Hubble helps uncover the mystery of the dimming of Betelgeuse

Rodiano Bonacci
Agosto 14, 2020

And to add even more intrigue to the story, the star appears to be dimming again, which is unexpectedly early based on what astronomers know about the star. Their observations are part of a three-year Hubble study to monitor variations in the star's outer atmosphere.

Betelgeuse is an aging, red supergiant star that has swelled in size as a result of complex, evolving changes in the nuclear fusion processes in its core. It's one of the brightest stars in our sky. Stars supernova when they are at the end of their lives having run out of fuel after millions of years.

Since Betelgeuse is so much bigger than our Sun - if it were placed at the centre of the solar system its perimeter would go beyond Jupiter - it's also losing mass at a much faster rate, almost 30 trillion times higher.

By looking at Betelgeuse at UV wavelengths, researchers were able to get a better look at the star's surface and atmosphere. Because they've observed it so much, the scientists expect it to go through a dimming and brightening cycle every 420 days. But then, its brightness dipped by two-thirds and the change was visible to the naked eye.

"This material was two to multiple times more glowing than the star's typical brilliance", said Andrea Dupree, partner chief at the Harvard-Smithsonian Center for Astrophysics and lead creator on the examination, in a NASA discharge. By April 2020 it had returned to normal brightness. Luckily, the darkening occasion happened similarly as Hubble researchers were hoping to watch Betelgeuse with the telescope, giving an opportunity to comprehend why the star had started to go dim.

Astronomers looking through the Hubble data saw dense material that had been heated moving through the star's atmosphere in fall 2019, from September to November.

Hubble clocked the material moving at 321,869km/h. The next month, a bunch of ground-based telescopes spotted a diminish in brightness in the star's southern hemisphere.

Ultraviolet observations by the NASA/ESA Hubble Space Telescope suggest that the dimming was probably caused by an huge amount of superhot material ejected into space. The observations continued, and now, Hubble offers a timeline for scientists to follow, like breadcrumbs leading back through time to find the odd dimming source.

Dr. Dupree and colleagues began using Hubble early past year to observe the red supergiant.

The ultraviolet-light sensitivity capabilities of the telescope allowed researchers to see through the layers above the star's surface - a region that clocks in at more than 20,000 degrees Fahrenheit.

This sudden dimming has mystified astronomers, who scrambled to develop several theories for the abrupt change.

Using the Hubble Space Telescope, scientists succeeded in seeing the material as it left Betelgeuse's noticeable surface and then moved out through the atmosphere before the cloud formed. But in over a century-and-a-half, this has not happened to Betelgeuse.

"These ultraviolet observations appear to provide the connecting link between the known large convective cells in the photosphere and the mass ejection event that cooled to form the dust cloud in the southern hemisphere imaged in 2019 December, and led to the exceptional optical dimming of Betelgeuse in 2020 February", the researchers wrote.

What's more, new perceptions recommend the red supergiant star is dimming once more.

This interpretation is consistent with Hubble ultraviolet-light observations in February 2020, which showed that the behavior of the star's outer atmosphere returned to normal, even though visible-light images showed that it was still dimming.

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