Gravitational waves are caused by calamitous events in the Universe. Neutron stars that finally merge after circling each other for a long time can create them, and so can two black holes that collide with each other. But sometimes there's a burst of gravitational waves that doesn't have a clear cause.
One such burst was detected by LIGO/VIRGO on January 14, and it came from the same region of sky that hosts the star Betelgeuse. Yeah, Betelgeuse, aka Alpha Orionis. The star that has been exhibiting some dimming behaviour recently, and is expected to go supernova at some point in the future.
Might the two be connected?
Betelgeuse is a red supergiant star in the constellation Orion. It left the main sequence about one million years ago and has been a red supergiant for about 40,000 years. Eventually, Betelgeuse will have burned enough of its hydrogen that its core will collapse, and it will explode as a supernova.
Recently, Betelgeuse dimmed. That set off all kinds of speculation that it might be getting ready to go supernova. Astrophysicists quickly poured water on that idea. There's no exact number, but it's estimated that Betelgeuse won't go supernova for another 100,000 years. But when a star dims, there's clearly something going on.
Is this new burst of gravitational waves connected to Betelgeuse's recent dimming? To its future supernova explosion?
Astronomers understand that Betelgeuse is a variable star, and its brightness can fluctuate. Stars like Betelgeuse aren't just static entities. It's a semi-regular variable star that shows both periodic and non-periodic changes in its brightness.
The kind of gravitational waves that LIGO detected are called burst waves. It's possible that a supernova could produce them, but Betelgeuse hasn't gone supernova and won't for a long time.
Some think that the detection of gravitational waves in Betelgeuse's direction is unrelated to the star itself. In fact, the detection of the burst waves may not have even been real.
Christopher Berry is an astrophysicist studying gravitational waves at Northwestern University's Center for Interdisciplinary Exploration and Research in Astrophysics. On Twitter he spoke up about the gravitational burst waves.
New gravitational-wave candidate?https://t.co/AOqqdpeiWi#S20014 was found by an unmodelled burst search, I'm always skeptical of these, as they are easily confused with glitches— Christopher Berry (@cplberry) January 14, 2020
False alarm rate: 1 per 25 yr
Rating: 🧙♂️😐 pic.twitter.com/JuopetwKjq
Andy Howell from Las Cumbres Observatory studies supernova and dark energy. He had something to say on Twitter too, and appeared to be having fun with the whole thing. He even walked outside to check up on Betelgeuse after the detection of the burst gravitational waves.
For the record, I do know that it can take hours for the shock to reach the surface. I didn't point that out initially because I didn't want people staying up all night to watch Betelgeuse. I was mostly joking (but I did walk outside because I couldn't resist).— Andy Howell (@d_a_howell) January 14, 2020
It isn't Betelgeuse blowing up because:— Andy Howell (@d_a_howell) January 14, 2020
- It is outside the GW localization region.
- The burst might not even be real.
- The burst was probably too short.
- No neutrinos were detected
- Betelgeuse's dimming is well explained.
Me walking outside to check = buying a lottery ticket
So there you have it. No supernova for now, anyway. The burst gravitational waves may just be a glitch, and Betelgeuse's dimming is well-understood and not a threat.
One day Betelgeuse will explode, and our night sky will change forever. But for us here on Earth, that supernova poses no problem.
An exploding star is an awesome event. And it produces a cataclysm of deadly radiation. X-rays, ultraviolet radiation, and even stellar material are ejected with great force. The deadliest radiation is gamma rays, and Betelgeuse likely won't even produce any of those when it blows.
But in any case, we're about 700 light years away from Betelgeuse, and that's way too much distance for us to worry.
The biggest fallout is that the Orion constellation will change forever. And there'll be a new object to study in the sky: a supernova remnant.