This illustration shows how binary stars interact with a supermassive black hole to create a population of hypervelocity stars that wind up getting gravitationally kicked so strongly, they get ejected from their home galaxy. This process should be at play in any galaxy with a supermassive black hole, including the nearby Large Magellanic Cloud (LMC), shown at right. As a result, many hypervelocity stars originating from the LMC should now exist within the Milky Way. (Credit: CfA/Melissa Weiss)
Just 165,000 light-years away, the Large Magellanic Cloud is suspected to house a supermassive black hole. At last, evidence has arrived.
Throughout the Universe, practically all galaxies house a supermassive black hole.
Messier 87, best known as the supermassive galaxy whose black hole was first imaged by the Event Horizon Telescope, has its relativistic jets and the shockwaves created by their material imaged in the infrared by Spitzer, amidst the mass of shining stars (in blue). Messier 87 is the most massive (and second-brightest) galaxy within the entire Virgo cluster of galaxies, and it is the central black hole that generates these relativistic jets. (Credit: NASA/JPL-Caltech/IPAC)
Whenever actively feeding, they spew out energetic radiation.
This field of view, corresponding to about 1/15th of a square degree, shows the Chandra deep field south, and represents a total of around 2000 hours of total observing time. Approximately 5000 supermassive black holes were detected, with a small amount of hot gas around a few objects appearing as diffuse and extended, rather than point-like, sources. (Credit: NASA/CXC/Penn State/B.Luo et al.)
This activity abounds at the Milky Way’s center, too.
The supermassive black hole at the center of our galaxy, Sagittarius A*, emits X-rays due to various physical processes. The flares we see in the X-ray indicate that matter flows unevenly and non-continuously onto the black hole, leading to the flares we observe over time. In X-rays, no event horizon is visible at these resolutions; the “light” is purely disk-like. (Credit: NASA/CXC/Amherst College/D.Haggard et al.)
However, at only ~27,000 light-years distant, our black hole is more directly observable.
This 20-year time-lapse of stars near the center of our galaxy comes from the ESO, published in 2018. Note how the resolution and sensitivity of the features sharpen and improve toward the end, all orbiting our galaxy’s (invisible) central supermassive black hole. Practically every large galaxy, even at early times, is thought to house a supermassive black hole, but only the one at the center of the Milky Way is close enough to see the motions of individual stars around it, and to thereby accurately determine the black hole’s mass. Similar techniques could reveal intermediate mass black holes within globular clusters, albeit over longer timescales. (Credit: ESO/MPE)
