October 3, 2018
At vast cosmic distances, supermassive black holes called quasars gobble up matter into accretion disks that shine so brightly, they overpower the light from entire galaxies. Closer to home, compact objects called microquasars give astronomers a scaled-down taste of the processes at work inside the faraway behemoths. Now, an international collaboration of researchers has announced in the journal Nature that they’ve detected the first gamma-ray signal from the ends of the two jets spewing out of a Milky Way microquasar.
The microquasar they observed, SS 433, is either a black hole or a neutron star in a binary system about 15,000 light-years from Earth. As it sucks in matter from its run-of-the-mill stellar companion, SS 433 is not only surrounded by a hot, swirling accretion disk of material, it also shoots out jets at 26 percent the speed of light. SS 433 is one of only about a dozen identified microquasars in the Milky way, and one of only a few of those from which gamma rays —an extremely high-energy form of light — have been seen.
This is a newfound way to produce high-energy gamma rays in microquasars. The discovery was made possible by the fact that SS 433’s jets are not pointed directly toward Earth, allowing the astronomers to spot the two different ends of the jets, which isn’t possible when an object’s jets are pointed at us, rather than sideways.
“SS 433 is an unusual star system and each year something new has come out about it,” said Segev BenZvi of the University of Rochester, and a co-author of the study.