from
https://www.sciencedaily.com/releases/2021/06/210616113835.htm

Mystery solved: Dust cloud led to Betelgeuse's 'Great Dimming'
Date:
June 16, 2021
Source:
Harvard-Smithsonian Center for Astrophysics
Summary:
When Betelgeuse, a bright orange star in the constellation of Orion,
lost more than two-thirds of its brightness in late 2019 and early 2020,
astronomers were puzzled.
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FULL STORY
When Betelgeuse, a bright orange star in the constellation of Orion,
lost more than two-thirds of its brightness in late 2019 and early 2020,
astronomers were puzzled.

What could cause such an abrupt dimming?

Now, in a new paper published Wednesday in Nature, an international team
of astronomers reveal two never-before-seen images of the mysterious
darkening -- and an explanation. The dimming was caused by a dusty veil
shading the star, which resulted from a drop in temperature on
Betelgeuse's stellar surface.

Led by Miguel Montargès at the Observatoire de Paris, the new images
were taken in January and March of 2020 using the European Southern
Observatory's Very Large Telescope. Combined with images previously
taken in January and December 2019, the astronomers clearly capture how
the stellar surface changed and darkened over time, especially in the
southern region.

"For once, we were seeing the appearance of a star changing in real-time
on a scale of weeks," Montargès says.

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According to the astronomers, this abrupt dimming was caused by the
formation of stardust.

Betelgeuse's surface regularly changes as giant bubbles of gas move,
shrink and swell within the star. The team concludes that some time
before the great dimming, the star ejected a large gas bubble that moved
away from it, aided by the star's outward pulsation. When a patch of the
surface cooled down shortly after, that temperature decrease was enough
for the heavier elements (e.g. silicon) in the gas to condense into
solid dust.

The new findings match Andrea Dupree's previous observations of
Betelgeuse using the Hubble Space Telescope. Dupree, an astronomer at
the Center for Astrophysics | Harvard & Smithsonian and a co-author on
the new paper, captured signs of dense, heated material moving through
the star's atmosphere in the months leading up to the great dimming.

"With Hubble, we could see the material as it left the star's surface
and moved out through the atmosphere, before the dust formed that caused
the star to appear to dim," Dupree says.

Dupree found that the material moved about 200,000 miles per hour as it
traveled from the star's surface to its outer atmosphere. Once the gas
bubble was millions of miles from the hot star, it cooled and formed a
dust cloud that temporarily blocked the star's light.

The star returned to its normal brightness by April 2020.

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Dupree, who has been studying Betelgeuse since 1985, hopes to continue
studying the star in hopes of catching it eject another gas bubble.

"Betelgeuse is a unique star; it is enormous and nearby and we are
observing material directly leaving the surface of the supergiant," she
says. "How and where material is ejected affects our understanding of
the evolution of all stars!"

Video 1: https://www.youtube.com/watch?v=SK_A7fegeOw

Video 2: https://www.youtube.com/watch?v=G6HEB6G4Ros

Story Source:

Materials provided by Harvard-Smithsonian Center for Astrophysics. Note:
Content may be edited for style and length.

Journal Reference:

M. Montargès, E. Cannon, E. Lagadec, A. de Koter, P. Kervella, J.
Sanchez-Bermudez, C. Paladini, F. Cantalloube, L. Decin, P. Scicluna, K.
Kravchenko, A. K. Dupree, S. Ridgway, M. Wittkowski, N. Anugu, R.
Norris, G. Rau, G. Perrin, A. Chiavassa, S. Kraus, J. D. Monnier, F.
Millour, J.-B. Le Bouquin, X. Haubois, B. Lopez, P. Stee, W. Danchi. A
dusty veil shading Betelgeuse during its Great Dimming. Nature, 2021;
594 (7863): 365 DOI: 10.1038/s41586-021-03546-8
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Harvard-Smithsonian Center for Astrophysics. "Mystery solved: Dust cloud
led to Betelgeuse's 'Great Dimming'." ScienceDaily. ScienceDaily, 16
June 2021. <www.sciencedaily.com/releases/2021/06/210616113835.htm>.

a425couple wrote on 18/6/21 2:42 am:
> from
> https://www.sciencedaily.com/releases/2021/06/210616113835.htm
>
> Mystery solved: Dust cloud led to Betelgeuse's 'Great Dimming'
> Date:
> June 16, 2021
> Source:
> Harvard-Smithsonian Center for Astrophysics
> Summary:
> When Betelgeuse, a bright orange star in the constellation of Orion,
> lost more than two-thirds of its brightness in late 2019 and early 2020,
> astronomers were puzzled.
> Share:
>
> FULL STORY
> When Betelgeuse, a bright orange star in the constellation of Orion,
> lost more than two-thirds of its brightness in late 2019 and early 2020,
> astronomers were puzzled.
>
> What could cause such an abrupt dimming?

Late 2019 early 2020!! Maybe Betelgeuse caught a does of CoViD-19 ....
and then recovered!! ;-P
--
Daniel