NASA Space 'Archaeology' Reconstructs Dead Star

Astronomers have used the remains of an ancient, dead star to uncover information about how stars explode and form black holes.

The astronomers reconstructed the makeup of the long-dead star that exploded in a violent supernova more than a million years ago.

Using data collected by NASA's Chandra X-ray Observatory, researchers led by Noa Keshet, Ehud Behar and Timothy Kallman of the Goddard Space Flight Center, conducted what they describe as "supernova archaeology."

The term refers to astronomers learning about the past from scattered remains in space, much like how terrestrial archaeologists examine the Earth.

The study focused on a system known as GRO J1655–40, a binary pair consisting of a black hole and a companion star. Today, the black hole has nearly seven times the mass of the sun, while its companion is about half as massive.

The system began as two luminous stars, one of which ended its life in a supernova, scattering material across space.

Some of the outer layers from the exploding star then rained down on the companion star, only to later be pulled back by the black hole's gravity.

While most of this matter was consumed, some formed a swirling disk around the black hole. Through magnetic forces and friction, that material was ejected in powerful winds.

In 2005, Chandra observed GRO J1655–40, capturing the X-ray brightness of its emissions across different wavelengths. Embedded in that light were signatures of individual elements found in the black hole's winds.

The presence of these elements served as a kind of chemical fingerprint of the long-gone star. By comparing the X-ray data with computer models of stellar explosions, the team concluded that the original star was about 25 times the mass of the sun and was much richer in elements heavier than helium in comparison with the sun.

This information offers a rare insight into stellar evolution and the conditions that can lead to black hole formation. The analysis also paves the way for more supernova archaeology studies using other outbursts of double star systems.

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Reference

Keshet, N., Behar, E., & Kallman, T. (2024). Supernova Archaeology with X-Ray Binary Winds: The Case of GRO J1655−40. The Astrophysical Journal. https://iopscience.iop.org/article/10.3847/1538-4357/ad3803