A star disappeared as astronomers watched. Now James Webb Space Telescope has some answers

Mary Raleigh
14/10/2023

In 2009, a celestial enigma unfolded as a massive star, 25 times the mass of our Sun, mysteriously vanished from sight.

Known as N6946-BH1, this star had initially shown signs of becoming a supernova, brightening to a luminosity of a million suns. However, instead of exploding, it faded away, leaving astronomers puzzled. Attempts to locate it using the Large Binocular Telescope (LBT), Hubble, and the Spitzer space telescope yielded no results. The star was then labeled a “failed supernova,” with the prevailing theory suggesting that it had collapsed into a black hole.

The recent deployment of the James Webb Space Telescope (JWST) has provided new data that could potentially solve this cosmic mystery. A study published on the arXiv preprint server utilized data from JWST’s NIRCam and MIRI instruments to identify a bright infrared source at the position where N6946-BH1 was last observed. This source is believed to be a remnant dust shell, possibly material ejected from the star as it brightened. Another possibility is that it could be an infrared glow from material falling into a black hole.

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

Interestingly, the study also revealed not just one, but three remnant objects at the star’s last known position. This new finding challenges the failed supernova theory, suggesting that the 2009 brightening could have been the result of a stellar merger. The data leans more towards this merger model but does not entirely rule out the failed supernova theory.

The discovery has significant implications for our understanding of supernovae and stellar mass black holes. It raises questions about whether massive stars necessarily become supernovae before transforming into black holes. N6946-BH1 is located in a galaxy 22 million light-years away, and the fact that JWST could distinguish multiple sources at that distance is a testament to its capabilities. As more data becomes available, astronomers hope to differentiate between true failed supernovae and stellar mergers, enhancing our understanding of the final stages of stellar evolution.

The findings not only add a new layer of complexity to our understanding of stellar life cycles but also showcase the incredible capabilities of the James Webb Space Telescope in unraveling cosmic mysteries.

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