Images of Betelgeuse from different months during its "Great Dimming". Credit: M. Montargès et al. / ESO

Mystery Dimming of Star in Orion’s Constellation Solved—Here’s What You Need to Know

Initially, astronomers believed that Betelgeuse was about to explode but new images of the star revealed a different reason for its "Great Dimming".

Astronomers using ground-based telescopes have confirmed that the Great Dimming of Betelgeuse, which occurred a couple of years ago, was indeed caused by a dust cloud formed as a result of the ejection of plasma from the star’s photosphere. According to scientists, this event is not a sign of the imminent explosion of Betelgeuse as a supernova.

Everything you need to know about Betelgeuse and its Great Dimming

1. Betelgeuse is of great interest to astrophysicists – this red supergiant, being one of the largest known stars, is at the end of its evolutionary path.

2. The star is estimated to be eight million years old and could explode as a Type II supernova in the next ten thousand years.

3. Red supergiants represent the most common final stage in the evolution of stars with an initial mass from 8 to 30-35 solar masses, and during this stage, they are actively losing mass due to poorly understood mechanisms.

4. The loss of mass strongly affects the further evolution of the star, thus, studying Betelgeuse, astronomers can compose a more complete picture of the finals of the life of massive stars.

The Great Dimming of Betelgeuse shown in this short video made of images from different months in 2019 and 2020. Credit: M. Montargès, L. Calçada, ESO
The Great Dimming of Betelgeuse shown in this short video made of images from different months in 2019 and 2020. Credit: M. Montargès, L. Calçada, ESO

5. In the period from November 2019 to March 2020, the brightness of the star dropped to a record level (Great Dimming), which was also interpreted as Betelgeuse’s readiness to explode, but later its brightness recovered to normal values.

6. There were several versions of what happened: a local decrease in the effective temperature of the star, shading by a dust cloud that either just formed, or passed through the star’s disk, or a change in the angular diameter of Betelgeuse. The dust hypothesis was soon confirmed, but there was also evidence for versions not related to the influence of dust.

7. A group of astronomers led by Miguel Montargès from the Paris Observatory published the results of the analysis of observations of Betelgeuse using the SPHERE spectropolarimeter installed on the VLT telescope and the GRAVITY receiver operating on the VLTI interferometer between January 2019 and March 2020.

Location of the red supergiant Betelgeuse in Orion. Credit: ESO/N. Risinger (
Location of the red supergiant Betelgeuse in Orion. Credit: ESO/N. Risinger (

8. The researchers concluded that the Great Dimming is not a sign of an imminent Betelgeuse explosion as a supernova and was caused by dust formed during condensation in a plasma bubble ejected from the star’s photosphere earlier, possibly as a result of its pulsations.

9. It is assumed that the total mass of dust can be equal to (2.3–8.5) × 10 –2 the mass of the Earth, which is 35 to 128 percent of the average annual mass loss of a star, and the process of dust formation itself took place within several radii from Betelgeuse.

10. Scientists believe that Betelgeuse and other red supergiants can exhibit two modes of mass loss: a constant, uniform outflow of gas with a small fraction of dust from a star and episodic, localized plasma ejections that can trigger efficient dust formation processes.

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Carter, J. (2021, June 16). Betelgeuse: Its Mysterious ‘Great Dimming’ Explained At Last. Forbes.
Castelvecchi, D. (2021, June 16). Why the supergiant star Betelgeuse went mysteriously dim last year. Nature News.
European Southern Observatory. (n.d.). Mystery of Betelgeuse’s dip in brightness solved.
Montargès, M., Cannon, E., Lagadec, E., Koter, A. de, Kervella, P., Sanchez-Bermudez, J., Paladini, C., Cantalloube, F., Decin, L., Scicluna, P., Kravchenko, K., Dupree, A. K., Ridgway, S., Wittkowski, M., Anugu, N., Norris, R., Rau, G., Perrin, G., Chiavassa, A., … Danchi, W. (2021, June 16). A dusty veil shading Betelgeuse during its Great Dimming. Nature News.
Wall, M. (2021, June 17). Mystery solved? Dust cloud caused Betelgeuse star’s weird dimming, study finds.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. My experience as a freelance writer began in 2018 but I have been part of the Curiosmos family since mid-2020. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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