A STAR IS BORN

A STAR IS BORN

                                                                                                                -Srinanda Nath

I refuse to believe that you haven’t once in your life, stared at the night sky and wondered what’s out there! To a layman, the night sky is a canvas, where he sees stars and occasionally, he may recollect having heard about a comet/shooting star. To most, the night sky is where you go, once you die, and you magically get transformed into a celestial body. Guess what? They are not 100% wrong about that! 

Stepping into geology, you probably know about the grand inauguration (sadly we weren’t invited) that we had 13.7 billion years ago, the Big Bang; if you don’t, I expect that you must have heard about the namesake show (P.S. please don’t get your hopes up, the show has nothing to do with the Big Bang). Everything that you see and touch around you, was created during this event that we call the Big Bang. Contrary to the name, there wasn’t a bang, it was an event which marked the beginning of an expansion, rather than an explosion. You could imagine it somewhat like a point (what we normally call a Singularity), which started expanding and continued to expand till it was more like a volume. Space as we see now, came into existence owing to this expansion, and time as well. We like to think that there wasn’t time before the Big Bang. Space and time, the two words that all sci-fi directors love, came into existence because of the Big Bang (it really breaks my heart to not see Big Bang in the credits). Questions like why and how did the Singularity appear, are still unknown? From the Singularity, the universe started expanding exponentially (something we call a cosmic inflation), following which there was a fall in temperature, just as we would expect with any matter that expands. This expansion that started 13.7 billion years ago continues till this day and age. So, what was there in all the space that the Big Bang created? Matter, as we know it, was also the contribution of the Big Bang (we really don’t give Big Bang the credit it deserves!). Just 3 minutes after the beginning of the expansion, matter started to synthesize and continued roughly about 17 minutes. A lot of you would be ready to shoot me in the face with facts like ‘matter can neither be created nor destroyed’, but Big Bang isn’t your regular event, the temperature and density of the ambient universe was conducive enough to perform nuclear fusion then. Elements like H and He came into existence. 

                              Fig.1.1- A timeline showing the events following the Big Bang

 All the other elements we now know of, where eventually synthesized in stars or supernovae. But hey, how did stars form?! I thought we just had space and a couple of elements. Sorry to disappoint, but stars are nothing extra-ordinary, it’s just a molecular cloud (not your regular cloud with water vapor, but something similar) with elements like H and He, mostly. When a molecular cloud collapses, a star, something like our Sun forms. A radiating ball of energy. Just like our Sun, the temperature in stars is expected to be significantly high, once again an environment is formed where nuclear fusion is a possible process. In stars elements like C, Ne, O, Si and Fe form. As more and more heavier elements form in stars, nuclear fusion becomes increasingly difficult. Stars which are massive, often explode. An explosion of a star is called a supernova. This unlike Big Bang is an explosion! The explosion/ Supernova releases immense amount of energy and radiation, and sends shock-waves into the interstellar medium.  Collapse of the star, followed by the explosion, i.e., supernovae, is the main cause instrumental in forming other heavier and newer elements.

                      

                               Fig.1.2- Crab nebula CREDIT: NASA/ESA/ASU/J. HESTER

 Conclusively, you are mostly C, H and O. Death is followed by annihilation of the body, wherein these elements shall return to the Earth. A star, pretty much like us is mortal. A time will come when our Sun shall die too and our galaxy with it. Our Sun is sadly (or gladly) not the big guy we expect it to be. It's actually on the smaller side of the spectrum and hence shall not burst into a supernova. Rather it will one day run out of fuel and shall go quietly into the night. But in the process Earth and the other planets will be vaporized. We shall become a part of space, and may even be welcome as constituents of new galaxies that form from the leftovers of this one. I don’t know what he was thinking but Longfellow was right on point when he said, “Dust thou art, to dust returnest”. So, don’t be skeptical when your elders point out to a star and introduce you to your predecessors. In any case, for the time being, just be glad that you are stardust!