JWST spotted an incredible number of supernovae in the early universe

Astronomers using the James Webb Space Telescope (JWST) have found an astonishing number of supernovae in the distant universe, including the farthest ever confirmed. Their discoveries have increased the amount of known supernovae in the early universe by a factor of 10.

The researchers found 79 new supernovae by taking two images of the same tiny patch of the sky, one in 2022 and one in 2023. “It’s actually so small that if you took a grain of rice and held it at arm’s length that would be the size of the patch,” said Christa DeCoursey at the University of Arizona while presenting this work at a meeting of the American Astronomical Society in Wisconsin on 10 June. “We spent over 100 hours of JWST (observing) time on each image, so these are very, very deep images.”

The astronomers then compared the two images with one another and with pictures of the same area taken previously by the Hubble Space Telescope, looking for bright spots that were present in one image but not the others.

These spots are stars that had been shining relatively dimly before exploding in bright supernovae and fading out. Several of them are candidates for the most distant supernova ever found, although their distances have not yet been confirmed. And one is definitely the most distant ever confirmed – it blew up when the universe was only about 1.8 billion years old.

Supernovae like these probably created the heavy elements that are now spread throughout the universe, so they contain fewer of these elements than modern supernovae do. “The universe was fundamentally different at this early phase than the times that Hubble, and particularly ground-based surveys, were probing in the past,” said Justin Pierel at the Space Telescope Science Institute in Maryland during the presentation. “This is really a new regime that JWST has opened.” Observations in that regime could help reveal what the first stars were like.