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An international team of astronomers among whom dr. Giovanna Pugliese of the Anton Pannekoek Institute of the University of Amsterdam has discovered heavy elements in the wake of a bright gamma-ray burst in a galaxy about 1 billion light-years away. The burst occurred on March 7, 2023, when presumably two neutron stars merged to form a so-called kilonova. It is the first kilonova whose aftermath was observed using the James Webb Space Telescope. The researchers publish their findings Thursday in the journal Nature.
A black background with a cluster of galaxies at the bottom right, fuzzy spots in blue and yellow. The largest galaxy is blue-purple and has the shape of a vortex. There is a relatively bright red dot in the top left corner. This is the gamma-ray burst coming from the large galaxy in the lower right.
Image obtained with the James Webb Space Telescope of the bright gamma-ray burst GRB230307A. The burst probably occurred when two neutron stars merged to form a so-called kilonova. The neutron stars may have been ejected from the galaxy at the lower right. (c) NASA, ESA, CSA, Andrew Levan

The gamma-ray burst, GRB230307A, is the second brightest burst in the 50 years since the search for gamma-ray bursts began. GRB230307A is a thousand times brighter than the typical gamma-ray burst. The burst lasted a long time, about 200 seconds.

Further investigation with multiple telescopes on Earth and in space revealed that the burst originated from a kilonova. The kilonova probably occurred when two neutron stars merged in a galaxy 1 billion light-years from Earth.

"There are only a mere handful of known kilonovas, and this is the first time we have been able to look at the aftermath of a kilonova with the James Webb Space Telescope," said research leader Andrew Levan (Radboud University, the Netherlands). He was also involved in the first detection of a kilonova back in 2013.

Thanks to the Near-Infrared Spectrograph of the James Webb Space Telescope, developed partly in the Netherlands, the researchers saw peaks in the infrared spectrum of the kilonova that correspond to the typical fingerprint of the element tellurium. The astronomers also observed hints of rare earth elements.

In the future, the researchers hope to do combined observations of kilonovas more often. This will allow them to solidify the theory about the formation of heavy elements in kilonovas.

Scientific paper
JWST detection of heavy neutron capture elements in a compact object merger. By: Andrew Levan et al. In: Nature. [original | preprint (pdf)]

This work has been published in the journal Nature, and made use of many ground and space based telescopes including the facilities of the James Webb Space Telescope, the Chandra X-ray Observatory, the Neil Gehrels Swift Observatory, the Fermi Space Telescope and the facilities of the the European Southern Observatory (ESO), the Gemini Observatory, the Australia Compact Telescope Array, and the MeerKAT telescope.