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
There are three sizes of Black Hole, Primordial, which are about the size of a single atom but its mass can be as much as a mountain. A primordial black hole could essentially be created when a meteor hits the Earth`s atmosphere. There`s nothing to worry as they are so small, there would be no effect on us down on planet Earth. Ref: IFL Science
The most common form of Black Holes are stellar Black Holes which are created when a star collapses in on its self. They can have a mass twenty times the mass of the Sun but in size, they could be no bigger than a 20 mile diameter sphere. They`re the most common because they out number the largest black holes which is next.
The third type of Black Hole is the largest, the supermassive black hole which we`ll just touch on now, they are at the centres of galaxies through the universe. Ref: N.A.S.A
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. The motion of other stars nearby can give you an idea that a black hole is nearb. 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, Reference is the same as the one in the previous section.
The path that a star will take will depend on its size. Our Sun, which in comparison to us is massive, it is also small compared to other stars in the universe. Our Sun is a pea compared to the size of VY 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. The diagram at N.A.S.A. will be explain what I`m saying.
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. Ref: N.A.S.A.
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. It is believed a White Hole has been discovered on June 14 2006 by the N.A.S.A. Swift satellite. The White Hole formally known as GRB 060614 was discovered by the satellite noticing an extraordinary powerful Gamma-Ray Burst in the minor constellation of Indus.
gamma-ray bursts tend to last seconds, this particular GRB lasted for 102 seconds which is why they believed it to be a sign of a White Hole. The features of the GRB matched with what we knew about White Holes hence the opinion it was a white hole. Ref: Astronaut
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.
Supermassive Black Holes can contain millions or billions times the mass of a regular black hole hence why they`re named so. As to how the Supermassive Black Holes were created, the jury is still out on this one. There are theories that a black hole at the centre of the galaxy just grew over the millions and billions of years to what they are today by consuming material from stars or other black holes.Ref: Swinburne University
Whilst most galaxies will have a supermassive black hole, one galaxy has opted to get rid of theirs. In the galaxy 3c 186 in the constellation of Lynx, the supermassive black hole is moving out of its central location. The most likely explanation is that it had collided with another supermassive black hole and was forced out. The speed at which it is moving out of its quasar is 1,300 miles a second. To put that into comparison, the solar system is orbiting its central galaxy at a speed of 15 miles a second. Ref: Extreme Tech
Like humans, the Universe 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. The next nearest is Cygnus-X1 which is the one that is probably more well known.
In September 2015, LIGO (Light Interferometer Gravitational Wave Observatory) announced that they had found evidence of gravitational waves caused by a collision between two black holes 1.3 billion light years from Earth. Gravitational Waves were first theorized by Albert Einstein in his theory of relativity but only known proven. The exact location in terms of constellation hasn`t been released but they`ve said the constellation is a southern hemispheric constellation so that rules out Ursa Minor and others then. Ref: Caltech
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.