Bright Supernova Blazes in M101, the Pinwheel Galaxy

Updates:

The Gemini North Telescope, which just came online again after a refurbishment of its primary mirror, has obtained a stunning image of the supernova:

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I heard the news about a magnitude-14.9 supernova in the galaxy M101 in Ursa Major on Friday evening, May 19th. That same night, a major auroral display lit up the sky here in northern Minnesota. Although the lights were spectacular, I couldn't wait to get my eyes on the new star. As soon as the aurora faded back, I set the telescope up for a look.

Never mind 14.9. The star had skyrocketed to magnitude 13.5 just 11 hours after discovery. It continues to rise. As of Sunday night, May 21st, it had climbed to magnitude 11.1 and showed no signs of stopping. In the space of a weekend, the supernova became within reach of a 4.5-inch telescope!

Superstar supernova hunter Koichi Itagaki discovered the new object, designated SN 2023 ixf, on May 19.7 UT, immediately southwest of the prominent HII region NGC 5461. The pair contrast splendidly in one of the galaxy's outer spiral arms.

At 245× in my 15-inch Dob, NGC 5641 is a small, slightly elongated puff with a distinct, near-stellar core. A 2004 study with the Hubble Space Telescope revealed it holds three massive, young star clusters similar to the colossal stellar nursery R136 located in the Tarantula Nebula in the Large Magellanic Cloud. Supergiants are frequently found within large clusters that knot galactic spiral arms. Might this one have a connection to its fertile neighbor?

Spectra indicate that SN 2023ixf is a Type II supernova — the catastrophic destruction of an aging supergiant star. Massive suns fuse simpler elements into more complicated ones all the way up to iron. Each step liberates energy that pushes back against the force of gravity and stabilizes the star. But the buck stops at iron. Stable as a proverbial brick house, it takes crazy amounts of energy to fuse it — energy the star can't produce. No longer able to beat back gravity's crush, the star suddenly collapses. Material falling inward bounces off the shrinking core, creating shock waves that rebound outward and rip the supergiant apart in a titanic explosion. Type II events leave a neutron star or black hole in their wake — the tiny remnant of a life lived bigly.

M101 is one of the most photographed galaxies in the sky, so astronomers immediately began looking for pre-discovery images that would record the early stages of the explosion as well as to identify a potential progenitor. Photos taken by amateur astronomers David Kennedy and Bronco Oostermeyer at 33, 18, and 9 hours prior to discovery show the supernova's brightness quickly rising from fainter than magnitude 21-22 to ~17.3 and ~15.3 magnitude, respectively. Meanwhile, a serendipitous time-lapse by a Chinese amateur captured the onset of the explosion on May 18th between 19:30 and 20:30 UT.

Although it's still early in the discovery phase, The Astronomer's Telegram posted an observation identifying a potential progenitor star — an approximately 15-solar-mass red supergiant ensconced in a circumstellar dust shell. Observers may remember SN 2011fe, the last bright supernova seen in M101. Discovered in August 2011, the Type Ia blast reached a peak magnitude of 9.9, easy quarry for a 60mm telescope. Will 2023ixf surpass it?

However bright the supernova may become, we're in for a wild ride. To find it, start at Mizar in the bend of the Big Dipper's handle and follow the star chain (a veritable yellow-brick road) leading from Mizar to M101. SN 2023ixf lies 3.8′ east and 2.2′ south of the galaxy's center. To make your own chart go to in-the-sky.org and search for M101. Any questions? Feel free to ask.

I'm excited for the nights ahead and hope you are, too. I know a lot of us are dealing smoke from Canadian wildfires. To stay abreast of smoke trends NOAA offers a Fire and Smoke map and detailed forecast. For updated information and current images of the supernova visit David Bishop's Latest Supernovae.

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