A Galaxy is a large grouping of stars that orbit round a common point, normall a supermassive black hole which is what is at the centre of our galaxy. Our star `The Sun` is one of many billions of other stars that that make up The Milky Way Galaxy. Our Milky Way is in turn, one of many billions of galaxies that make up the physical part of the universe. Galaxies also include comets, asteroids, nebulas, planets etc. Most galaxies are moving away from us but the famous Andromeda galaxy is moving towards us. No need to panic, it will not happen for millions and millions of years and by that time, the entire human race will have be gone, either dead or on another planet. It had been once thought that all the stars in the Universe was in the Milky Way but that all changed in the 1920`s during what is known as the Great Debate,
No-one knows for sure, some say it`s a super-star, a collection of bright stars or a super-black hole. The centre of the Milky Way is so far away, we`ve not yet been able to determine what is there as yet. What we do know is that we are in the suburbs of the galaxy.
Jan Hendrik Oort calculated that the centre is in the direction of the constellation of Sagittarius . The centre of the Galaxy is commonly referred to as Sagittarius A*. It is estimated at a distance of 26,000 Light Years from Earth.
A Solar System is the smallest of the three subject matter, it covers the area of a Star`s Heliosphere. Inside the solar system is the star and all the orbiting Planets, Asteroids, etc. A solar system may not even contain any planets. A Galaxy is a grouping of stars made up of millions and billions of solar systems. The Universe is the biggest of all, it encompasses everything there is, including every galaxy, every star, all matter, everything full stop.
The centre of the Galaxy is estimated at between 25,000 light years plus or minus a few thousand. We are at the edge of the galaxy so getting out of the Milky Way is quicker that getting to the centre. A light year is 5,878,625,373,183.608 miles, therefore the centre of the galaxy is very very far away.
Excluding the Milky Way, the nearest galaxy to us is the Andromeda Galaxy which is 2.5 million light years away. It won`t always be the case though, whilst most galaxies are moving away from us, the Andromeda galaxy is moving towards us with an expected collision happening in approximately 4.5 Billion years time so you got nothing to worry about then. When the galaxy hits us, it is expected that the Milky Way may end up looking like the Tadpole Galaxy, in the constellation of Draco. It is 400 million light years away.
Different religions/regions have different views as to how the galaxy came into creation. The term comes from Roman/Greek mythology where after the birth of Heracles, Hera spilled her breast milk in anger of not being the babys mother. Another variation says that it was spilled when Heracles was caught drinking Hera`s milk and was pushed off. The word galaxy derives from the greek word for milk, gala. In the beginning, when they looked up at the stars they saw a cloudy/milky area hence the name.
A galaxy may be referred to as a NGC or M number, what are they? Galaxies, Nebulas and star clusters were first catalogued by Charles Messier, a French Astronomer. His first catalogue consisted of45 was published in 1774 then grew to 103 in 1781 then finally 110. Later in 1880, the new General Catalogue was started by J.L.E.Dreyer using observations from Sir William Herschel. It contains nearly 8000 objects. Some objects can have both a M number and a NGC number as well. For example, the Andromeda Galaxy is known as both M31 and NGC224.
At the moment, the largest galaxy we know of is the IC 1101, an elliptical galaxy that is at the heart of a group of galaxies known as the Abell 2029 Galaxy Cluster. The galaxy was discovered by Sir William Herscel. The galaxy is estimated at being over 6 million light years in diameter with trillions of stars. To put that in context, the Milky Way is a 1/50th the size of the IC 1101. The IC 1101 can be seen in the constellation of Virgo.
There are four main types of Galaxies, ( Spiral, Lenticular, Irregular and Elliptical ). There are subtypes as well, for example, clockwise spiral and anti-clockwise. The best way to explain the different typesis to show you what they look like. The Andromeda galaxy is . Irregular Galaxies also include Starbust Galaxies and Ring Galaxies, example of the former is below. Irregulars lack any shape or definition that the othertypes do hence their name. Lenticular are said to be lens like in nature.
Whilst most galaxies are currently moving away from us as a result of the Big Bang. The Andromeda Galaxy is currently on a collision course with the Milky Way. It is moving at a 75 miles a second. Whilst on Earth, that is a super fast speed, it space, it is not that fast considering how far away the Andromeda galaxy is from us. The Andromeda Galaxy is not expected to hit Milky Way for at least 3 billion years. In 3 billion years, the human race unless it has got off this planet will no longer exist because The Sun would`ve made the planet inhabital. The below video is something that NASA shared on Youtube which explains more about galaxy merging and how the MIlky Way and Andromeda galaxy will merge.
|M110||Satiellite Galaxy of M31||Andromeda|
|Le Gentil Satellite Galaxy of M31||Satiellite Galaxy of M31||Andromeda|
|Andromeda Galaxy||Spiral Galaxy||Andromeda|
|NGC1569||Dwarf Irregular Galaxy||Camelopardalis|
|Whirlpool Galaxy||Spiral Galaxy||Canes Venatici|
|M106||Spiral Galaxy||Canes Venatici|
|M94||Spiral Galaxy||Canes Venatici|
|Sunflower Galaxy||Spiral Galaxy||Canes Venatici|
|M85||Spiral Galaxy||Coma Berenices|
|M88||Spiral Galaxy||Coma Berenices|
|BlackEye Galaxy||Spiral Galaxy||Coma Berenices|
|M91||Spiral Galaxy||Coma Berenices|
|M98||Spiral Galaxy||Coma Berenices|
|M99||Spiral Galaxy||Coma Berenices|
|M100||Spiral Galaxy||Coma Berenices|
|Large Magellanic Cloud||Dwarf Galaxy||Dorado|
|Spindle Galaxy||Lenticular Galaxy||Draco|
|Tadpole Galaxy||Barred Spiral Galaxy||Draco|
|NGC1300||Barred Spiral Galaxy||Eridanus|
|NGC 6050 Interracting Spiral Galaxy||Interracting Spiral Galaxy||Hercules|
|Pegasus Dwarf Irregular Galaxy||Dwarf Irregular Galaxy||Pegasus|
|Pegasus Dwarf Spheroidal Galaxy||Dwarf Spheroidal Galaxy||Pegasus|
|The Triangulum Galaxy||Spiral Galaxy||Triangulum|
|Small Magellanic Cloud||Dwarf Galaxy||Tucana|
|M108||Spiral Galaxy||Ursa Major|
|M109||Spiral Galaxy||Ursa Major|
|NGC2787||Lenticular Galaxy||Ursa Major|
|Pinwheel Galaxy||Spiral Galaxy||Ursa Major|
|M102||Spiral Galaxy ( Maybe 101 )||Ursa Major|
|Bodes Galaxy||Spiral Galaxy||Ursa Major|
|Cigar Galaxy||Irregular Galaxy||Ursa Major|
|M84||Lenticular (S0) Galaxy||Virgo|
|M86||Lenticular (S0) Galaxy||Virgo|
|Sombrero Galaxy||Spiral Galaxy||Virgo|
|IC1101 Galaxy||Elliptical Galaxy||Virgo|