National Popcorn Day was this past Monday, and many Americans took this opportunity to consume some delicious salted butter on their favorite edible vehicle: popcorn! But popcorn is more than just one of the most delicious and popular American snacks, it also serves as a good analogy for events that are constantly occurring in the cosmos.
Imagine that a massive - at least 8 times more massive than our sun - star is represented by a corn kernel. When this kernel is placed in the microwave and heated it heats up and eventually pops. All the heat that is imparted on the kernel through the microwave's microwaves (that's why it's called a microwave after all) is released in three ways: light, sound, and heat. Unfortunately most of us can't witness the first of these three methods of energy release because the popped kernel does not glow in the visible part of the electromagnetic spectrum - unless you begin burning it of course. But heating the kernel does cause it to glow brighter in the infrared part of the electromagnetic spectrum.
The release of energy through sound and heat, on the other hand, are a lot more evident. It's precisely the sound, or popping, that reassures us that our popcorn is being cooked. But in addition to acting as a great cooking timer, the popping is also an effective way for the, now, popped kernels to lose energy. Finally, the popcorn loses the rest of its excess energy through the dissipation of heat to the air or surrounding medium.
But what happened when the kernels were heated and why did they pop? As it turns out, kernels aren't as dry as they appear. In fact, they have quite a bit of water inside their shells, which causes the kernel to vibrate when heated. Eventually the built up pressure becomes large enough such that it is able to overcome the shell's structure and it causes the kernels to pop.
So, what does this have to do with science? And specifically with the cosmos? Well, let's go back to our kernel - star analogy. Much like a kernel that's being heated in the microwave, a star also experiences extreme outward pressures. In a star, this pressure is due to nuclear fusion - the combination of at least two atomic nuclei into a new, and typically more massive, nucleus. Much like the kernel however, the star's outward pressure is fighting against a force pushing inwards: the gravitational force. The interplay between these two forces causes the star to significantly vary in size during its lifetime.
Unfortunately this is where the analogy breaks down. Unlike with kernels that pop when the internal pressure overcomes their shell, stars cause supernovae (Type II Supernovae in particular) after their internal pressure disappears and the gravitational force inwards wins out. This quick stellar (pun intended) collapse, causes a violent explosion, which we refer to as a Type II Supernova. Supernovae are more than exciting explosions, however. They are also the only way by which heavier elements (i.e. anything heavier than iron) form - naturally that is.
But the analogy doesn't completely break down! Whether you're talking about kernels or massive stars, one thing remains true: the popped product (popcorn / byproduct of a supernova) is a lot more beautiful, and delicious, than what you started out with.
To learn more about astrophysics, check out the college stellar astrophysics webpage here!
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