In 2009, a Massive Star Vanished. JWST Might Have Figured Out What Happened.

A gigantic star 25 times as large as the Sun simply disappeared in 2009.

Okay, so it wasn't really that easy. It went through a period of brightening and increased in luminosity to a million Suns, appearing to be about to go supernova.

But instead of blowing up, it eventually faded. And despite employing the Large Binocular Telescope (LBT), Hubble, and Spitzer space telescopes, astronomers were unable to see the star.


The N6946-BH1 star is now regarded as a failed supernova. Astronomers believe the star imploded to create a black hole rather than causing a supernova, hence the BH1 in its name. But that is just speculation.

Illustration of how a failed supernova can become a black hole. (P. Jeffries/STScI/NASA/ESA)

Only one thing is certain: after briefly becoming brighter, it became too dim to be seen with our telescopes. But the James Webb Space Telescope (JWST) has changed that.

The new study, which was released on arXiv, examines information obtained by the NIRCam and MIRI instruments on the JWST. It displays a prominent infrared source that resembles a shell of dust that was once around the original star's location. This would be in line with material being released from the star as it rapidly became brighter.

A less plausible possibility is that the infrared glow is caused by material falling into the black hole.

Images of BH1 show three sources, not one. (Beasor et al 2023)

Surprisingly, the researchers discovered not just one, but three leftover objects.

This lessens the likelihood of the failed supernova model. These three sources were combined in earlier observations of N6946-BH1 because the resolution wasn't good enough to tell them apart.

Therefore, it is more plausible that a star merger was the cause of the 2009 brightening. What seemed to be a big bright star was actually a stellar system that became brighter when two stars combined, then faded.

The failed supernova hypothesis cannot be ruled out even if the data tends to support the merger model. And it complicates how we comprehend supernovae and stellar mass black holes.

Stellar-mass black holes exist and are rather abundant, according to gravitational wave observations made by LIGO and other observatories. Thus, some enormous stars do eventually collapse into black holes.

But it's still unclear if they first go supernova. It is difficult to envision how the greatest star black holes might have formed following supernovae, despite the fact that regular supernovae can have enough residual mass to become black holes.

Considering that N6946-BH1 is located in a galaxy 22 million light-years away, it is remarkable that JWST can distinguish between different sources. It also gives astronomers optimism that other stars like it will one day be discovered.

With additional information, we should be able to determine the difference between actual failed supernovae and stellar mergers, which will aid us in understanding the final stages of stars as they approach stellar-mass black holes.

Research Paper

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