Note: The first photo of a black hole
In 2019, scientists released the first photo of a black hole, a photo "taken" by 8 radio telescopes from different parts of the world working together, or a composite photo.
This image tells us that a black hole does exist, but it's not a hole, or nothingness, it's a celestial body, like our sun, and other planets, only because its gravitational pull is so strong that our existing laws of nature don't work for it.
Illustration: The black hole effect in Interstellar
Of course, light can't escape the gravitational pull of a black hole, so it's not easy to "take" a picture of it, and it's not easy to prove its existence.
So, under the strong gravitational force of a black hole, what happens to objects that are accidentally "sucked in" by the black hole? Where does the inhaled substance end up?
A star being swallowed up by a black hole, source: Mark A. Ga
It is very rare for black holes to devour other celestial bodies
In fact, we can hardly observe anything else being swallowed apart from stars being swallowed up by black holes, and star phagocytic events are very rare and very unlikely to occur.
Using existing observations, scientists have calculated that within the Milky Way, there may not be more than one event in the Milky Way where a star is swallowed up by a black hole every 100,000 years.
Many people may wonder why it is so difficult to swallow a star because the gravitational pull of a black hole is so great.
In fact, the reason is very simple, the black hole's gravitational pull on the outside world is also in line with the laws of nature, we can think of it as a star with a greater gravitational force, and the stars around it are like our earth around the sun, revolving around the black hole, rather than being directly sucked into it.
Most of the time, the objects orbiting black holes, like Earth, will move steadily in their orbits, but sometimes they will be disturbed by other interferences, such as when two massive objects meet at close range, their gravitational pull will disturb each other's orbits.
Stars swallowed up by black holes, source: NASA/JPL-Calte
When this interference occurs, it has three situations, either slightly off the original orbit and continues to move steadily, or it is directly ejected, or it is pushed into the black hole.
It's a bit like the Earth moving steadily within the solar system and then being hit by asteroids from time to time.
Stars are swallowed up by black holes
When a "hapless" star is destined to fall into a black hole, it is actually the same as a smaller mass object falling into a larger mass object, except that the star "crashes" much brighter.
Image source: J. Guillochon
In the beginning, the star will be affected by tidal forces, and the black hole's gravitational pull on the near side of the star is stronger than the far side, and when a certain distance is reached, the force difference from one side to the other side will be greater than the gravitational pull of the star itself, which is called the tidal radius.
When this happens, the star is stretched along its motion like a spaghetti at the beginning, starting with an ellipsoid and then a long strip.
At this time, it is also very interesting inside the star, due to the influence of the black hole's gravity, the star's own gravity is not enough to maintain its own density and pressure, so the nuclear fusion reaction inside it will gradually stop.
The last part of the star is sucked in and part is thrown out
Next, the star will completely disintegrate, but there is much controversy about the distribution of matter after the star disintegrates, or how much stellar material enters the black hole, but it is certain that not the entire star is sucked in by the black hole.
A portion of this material (perhaps only 10%) will enter the black hole and add mass and energy to the black hole, but 90% of the material will be re-ejected, and this thrown part can promote the formation of new star systems.[1]
The reason why a black hole can't swallow the entire star is simple, the black hole is a gravitationally strong but relatively small size of the object, which is in stark contrast to the size of the star, so most of the star's material will be accelerated and ejected.
图源:ESA/L.
The parts of the star that are actually swallowed up by the black hole glow brightly before sliding across the black hole's event horizon (the area from which light cannot escape).
This is the last light emitted by a star before it completely disintegrates, and it may be one of the most dynamic and brightest events in the universe.
This phenomenon of a star being torn apart by a black hole is called a tidal tearing event, and the flare it erupts is similar to that of a supernova, but the supernova erupts much more frequently, and astronomers can identify both events by analyzing the spectrum.
While a single star can take millions of years to form and can emit light for billions of years, a tidal tearing event takes only a few hours and a star completely disintegrates.
Note: Large black holes have been discovered by radio telescopes
It's really rare, though, and astronomers have been watching tidal tearing events since the 1990s, and so far only about 100 have been observed in total, and most of them are candidates.
At last
The center of each galaxy is thought to be a supermassive black hole, and all the stars in the galaxy orbit this black hole.
Illustration: Sagittarius A* detected X-ray flares
For example, the center of the Milky Way, Sagittarius A*, a region with a mass of more than 4 million solar masses and a radius of only about 6.7 billion kilometers, is the region where the black hole is located, and the stars around it are moving rapidly around it.
When a star is swallowed by it, in addition to the part that is actually absorbed by it, there is actually a large part of it that is directly thrown out of the Milky Way, of course, there are also parts left in the Milky Way, and these three are the final destination of a star swallowed by a black hole.
Black holes are the most extreme celestial bodies in the universe, and they are also very interesting, and many scientists have tried to solve the mysteries, but a seemingly simple question is whether there are black holes after galaxies, or there are black holes after galaxies, which is still a mystery!
Resources:
Ethan Siegel.No, Black Holes Don't Suck Everything Into Them.forbes.2019.6.19