Asteroid in conjunction?

https://www.legacysurvey.org//viewer/?ra=345.1849&dec=2.5020&layer=hsc-dr2&zoom=15

It looks like there may have been an asteroid passing in front of this galaxy - the dark dot is not present in other layers.

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Would appear so. Kinda small for an asteroid in HSC, but I guess it could be a TNO or something. Also possible its a SN.

I guess if it were debris from a SN it would be present in other images too, which is why I think it’s perhaps an asteroid. It has about the right sort of declination to be one.

I was thinking more that we were seeing the explosion itself rather than debris. I suspect the HSC epochs were different to those of legacy, and SNe dont tend to last all that long, so its possible a SN would appear in HSC but not legacy (HSC goes deeper & higher res too).

Could definitely be an asteroid though. I might see if I can pull the single exposures from HSCLA.

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Wouldn’t a SN shine brighter than the galaxy itself rather than being darker?