A long time ago, in a galaxy not so far away, a star at the center of NGC 7392 was ripped apart by a supermassive black hole. Light from the black hole’s dinner light finally reached Earth in 2014 – and now astronomers have detected it in their data.
This newly discovered eruption from the center of NGC 7392 is the closest known example of a tidal perturbation event (TDE), in which a star is pulled in by the massive gravity of a black hole. The results were published on April 28 Astrophysical Journal Letters. (Opens in a new tab)
The starving black hole was found about 137 million light-years from Earth, or about 35 million times the nearest star to the Sun, Proxima Centauri. As far as it is, astronomers have only observed about 100 of these events so far, and they’re four times closer than the previous title holder of “nearest TDE from Earth.” Scientists detected TDE in infrared, a different wavelength than most conventional TDE detectors, which typically come in X-ray, ultraviolet, and optical light.
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“Finding a TDE this close means that, statistically speaking, there must be a large number of such cases that were blinded by conventional methods,” said the lead author. Christos Panagiotto (Opens in a new tab)an astronomer at the Massachusetts Institute of Technology, in the current situation (Opens in a new tab). “So if we want a complete picture of black holes and their host galaxies, we should try to find them in infrared.”
After TDE was first detected in observations from the NEOWISE space telescope, Panagiotou and his collaborators sifted through data from several observatories and space telescopes to extract more information about NGC 7392’s supermassive black hole. They wanted to solve the mystery of why DTE appears only in the infrared.
Previously detected TDEs appeared mostly in so-called green galaxies, which did not produce as many stars as the more active blue galaxies, but did not completely burn out to form stars like the red galaxies. However, NGC 7392 is a blue galaxy – it’s spewing out many new stars and creating a lot of dust in the process. This dust obscures the center of the galaxy, where the supermassive black hole lives, in optical and ultraviolet light. But infrared light allows astronomers to look through this dust to see what’s going on.
This discovery indicates that astronomers should look for TDE in infrared light as well.
“Using infrared probes to capture dust echoes of hidden TDEs has already shown us the presence of clusters of TDEs in dusty star-forming galaxies that we’ve lost.” Sophie Gesari (Opens in a new tab)An astronomer at the Space Telescope Science Institute, who was not involved in the study, said in a statement.
By looking for TDEs in the infrared as well, scientists can get one step closer to understanding how black holes collapse into stars.
Originally published in Live Science.com.