Bright, young supernova now visible in M101

When a massive star dies, it goes out with a bang, creating a stunningly bright explosion that can temporarily change the look of the night sky. The brightest and closest may be visible with the naked eye, but even those in distant galaxies can be easily spotted with amateur equipment from your backyard. And now, just such an opportunity has appeared: A supernova just went off in the nearby spiral galaxy M101 (NGC 5457) and you can find it tonight in the sky.

Tau.Neutrino said:

Bright, young supernova now visible in M101

When a massive star dies, it goes out with a bang, creating a stunningly bright explosion that can temporarily change the look of the night sky. The brightest and closest may be visible with the naked eye, but even those in distant galaxies can be easily spotted with amateur equipment from your backyard. And now, just such an opportunity has appeared: A supernova just went off in the nearby spiral galaxy M101 (NGC 5457) and you can find it tonight in the sky.

Yes. I noticed that. This nearby galaxy has had more supernovas than any other nearby galaxy. Supernovas occur there more often than in the Milky Way, Andromeda and Magellanic clouds. This one is a Type II supernova, so we should be easily ably to pick out the progenitor star, the Hubble telescope has already taken detailed images in a thorough survey of this galaxy.

The previous one in this galaxy has a progenitor described as follows:

“ On the Nature of the Progenitor of the Type Ia SN2011fe in M101

The explosion of a Type Ia supernova, SN2011fe, in the nearby Pinwheel galaxy (M101 at 6.4 Mpc) provides an opportunity to study pre-explosion images and search for the progenitor, which should consist of a white dwarf (WD), possibly surrounded by an accretion disk, in orbit with another star. We report on our use of deep Chandra observations and Hubble Space Telescope observations to limit the luminosity and temperature of the pre-explosion WD. It is found that if the spectrum was a blackbody, then pre-SN WDs with steady nuclear burning of the highest possible temperatures and luminosities are excluded assuming moderate n H values, but values of kT between roughly 10 eV and 60 eV are permitted even if the WD was emitting at the Eddington luminosity. This allows the progenitor to be an accreting nuclear-burning WD with an expanded photosphere 4-100 times the WD itself, or a super-critically accreting WD blowing off an optically thick strong wind, or possibly a recurrent nova with luminosities an order of magnitude lower than Eddington. The observations are also consistent with a double degenerate scenario, or a spinning down WD that has been spun up by accretion from the donor.”

In other words, we don’t know what it was, but it wasn’t what we expected – ie. it ain’t a normal white dwarf, with or without an accretion disk.

The new one comes with “a possible progenitor star, weighing in at some 15 times the mass of the Sun”.

https://www.astronomerstelegram.org/?read=16042

“Spitzer constraints on pre-explosion variability of the SN 2023ixf progenitor … the SN star field was serendipitously imaged at many additional epochs between 2012 and 2019 by Spitzer”. The possible progenitor star “does not exhibit significant flux changes in the preceding ~20 yrs before the explosion (which, if would be detected, could be an indication of pre-explosion eruptive mass-loss processes, if this object is the progenitor) … circumstellar dust may be a factor”.

In other words, we don’t know what the progenitor of this new supernova is either, but it wasn’t what we expected.

In other words, astrophysicists still know sweet FA about the causes of supernovas. A chastening thought.