As the red supergiant Betelgeuse is returning to its normal levels of brightness and intensity, astronomers have taken the star’s temperature to identify the cause of its recent dimming. And no, it wasn’t about to explode , instead it was engulfed in a large cloud of dust, causing the star to darken its light for a while.
So despite everything, it is not about to go supernova, but it is a normal event in the stars:
“We see this all the time in red supergiants, and it is a normal part of their life cycle,” said astronomer Emily Levesque of the University of Washington (USA). “Red supergiants will occasionally spew material from their surface, which will condense around the star as dust. As it cools and dissipates, the dust grains will absorb some of the light that is directed at us and block our view.” (What has happened now).
Thus, the cause of the star’s dimming, which began in October 2019 , was not the sign of an imminent supernova but rather … that it is “dirty”, covered in a layer of dust made of its own essence discarded, as if they were the dead skin cells of the human being; However, just because it isn’t exploding as a supernova doesn’t mean it won’t do so in the next 100,000 years when its core collapses, astronomers say.
Powder wrapped
To determine what had caused this decrease in brightness, whether newly formed dust that was absorbing some of the Betelgeuse light or huge convection cells that had drawn hot material to the surface, where it had cooled before falling back inside, the Scientists decided to measure the temperature of the star (something that is not easy at all).
“A simple way to distinguish between these possibilities is to determine the effective surface temperature of Betelgeuse,” said Philip Massey, an astronomer at the Lowell Observatory.
How do you measure the temperature of a star?
Scientists cannot simply point a thermometer at a star and obtain the reading or data, but by observing the spectrum of light emanating from a star, its temperature can be calculated.
When astronomers calculated Betelgeuse’s temperature in mid-February, they found it to be about 3,325 degrees Celsius, just 50-100 degrees cooler than the temperature recorded in 2004, years before the star began to decline dramatically.
If Betelgeuse were dimming due to instability in the core, the theory would be pointing to an imminent supernova; but of course, we would have seen a much greater decrease in temperature. “A comparison with our 2004 spectrum immediately showed that the temperature had not changed significantly,” Massey said. “We knew the answer had to be dust.”
“Red supergiants are very dynamic stars,” say the authors. “The more we can learn about their normal behavior (fluctuations in temperature, dust, convection cells), the better we can understand them and recognize when something really unique, like a supernova, can occur.”
Referencia: Emily M. Levesque, Philip Massey. Betelgeuse Just Isn’t That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse. arXiv:2002.10463 [astro-ph.SR]. arxiv.org/abs/2002.10463
