“I have a heart for every star in the universe. There’s one dying every day, but somewhere in the expanse, there is another emerging”
We look up to the night sky we see little stars sparkling like diamonds. It is getting harder to see them with all the flickers and flashes of artificial city lights all around us, stars still fascinate us and have done so for centuries. Stars and constellations meant a lot to ancient civilisations. They marked their calendars with them. They thought they could predict the future through their position in the night sky. Stars could have carried mysteries with them for our ancestors now science has blessed us with knowledge about them. Have you ever asked yourself what are these stars, anyway? How are they formed? How did they even get there in space? Well, I have tried to answer a few questions in this post. Stay tuned!
Stars are large astronomical bodies found throughout space. Technically stars are these immense spheres of luminous plasma held together by their own gravity. Simply stars are massive spheres that burn from the inside out. This burning produces heat and light necessary for life to thrive.
How do stars glow all the time? How do they produce the heat and light that keeps them glowing? Well, they contain lots of hydrogen atoms (the lightest kind of Atom) actively combining with other hydrogen atoms to form Helium. We call this process Nuclear fusion. Nuclear fusion produces an immense amount of energy as it takes place. This process keeps the star glowing. When the star runs out of hydrogen, they stop shining. Now we know how stars work, but how did the object get there in the first place?
You might think of the Universe as a vast emptiness called space with a few galaxies here and there, that is not the case. Galaxies contain an interstellar medium made of dust and gas called stellar nurseries or Nebula. Imagine a room full of smoke and dust actively combining with each other, the smoke is dense and full of dust at some places in the room and the smoke has less dust in other places of the room. That’s how the interstellar medium looks. Similar to the smoke and dust room the interstellar medium also has different densities in different areas. The areas with high-density form molecular clouds. Stars form in these molecular clouds.
Though star formation feels like a complicated mechanism, the recipe for star formation is quite simple. All we need is Hydrogen, Gravity, lots and lots of time, that’s it!
Why hydrogen? It is the simplest of all elements and we find it in the interstellar medium. Almost 99% of the interstellar medium is composed of gas and of this 75% is hydrogen. We also find small traces of Helium. Hydrogen thus plays a major role in being an integral component. Gravity makes the matter stick together if there is no gravity we will simply end up in a universe with particles floating all over. We sure don’t want that.
All this sure doesn’t happen in a single day, it takes almost 10 million years to form a star. We must add patience to the ingredients list.
A Nebula is an enormous cloud of gas and dust thrown out into space by dying stars. This gas and dust clump together they get bigger and bigger. Their gravity increases with their size. Ultimately, it grows enormous and collapses from its own gravity. The destruction causes the material at the core of the cloud to heat and this fiery core is the beginning of a star.
Cold clouds form stars with lower mass. Giant clouds that are hotter form more massive stars. Stars also form in compact, dense clouds of gas and dust called Bok Globules (named after the scientist Bart J. Bok). We consider Bok Globules star-forming cocoons.
Protostars are very young stars at the earliest stage of their life cycle whose cores haven’t formed yet. The gas cloud collapses towards the centre under gravity and builds a low mass protostar. A pancake looking disc of gas and dust surrounds the young star. It makes protostars hard to observe. Imagine a sunny side up egg, the yolk is surrounded by the egg white like a disk, similarly; the protostar is in the centre and the gas cloud surrounds it.
The gas, dust and the other fragments in the disk continue to rain into it. The protostar enters pre-main sequence stage after all it dispenses the material in the disk.
The above process is how individual stars form, what about star clusters? How are they formed?
The interstellar gas clouds remain under equilibrium until they attain a particular mass known as Jean’s mass. Beyond that mass, the cloud collapses on itself because of the internal gravitational pull. Molecular clouds of extreme density collapse under gravity to form thousands of stars almost instantaneously. This event form star clusters.
Events such as molecular clouds colliding with each other, nearby supernova explosions, galactic collisions can also result in star formation.
Our sun is a star we live deriving its energy. Learning about other star systems and their origins can help us trace out our own history.
Planets form from particles in a disk of gas and dust, colliding and clinging together as they revolve around a Star. Earth took form the same way.
Studying the origin of stars is almost same as looking at our own past.
We are all made of star-stuff!
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Originally published at https://www.nerdsstuff.in on October 25, 2020.
