Betelgeza stains have fooled scientists. They thought the star was dying, but we would wait for the fireworks

At the turn of 2019 and 2020, Betelgeza became the real queen of the night sky. Astronomers have long known that the star is approaching the end of its life and we have large fireworks ahead. It is no wonder then that its sudden loss of brightness electrified both professional astronomers and lovers of sky observation.

Astronomers working under the direction of Thavisha Dharmawardena from the Institute of Astronomy Max Placek proved that the star’s brightness was most likely caused by huge patches on the star’s surface. Such a theory contradicts the previous one, saying that the star spewed large amounts of dust, which obscured it for some time.

Betelgeuse suddenly began to fade away

Red giants like Betelgeuse often change their brightness. The problem, however, is that between October and April, the brightness of Betelgeuse fell by as much as 40 percent. This is a huge and unusual drop in brightness. Betelgeuse itself is about 500 light-years away from Earth, so it is a relatively bright star in the sky visible in the upper arm of the Orion Constellation.

Some astronomers even wondered if we were observing the last breaths of the star before the supernova explosion. However, the team from Heidelberg has now proved that the star’s brightness decreases due to temperature changes in its photosphere. The most likely source of such temperature changes is the presence of giant star patches that resemble sunspots in many respects, only covering at least 50 to 70 percent at a time. star surface.

At the end of their lives, stars like the Sun pass into the red giant stadium. When there is a shortage of fuel inside the star, the processes that sustain the energy release process also change. The stars begin to pulsate, become unstable and change brightness in cycles lasting from hundreds to thousands of days. Betelgeuse is a red supergiant, i.e. a star about 20 times more massive than the Sun and 1000 times larger. If such a star were placed in the center of the solar system, its surface would be between Mars and Jupiter. All rocky planets would be inside it

says Dharmawarden.

Maybe Betelgeza hid behind her own dust ?

Given the huge size of the star, its gravitational pull is relatively low. Thanks to this, during subsequent pulsations, the outer layers of the star come off the surface of the star. Moving away from it, they cool down, form larger groups of atoms and molecules, accumulating in dust grains with time. This is how red giants spread heavy elements into space, from which, for example, rocky planets form.

For this reason, astronomers have suspected for some time that a lot of gas has broken off from Betelgeuse, from which dust has formed, which in turn obscured the star and hence the decrease in its brightness observed on Earth.

Telescopes say it’s not dust

To test this hypothesis, Dharmawarden and his team analyzed new and archived data from APEX and JCMT telescopes. Both instruments observe the universe in terms of submillimeter radiation. It is in this area that interstellar dust can be studied, and the cool dust shines very clearly in it.

We were surprised because it turned out that the brightness of Betelgeuse also in this range of radiation decreased by 20 percent. This means that the amount of dust around the star has not increased. In that case, the star itself is responsible for the decrease in brightness.

says Steve Mairs from the East Asian Observatory.

Stains, stains , lots of stains

According to the laws of physics, the brightness of a star depends on its diameter and the temperature of its surface. If the star decreases, its brightness should decrease at all wavelengths of radiation. In turn, the change in temperature affects different bands of the electromagnetic spectrum differently. The decrease in brightness observed in Betelgeuse in the visible range and on submillimeter waves matches the decrease in the average surface temperature of the star by 200 degrees Celsius.

It is worth noting, however, that we are talking about average brightness, and it is more likely that only some parts of the surface will decrease in brightness. High-resolution photos of the star taken in December 2019 show that the surface of the star has areas of different brightness. Research and observation results indicate that the surface of the star may have spots covering 50 to 70% of the surface. Although star spots are nothing new, such large spots are rare. We do not know how long they can stay afloat.

What’s next?

In the case of the Sun, the number of patches increases and decreases around the 11-year cycle. It is not known, however, whether the same happens with red giants, because their interior is significantly different from the interior of our Day Star. The observations of Betelgeuse in the coming years will allow researchers to determine whether the decrease in its brightness was one-off or cyclical. Either way, this star will not cease to surprise us for a long time.

Betelgeza stains have fooled scientists. They thought the star was dying, but we would wait for the fireworks