Waiting for Betelgeuse: what's up with the tempestuous star?

SOUL-DRIFTER

Life Long Researcher
Think of what the night sky would look like if this giant went supernova.
Probably would leave behind a black hole.

by David Dickinson, Universe Today
waitingforbe.jpg


Have you noticed that Orion the Hunter—one of the most iconic and familiar of the wintertime constellations—is looking a little… different as of late? The culprit is its upper shoulder star Alpha Orionis, aka Betelgeuse, which is looking markedly faint, the faintest it has been for the 21st century.
When will this nearby supernova candidate pop, and what would look like if it did?
Source: https://phys.org/news/2019-12-betelgeuse-tempestuous-star.html
 

pigfarmer

tall, thin, irritable
The light we see now left Betelgeuse about the time the Black Death was wiping out more than half the population of Europe. I guess we'll find out eventually if anything's happened since.
 

wwkirk

Divine
The light we see now left Betelgeuse about the time the Black Death was wiping out more than half the population of Europe. I guess we'll find out eventually if anything's happened since.
That is not really that far away considering the vastness of space.
 

nivek

As Above So Below
Google says Betelgeuse is about 642.5 light years away from Earth, would we notice any repercussions if and when it goes supernova?...

...
 

The shadow

The shadow knows!
Google says Betelgeuse is about 642.5 light years away from Earth, would we notice any repercussions if and when it goes supernova?...

...
Nope the shock wave will have disappeared by the time it reaches us.
 

pepe

Celestial
The orion system has a very close meaning to me as it resembles my late father's golf swing to a tee. Slight reverse pivot was his only weakness and is present, betelgeuse is his head, to which I nod at every time I see it with a few words.
 

SOUL-DRIFTER

Life Long Researcher
Nope the shock wave will have disappeared by the time it reaches us.
The bigger the star the bigger the resulting explosion.
This would go from simple nova to the super-nova class, possible leaving behind a black hole.
Would the x-rays and gamma-rays be dissipated to safe levels by the time it reaches us is the question.
 

pepe

Celestial

We would be so lucky to see such a show but highly unlikely to happen in our time. It's stated a few million years for a star to die, under a quarter a second for it to collapse, a few hours for the shock wave to reach the surface, a few months to brighten and a few years to fade.

We have a ten billion year bulb and exist on a twelve billion year ball and no one knows when the light was switched on.

Experts claim we aren't being pulled in but the think we are. Takes so long there is no term for it yet and if the star has the right timing and size it could use the planets as fuel. Pulling everything in with the intent of accumulating maximum matter to reseed the optimum amount.

Nature works on that basis here and it just feels right to think maximising chance would follow suit out there.

Most failing but enough succeeding.
 

nivek

As Above So Below
Betelgeuse Isn't Exploding: Mysterious Dimming Turns Out to Be Giant Dust Sneeze

The official verdict is in. As the red supergiant Betelgeuse once again returns to normal brightness levels, astronomers have taken the star's temperature to identify the cause of its recent dimming.

It turns out the star wasn't fluctuating internally; rather, Betelgeuse sneezed out a huge cloud of dust, which obscured its light for a while.

This means that the star isn't, as some had hoped, about to go supernova; in fact, it's a pretty well-understood event for a star of Betelgeuse's advanced age.

"We see this all the time in red supergiants, and it's a normal part of their life cycle," said astronomer Emily Levesque of the University of Washington.

"Red supergiants will occasionally shed material from their surfaces, which will condense around the star as dust. As it cools and dissipates, the dust grains will absorb some of the light heading toward us and block our view."

Betelgeuse caught the attention of astronomers late last year when it started plummeting in brightness. Between September 2019 and January 2020, its brightness dimmed significantly - enough to be noticeable with the naked eye.

This caused a bit of a kerfuffle. Because Betelgeuse - only about 700 light-years away, in the constellation of Orion - is one of the brightest stars in the sky. It's very old, for its kind - around 8 to 8.5 million years old. In fact, it's in the final stages of its lifespan: Betelgeuse is dying.

The ancient star's main-sequence days of fusing hydrogen in its core are done; it ran out of hydrogen some time ago, and is now fusing helium into carbon and oxygen.

Eventually, Betelgeuse's core will fuse heavier and heavier elements, ultimately resulting in a buildup of iron that will cause the core to collapse - and the old star will explode in an epic supernova.


betel-lopsided.jpg

(ESO/M. Montargès et al.)

One of the signs of such an explosion being imminent is a dramatic dimming of the star, but astronomers have predicted that Betelgeuse is still at least a few tens of thousands of years from the point of erupting into a supernova.

So you can see why its recent shenanigans had everyone intrigued, especially since its dimming was lopsided - occurring only on a part of the star.

Hypotheses included some internal convection process that was cooling the star's surface. (This would be pretty weird.) Another possibility was a giant cloud of dust and gas ejected by the star as it loses mass.

Hence, astronomers were looking very closely. On February 14 this year, they took observations to obtain Betelgeuse's spectrum - a breakdown of light by wavelength that can tell us a lot about a star's chemistry. A star such as Betelgeuse would usually be too bright for a detailed spectrum, but the researchers used a special dampening technique to reduce the light to a workable level.

One of the things a spectrum can reveal is the temperature of the star, through analysis of what we know as 'spectral lines'. Emission lines on a spectrum indicate where light is being emitted, while absorption lines indicate where it is being absorbed; we know that different elements have specific lines, and these can be used to infer the star's temperature.

What the researchers were looking for were the absorption lines of titanium oxide, which can accumulate in the upper layers of cool giant stars. Abundance of titanium oxide correlates with the temperature of the star.

According to the abundance they found, Betelgeuse's temperature is around 3,325 degrees Celsius (6,017 Fahrenheit). That's consistent both with a measurement taken by the team in 2004; and with a measurement of 3,317 degrees Celsius taken in 2011.

It's also significantly warmer than would be expected for convection processes.

"A comparison with our 2004 spectrum showed immediately that the temperature hadn't changed significantly," explained astronomer Phillip Massey of Lowell Observatory.

"We knew the answer had to be dust."

Last month, after the team had taken their observations, Betelgeuse stopped dimming and started brightening again. So supernova is once again off the table, for now.

But the glinting red star still represents an excellent opportunity to learn more about the late stages of a giant star's lifespan, so you can bet astronomers will keep studying it closely.

The research has been accepted into The Astrophysical Journal Letters and is available on arXiv.

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