As of: March 18, 2024, 9:56 a.m
By: Tanja Banner
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The surface of the red supergiant Betelgeuse is bubbling, a research team says.
(Artist's impression) © Max Planck Institute for Astrophysics/Ma, Jing-Ze et al.
2024
The rapid rotation of the giant star Betelgeuse is confusing science.
Could the star's boiling surface create an illusion?
Munich – Betelgeuse, a red giant star, is one of the largest stars known to us.
It is about a thousand times larger than the sun.
If it were at the center of our solar system, it would reach as far as Jupiter.
Betelgeuse shines brightly in the night sky and is visible to the naked eye in the constellation Orion.
Some time ago, astronomers noticed that its brightness was mysteriously decreasing.
Although the mystery surrounding this phenomenon now seems to be solved, Betelgeuse is now causing confusion again.
Observations suggest that the star is rotating much faster than expected.
However, an international team of researchers led by the Max Planck Institute for Astrophysics (MPA) in Munich is questioning this theory.
The group led by graduate student Jing-Ze Ma suspects that the sophisticated telescopes that detected the star's rapid rotation may actually have observed something else: Betelgeuse's bubbling surface.
Giant star Betelgeuse appears to be rotating faster than expected
A star the size of Betelgeuse shouldn't be rotating quickly.
However, current observations suggest that the red giant is rotating at a speed of 18,000 kilometers per hour.
This is two orders of magnitude faster than would be expected from a developed single star, according to a statement from the MPA.
Using the ALMA telescope, researchers discovered a “dipolar radial velocity map” for Betelgeuse’s surface.
While one half of the star appears to be moving closer to observers, the other half appears to be moving away.
The data was interpreted as evidence of rapid rotation of Betelgeuse.
However, the star is not a perfect, round ball.
A physical process called convection causes the giant star's surface to pulsate.
This phenomenon of convection is known from everyday life, from boiling water.
The bubbles that rise in boiling water are an example of this.
Boiling bubbles rise to the surface of Betelgeuse
At Betelgeuse, however, this process is much more intense, according to the MPA.
The boiling bubbles that rise to the star's surface can be as large as the Earth's orbit around the Sun and then cover a large portion of the star's surface.
Not only the size but also the speed of the bubbles is hard to imagine: when rising and falling, they reach a speed of up to 108,000 km/h - faster than any manned spaceship.
But what does Betelgeuse's bubbling surface have to do with the star's rapid rotation?
Jing-Ze Ma's research team suggests an alternative explanation for the rapid rotation: the bubbling surface could simulate rotation.
While a group of bubbles rises on one side of the star, a group of bubbles on the other side sinks.
“Like a science fiction movie”
Given the limited resolution of the ALMA telescope, such movements could appear blurry when observed - a dipolar velocity map would be created, the research team said in a study
published in
The Astrophysical Journal Letters .
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“Most stars are just tiny points of light in the night sky.
“Betelgeuse is so incredibly large and close that we can observe and study its boiling surface with the best telescopes,” says Selma de Mink, who worked on the study.
“It still feels a bit like a sci-fi movie, as if we traveled there to see it up close.”
Lots of questions about boiling stars like Betelgeuse
Co-author Andrea Chiavassa emphasizes: “There is so much we don’t yet understand about gigantic, boiling stars like Betelgeuse.
How do they really work?
How do they lose mass?”.
He adds: “We are working very hard to make our computer simulations better and better.” New data is currently being analyzed to put the MPA team’s predictions to the test.
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