Irregular Galaxy – Types , Size, Mass, Formation And Examples

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Topic : Irregular galaxy – Types , Size, mass, Formation and examples


When we hear the word “galaxy” the first thing which comes in our mind is our milky way galaxy. But Did you know what type of galaxy is milky way ? If you know then that’s awesome and If you don not know then for your information our milky way galaxy is a spiral galaxy.

Now the question is. Is there only one type of galaxy in the whole universe ? Well, the answer of this question is no.

There are mainly three types of galaxies:

1) Elliptical Galaxies
2) Spiral Galaxies
3) Irregular galaxies

So, Today in this Article we will learn about Irregular galaxies. Firstly let us define galaxy.

What is a Galaxy ?

Basically, A galaxy is such place or system where massive stars, planets, stellar remnants, dust particles , gases, dark matter and many other objects are bounded due to gravitational force.
So, after defining galaxy, now let us move forward and talk about Irregular galaxies in detail.

What is an Irregular galaxy ?

An irregular galaxy is a type of galaxy which does not have a specific shape or structure. That means these types of galaxies does not have a regular structure like Elliptical and Spiral galaxies.

Types of Irregular Galaxies :

There are mainly three types of Irregular galaxies :

1) Irr- I galaxy
2) Irr- II galaxy
3) dIrr galaxy

Now , Let us talk in detail about these Irregular galaxies.

1) Irr- I galaxy :

These type of Irregular galaxies have some regular structure but these regularity is not enough to place them into the Hubble sequence.

Hubble Sequence: In very simple word Hubble sequence is a classification scheme for galaxies,
Which classify galaxies according to their category.
There are two forms of Irr-I galaxies:

• Sm galaxies : These subtype of galaxies have some spiral structure , but thats not enough.
• Im galaxies : These subtype of galaxies do not have spiral structure.

2) Irr-II galaxy :

In the first type ( Irr-I ) galaxies we saw there are some structures but in Irr-II galaxies there are no structures. These galaxies are structure less. That is the reason why they are not placed in Hubble sequence.

3) dIrr galaxy :

These type of galaxies are Irregular dwarf galaxies. And also they are used to understand the evolution of galaxies due to presence of high levels of gases. So, overall these type of galaxies are very important and superior to understand the formation of galaxies in the early age of universe.

Size of Irregular galaxies :

The Irregular type galaxies are small in Size. If we Compare them with other type galaxies then, it is estimated that the collection of all irregular galaxies are about a quarter of all galaxies combined.

Mass of Irregular galaxies :

As I have mentioned above that irregular type galaxies are small in size and due to this they also have less mass as compared to other type of galaxies. It is estimated that Irregular galaxies may have about one – tenth of mass as compared to our milky way galaxy.

Formation of Irregular galaxies :

How do irregular galaxies form ?
Like all galaxies formation of these Irregular galaxies are also same. The formation of a galaxy is a very complex topic ( we will discuss it in the other article).

There are many theories which explains how the galaxies are formed , But there is no any accurate explanation for the formation of galaxies.

Now let us move to the topic.
There are some Irregular galaxies which were spiral or Elliptical in the early phase. But they deformed into a Irregular galaxy due to gravitational force of massive objects.

Some Famous Irregular galaxies name :

1) Magellanic Clouds :

Magellanic Clouds are classified as irregular dwarf Galaxy. Though it has a structure like a bar , But still it falls in the Category of Irregular galaxy.

2) IC 4710 galaxy :

IC 4710 galaxy is a Irregular dwarf galaxy , It is located in the Southern constellation of Pavo. It is estimated that , this galaxy is approximately 34 million light years away from us.

3) IC 3583 galaxy :

IC 3583 is an irregular galaxy which is located in the Virgo Constellation which is approximately 30 million Light years away from us.

4) UGC 4459 galaxy :

This Irregular dwarf galaxy is located in Ursa major constellation which is 11 million light years away from us.

About the Post :

In this article we have learnt about Irregular galaxy. In this section of Irregular galaxy we saw types of Irregular galaxy, size of Irregular galaxy, mass of Irregular galaxy and also we saw how irregular galaxies are formed.

I hope you enjoyed reading this article on Irregular galaxy. So, that’s it for today . I will see you in the next article have a good day.

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What Are Gravitational Waves ?