("height") in units of solar radii, against the observation time. The arc of the plot points shown here is very typical what we see for most non-Kreutz comets. You can see the perfect alignment and timing between Jiangao's C3 observations, and Hanjie's C2 observations (circled in blue). So there is no debate here -- they are the same comet.

For Jiangao's other report, things are less clear. It is on a slightly different trajectory to the earlier report, and I lost sight of it around 18:30UT on Mar 23. Hanjie's recent C2 object is visible from ~03UT on March 25. As you can see from the height-time plot below, if I put both sets of observations on the same axes, there is a large gap in time and a very large "?".

The blue line I drew could be correct, meaning these are the same comet. But it could also be incorrect, and these are two different comets. [EDIT: as shown in this, which is again just another hand-drawn possibility.] Right now I simply do not know, and of course the answer to the question will be extremely important in telling us where we are regarding SOHO comet numbers... The good news is that we can use orbit calculations to tell us with confidence if these are the same comet or not. We will hopefully have that answer soon. We will also make sure (as best we can) that none of these comets are the return of "known" SOHO comets from the past. (This was definitely not an ideal time for the comet discoveries to become complicated, but that's why we love them!)

I know many of you were expecting a big announcement, given how many 'endorsed' reports we have had lately. But that announcement will need to wait. in the meantime, you should all certainly keep searching for comets!

As always, please email me with any questions, comments, corrections, etc.

Karl