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Explanation of nearby “supernova” stars dimming



Artwork: Areca is a super-large red star, nearly 1,000 times larger than the sun
Artwork: Areca is a super-large red star, nearly 1,000 times larger than the sun

Astronomers say that last year, the huge cool spots on a “super-giant”

; star close to Earth were responsible for its surprising darkening.

Red giant stars like Betelgeuse often change in brightness, but fell to 40% of their normal value between October 2019 and April 2020, which surprised astronomers.

Researchers now say that this is caused by a huge cool zone, similar to the sunspots seen on our own parent star.

There have been speculations that betel nut will become a supernova.

However, the star began to recover, and by May 2020, it had returned to its original brightness.

Betel nut, about 500 light years away from the earth, is on the verge of extinction. But it is not clear when it will explode. It may take hundreds of thousands or even a million years.

However, when the star’s fuel is exhausted, it will first collapse and then bounce back in a spectacular explosion. The earth is not dangerous, but betel nut will glow greatly in weeks or months.

It should be visible during the day and can be as bright as the moon at night.

Because it takes about 500 years for light to reach us, we will look at events that have occurred in the past few centuries.

Various schemes have been proposed to explain the latest changes in stellar brightness.

Astronomers had previously thought that the dust produced by stars would cover up stars and cause a sharp drop in brightness.

Red giant stars exhibit a behavior called pulsation, which is caused by changes in the area and temperature of the star’s surface. The pulsation can eject the outer layer of the star relatively easily.

The released gas cools down and develops into a compound that astronomers call dust.

The brightness of betel nut changes before and during darkening. Asymmetry leads the author to conclude that there is a huge star point
The brightness of betel nut changes before and during darkening. Asymmetry leads the author to conclude that there is a huge star point

To test the dust idea, astronomers used the Atacama Pathfinder Experiment (APEX) in Chile and the James Clerk Maxwell Telescope (JCMT) in Mauna Kea, Hawaii. These telescopes can measure electromagnetic radiation in the sub-millimeter wave spectral range. The wavelength of this radiation is one thousand times the wavelength of visible light.

This part of the electromagnetic spectrum is particularly suitable for observing the distribution of cosmic dust.

Steve Mairs, co-author of the Taiwan East Asia Observatory who cooperated with JCMT, said: “What surprised us is that even in the sub-millimeter wave range, betel nuts are dimmed by 20%.”

The researchers say the results are incompatible with the presence of dust. Astronomers say that, instead, changes in the temperature of the light sphere-the luminous surface of the star-are most likely to cause a decrease in brightness.

“Since December 2019, the corresponding Betelgeuse high-resolution images show areas of varying brightness. Together with our results, this clearly shows that huge star points cover 50% to 70% of the visible surface, and the temperature Below the bright star Peter Scicluna, co-author of the Southern European Observatory (Eso).

“In comparison, a typical sunspot is the size of the Earth. The star spot of Areca is one hundred times larger than the sun. The sudden decline of Areca does not mean that it is becoming supernova. The size of the star point.” The author Professor Albert Zijlstra said.

Compared to our sun, betel nuts are about 20 times heavier and about 1,000 times heavier. If placed in the center of the solar system, it will almost reach Jupiter’s orbit.

The results of the study were published in the Astrophysical Journal Letters.

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