Nebula

 Hey guys! Welcome back to my blog. From the title, it is evident that this blog is all about nebula. 

An introduction about nebula has been given in my previous blog titled- white dwarf (White Dwarf). If you haven’t checked it yet, I would recommend you to read that first for a better understanding. To shoot up your curiosity, let’s see some of their images of different types of Nebula.

                  Credit & Copyright: Imaging - Josch Hambsch, Processing - Karel Teuwe

This one is known as the Helix Nebula; the closest planetary nebula with the following details: 
Diameter: 2.87 light-years
Distance: 655 light-years from earth
Constellation: Aquarius.

Credit: H. Bond et al., Hubble Heritage Team (STScI / AURA), NASA

Below is an image of the Ring Nebula taken by the Hubble telescope. 

It has the following details:

Diameter: 2.6 light-years 
Distance from the Earth: 2,283 light-years
Constellation: Lyra

So, let’s move on,

1.     What are nebulae?

The word "nebula" comes from the Latin word for "cloud". It is the basic building block of the universe.

In simple terms, it is a cloud of gas and dust.

 A nebula can be formed in several ways:

1. One of the ways is from a dying star. When a star loses its fuel and compresses itself due to gravity, it bursts out forming a very small dense object. When they explode, it gives out gas and dust. These accumulate to form a cloud-like structure around the object forming a nebula.
2. The other way is when different atoms come close together, the star starts clumping up. The more they come together, the more the gravitational force is. This gravitational force tends to pull particles together forming denser objects every time. After a very long time,  we get a gaseous cloud known as nebulae.

 2. Composition of a nebula:

It consists of 90% hydrogen, 9.9%helium, and 0.1%heavy elements like carbon.

3. How are they the basic building block of our universe?

Let's look at it from the big bang. After the big bang, the entire universe was most likely a nebula, which was cold and dense but contained hot gaseous balls on the interior. Since a nebula is a cloud of gas and dust, and gravity exists everywhere, the gas and particles tend to clump together. These aggregates grow in size, and the gravity rises as well. 

They become so large that the atoms begin to collapse beneath their gravity. This collapse warms the material at the nebula's centre, forming a hydrogen-rich star. The heat combines with hydrogen to generate helium. It goes on and on until it runs out of fuel, at that point it bursts out, releasing all of its materials, and this dust and gas form a nebula, forming stars of the next generation, but these stars contain far more diverse elements than the previous generation because the previously contained elements react with different types of gases to form diverse elements.

So, this lifecycle happens again and again with each generation having new varied elements forms the sun, planets and so much more…… and it is being said that our sun is the third-generation star.

 The fact that nebula can form stars, they are considered to be the basic building block of our universe and are also known as star nurseries.

                                            Credit: J. Hester, P. Scowen (ASU), HST, NASA

The one above is a stunning Hubble image of M-16 or Eagle Nebula. They are also known as the "Pillars of Creation." M-16 is an active star-forming region that also hides newborn stars in their wispy columns. Although this is not Hubble’s first image of this iconic feature of the Eagle Nebula, it is the most detailed. The blue colors in the image represent oxygen, red is sulfur, and the green represents both nitrogen and hydrogen. 

Nebulae are quite large. They are among the largest objects in the galaxy. Many of them are dozens or even hundreds of light-years across interesting right?

Fact: Orion nebula which is present in the Orion constellation is one of the brightest nebula present. These nebulae could be seen with a naked eye or a bioscope.

Credit: BBC Science

4.    4. CLASSIFICATION OF NEBULAE

tThey can be classified as:

1.     1. Diffuse nebulae

2.     2. Planetary nebulae

Diffuse nebula - nebulae that have no well-defined boundaries, they have unequal distribution of dust and gas. They can be further divided into dark nebula and luminous nebulae.

A dark nebula - is a nebula that has a very high concentration of gas and dust and they block the light coming behind them. These can be seen only with infrared rays ex. Horsehead Nebula.

Luminous nebulae - are nebula that can emit light.

This type of nebula is further classified into Reflection and Emission nebula.

Reflection nebulae -  are clouds and dust which reflect the light of a nearby star ex Pleiades nebula.

An emission nebula - is nebulae that can produce light on its own, unlike a reflection nebula it does need a source like a star to produce light. ex Orion Nebula.

Planetary nebulae - It is formed due to the explosion of a star mass less than our sun. When the star loses its fuel and compresses itself due to gravity it burst out forming a very small dense object known as the white dwarf. When they explode it gives out so much gas and dust that accumulate to form a cloud-like structure around the white dwarf known as the planetary nebulae. ex Ring nebula.

That’s all about nebula guys. I will see you again in my next post with an interesting topic. If you guys have any doubt, please do ask them in the comment box, and don’t forget to give your feedback which motivates me every time!