In short, a Black Hole is an object in space whose gravity is so powerful that nothing can escape its gravity pull. The common theory for their creation is that they were created when a massive star explodes. A massive star is one that is many times bigger than our Sun. All stars will die eventually, once their fuel has runs out. When they do, they become one of three items in space, a white Dwarf, a neutron star or a black hole. Particles from the star that do not form into one of those will journey into space and get pulled into being an object round another star. It is believed that a star close by Earth exploded and its left over material was used in the creation of our planets. A black hole`s gravity is so strong that they can pull in light. They can destroy anything that gets in their way including our own Sun and any Star even if they`re ten times bigger than the star that our planet orbits. If you were in a spaceship that is faced with a black hole in its path, you would be lucky to escape. The Black hole would pull you into its core and crush you to a pulp. If you end up being pulled into a black hole, your ship will be destroyed and then spurted out either at the top or the bottom of the black hole. It has been estimated that there could in fact be 100 million black holes in our galaxy alone.
Black Holes have featured in science fiction such as in Disney`s eighties film `The Black Hole` where a scientist plans to travel through a Black Hole and take some unwilling passengers along for the ride. It has also featured in Andromeda where the main protagonist Dylan Hunt was trapped in the event horizon of a galaxy
You can`t look up into the sky and spot a black hole because they and the space that they inhabit is black. You look for tell tale signs that they are about. You can see a black hole when it is devouring a star like in the case of Cygnus X-1 as below or you can see it as it moves in front of something. A black hole could creep up on the solar system without us spotting it but there would be tell tale signs it was coming, changes in gravity of the Sun and surrounding space. There`s has been no changes been noticed so we`re safe for now and for a very long time,
The path that a star will take will depend on its size. Our Sun, which in comparison to us is massive, it is small compared to other stars in the universe. Our Sun is a pea compared to the size of YV Canis Major which is the size of a house. Although not exactly proportionally, it is to give you some idea of how small our Sun in. Or put it another way, if YV Canis Major was in the place of the sun, it diameter would extend to past Jupiter. There are even bigger stars out there such as the UY Scuti. Getting back to the subject in hand, a star the size of the Sun would become a White Dwarf. A white dwarf will shine for years and years eventually turning into a black dwarf. Given the believed number of years it takes for a white dwarf to become a black dwarf, there are no black dwarfes out there. If the star is over 1.4 times the size of the Sun, it will turn into a Neutron Star. A Neutron star is a star full of Neutrons hence its name. The biggest stars will collapse in on themselves and be so gravitally strong that they become black holes. 1
They`re out there, you can`t see them like you can see the planets, the moon or the stars but they are there. It is because they are the same colour as the void of space that we can`t see them straightaway. With a bit of patience and the right equipment, we can find them. The most famous Black hole that has been discovered is "Cygnus X-1", no points for guessing its in the constellation of Cygnus, the Swan. The picture below is N.A.S.A`s artists impression of what Cygnus X-1 looks like. Cygnus X-1 is close to a star and feeding off it, pulling matter from the Sun into the hole. The star that is nearest to the black hole is name HDE 226868.
Since the 1970s, more have been discovered. The only way to spot one is to watch an area of space; if the lights from the stars change inexplicable then it could be put down to the fact that the light is being affected by the black hole. A black hole could be close by but we would get some time to escape. They move slowly through space. There`s no knocking it off course like we would with a meteor. The only thing we could do is run and find another solar system to inhabit if we get the technology in time. The below diagram shows roughly where the black-hole is in relation to the constellation.
It is the point from the black hole at which not even light can escape. If you reach that point, your spacecraft will need to travel many times the speed of light to escape.
In constrast to a black hole, a white hole is the other end of a black hole. All the material that is sucked into a black hole is ejected out through a white hole. Whilst nothing can escape from being pulled into a black hole if you`re too close, the reverse of the white hole is nothing can get into a white hole. The fact that no white holes have been positively identified are used by black hole detractors that black holes don`t exist. Although when updating this page, I came across io9 which says we may have found one. The distractors to white holes will say that all the black holes are facing us so their white holes are not visible. Given that space is so large and so many black holes, how can they all be facing us?
The name gives it away, they`re bigger and more powerful than the regular black holes such as Cygnus X-1. These black holes are at the centres of galaxies such as our own the milky way. The location of our own Supermassive is on the borders of constellations Sagittarius and Scorpius and is about 25,000 light years plus or minus a few thousand. The picture below is roughly where the centre of the galaxy is. If you can locate Al Nasl and follow on diagonal direction upwards, you should see it but its probably not visible with the naked eye though. These Black Holes can be grouped into Radio Galaxies, Blazars and quasars as they can all be active, shooting particles from their centres to millions of miles away.
Like humans, the Unvierse will be born, live and then die. It was born 13.8 Billion Years ago give or take thousands of years, it is currently "living" and then as stars fade, some will turn into white dwarf stars then into black dwarf. Some will turn into black holes and they will become very prominate in the Degenerate Era, once the Stelliferious Era, the Era of the stars has ended. Even black holes will eventually disipate but that will take immense number of years, there`s not enough atoms in the universe to signify how long until the universe is back to what it was like before the big bang.
The current nearest black hole that has so far been discovered is V616 Mon in the constellation of Monoceros. It is about 3,000 light years away so too far to directly affect us. ref:Phys. The next nearest is Cygnus-X1 which is the one that is probably more well known.
To spot a black hole, you look for a dip in brightness as the black hole moved across the skyline. We wouldn`t know about it until it came to within a light year away from us, about the distance the Oort Cloud is from us. The comets in the cloud would be sent towards us but the real scarey stuff is when it comes closer as it will pull apart the asteroids in the kuiper belt sending them towards us. The black hole would easily rip apart the gas giants and then move closer towards us. Life on the planet would be destroyed long before it hit us.
There are no black holes nearby so don`t be having nightmares and dreaming about them because its unlikely to happen, As the article says, the odds of being hit by a black hole is one in a trillion. You have better chance of being hit by lightning. ref:SpaceAnswers
Our galaxy is on a collision course with the Andromeda galaxy but that will be so far in the future, billions of years in fact but when it does happen the two supermassive black holes at the centres of each galaxy will collide and create a new black hole. The result will be new star creation.