[Friends_of_SSASTROS] Is Tsuchinshan Already Dying?

[Mike McCabe]

Greetings Members and Friends of the SSAS,
A little over a month ago I sent out an email on the topic of comet C/2023 A3 Tsuchinshan-Atlas about how preliminary estimates showed it possibly brightening into the negative-magnitude range in early October. Well, it appears that things might be changing. But first, a little side diversion;
I've long posited that comets need to have cool names no matter what, and that none of this clinical sky-survey garbage will do when an object has traveled as long and far as comets do just to visit us. I've even been known, on occasion, to rename them myself when they're assigned with unmemorable identifications like a prison number or something like that. So far the IAU has yet to spank me, so I guess we're all good. But this comet needs no name change. Tsuchinshan is totally awesome, but for the life of me I can't understand why not one offering has been made as to how to properly pronounce it! So, with the disclaimer that I'm no expert in linguistics, I will provide my wholly Americanized take on it; Sooch-In-Sharn. If we happen to have an authority in the group on Chinese names and how to pronounce them , I would sincerely appreciate any input on the rightness or wrongness of this interpretation. Thank you.
Now back to Tsuchinshan's performance. In mid April I posted its lightcurve as seen on the COBs (Comet Observer's Database) website;
In mid-April Tsuchinshan was still brightening steadily and was projected to go right past zero magnitude and into the super-bright realm of the negative magnitudes.
But my oh my what a difference a month can make;

At the beginning of May, Tsuchinshan essentially flat-lined and has leveled off at a brightness of about mag. 10.2 - 10.3 or so. What this means, as with all things to do with comets, is a mystery.
So, should we be writing off Tsuchinshan already? It's hard to say. Based on what we've seen so far, the comet should have brightened over the month of May. Back on April 16th it was at a distance of 1.98au from us (about 186 million miles) and today, May 28th, it stands 1.78au from us (so about 18.6 million miles closer) but it hasn't brightened at all during that period. That definitely has to make you wonder what's going on with it. Comets generally don't take naps in preparation for the big show. In fact comets are famously averse to any schedule whatsoever, but we love them anyway.

However, if a comet stays on course without breaking up, there are certain scheduled events that in spite of all their spontaneous I'll do what I want when I want behavior, even they can't avoid; if Tsuchinshan makes it, it is slated for a perihelion passage (closest to the Sun) on Sep28 of this year when it will come within .39au or 36 million miles of ol' Sol. If it survives that, it will then make its closest approach to Earth on Oct13, when it will pass withing .48au or about 45 millions miles from us.
The mainstream media, doing what mainstream media does, is standing pat on Tsuchinshan brightening to a potential naked-eye object in October, but interestingly, the articles I've been seeing have been adjusted to the 'new' projection of about magnitude 2 or so. Some are better than others. Here's one that seems fairly well grounded on the topic;
Bright comet headed toward Earth could be visible with the naked eye


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Bright comet headed toward Earth could be visible with the naked eye

The incoming comet Tsuchinshan–ATLAS might become as brilliant as Venus during its close approach to Earth this ...
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Keep Looking Up!
Mike M.
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