How Quickly Do Black Holes Form?

A star can burn its hydrogen for millions or even billions of years. But when the party’s over, black holes form in an instant. How long does it all take to happen.

Uh-oh! You’re right next to a black hole that’s starting to form.

In the J.J. Abrams Star Trek Universe, this ended up being a huge inconvenience for Spock as he tried to evade a ticked off lumpy forehead Romulan who’d made plenty of questionable life choices, drunk on Romulan ale and living above a tattoo parlor.

So, if you were piloting Spock’s ship towards the singularity, do you have any hope of escaping before it gets to full power? Think quickly now. This not only has implications for science, but most importantly, for the entire Star Trek reboot! Or you know, we can just create a brand new timeline. Everybody’s doing it. Retcon, ftw.

Most black holes come to be after a huge star explodes into a supernova. Usually, the force of gravity in a huge star is balanced by its radiation – the engine inside that sends out energy into space. But when the star runs out of fuel to burn, gravity quickly takes over and the star collapses. But how quickly? Ready your warp engines and hope for the best.

Here’s the bad news – there’s not much hope for Spock or his ship. A star’s collapse happens in an instant, and the star’s volume gets smaller and smaller. Your escape velocity – the energy you need to escape the star – will quickly exceed the speed of light.

You could argue there’s a moment in time where you could escape. This isn’t quite the spot to argue about Vulcan physiology, but I assume their reaction time is close to humans. It would happen faster than you could react, and you’d be boned.

But look at the bright side – maybe you’d get to discover a whole new universe. Unless of course Black holes just kill you, and aren’t sweet magical portals for you and your space dragon which you can name Spock, in honor of your Vulcan friend who couldn’t outrun a black hole.

Artist’s impression of the supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. Credit: ESO/L.Calçada
Artist’s impression of the supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. Credit: ESO/L.Calçada

Here we’ve been talking about what happens if a black hole suddenly appears beside you. The good news is, supernovae can be predicted. Not very precisely, but astronomers can say which stars are nearing the end of their lives.

Here’s an example. In the constellation Orion, Betelgeuse the bright star on the right shoulder, is expected to go supernova sometime in the next few hundred thousand years.

That’s plenty of time to get out of the way.

So: black holes are dangerous for your health, but at least there’s lots of time to move out of the way if one looks threatening. Just don’t go exploring too close!

If you were to fall through a black hole, what do you think would happen? Naw, just kidding, we all know you’d die. Why don’t you tell us what your favorite black hole sci fi story is in the comments below!

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3 Replies to “How Quickly Do Black Holes Form?”

  1. Um, this sounds very wrong to me.

    Remember, when a star becomes a black hole it doesn’t magically increase its gravity; it just becomes more concentrated so that the distance between you and the black hole can be arbitrarily small.

    So if your spaceship is in a region of space that … any moment now … is about to be encompassed by the event horizon of a black hole, then, already, your spaceship is INSIDE A STAR. Which is pretty uncomfortable to begin with.

    Point is, there are no circumstances where a region of space you might conceivably fly your spaceship through just BEFORE a black hole forms might suddenly become a red zone AFTER it forms.

    Am I wrong somehow? Persuade me.

  2. I think you are right. As far as I know it is only the core of a Star that turns into a Black Hole and not the entire surrounding plasma. Take Betelgeuse for example, this star is expanding more and more long before the core even runs out of fuel. According to Wikipedia the radius is anywhere between 1.5 and 8.9 AU. And what’s even worse the star is pulsating and surrounded by all kinds of “nasty stuff” that would destroy any craft long before you would even reach the edge of the star not to mention the core itself.

    But even if you take a smallest possible Star that could turn into a Black Hole the circumstances are similar.

    In my understanding there is no way you could ever get close to a Black Hole that is about to form.

    OTT: Since this is my first comment here I want to say Hi to the community here. I’ve been a long time reader of this site, including the comments. Also, thanks to the staff of UT for keeping me informed of all these wonderful things.

  3. I’d agree with Adrian and Dirk here. To put it simple, if Spock is in a ship around a star, than that ship already HAS the escape velocity to avoid falling onto the star. When it starts to shrink to form a BH, that star does NOT gain mass. (If it explodes as a Supernova, it will, of course lose mass, but you mention no problem of Spock trying to avoid Supernova debris, so let’s ignore that part of the story). So, all Spock needs to do, is to keep his velocity and he will not fall into the black hole. Anyway: only if Spock were FALLING onto the surface of the star before the explosion, and he somehow survives that AND the Supernova explosion, still standing on the surface of the star, then his escape velocity would soon reach the speed of light – in the very moment of the birth of the black hole. Is that poetic? :-))

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