Astronomers have been able to see a bright object known as SDSS1133 since 1950. Observations by instruments such as the W. M. Keck Observatory and NASA’s Swift satellite have labeled it as a supernova. However, an international team of researchers have gone back and re-examined all of that old data, and don’t believe it is an ordinary supernova. While they haven’t come up with a definitive answer yet, the team has come up with two options that are both pretty exciting: SDSS1133 could be a new type of supernova that radiates much longer than normal, or it's the first known supermassive black hole that doesn’t exist at its galaxy’s core. Michael Koss from the University of Hawaii was lead author of the paper, which was published in Monthly Notices of the Royal Astronomical Society.
After the older data had been reviewed, Koss and his team took new images with the 10-meter Keck II telescope at Keck Observatory. These high-resolution, infrared images revealed that SDSS1133 appeared as if it had undergone a violent event in its past.
“When we analyzed the Keck data, we found the emitting region of SDSS1133 is less than 40 light-years across, and that the center of Markarian 177 shows evidence of intense star formation and other features indicating a recent disturbance that matched what we expected for a recoiling black hole,” co-author Chao-Ling Hung said in a press release.
If SDSS1133 is a black hole, it is associated with Markarian 177; a dwarf galaxy 90 million light-years away in the bowl of the Big Dipper. While most black holes are found at the core of the galaxy, SDSS1133 is 2,600 light-years away. The data suggests that after a merging event between two galaxies, the black hole was essentially booted out on its own. This could have occurred due to competing directionality of spins and gravitational wave emissions between the two black holes in the galaxies.
"We suspect we're seeing the aftermath of a merger of two small galaxies and their central black holes," explained co-author Laura Blecha. "Astronomers searching for recoiling black holes have been unable to confirm a detection, so finding even one of these sources would be a major discovery.”
While data does fit the team’s model that SDSS1133 is a supermassive black hole that has been ejected out of its galaxy, there is also a possibility that it is a supernova unlike anything that has been seen before. The area got brighter over a longer period of time than is typically seen in supernovae. It could have been a massive star that had gone through a series of eruptions before the supernova explosion.
"With the data we have in hand, we can't yet distinguish between these two scenarios," Koss added. "But, one exciting discovery made with NASA's Swift is that the emission of ultraviolet light of SDSS1133 hasn't changed for a decade, which is not something typically seen in a young supernova remnant.”
The researchers plan to study SDSS1133 at ultraviolet wavelengths in 2015 using the Hubble Space Telescope’s Cosmic Origins Spectrograph.
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