If a big enough comet hits the Earth, we all die.
But what happens if it hits the Sun?
Hmmm…
Hey guys, Amy with you getting nerdy about space-impacts on DNews today.
Comets, sometimes referred to as dirty snowballs, are giant blocks of ice and rock way out in
the Oort Cloud, the distant region home to icy planetesimals left over from our Solar
System’s formation.
They trace elliptical orbits around the Sun.
As they approach, the heat and force of the solar wind melts some of the ice, turning
it into a gorgeous, gaseous tail that astronomers love.
But some comets aren’t so lucky and whip really close to our star.
These are called Sungrazers, and they can pass within a few thousand miles of the Sun’s
surface.
But the Sun isn’t exactly solid.
It’s a mass of incredibly hot gas, mainly hydrogen.
The outermost layer is called the Solar Corona, where temperatures can be millions of degrees
Kelvin.
So what happens when a dirty snowball gets too close to something that big and hot?
Well, it’s not great for the snowball.
We know the Sun has a strong gravitational environment, so one potential death factor
for comets is the Sun’s Roche Limit.
This is the imaginary line around the Sun where if a body gets any closer it could be
ripped apart by tidal forces.
But not always.
Survival depends on that body.
If the comet doesn't have a firm enough central mass, it will be ripped apart by the Sun’s
gravitational forces — think pulling apart cotton candy.
But if the comet so frozen solid it can pass inside the Roche Limit and survive.
It’d be like trying to pull apart a jawbreaker.
It can’t happen.
Counterintuitive as it might be, it's not the Corona that poses the biggest threat to
comets; it’s not dense enough to transfer enough heat.
It’s actually solar radiation, the electromagnetic energy emitted by the Sun, that’s the danger.
This is the same radiation that causes sunburns, so it’s super intense up close and powerful
enough to sublimate ice in comets and crack apart rocks.
If the ice melts and the rock cracks, this can weaken the comet’s overall structure,
making it less likely to survive its encounter with the Sun.
But some comets, even Sungrazers, still survive!
Comet Lovejoy survived its close encounter with the Sun in December of 2011.
Astronomers observed the comet after it passed through the solar Corona.
It looked like its nucleus (the comet’s head if you will) had vanished and the tail
was longer and brighter.
Researchers concluded that the Coronal heat vaporised the ice and cracked away the rocky
body, which dissipated into the long, bright tail.
So it was worse for the wear, but alive!
Comet ISON had a similar success story in 2013; astronomers suspect it was broken apart
but the parts continued traveling together and eventually bunched up to look brighter
after its encounter with the Sun.
But what about if a comet actually hits the Sun?
Well, again, it's not solid, but that can still happen.
A big enough comet pulled into the Sun would be accelerated to more than 370 miles per
second, at which point, drag from the Sun’s atmosphere would flatten the comet with enough
force that it would explode in an airburst, releasing ultraviolet radiation and X-rays.
It could be as powerful as a magnetic flare or coronal mass ejection but in a smaller
area, sparking sun quakes.
These are all effects astronomers can see with modern instruments, but it's not going
to do any damage to the Earth.
Isn’t space just awesome?
And so many things going smashy, and not just comets!
NASA used to smash spent spacecraft into the Moon for science!
I can tell you why over on my own channel, Vintage Space.
But regardless of what else is happening in space, the Sun always looks awesome!
I tell you why in this video right here.