For example, some giant “planet” the size of our sun which has a surface like the moon, floating through space in darkness.
Tangentially, how are we sure that black holes aren’t these? Are we misinterpreting absence of light as black holes when instead they could just be large dark objects?
In: 9
Bright things are hot and easy to see, so we find them easily.
If something were the size of our sun, it would be another star.
Stars are so massive that they compress atoms in their core until they start nuclear fusion. Which releases a ton of heat and light, which we can see and measure. Even though stars are made of gas, something that large made of rock just isn’t feasible without a ton of gas as well. The universe 73% hydrogen. Anywhere there’s a solar mass worth of rock, theirs going to be 3x that much hydrogen gas.
Large dark objects that aren’t black holes do exist, they’re called neutron stars. Stars that have died via supernova but aren’t large enough to form a black hole will collapse down enough so their protons and electrons fuse together to make neutrons. This ends up being a massive black ball that spins around really fast, but light can still escape its pull, so it is not a black hole. Neutron stars are made of mostly neutrons, hence the name, we call this material nuetronium.
Black dwarves are also possible, however the universe isn’t old enough for one to exist. When a star like our sun dies, it becomes a white dwarf, and begins to emit light very slowly as it cools down. After about 100 trillion years, we believe a white dwarf will have cooled down enough to not emit light and become a black dwarf. This would be the most massive object that has a surface made of common matter.
Black holes aren’t really made of anything. A black hole is formed when so much matter is packed so densely (like during a supernova) that it creates a gravitational field strong enough that not even light can escape. Theoretically, at the center of a black hole is a point (0 height, length, and width) with all of the mass of a black hole. This is called a singularity, and it is impossible to observe. The big black orb you see when you look at a black hole isn’t actually the black hole, it’s the event horizon. It appears black because there is no light coming from it. If light were to come from behind, it would be sucked into the black hole. If we wanted to bounce light off of it and have that return to us, it would get sucked in. It’s literally a hole through spacetime. There is nothing there.
Latest Answers