Happy #BlackHoleFriday! 🕳
In celebration of these fascinating phenomena, here are some common questions and answers about black holes: a thread 🧵⤵️
In celebration of these fascinating phenomena, here are some common questions and answers about black holes: a thread 🧵⤵️
Q: What is a black hole?
A: A stellar black hole is actually the superdense remains of a very big star that imploded and collapsed in on itself. The pull of gravity there is so strong that not even light escapes their pull, hence why we call them "black" holes!
A: A stellar black hole is actually the superdense remains of a very big star that imploded and collapsed in on itself. The pull of gravity there is so strong that not even light escapes their pull, hence why we call them "black" holes!
Q: Why can't light escape a black hole?
A: Within the event horizon of a black hole, space is curved to the point where all paths that light might take to exit, point back inside. Another way to look at it: the escape velocity is faster than the speed of light.
A: Within the event horizon of a black hole, space is curved to the point where all paths that light might take to exit, point back inside. Another way to look at it: the escape velocity is faster than the speed of light.
Q: Why don't we see more black holes?
A: There are an estimated 10 million to 1 billion black holes in our galaxy. The problem is, stellar black holes are very hard to detect as they do not emit strongly at most wavelengths and produce only modest amounts of emission.
A: There are an estimated 10 million to 1 billion black holes in our galaxy. The problem is, stellar black holes are very hard to detect as they do not emit strongly at most wavelengths and produce only modest amounts of emission.
Q: Where does the matter that a black hole consumes go?
A: Much of the matter that a black hole attracts forms an accretion disk of matter rotating around it. As matter enters the event horizon of the black hole, we can only speculate as to what happens to it.
A: Much of the matter that a black hole attracts forms an accretion disk of matter rotating around it. As matter enters the event horizon of the black hole, we can only speculate as to what happens to it.
Q: How do you know a black hole is a black hole when you see it?
A: Black holes give us clues by how they influence the motions of other objects, such as stars and gas, that happen to be near them. (1/3)
A: Black holes give us clues by how they influence the motions of other objects, such as stars and gas, that happen to be near them. (1/3)
For example, stars that pass near a black hole have their motions bent in such a way as to tell us that there must be a very large mass pulling them. Since we see no light coming from the region of the mass, we know that it must be a black hole. (2/3)
When gas/dust is drawn into a black hole, it gets heated to very high temperatures, which causes it to glow. The properties of that glowing gas also give us strong clues as to the presence of a black hole. (3/3)
Have more questions about black holes?
Learn more at: public.nrao.edu/radio-astronom…
or search "black hole" on Ask an Astronomer: public.nrao.edu/ask
Learn more at: public.nrao.edu/radio-astronom…
or search "black hole" on Ask an Astronomer: public.nrao.edu/ask
• • •
Missing some Tweet in this thread? You can try to
force a refresh
