Universe ID: 10082

Swift Probes Exotic Object: 'Kicked' Black Hole or Mega Star?

Released on November 19, 2014

Zoom into Markarian 177 and SDSS1133 and see how they compare with a simulated galaxy collision. When the central black holes in these galaxies combine, a "kick" launches the merged black hole on a wide orbit taking it far from the galaxy's core.

Credit: NASA's Goddard Space Flight Center/L. Blecha (UMD)

An international team of researchers analyzing decades of observations from many facilities, including NASA's Swift satellite, has discovered an unusual source in a galaxy some 90 million light-years away. The object's curious properties make it a good match for a supermassive black hole ejected from its home galaxy after merging with another giant black hole.

An alternative explanation for the source, called SDSS1133, is just as intriguing. It may be the remains of a massive star called a luminous blue variable (LBV) that exploded as a supernova. These stars undergo episodic eruptions that cast large amounts of mass into space long before their final blast. Interpreted in this way, SDSS1133 would represent the longest period of LBV eruptions ever observed, followed by a terminal supernova explosion in 2001.

Whatever SDSS1133 is, it's persistent. The team was able to detect it in astronomical surveys dating back more than 60 years.

The mystery object is part of the dwarf galaxy Markarian 177, located in the bowl of the Big Dipper, a well-known star pattern within the constellation Ursa Major. Although supermassive black holes usually occupy galactic centers, SDSS1133 is located at least 2,600 light-years from its host galaxy's core.

In June 2013, the researchers obtained high-resolution near-infrared images of the object using the 10-meter Keck II telescope at the W. M. Keck Observatory in Hawaii. They reveal 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.

A simulation of two colliding galaxies (left) shows how their coalescing supermassive black holes can launch the resulting larger black hole (dot, lower left) on a wide orbit. Right: Compare the simulation with this Keck II near-infrared image of Markarian 177 and SDSS1133 (lower left).

Credit: Simulation, L. Blecha (UMD); image, W. M. Keck Observatory/M. Koss (ETH Zurich) et al.

SDSS1133 (bright spot, lower left) has been a persistent source for more than 60 years. This sequence of archival astronomical imagery, taken through different instruments and filters, shows that the source is detectable in 1950 and brightest in 2001.

Credit: NASA's Goddard Space Flight Center/M. Koss (ETH Zurich)

A computer simulation of colliding galaxies shows how merged supermassive black holes can be placed in an elongated orbit. The simulation begins with disks of stars, gas and dark matter representing two galaxies of comparable mass; only the stars are shown. The galaxies make a close pass that results in trong tidal distortions that warp their disks. These disturbances trigger instabilities that drive gas to the galaxy centers, where it forms new stars and fuels the supermassive black holes. Before the galaxies completely merge, their black holes spiral together and coalesce. Gravitational waves emitted in the merger create a “recoil kick” that ejects the black hole from the galaxy's center; in this case, the kick is 90 percent of the escape speed. The simulation stops just as the black hole reaches the farthest point of its orbit, which is why it slows down in the last few frames. The video represents an elapsed time of about 2.7 billion years. The simulation took five days to complete on the Odyssey computing cluster at Harvard University.

Credit: L. Blecha (UMD)

The dwarf galaxy Markarian 177 (center) and its unusual source SDSS1133 (blue) lie 90 million light-years away. The galaxies are located in the bowl of the Big Dipper, a well-known star pattern in the constellation Ursa Major.

Credit: Sloan Digital Sky Survey

Using the Keck II telescope in Hawaii, researchers obtained high-resolution images of Markarian 177 and SDSS1133 using a near-infrared filter. Twin bright spots in the galaxy's central region are consistent with recent star formation, a disturbance that hints this galaxy may have merged with another.

Credit: W. M. Keck Observatory/M. Koss (ETH Zurich) et al.