Betelgeuse goes dark behind a homemade dust cloud

The mystery of the temporary eclipse of the star Betelgeuse that has preoccupied astronomers for the past few years has finally been solved. Turns out it wasn’t a massive gas loss, which would be a sign of a massive stellar explosion (supernova). His explanation, which was also put forward last year, is less exciting.

Betelgeuse darkens behind a cloud of dust, rising from the star itself. Special, but not a supernova predecessor. Astronomers, in part the same as those who put forward the previous theory, confirm this claim with new measurements and computer simulations. The team, led by French astronomer Miguel Montargues, not only solved the mystery of the eclipse; The study also provides new insights into the late stages of a star’s life.

Also read: Betelgeuse blows hot gas bubbles

Betelgeuse is a red giant, visible to the naked eye in the constellation Orion. The red giant’s color comes from the relatively cold surface; Around 3000 ° C – The temperature of the sun (white – yellow) is about 5500 ° C. As the name suggests, red giants are very large. Betelgeuse is almost a thousand times the size of the Sun. If Betelgeuse were in the Sun’s position, Mars would swallow and orbit Jupiter just above the Sun’s surface.

forbidden

From November 2019 to March 2020, Betelgeuse’s brightness decreased. This in itself is not strange. A giant red star pulsates, sometimes a little bigger and sometimes a little smaller. As this shape changes, the amount of light emitted also changes slightly. But the brightness drop is now unbelievably strong. The researchers concluded this from measurements of Betelgeuse over the past 100 years made by amateur astronomers around the world to American Variable Star Observer Association. “In those measurements we found no indication of stellar weakness in the last 100 years as it is today,” said Alex de Kotter, an astronomer at the University of Amsterdam and co-author of the study.

Last summer, astronomers found a possible explanation for the mysterious flaw. It has been known for some time that pulsars sometimes emit gas. As this gas leaves the star, it cools and the dust particles condense into this gas. Betelgeuse can hide behind this cloud of dust particles, partially blocking the bright light from the star from reaching Earth.

The place where it happened

this week to conclude Montargues and colleagues at nature That this statement is true. There are two strong indications for this. The first resulted from measurements in different types of light indicating that dust clouds were indeed the cause. Dust clouds absorb visible light, but allow infrared light to pass through. If you place the measurements next to each other, you can see that only visible light is blocked while Betelgeuse is reduced in brightness. The second clue is that the computer model, which simulates the size and location of the dust cloud, fits the observations.

Big stars like Betelgeuse are known to die spectacularly; With a big bang. Sometimes, just before this supernova occurs, a star emits more gas than usual. Is very low brightness a sign of increased amounts of gas being lost and thus a sign of a supernova? “Unfortunately not,” said de Cotter. “The extreme drop in brightness is not due to a marked loss of gas. The amount of gas lost itself is normal. The reason for the decrease in brightness is the dust cloud that lies exactly between Betelgeuse and Earth.”

It might also take another hundred thousand years

Alex de Cotter astronomer

However, according to de Cotter, we do not have to despair about the existence of supernovae. “However, red giants have also been observed not to exhibit any strange behavior before they die. If Betelgeuse was one of them, the spectacle could start at any moment, but it might also take another hundred thousand years. Yes.”

Importantly, the study also provides new knowledge about the late stages of stellar life, said Jaco Fink, an astronomer from the University of Amsterdam who was not involved in the research. “I think it’s amazing how researchers have shown Betelgeuse, which is about 700 light years away, up close using modern techniques. Astronomers assume that gas loss at this point occurs evenly throughout the star. But thanks to these new and detailed observations, we now know that Gas sometimes explodes from one side and sometimes from the other.”

–