Dark Cosmic Mysteries Illuminated

In deep-space games of "I Spy," U of A physicists have led a group of international astronomers to a major win.

Using data from some of the world's most advanced observatories, Gregory Sivakoff, assistant professor in the Department of Physics, and his students helped discover two never-before-seen phenomena - stealth black holes and ultraluminous X-ray bursts.

"The mind-boggling large size of the universe provides ample opportunity to discover the exotic, discover the beautiful, discover the rare and discover the important." - Gregory Sivakoff

Stealth Black Holes

Combining data from NASA's Chandra X-ray Observatory, Hubble Space Telescope and the Very Large Array, Sivakoff led a group of researchers in the discovery of a stealth black hole being orbited closely by a star about a 10th to a fifth as massive as our sun. Systems like this are usually called X-ray binary systems (two stars that orbit around their common centre of mass and emit X-rays). This stealth black hole binary system was hidden by its relative lack of electromagnetic signals. The findings suggest there may be many such black hole systems in our galaxy that have gone unnoticed.

Ultraluminous X-ray Bursts

In two galaxies not so far away, Sivakoff and a second group of international colleagues have made another unprecedented discovery - objects that flare spontaneously and erupt with hundreds or thousands of times more X-rays than typical bright X-ray binary systems. In astronomy, Sivakoff explains, discoveries of flaring sources with new properties have proven extremely important; their flaring properties often reveal intriguing physical origins. He is optimistic this will be the case once more.