Short Notes on Galaxy

Before the 20th-century, people did not know anything about galaxies. Ancient Greeks discovered a stream of milk in the sky in their time, and this stream of milk can be perceived as our Milky Way Galaxy. Polynesian sailors saw something like sharks who were eating clouds. Later, they were believed to be some hazy visuals of the Milky Way galaxy. This short note on Galaxy covers all you need to know.

What is a Galaxy?

A galaxy is a collection of billions of stars, solar systems, gas, dust, black holes, moons, etc. An astronomer named Abdul Al-Rahman Al Sufi saw a large Magellanic Cloud in 964 AD, perceived as the Andromeda Galaxy. Though Al Sufi thought it was a cloud, it was a galaxy in reality. 

There are also many unidentified celestial bodies in the Galaxy, and we will read more about them in this article. The Galaxy in which the Earth resides is called the Milky Way Galaxy.

What is in the centre of every Galaxy?

The centre of any galaxy is called its galactic centre. Astronomers believe a massive black hole is at the centre of every Galaxy. For example, in the Milky Way Galaxy, a massive black hole contains 4 million solar masses. 

• Isaac Newton predicted the black hole in the 1940s. 
• Later, scientists from NASA reportedly spotted a massive black hole in the Milky Way Galaxy. 
• The black hole was seen blowing hot bubbles and bright gas. 
• This black hole is about 900 million light-years away from the Earth. 
• The black holes feed on their surrounding stars or solar systems. 
• The Milky Way Galaxy’s black hole is equivalent to billions of suns. 
• It is pretty common to have two or more black holes. Recently, an astronomer predicted that there might be more than one black hole in the Milky Way Galaxy too.

Different types of Galaxies

There are different types of galaxies present in the cosmos. Here are the different types of galaxies that have been discovered so far:

• Spiral Galaxy: Spiral Galaxy is a twisted collection of Stars and other celestial bodies. They have circular symmetry and a nucleus encircled by an outer disk. They are said to be very beautiful and are often made up of young stars—for example, the Andromeda galaxy.

• Elliptical Galaxy: Elliptical Galaxies are gigantic. They are said to be ancient. An elliptical Galaxy contains trillions of stars within it. For example, M87 (NGC 4486) 

• Irregular Galaxy: This type of Galaxy does not have any particular size. They are made up of a large amount of gas and dust. This type of Galaxy in the Universe is rare and is often young. The typical examples of such galaxies are Small and Large Magellanic Clouds.
• Lenticular Galaxy: This type of Galaxy has a central bulge surrounded by a flattened disk. It contains a small amount of dust and gas. Cartwheel Galaxy is a typical example of this type of Galaxy. 

• Dwarf Galaxy: Dwarf galaxies are very rare. They are found in galaxy clusters and are highly luminous—for example, the Large Magellanic Cloud.

• Barred Spiral Galaxy: This type of Galaxy is also in the form of a spiral, but its centre contains an extended bar in it. For example, the Milky Way galaxy and M58 (SBc)

What type is the Milky Way Galaxy?

• The Milky Way Galaxy comprises dust, gas, energy, a solar system, and stars. 
• It is a spiral galaxy. 
• It looks like a spin wheel from the top. 
• NASA predicts that our Galaxy contains 100 billion stars. 
• The planets orbit around the Sun, and the Sun orbits around the milky way. The Sun takes 250 million years to go near the centre of the milky way. 

There are billions of galaxies in the Universe. We can only see two or three galaxies with clear eyes. Andromeda is the nearest Galaxy, which can be seen through clear eyes. Scientists researched that Andromeda is getting close to our Galaxy. So, in 4.5 billion years, there may be a collision between Andromeda and the Milky Way. 

Conclusion

The Universe is a very mysterious place, and there are still many things we do not know about it. Galaxies form a significant part of the Universe. They are made of different elements and gases. Astronomers believe that Helium and Hydrogen gases are pulled into the galaxies to create new stars. Then these new stars produce Carbon, Oxygen, Iron, and other minerals. There are also reported supernova explosions in galaxies. So, we can say that the Galaxy is a very mysterious collection.