A star with a long tail of disrupted gas moves along the foreground. A large black hole sits in the background.

Star ripped apart by supermassive black hole

It’s a star!
It’s a supernova!
No, it’s … a Spinning Black Hole Swallowing a Star!

In the very first issue of the new journal Nature Astronomy, former Oskar Klein Centre (OKC) post-doc Giorgos Leloudas (now at the Weizmann Institute of Science and Dark Cosmology Centre) suggests a new interpretation for the event ASASSN-15lh, formerly known as the most luminous supernova ever.

Leloudas and colleagues performed follow-up observations after the luminous event and found that with ten months of additional data the event no longer resembled that of a supernova. Co-investigator, Christoffer Fremling from the OKC, did all of the image subtraction to extract the light curve for this event.  Instead, they suggest, ASSASN-15lh was a star ripped apart by a supermassive black hole – a tidal disruption event.

One interesting aspect is the suggestion that this supermassive black hole might be rotating rapidly, says co-investigator Jesper Sollerman from OKC. Maybe these kind of tidal disruption events will become a way to explore the rotation of supermassive black holes billons of light years away.

The research paper discussing these results is available here in Nature Astronomy (arXiv version).  The video below shows a spinning supermassive black hole as it rips a star apart (artist’s impression).

[Top image: This artist’s impression depicts a sun-like star close to a rapidly spinning supermassive black hole, with a mass of about 100 million times the mass of the sun, in the centre of a distant galaxy. Photograph: ESO, ESA/Hubble, M. Kornmesser]

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