IMAGE: Artist’s impression of the gaseous disk around the supermassive black hole. Hot spots circling around the black hole could produce the quasi-periodic millimeter emission detected with ALMA. CREDIT: Keio University
In 2017, the Atacama Large Millimeter/submillimeter Array (ALMA) stared toward our system’s heart of darkness, Sag A*, a 4 million solar mass black hole. There they found a flicker of light, hanging on, in a mind-breaking orbit. Some small radio emitter has been found orbiting at just 0.2 AU from Sag A*. This is half the size of Mercury’s orbit!
According to team member Tomoharu Oka, “This emission could be related with some exotic phenomena occurring at the very vicinity of the supermassive black hole.” Whatever it is, the emitter is giving us yet one more test of relativity. As the light source orbits Sag A*, relativity says we should see the emission greatly amplified when its motion is moving toward us. It is this amplification they believe is being seen.
This bit of emission probably isn’t anything out of the norm – it is just newly noticed. It is perfectly normal for hotspots to exist in disks of material like the disk around Sag A*. What makes ...