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[h/t to BeninSC.]
Betelgeuse is the second brightest star in the constellation Orion, located on the hunter’s right shoulder. Betelgeuse is a a red supergiant, with a mass between 14 and 19 times the mass of our Sun. Red supergiant stars have short lifetimes that end in spectacular supernovae. Betelgeuse was observed to be dimming recently, raising concerns that the star might be getting ready to go supernova. (Betelgeuse in about 600 lightyears away from Earth, which is close enough for a supernova to make a spectacular sky show, but far enough for the radiation not to endanger life on Earth.) As it happened, the observed dimming was simply due to the star burping out a significant amount of stardust, which caused the dimming of the star by blocking a significant amount of its emitted light. The star may still go supernova at any time between now and 100,00 years from now—in fact, it may have already exploded, and we won’t know until the light of the explosion crosses the distance, which would take 600 years. However, astronomers have noticed that Betelgeuse displays behavior not typical among red supergiant stars, and a recent study has offered a novel explanation of this odd behavior.
All stars start out as gas clouds consisting mainly of hydrogen, contracting due to gravitational attraction. Eventually, pressures at the center of the proto-star rise to the level where the process of nuclear fusion starts to convert the hydrogen into helium. You might think that a large star, with its larger supply of hydrogen, would have a longer lifetime than a smaller one, but you’d be wrong. The larger the star, the shorter its lifetime—supergiants have lifetimes much shorter than stars like our Sun. Indeed, Betelgeuse, nearing the end of its life, is estimated to be just 10 million years old, while the Sun, currently about 4.6 billion years old, is expected to continue pumping out light for another ~5 billion years. When the hydrogen starts to run out, the supergiant switches to fusing its product helium into heavier elements, which causes the star to expand and turn red.
However, there are two observed properties of Betelgeuse that set it apart from other red supergiants. First, far more nitrogen has been detected in its outer regions than is typical of such stars, which suggests that the interior of the star has been roiled recently. Second, the star appears to be spinning at a much faster rate than other supergiants. In an attempt to find an explanation for these anomalies, the recent study presents the results of a simulation based on the assumption that Betelgeuse started out as a binary star system, and that in the recent past (on the astronomical time scale), the larger of these two stars consumed the smaller one.
As the supergiant star aged, its atmosphere extended to the orbit of its companion, the simulation revealed. The companion star's gravity funneled that material onto itself, increasing its own mass. Eventually, the companions started swimming through so much material that this caused friction, thus slowing the companion and drawing it inward. What happened next depended on a variety of factors, including the speed of the companion, the stars' relative masses, and how much of the primary star's atmosphere had been extended.
Sometimes the merging stars briefly flared, resulting in a significant loss of mass and thus a much smaller, highly disrupted star, the simulation showed. But in Betelgeuse's case, the merger was much quieter. The companion plunged into the primary star's atmosphere, spiraling inward and eventually merging with the helium core. This process released an enormous amount of energy, ejecting some of the star's material into space in jet-like outflows roughly equivalent to 60% of the sun's mass.
The influx of new material from the companion star disrupted the helium core, briefly returning the newly merged star to a hydrogen core fusing stage, the simulation showed. This didn't last long, however, and the newborn Betelgeuse soon became a red supergiant again.
The turbulence from this merger caused heavier elements such as nitrogen to rise to the atmosphere of the star where astronomers have detected it. Further, the angular momentum of the smaller companion would have been added to the larger star’s rotational angular momentum to speed it up. This is all speculation, of course, but it’s nonetheless a neat solution to an odd puzzle. The proof won’t be available until the star goes supernova, and its internal composition can be observed directly.
Comments are below the fold.
Top Comments (August 8, 2024):
From inkstainedwretch:
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From belinda ridgewood:
Joan McCarter posted a diary on tfg's whining about having to run against Harris, and there were some entertaining comments.
First, Shellz had a theory on how tfg arrives at his rally attendance numbers, and alx9090illustrated how that would work.
Then, it was angry marmot FTW with the fake Shakespeare quote of the day!
Highlighted by raboof:
This comment by zenbassoon in tadzio148’s recommended post Is Trump Quitting?
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