Sagittarius A*, the supermassive black hole at the center of the Milky Way, is relatively quiet, usually exhibiting only minimal fluctuations in brightness.
Sagittarius A* Black Hole 75 Times Brighter Than Normal
The black hole, however, was caught acting strangely in May this year. Astronomers who were observing the skies using the Keck Observatory in Hawaii noticed that the black hole all of a sudden became 75 times brighter in near-infrared wavelengths before subsiding back to normal levels.
Tuan Do, from the University of California Los Angeles, said they initially thought that the flare was from the nearby star S0-2 because scientists who have been observing Sagittarius A* over the past two decades have never observed it to be that bright.
Do and colleagues, however, eventually realized the source of the flare was the black hole. They were also able to capture the strange brightening in a timelapse.
"The black hole is always variable, but this was the brightest we've seen in the infrared so far," Do posted on Twitter. "It was probably even brighter before we started observing that night!"
What Causes Black Holes To Light Up?
Black holes do not emit radiation that can be detected by current instruments, but objects nearby do that when the black hole's gravitational forces produce immense friction that in turn produce radiation.
When viewed from a telescope that uses the infrared range, this radiation is translated into brightness. Thus, something may have gotten close enough to be pulled by gravity when the surroundings of a blackhole flare brightly.
S0-2 Star And Gas Cloud G2
The researchers think of two objects that may have caused the unusual flare. One is the S0-2 star, which made its closest approach to the black hole during its 16-year elliptical orbit around Sagittarius A*. The star may have passed too close to the black hole last year that it changed the way gas flows into the black hole.
The other object is a gas cloud called G2, which approached within 36 light-hours of the black hole in 2014.
The researchers hope that more observations of Sagittarius A* could shed light on what the black hole is doing.
Additional multi-wavelength observations will be necessary to both monitor Sgr A* for potential state changes and to constrain the physical processes responsible for its current variability," the researchers wrote in their study to be published in the Astrophysical Journal Letters.
