Origin of Stars & Planets

Stars, these amazingly bright bodies that litter the night sky are the basis for all life. Our sun is a star and it’s actually brighter than majority of those in the universe. It is mostly made of hydrogen and it uses this hydrogen via nuclear fusion to create helium (4 Hydrogen when fused form one atom of Helium), light and heat. It’s similar to an ongoing thermonuclear bomb. What’s important to note is that Helium weighs a lot, as more is made it lodges itself around the core of the Sun. This causes an increase in pressure (because of an increase in weight) and through a mechanism similar to friction, the core of the star heats up. The hotter the core becomes, the faster nuclear fusion occurs. Throughout the history of our sun, it’s temperature has increased, it’s become brighter and it is continuously increasing its rate of fusion. But for the moment, it is only creating helium. Eventually, our sun will run out of hydrogen and begin to fuse helium, at this point its temperature will skyrocket because of the huge amount of pressure on the core. The sun will begin to expand because of the huge increase in nuclear reactions. Here, the temperature will be so hot that it will fuse helium into all elements up to carbon (some larger stars can create iron). This will happen until it can fuse no more and ejects its outer coat (all the helium and other elements) into space. This will probably destroy the inner planets such as Mercury and Venus and possibly us as well (don’t worry, it’s not going to happen for 4 billion years). Our star’s death will be relatively uneventful because it is not that larger. However, larger stars die through a supernova, it’s the explosion of a star and it causes the release of both a very powerful destructive force and radiation. However, here’s the kicker: the supernova’s heat is so high it will quickly produce a vast number of elements above iron! All rarer elements are created by supernovas! This is why stars are often referred to as factories, as their cycle of death and rebirth gives rise to progressively rarer elements.

This leads us to star creation, stars form after other stars die. Dying stars eject their elements and eventually this forms a cloud of dust: a nebula. Eventually, this cloud will begin to collapse and as it does so, it will begin to spin and increase in heat and speed until enough matter is gathered at the center to form a new star. Around the star, dust will remain and through gravity (attraction of matter) small rocks will form until they themselves collide with other rocks to form a larger rock (planetesimals) and so on until you have planets. Inner planets are are called terrestrial planets, they are mostly made of rock with very little water. Why little water? Because it is too close to the sun and water would evaporate. In contrast planets further away (think of our solar system, Jupiter, Saturn and their moons) are full of ICE water. They are so far away water freezes and can remain part of the growing planet. It’s a common misconception that water is rare, it’s actually abundant throughout the universe. Most of the water that exists on earth was actually brought in by ice-rich comets that spend most of their existence very far from the sun, even further than Pluto. This is actually the method used within Spore, comets are smashed into planets to create oceans. Comets are remnants of our early solar system, which is why scientists love to study them as they pass by earth (and because they are beautiful sight, of course).

Let’s talk about earth for a minute. Now if all elements on earth have come from dead stars, what does that mean about us? if you think about it, the building blocks for everything is our body originated from dead stars - hence, we are made of stars. It’s a pretty profound statement to make, but it is accurate given our current scientific understanding of the origin of the stars/planets and the universe itself.

If you are interesting in learning more about our early universe and how it came to be and other astronomy related topics, I highly recommend you check out the PBS NOVA:Origins series (free and online).

Note: Most my background is in physiology/anatomy/pathology, hence I’m a bit away from my field of expertise. If you have any further insight into the subject or have noticed inaccuracies in what I’ve said, feel free to contact me at thx@sporenormous.com