A lot of the larger celestial bodies within the universe follow 1 of 2 paths or life cycles. Depending on which one it follows can lead to some pretty amazing structures. Let’s have a look at space and some of it’s more awesome inhabitants; in particular, black holes.
We won’t go back to the beginning of the universe but we’ll start with space clouds called nebulae. Due to gravity, there are areas in space where gas and dust clumps together because matter wasn’t evenly distributed at the beginning. Over time, the particles are more and more attracted to one another and grow larger as they combine. If the right conditions are met then this clump of dust and gas can be the birthplace of a protostar giving it the name of a star forming nebulae. Depending on the size of the clump determines the life cycle that it follows. We’ll quickly run through the cycle that our Sun is going to follow so that we can move on to the cooler outcomes.
There are 2 basics stars that can be ‘born’ from a nebulae; a dwarf star like our sun that burns slowly with below average luminosity (brightness) lasting billions of years, or a massive star that is larger, burns brighter, faster and dies dramatically after millions of years. Regardless, both stars go through a phase known as the main sequence. During this phase hydrogen is fused together to form helium with radiation being emitted. During this sequence, there is a balance between the gravitational force inwards and the core nuclear fusion force outwards. From this point onward however, the stars go through puberty and start to experience existence differently.
Once all of the hydrogen has fused into helium, fusion between helium occurs creating heavy elements like carbon and oxygen. As this occurs the size of the star grows because the fusion of helium produces more energy as radiation and the star becomes a red giant. This process is going to occur to our Sun and when it does, it will engulf all of the planets all the way to us; but this won’t happen for a couple million years so don’t worry yet. Over time as the star slowly continues to expand, gravity has a less of an effect around the edge of the star; resulting in it losing some of its atmosphere. Eventually we’re left with a planetary nebulae, a cloud of gas and dust surrounding a very dense, very hot core. These two separate with the cloud becoming a nebulae again leading to the potential creation of new stars and the core becomes a white dwarf. A white dwarf, also known as a degenerate dwarf, is a structure that is the size of Earth with the mass of the sun. Now for the exciting stuff.
Unlike dwarf stars, massive stars can fuse larger atoms all the way to iron because of the immense gravity and temperature experienced within the core. Any element past iron requires energy instead of it releasing energy when fused so this is the largest element fused within a star. As it moves through the other elements, the outward core nuclear fusion force increases and the star becomes a red super-giant. Once it reaches a core completely made of iron, core nuclear force outwards dramatically decreases and the star starts to collapse under it’s own gravity. The sudden collapses cause all of the matter to rush together in an instance and bounce back; resulting in a supernova. The resulting structure depends on the size of the star that has just ‘died’. Most of the time, a neutron star is a result with the rest of the atmosphere of the star blowing away because of the supernova. A neutron star is the densest and smallest known star within the universe that is made entirely of neutrons (subatomic particles of an atom). If the star has a large enough initial mass then, at death, it becomes a black hole.
A black hole is an incredible phenomena in which all mathematical laws of the universe simply don’t work well. The gravitational pull of these massively dense structures prevents light from escaping and also freezes time. Not only are these structures phenomenal but we can only speculate as to what they look like. We’re currently using an array of 10 radio telescopes across the planet to try and get a clearer image of the black hole (Sagittarius A*) that currently resides at the center of the Milky Way galaxy. Scientists have been attempting this for awhile but unfortunately, the resolution of the images haven’t been great enough to create an accurate image. That is not until later on this year when some of the scopes are being swapped out in hopes of making the image clearer. The hardest thing about taking a picture of a black hole is the fact that, because light can’t escape its gravitational pull, that we can’t see them; regardless of the electromagnetic radiation we use. They can only been seen due to the effects that is has on matter and light around it. Let’s hope that speculation of their appearance can be laid to rest in the coming year.
When actually looking at a black hole, you’re seeing the event horizon and for anything to move pass this horizon, it needs to be traveling faster than the speed of light; so it isn’t possible if you get too close to one. The hole part of the black hole is where we can find a singularity. This is something that may be infinitely dense and doesn’t have any surface or volume or something else; we simply don’t know. We’re not even sure of what would happen if you were to pass through the event horizon of a black hole but there are some hypotheses. Option 1 is you die a very quick death because the magnitude of gravity increases as you move closer to the ‘center’, eventually resulting in you being pulled a part into a string of plasma approximately one atom across. Option 2 is you die a very, very, very quick death as you collide with a wall of energy just pass the event horizon becoming immediately destroyed in the most complete fashion. Even though they’re eating up everything that passes the event horizon, they will eventually evaporate because of something called Hawking Radiation. This is a process in which particles are emitted by black holes resulting in the black holes losing energy. They believe that black holes will also be involved in the Big Bounce which you can read more about here. Regardless of if we get a better picture or continue to learn more about; black holes are incredibly awesome structures to see in space. Or not see. You know what I mean.