Betelages is dimming again


As you thought it was safe to go back to ignoring Bethelues, the Red Giant star started acting again. After dimming in its first round, and then brightening, Bethelues is now slowing down once again.

In addition, this new dimming is inconsistent with Bethelues’ current brightness variation cycle – so, once again, the star is making headlines.

Beteluse, 700 light years away in the constellation of Orion and one of the brightest stars in our sky, is also one of the most interesting. This is because it is very old, about 8 to 8.5 million years old, and practically at the door of death, for a star.

It is thought to be between 10 and 25 times the mass of the Sun, and spends most of its life as a warm, blue-white giant star. Now, fusing hydrogen to its main-order days is done in the stellar core; Some time ago Betelgeuse ran out of hydrogen, and it is now mixing helium into carbon and oxygen.

Once it runs out of helium, it will fuse heavier and heavier elements, creating an iron buildup in the core that will eventually cause the star to go supernova. But, although it is to be expected dramatically just before the Great Kaboom, this time is not yet upon us. It would be, astronomers predict, a few tens of thousands of years.

Its dimming event, nicknamed the Great Feinting, which took place between September 2019 and February 2020, was decidedly dramatic, reducing the star’s brightness by nearly 25 percent.

Betelgeuse is a semi-regular variable star, which means that its light is slightly less on regular cycles. The longest of these cycles is around 5.9 years. Another 425 days. Great fainting was very close to the minimum of both these cycles, but it turned out that they had little to do with the incident.

Astronomers are now pretty sure that it was just a sneeze: Bethelues fired off a bunch of material that had been partially obscured for a time; It is not uncommon for a star of such a respectable age.

In March, Washington University astronomer Emily Levesque said, “We see it all the time in the red supergiant, and it’s a normal part of their life cycle.”

“Red supergiant will sometimes shed material from their surfaces, which will condense around the star as dust. As it cools and spreads, the dust grains will move towards some light and block our view. Will give.

So, that mystery is solved. But the new dimming will also need to be investigated. While it is not as dramatic as the Great Faint, it does not correspond to the star’s variability cycles.

Betelges’ next glow peak is due to take place … well, now-ish, August and September 2020. Therefore, it should gradually be bright throughout the year.

The brightness of the star is actually a bit difficult to track, as the position of Beteluse in our sky went behind the sun from May to early August. But NASA’s Solar and Terrestrial Relations Observatory (STEREO) is in a solar orbit that trails behind the Earth, meaning it could keep an eye on Bethelues for part of the time that was obscured by Earth’s view.

STEREO’s vision of Beteluse. (NASA / Stereo / HI)

And, from May to July, when STARO was watching it, Tara was not shining. Quite the opposite.

“Surprisingly, rather than increasing brightness or continuing the level, Beteluse has decreased from ~ May to ~ 0.5 mag from mid-May to mid-July,” said Andrea Dupree of the Harvard Smithsonian Center in Astrophysics, an astronomer A team of scientists headed by telegram dispatched.

“Star retarded at 5 mmg / day, extending STARO observations.”

The good news is that Betelgeuse is once again visible in our skies, so further observations can be made. STEREO’s heliocephalic imager recorded the brightness of the star in visible light, but may reveal more tools, for example, temperature changes – to confirm or rule out sunspot activity – and whether the star is changing in size, as in That the case of the Great Faint was found.

According to its 425-day cycle, Bethelges was due to slow down in April 2021. But, aside from its known cycles, the star can be quite unpredictable, and there are complex variations in its light that we do not understand very well right now.

So, maybe this premature decrease can actually illuminate, helping us understand what’s going on inside which is actually a very silly, undeniable star. And, in turn, it can help us understand the processes that occur at the end of the life of massive stars, in their dying years.

“This will be important,” the researchers wrote, “to continue to closely follow Bethelges through 2020/21.”

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