Updated: Oct 24, 2019
Nebula, latin word for “Cloud”, are interstellar clouds in the universe composed of helium, plasma, hydrogen and dust and formed usually by gravitational collapse of gasses in the interstellar medium. Their particles that collapse have their own gravitational attraction and clump together hard enough to form these clouds.
However, they can also be formed by “Supernova remnant”, when stars eventually explode shooting out matter in all directions forming a nebula such as the “Crab Nebula”. The closest nebula to earth is known as “Orion Nebula”, which is at a distance of 1300 light years from us and stretches a distance of 25 light years.
Coolest part is that some nebulas have other nebulae inside of them such as the “Gum nebula” containing the “Vela Nebula” inside. Our sun will become a nebula in about 5 billion years from now! Nebulae are enormous in size and expand over hundreds of light years across and because of their sizes they can form stars inside of them which is also why they are also called “Star Nurseries”. Did you know that the coolest place to naturally exist in our known universe is the “Boomerang Nebula” with he temperature of -272 degrees celsius shirk is only one degree above ABSOLUTE ZERO!!!
An example would be the famous “Eagle nebula” with pillar-like structures which give birth to new stars also known as the “Star queen nebula” located in Serpens constellation. The stars inside a nebula are usually formed by the gas and dust clumping together under their gravitational pull, leading to contraction and increase in density making it hotter and eventually the hydrogen present inside ignites and new stars are formed, which emits ultraviolet rays and lights up the entire nebula, resulting in it being called an “Emission Nebula” usually pink or red because of the hot ray particles.
Another type of nebula is called a “Reflection Nebula”, named after their ability to reflect light from nearby stars and lack of ability to emit their own light, usually found in blue colour. However, an interesting phenomenon is. That the presence of a reflection nebula means their might be an emission nebula somewhere nearby!
“Planetary Nebula” is also another interesting nebula, which occurs when a star about the size of our sun runs out of its hydrogen fuel in its core and thus the hydrogen in the outer shell starts fusing and so the star starts expanding turning the star into a red giant. Later, the core of the red giant becomes so hot that it stars fusing helium atoms because of the hydrogen fusion in the core and eventually when the giant runs out of helium as well the star becomes unstable, which is when the outer shell of the star is ejected leaving it with the core alone known as a “White dwarf”, which still emits radiation.
The radiations ionise the gas atoms present in the surrounding creating the colourful displays known as planetary nebulas such as the “Cats eye”. Lastly we have the “Dark Nebula”, which can be seen against the backdrop of light (or background of our Milky Way”. They have such dense clouds and due to their dust particles such as frozen nitrogen and carbon monoxide, they nebula blocks any light from background stars and reflection nebulas!