How do Black Holes Form
Hello and welcome back to Life’s Biggest
Questions, I’m Ron McKenzie-Lefurgey.
Black holes are some of the most interesting
and mysterious objects in the universe.
There’s quite a bit we know about them,
and quite a bit that remains unknown.
While we may not know everything about them,
we do know a fair bit about how they come
about.
If you’re looking for more videos on black
holes, check out our video: What is on the
other side of a black hole?
Now get ready, it’s time to ask the question:
How do black holes form?
The idea of black holes was first posited
by geologist John Mitchell way back in 1783.
Referred to as “dark stars,” these were
stars that were so compressed, their gravitational
pull could cause the escape velocity to exceed
the speed of light.
They have so much gravity that even light
cannot escape their herculean pull, making
them appear dark.
Mitchell even suggested a way to determine
where these might be, by looking for systems
that behave as if they have two stars, when
only one is visible.
This was groundbreaking work that surprisingly
went forgotten for nearly two centuries since
many deemed it to be impossible.
However, his writings surfaced once again
in the 1970s, and were seen in a new light.
Now, it’s all fine and dandy to know WHAT
they are, but how do these holes form in the
first place?
How could so much mass be found in such a
small area?
It is taking immense self-control to avoid
making a yo mama joke right now.
Well, there are three main types of black
holes: Primordial, Stellar, and Supermassive
black holes.
Each type is believed to form in its own way.
Primordial black holes are the smallest, with
some being just the size of an atom but possessing
the mass of a mountain.
These are believed to have formed soon after
the big bang, during the radiation dominated
era.
The cosmic inflation of the time allowed for
the density contrasts required for the formation
of a black hole.
Stellar black holes, the ones most people
are familiar with, are somewhat larger.
A stellar black hole 10 miles in diameter
can possess as much as 20 times more mass
than our sun.
These are formed when the centre of a massive
star collapses onto itself, when it runs out
of nuclear fuel and produces a supernova.
If the mass of the core is below a certain
threshold, this will produce a compact star
in the form of a white dwarf, a neutron star,
or potentially a quark star.
If, however, the mass surpasses the Tolman-Oppenheimer-Volkoff
limit, it will continue to collapse until
a black hole is formed.
Finally, Supermassive black holes are the
largest, with some possessing the mass of
billions of suns.
These are found at the centre of massive galaxies.
While it’s largely agreed that they start
smaller and eventually grow to a larger size,
it’s not completely clear how they start
in the first place.
Some believe that it begins with a very massive
black hole, possessing hundreds of solar masses,
which then accretes matter from around it.
Others believe that a cluster of black holes
merges together to form a supermassive black
hole, and still others believe them to have
formed early in the universe, when large clouds
of gas collapsed together.
One thing’s for sure: These suckers are
big.
So, there you have it, Primordial black holes
are small and formed long ago, soon after
the big bang.
Stellar black holes are the result of dying
stars with a massive centre, and supermassive
black holes form by accumulating extra mass…
we’re just not quite sure how they start.
Thank you for watching Life’s Biggest Questions,
I hope this was interesting and informative,
and maybe even inspired you to look into it
further on your own.
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Until next time, I’m Ron McKenzie-Lefurgey
with Life’s Biggest Questions, wishing you
the best of luck, on your quest for answers.
