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Here’s a riddle for you:
What objects combine giant balls of neutrons, black holes, the search for aliens, and doomed stars?
Give up?
The answer is the blitzar: the flash from a type of hypothetical, dying neutron star.
If they exist, they could be the solution to a mystery astronomers have spent years
trying to solve.
And as a bonus, they’re pretty weird, too.
To understand blitzars, it helps to know a bit about neutron stars in general.
These objects can form when large stars die in gigantic explosions called supernovas.
If what’s left over after the supernova is massive enough, gravity will pull it all
into a black hole.
But if there’s a little less stuff left over, gravity will sort of force together
the protons and electrons from the old star’s core.
This creates an extremely dense ball of neutrons around fifteen kilometers across -- a neutron star.
Neutron stars aren’t quite dense enough to become black holes, but they’re close.
And they’re pretty extreme places in their own rights.
Just a teaspoon of neutron star has as much mass as Mount Everest, and its surface gravity
is almost a trillion times stronger than Earth’s.
But for this story, the most important thing about neutron stars is that they spin very
quickly -- sometimes as fast as a few hundred times a second.
They also have super-strong magnetic fields, which can push around any gas that might be
near the star.
As that gas moves, it emits radio waves.
This actually caused a bit of a kerfuffle back in the 1960s.
Those radio waves can be so rapid and orderly that, when scientists first found signals
from a neutron star, some people thought they had to be messages from aliens.
The signals were even named “LGM-1” -- short for “Little Green Men”.
Of course, LGM was renamed after we figured out what it was, and neutron stars are at
least a little less mysterious now.
Don’t get me wrong, though -- they’re still really weird.
And in some situations, neutron stars can be extra strange.
In fact, there’s one hypothetical scenario where these stars are so dense that they should’ve
been black holes from the beginning.
They’re called supramassive rotating neutron stars, and they’re the culprit behind blitzars.
The reason these stars wouldn’t have become black holes is because their rotation would
have spread out their mass just enough to avoid it.
See, spinning objects tend to bulge out because of inertia, so a spinning object is a little
bigger -- and a little less dense -- than a stationary one.
That difference could be just big enough that it stops those supramassive neutron stars
from collapsing.
But that couldn’t last forever.
Like other neutron stars, these would have powerful magnetic fields.
And over the years, those fields would carry enough energy away from the star and ultimately
make it contract.
After anywhere between a few thousand and a million years, it would actually contract
so far that it couldn’t hold off gravity any longer.
The star would suddenly collapse into a black hole, releasing a powerful burst of radio
waves as the magnetic fields get broken.
That powerful burst is a blitzar.
Now, we don’t have any concrete evidence that blitzars actually exist -- although there’s
no reason they shouldn’t.
But if they do, the fast radio bursts they create would look a lot like a phenomenon
scientists have been trying to figure out, called, well, Fast Radio Bursts.
Over the last few years, scientists have found more and more of these signals, called FRBs for short.
They’re exactly what they sound like: huge, quick bursts of radio waves.
So far, astronomers aren’t sure what causes them, and the ideas they do have are hard to test.
FRBs don’t usually repeat themselves, and we don’t know where to look for the next one.
All this uncertainty has -- maybe unsurprisingly -- led some people to speculate that FRBs
must be from aliens.
But scientists also have a few good, non-alien ideas for explaining FRBs, including some
that we’ve talked about before here on SciShow Space.
One other idea, suggested back in 2014 by a pair of European astronomers, is that blitzars
would be the perfect solution for at least some of these signals.
After all, blitzars are also huge radio bursts, and they also only happen once.
And if there were no gas around the supramassive neutron star before it collapsed, we probably
wouldn’t see any signals from it, either, like we did with LGM-1.
Of course, all of this means that blitzars would have to exist, which we don’t know yet.
To find them, scientists could look for glowing clouds near the FRB’s source, which might
be some gas that didn’t make it into the black hole.
But these clouds would be dim and hard to find -- especially for distant FRBs.
Still, we don’t know any real reason blitzars shouldn’t be out there, though, so there’s hope.
And if they are, it would mean that once again, neutron stars ruined our alien fun by being
so darn cool.
Thanks for watching this episode of SciShow Space!
If you’d like to keep exploring the weird, surprising, and awe-inspiring universe with
us, you can go to youtube.com/scishowspace and subscribe.
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