Nebulae: The ‘cloud’ of the outer space that give birth to stars 

We often hear people using the term ‘a star is born’. But our sky is full of millions of twinkling stars, the largest one being the Sun. The origins of most of the stars are unknown to mankind. In fact, it is likely that this information will remain unknown to us forever. But that doesn’t mean our astronomers will give up! So, where are these stars born from? Well, a nebula is the mother of a star.  

A nebula, which is the Latin term for ‘cloud’ in the outer space is made up of swirling gas and dust. Millions of nebulae can be found across our galaxy, the Milky Way and other galaxies in our universe. In fact, a nebula is a cloud that often forms right after a star explodes or dies. No wonder, astronomers consider nebulas involved in the birth and death of stars, that is their formation and expiration. Here, we will help you explore the different kinds of nebulae.  

Types of nebulae 
Nebulae can be categorised into various groups that are found in the star-forming region in outer space called H II or diffuse. H in H II refers to hydrogen gas, one of the key elements of stars. Whereas, the term ‘diffuse’ refers to large and irregular shaped nebulae. Here’s the most common kinds of nebulae. 

Reflection nebulae: The most common kind of nebulae is the one that contains clusters of hot and young stars within it. They are known as reflection nebulae and the clouds of gas and dust present within them are illuminated by the light reflected from these bright stars. In fact, these clouds of gas and dust often absorb radiation from stars and emit it as heat. This is when they are called absorption or emission nebulae. Example: The Triffid Nebula.  

Dark nebulae: Another common kind of nebulae are the ones that are both cold and dark in nature and stars may or may not originate inside them. They are called dark nebulae. They comprise of clouds of gas and dust containing rich amounts of hydrogen. Their alternative name is Bok globules, named after astronomer Bark Bok who discovered them in 1940. They are very dense in nature and rarely generates heat that indicates birth of new stars. Example: The Horsehead Nebula. 

Planetary nebulae: The kind of nebulae that accumulate clouds of gas and dust around a star for millennia before the death of the star are known as a planetary nebulae. As these nebulae gently blow their outer layers, they generate both light and heat, along with illuminated clouds of gas and dust, giving them a beautiful glow. These nebulae get their name from astronomer William Herschel who thought that they resemble planets. Example: The Crab Nebula.