C/2023 A3 (Tsuchinshan-ATLAS) spectrum

[Rob_K]

Here's a rough spectrum I took of this comet this morning. It is showing dominance of continuum (sunlight reflection off dust) with little or no sign of gaseous C2 emissions, i.e. a VERY dusty comet. It also has a sodium emission (marked) which should increase in strength as the comet approaches perihelion. I couldn't graph it as my software (RSpec) won't open on my new laptop. Have to sort that out!

The comet is still a reasonably difficult get in morning skies and with a bright Moon. But it's coming along nicely!

Cheers -

[joshman]

Very nice. I'm really not familiar with the spectroscopy side of things, what's the implication of it being more dusty than gaseous?

[Rob_K]

Thanks Josh. The dustier the comet, the brighter the post-perihelion display when forward-scattering of light comes into play. With my gear, I can only get spectra of bright comets but I’ve managed to do lots over the years and this is the dustiest spectrum that I’ve ever obtained.

Cheers -

[joshman]

So this would seem to indicate that it could end up being somewhat spectacular?

[Rob_K]

Yes and no! This comet is predicted to get very bright (minus magnitudes) when forward-scattering kicks in, but it will be very close to the Sun during this phase of its passage. So only the dedicated, well-prepared & experienced observers may be able to see it. Obviously there are risks to both people & equipment in trying to observe an object so close to the Sun. By the time it moves away from the Sun sufficently to observe in dark skies, it will still be a really nice bright comet, but not spectacularly bright. Of course it does have to survive perihelion but all the latest indicators have it at a size that should easily survive.

Cheers -

[foc]

Being a beginner SA 100 imager, I am surprised to see a comet image with little C2 but such a bright Sodium line. I am quite keen to see your next version with less moon and hopefully sun noise, and when our difficult weather allows

[Rob_K]

Thanks Ross. As I said earlier, this shows more dust than any bright comet I’ve been lucky enough to obtain a spectrum of, surpassing C/2011 L4 (PANSTARRS). That comet showed bright continuum but also had small C2 peaks rising from the curve. And it had a very bright sodium emission!

Comets come with a full range of dust/gas ratios and some of the gassy ones show very little continuum. The ‘serious’ amateur spectroscopists tend to remove continuum to target emissions and that’s fine, but I’m happy to do the easy yards which just characterise a comet.

Cheers -

[astronobob]

Interesting Rob, you saying being a dusty comet, I mentioned in other threads that this comet seems to have a very smooth tail, ,,, I assume the dusty particles being smaller would create the smoother look, who knows maybe, definitely no larger fragments dislodging and creating streamers and break-offs etc ..
I also assume the Sodium is not of the Salty flavour ;)
Good work bloke.