Long ago, in a galaxy not too far away, a supermassive black hole tore a star to pieces in the center of galaxy NGC 7392. A flash of light from a black hole dinner finally reached Earth in 2014 — and astronomers have just discovered it in their data.
This newly discovered explosion from the center of NGC 7392 is the closest example of a tidal perturbation event (TDE), in which a star is pulled away by the intense gravity of a black hole. The results were published on April 28 in Astrophysical Journal Letters. (Opens in a new tab)
The starving black hole has been spotted about 137 million light-years from Earth — or about 35 million times farther than Proxima Centauri, the closest star to the Sun. Although these sounds far away, astronomers have only observed about 100 of these events so far, and that’s 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 detections, which typically come in X-rays, ultraviolet light, and optical light.
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“Finding this close TDE means that, statistically speaking, there must be a large number of such events that conventional methods were blind to,” 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, we should try to find them in infrared if we want a complete picture of black holes and their host galaxies.”
After TDE was first detected in observations from the NEOWISE space telescope, Panagiotou and his collaborators sifted through data from several observatories and other space telescopes to search for more information about NGC 7392’s supermassive black hole. They wanted to solve the mystery of why this TDE only appears in the infrared. , rather than the more active wavelengths like others of its kind.
Previously detected TDEs have mostly appeared in so-called green galaxies, which don’t create as many stars as more active blue galaxies but don’t burn out completely in starmaking like red galaxies. However, NGC 7392 is a blue galaxy – spawning many new stars and creating a lot of dust in the process. This dust can obscure the center of the galaxy, where the supermassive black hole lives, in optical and ultraviolet light. But infrared light enables astronomers to look through this dust and see what’s going on.
This discovery indicates that astronomers should be looking for TDE in infrared light as well.
“Using infrared surveys to catch dust echoes of obscured TDEs has already shown us that there are a host of TDEs in dusty star-forming galaxies that we’ve been missing.” Sophie Butcher (Opens in a new tab)an astronomer with the Space Telescope Science Institute who was not involved in the study, said in the statement.
By looking for TDEs in the infrared as well, scientists can get one step closer to understanding how black holes feed on stars.
Originally published on LiveScience.com.