An unusual source of light has been spotted whose strange properties make it an excellent match for a supermassive black hole, one which was ejected from its home galaxy after merging with another giant black hole.
However, astronomers have not ruled out a different possibility. The source, known as SDSS1133, could also be the remnant of a massive star that erupted for a record period of time before destroying itself in a supernova explosion.
The unusual source of light, in a galaxy 90 million light-years away was discovered by an international team of researchers analyzing decades of observations from many facilities, including NASA’s Swift satellite,
“With the data we have in hand, we can’t yet distinguish between these two scenarios. One exciting discovery made with NASA’s Swift is that the brightness of SDSS1133 has changed little in optical or ultraviolet light for a decade, which is not something typically seen in a young supernova remnant,”
said lead researcher Michael Koss.
Cosmic Origins Spectrograph
Koss and his team say that the source has brightened in visible light considerably during the past six months. If maintained, that trend would support the black hole interpretation. For further detailed analysis, the team is planning ultraviolet observations with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope in October 2015.
Whatever SDSS1133 turns out to be, one thing it is is persistent. The team was able to detect it in astronomical surveys dating back over 6 decades.
“We suspect we’re seeing the aftermath of a merger of two small galaxies and their central black holes,” said co-author Laura Blecha, a leading theorist in simulating recoils, or “kicks,” in merging black holes. “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.”
The object is part of the dwarf galaxy Markarian 177. That galaxy is located in the bowl of the Big Dipper, a well-known star pattern within the constellation Ursa Major. Even though super-massive black holes usually occupy galactic centers, SDSS1133 is located at least 2,600 light-years from its host galaxy’s core.
Central Supermassive Black Hole
A collision and merger of two galaxies changes their shapes and causes new phases of star formation. If each galaxy possesses a central supermassive black hole, they will form a bound binary pair at the center of the merged galaxy before ultimately coalescing themselves.
Merging black holes unleash a huge amount of energy in the form of gravitational radiation, a consequence of Einstein’s theory of gravity.
Waves in the fabric of space-time ripple outward in all directions from accelerating masses. If both black holes have equal masses and spins, their merger emits gravitational waves uniformly in all directions. More likely, the black hole masses and spins will be different, leading to lopsided gravitational wave emission that launches the black hole in the opposite direction.
Reerence: Michael Koss, Laura Blecha, et. al. SDSS1133: an unusually persistent transient in a nearby dwarf galaxy. MNRAS (November 21, 2014) 445(1): 515-527.doi: 10.1093/mnras/stu1673
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