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Astronomers may have seen the afterglow from an epic event.

The remnants of stars that have died in supernova explosions are called kilonovas. Astronomers think they have seen an afterglow in the X-rays from the event.

The discovery team suggests that the sonic boom-like shock caused by the debris expanding out from the collision heated up the surrounding materials. X-rays were generated by the heating.

Scientists spot a bright flash so bright they can barely explain it.

An artist’s conception illustrates the aftermath of a “kilonova,” a powerful event that happens when two neutron stars merge.

An artist's conception illustrates the aftermath of a "kilonova," a powerful event that happens when two neutron stars merge. (Image credit: NASA/CXC/M. Weiss)

Astronomers caution that the finding is tentative and that a similar effect may be produced by materials falling towards a black hole. Either type of find would be the first known to science.

The research team is looking at something new in the aftermath of aneutron star merger. This gives us the chance to study and understand new physical processes that have not been observed before.

A 3D visualization of a neutron star.

A 3D visualization of a neutron star. (Image credit: Shutterstock)

The merger that produced the first-ever detection of a neutron star event was already known to science. The area is being studied to find out how it is evolving.

Astronomers spotted X-ray emissions soon after the event, using NASA's Chandra X-ray Observatory, but the emission began to fade in early 2018). The X-ray emission remained nearly constant, despite the decline in brightness.

The consistency in X-ray brightness was the reason why this was unusual.

It will take more study to figure out what the cause was. The researchers expect the X-ray and radio emissions to get brighter if it is indeed a kilonova. If it is a black hole, the output should decline or stay the same.

The study was published in The Astrophysical Journal Letters.

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