The singularity may be either a physical structure or a purely mathematical one, but right now astronomers don’t know which is true. It’s the final destination for anything falling into the event horizon. General relativity predicts that the very center of a black hole contains a point where matter is crushed to infinite density. This process makes the near jet considerably brighter, but greatly dims the rear jet. In cases where the jets happen to angle into our line of sight, we may only easily detect the one firing toward us due to Doppler beaming. The jets from supermassive black holes – the type found in the centers of most big galaxies – can reach lengths of hundreds of thousands of light-years. These jets fire out particles at close to the speed of light, but astronomers don’t fully understand how they work.
A small amount of material heading toward the black hole may suddenly become rerouted into a pair of jets that blast away from it in opposite directions. In black holes of all sizes, something strange can occur near the inner edge of the accretion disk. Credit: NASA/Swift/Aurore Simonnet (Sonoma State Univ.) A thin jet of high-speed particles emerges from just above the black hole. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. The black hole’s particle jets show off this effect even more dramatically.Ī thick accretion disk has formed around a black hole following the destruction of a star that wandered too close in this illustration. This is the optical equivalent of an everyday acoustic phenomenon, where the pitch and volume of a sound – such as a siren – rise and fall as the source approaches and passes by. Light streaming from the part of the disk spinning toward us becomes brighter and bluer, while light from the side the disk rotating away from us becomes dimmer and redder. Near the black hole, the disk spins so fast that an effect of Einstein’s theory of relativity becomes apparent. Viewed from most angles, one side of the accretion disk appears brighter than the other. Rings closer to the black hole become thinner and fainter. Here, light from the disk actually orbits the black hole multiple times before escaping to us. These rings are really multiple, highly distorted images of the accretion disk. These two effects produce a dark zone that astronomers refer to as the event horizon shadow, which is roughly twice as big as the black hole’s actual surface.įrom every viewing angle, thin rings of light appear at the edge of the black hole shadow. The event horizon captures any light passing through it, and the distorted space-time around it causes light to be redirected through gravitational lensing. The humps’ sizes and shapes change as we view them from different angles, and we see no humps at all when seeing the disk exactly face on. Light from beneath the far side of the disk takes a different path, creating another hump below. Light coming to us from the top of the disk behind the black hole appears to form into a hump above it. Astronomers call this process gravitational lensing. This is because the black hole’s gravitational field warps space-time, the fabric of the universe, and light must follow this distorted path. If we could see it up close, we’d find that the accretion disk has a funny shape when viewed from most angles. Isolated black holes that have consumed the matter surrounding them do not possess an accretion disk and can be very difficult to find and study. Matter gradually works its way from the outer part of the disk to its inner edge, where it falls into the event horizon. The gas settles into a hot, bright, rapidly spinning disk. A stellar-mass black hole paired with a star may pull gas from it, and a supermassive black hole does the same from stars that stray too close. Black holes grow by consuming matter, a process scientists call accretion, and by merging with other black holes. The main light source from a black hole is a structure called an accretion disk. But astronomers can observe black holes thanks to light emitted by surrounding matter that hasn’t yet dipped into the event horizon. Because light can’t escape, black holes themselves neither emit nor reflect it, and nothing about what happens within them can reach an outside observer.
So whatever passes into the event horizon is doomed to stay inside it – even light. Inside this boundary, the velocity needed to escape the black hole exceeds the speed of light, which is as fast as anything can go. We can think of the event horizon as the black hole’s surface. Background image credit: NASA’s Goddard Space Flight Center/Jeremy Schnittman
0 kommentar(er)
