Just yesterday, I posted a streak of stories on Instagram about the planned destruction of the Cassini spacecraft. In order, the stories went like this:
Actually, four of my friends pointed this out, but I put up the correction quite on time. Very obviously though, the first one to do so was Vaibhavi, who is brimming with pride at this achievement!
But now, I am going to draw your attention back to the mistakenly written sentence “Saturn enters the atomosphere of Saturn.” Why am I doing so? Because all the sayings about how it is good to make mistakes, they actually seem to be turning out just right.
After this typing error was pointed out to me, I was wondering how did I end up writing Saturn enters Saturn. It was kind of funny, until after repeating this sentence in my mind for nearly a dozen times, I thought about the possibility of Saturn actually entering Saturn! Which apparently is just a twisted and exaggerated way of saying – Saturn collapsing on itself!
Can the collapsing be for real?
This collapsing is a very common phenomenon in outer space. Several stars and other insterstellar bodies keep collapsing due to their own gravity. There was once this physicist called Wolfgang Pauli. In the most simple language, he said that no two particles of the same type can have the same quantum states. That means, if there are two electrons, they can’t exist in the same place at the same time, spinning in the same direction. So the particles within any interstellar body are continuously repelling each other. This counteracts the gravitational force of the body. Certain stars and some other bodies are so huge and dense that their gravity overcomes all the other balancing forces. This leads to the matter being drawn towards the center of mass of that body. There is a name for this mechanism – gravitational collapse.
Gravitational collapse is an essential mechanism for formation of structures in the universe. In fact, when stars collapse, depending on their initial masses, they can form three types of structures as explained below, but before that, just for your reference – the Sun is almost 330,000 times more massive than Earth! You may now read about these structures:
White Dwarfs When the stellar residue after collapse is so dense that its mass is nearly equal to the mass of Sun and the volume is almost equal to that of Earth, then it forms a white dwarf. The star from which it generates should be somewhere around 8-10.5 times the mass of Sun (solar mass).
Neutron Stars When the residue is the core of a star that’s around 10-30 solar masses, it generally forms a neutron star. Neutron stars are the densest kind of stars and have nearly twice the mass of the Sun constrained within a sphere of 10-20km diameter! In fact, a lump of neutron star matter the size of a sugar cube would weigh as much as all humanity! Feeling belittled already?
Black Holes Sometimes, when the mass of even the residues is so high that no other force can balance against the gravitational pull, the body collapses to form a black hole; say, 2-3 neutron stars coming together into one combined mass. And this matter is so dense that even Einstein’s theory of general relativity fails inside it!
If gravitational collapse is so common, can Saturn collapse too?
According to our knowledge of Saturn, it is a gas-giant. Gas-giant is the term given to giant planets that are mainly made up of Hydrogen. In the case of Saturn, Hydrogen makes up 96% of it! It’s only fair to call it a gas-giant. But despite Hydrogen being the major constituent, most of Saturn’s mass is NOT in the gaseous phase.
What if Saturn did have an all-gas matter? According to theories, a pocket of gas can undergo gravitational collapse if its mass is greater than the Jeans mass. Jeans mass is named after James Jeans who said that the Jeans mass of a gas cloud would depend on its temperature and density. BUT! The Jeans mass is actually thousands to tens of thousands of solar masses. That’s a lot of Suns! The problem is that the mass of Saturn is nearly equal to the mass of merely 95 Earths! While for a collapse, we need a mass of almost 33,000,000,000 Earths! Phew!
As a matter of fact, Saturn is so light that if you could manage to build a tub bigger than itself and fill it with water, Saturn would actually float! Its average density (0.687 g/cm3) is lesser than the density of water! Too light for a giant planet, isn’t it?
So as of now, we can surely see that Saturn is not collapsing anytime soon because the particles that make it up have sufficient space to repel each other and balance the planet against its own inward gravitational force.
Although, if we think hypothetically, and we even assume that Saturn does collapse on itself, we can very confidently dismiss the fact that it could form either a white dwarf, or a neutron star, or a black hole! It will, at most, explode after a certain point and blow all of its gases and other matter out in space which may or may not be destined to become a part of something bigger and better!