A new NASA video shows some of the black holes closest to Earth, as well as the stars that feed them.
The visualization shows 22 X-ray binaries in both our Milky Way galaxy and the neighboring Large Magellanic Cloud. In each pair, the black hole is shown as a black dot at the center of an orange-red accretion disk; the star is shown as a bluish- or yellowish-white sphere scaled to match its size, according to a NASA statement (opens in new tab) accompanying the video.
A black hole is a point in space where the pull of gravity is so intense that not even light can escape it. Black holes form when a star goes supernova, shooting vast amounts of matter into space while folding in or collapsing upon itself. (Don't fret: Our sun would need about 20 times its actual mass in order to turn into a black hole.)
The black hole of an X-ray binary can collect energy from its star in two ways. The first is that a stream of gas may flow directly from the star of the host galaxy into the black hole, swirling "like water goes down a drain" according to Scientific American (opens in new tab).
Other stars generate stellar winds, described (opens in new tab) by Hubble Space Telescope personnel as: "fast-flowing streams of particles that are emitted from a star." The extreme gravitational pull of a black hole allows it to slurp up some of this material.
Because black holes cannot emit light, scientists are unable to observe these objects directly using telescopes. However, matter falling into a black hole gradually heats up and glows, eventually in X-rays. It is on those X-rays that this visualization is based.
Although the visualization offers a sense of the variety of black holes, these objects are depicted here as being far larger in comparison to their companion stars and accretion disk than they actually are.
For example, take the first ever confirmed black hole, Cygnus X-1. Its surface, called the event horizon, only stretches about 77 miles (124 kilometers) across. However, the visualization shows Cygnus X-1 as being far larger, more in line with the black hole's mass than its volume.
The visualization's viewing angles demonstrate how we can see the systems from Earth, while the orbital motion shown is 22,000 times faster than observed.