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Astronomers were confused by Betelgeuse’s “Great Dimming” – now the mystery has been solved

These images were taken with an ESO ultra-large telescope using SPHERE equipment and show the surface of the unprecedented dimming red supergiant Betelgeuse that occurred in late 2019 and early 2020. .. The image on the far left was taken in January 2019. The stars were in normal brightness, and the rest of the images were taken in December 2019, January 2020, and March 2020, especially when the brightness of the stars was significantly reduced in the southern region. Brightness returned to normal in April 2020. Credit: ESO / M. Montargès et al.

The mystery of Betelgeuse’s diminished brightness has been solved

The astronomical community was confused when Betelgeuse, the bright orange star of Orion, became visibly dark from late 2019 to early 2020. A team of astronomers has released a new image of the surface of a star taken with the Very Large Telescope (ESO’s VLT) at the European Southern Observatory. This is a clear indication of how that brightness has changed. New research reveals that the stars were partially hidden by a cloud of dust. This is a discovery that solves the mystery of Betelgeuse’s “Great Dimming”.

Due to Betelgeuse’s diminished brightness (a change that is visible to the naked eye), Miguel Montalges and his team began turning the ESO’s VLT toward the stars in late 2019. The December 2019 image, when compared to previous images taken in January of the same year, showed that the surface of the star was significantly darker, especially in the southern region. But astronomers didn’t understand why.

The team continued to observe the stars during the Great Dimming, taking two images in January 2020 and March 2020 that they had never seen before. By April 2020, the stars had returned to normal brightness.


The astronomical community was confused when Betelgeuse, the bright orange star of Orion, became visibly dark from late 2019 to early 2020. A team of astronomers has unveiled a new study done with ESO’s Extremely Large Telescope and Extremely Large Telescope Interferometer to solve the mystery of Betelgeuse’s dimming. This ESOcast Light outlines the discovery. Credit: ESO

“Once upon a time, we saw the appearance of stars changing in real time on a scale of weeks,” says Montalges of Paris Observatory in France and KU Ruben in Belgium. The images currently available are the only images that show that the brightness of the Betelgeuse surface changes over time.

In their new study, today (June 16, 2021) NatureThe team revealed that a mysterious dimming was caused by a dusty veil covering the stars. And that was, in turn, the result of a drop in the temperature of the Betelgeuse stellar surface.


This animation is a combination of four real images of the red super giant Bethel Gius, first taken in January 2019, the other images in December 2019, January 2020, March 2020, Taken during the unprecedented dimming of the stars. All images that allow the surface of the star to be resolved were taken with the SPHERE instrument of ESO’s ultra-large telescope. Astronomers were confused by the diminished brightness of Betelgeuse, but later found that it was caused by a “dusty veil” that partially concealed the southern part of the star. Credit: ESO / M. Montargès et al. / L.Karsada

The surface of Betelgeuse changes regularly as giant gas bubbles move, contract, and expand in the stars. The team concludes that shortly before Great Dimming, the star emitted a large bubble that left it. Immediately after the patch on the surface cooled, the temperature drop was sufficient for the gas to condense into solid dust.

“We witnessed the formation of so-called stardust directly,” says Montalges. His work provides evidence that dust formation is very fast and can occur near the surface of a star. “Dust emitted from cool evolved stars, such as the ones we just witnessed, can be components of terrestrial planets and life,” said KU Ruben, who was also involved in the study. Emily Cannon adds.

Wide field of view of the empty area where Betelgeuse is located

This image shows the location of the red supergiant Betelgeuse in the constellation Orion (Hunter). As highlighted in this figure, Betelgeuse is very easy to see as the right shoulder of Orion without the need for a telescope. Credit: ESO / N. Risinger (skysurvey.org)

There was some speculation online that not only the result of a dusty explosion, but also the diminished brightness of Betelgeuse could indicate an imminent death in a spectacular supernova explosion. Since no supernovae have been observed in our galaxy since the 17th century, current astronomers have no idea what to expect from the stars leading up to such an event. But this new study confirms that Betelgeuse’s Great Dimming was not an early sign that the star was heading for its dramatic fate.


This artist’s animation shows a close-up view of Betelgeuse’s irregular surface with huge, dynamic bubbles and distant stars scattered in the background. As the “virtual camera” rotates from right to left, you’ll see a dusty mass condensed from the gas emitted by the stars, obscuring the southern region of Betelgeuse from different perspectives. Astronomers were confused when the red supergiant Betelgeuse became visibly dark in late 2019 and early 2020. Thanks to a new study conducted with the ESO telescope, the diminished brightness of Betelgeuse is the result of a “dusty veil” formed from matter emerging from the stars, partially hiding its southern region. I found out. New research shows that the star is likely to have released large bubbles that move away from it. As the surface patch (darkness in the animation) quickly cooled, the temperature drop was sufficient for the gas to condense into solid dust. Credit: ESO / L.Karsada

As Canon summarized, witnessing such recognizable star dimming was equally exciting for professional and amateur astronomers. Betelgeuse’s dimming breaks this illusion. “

The team used the spectropolarized high-contrast Exoplanet REsearch (SPHERE) instrument at ESO’s VLT to directly image the surface of Betelgeuse, along with data from the GRAVITY instrument at ESO’s Very Large Telescope (VLTI). I monitored the dimming stars. .. “It was an important diagnostic tool to determine the cause of this dimming event,” says Cannon, at the ESO’s Paranal Observatory in the Atacama Desert, Chile. “We were able to not only observe the star as a point, but also uncover the details of its surface and monitor it throughout the event,” Montargès adds.

Betelgeuse Star Chart

This chart shows the location of the very bright red supergiant Betelgeuse (Alpha Orion) in the famous constellation of Orion (Hunter). This map shows most of the stars that are visible to the naked eye in good condition, and the stars themselves are marked with red circles. The star itself is clearly visible to the naked eye, but the nebulae around it are not visible with a telescope. Credits: ESO, IAU, Sky & Telescope

Montargès and Cannon look forward to what the future of astronomy, especially ESO’s Extremely Large Telescope (ELT), will bring to the study of the red supergiant Betelgeuse. “The ability to reach unmatched spatial resolution allows ELT to directly image Betelgeuse in great detail,” says Canon. “It also greatly magnifies samples of red supergiants whose surfaces can be resolved by direct imaging, further helping to unravel the mystery behind the wind of these giant stars.”


This video takes viewers from the constellation of Orion to the surface of the supergiant Betelgeuse, which underwent unprecedented dimming in late 2019 and early 2020. As you approach the star, you will see the “flame” of the star, the cloud of dust. It was captured with a dramatic image taken with the VISIR device of ESO’s ultra-large telescope. The point displayed at the end of the zoom is a March 2020 image taken with an ESO ultra-large telescope using SPHERE equipment, showing the visible plane of Betelgeuse, sized close to Jupiter’s orbit. Credit: ESO / P. Kerbera / M. Montargès et al. , Digitized Sky Survey 2. Acknowledgments: E. Pantin, N. Risinger (skysurvey.org). Music: JB Monel (www.johanmonell.com)

See also: “Dusty Veil Covering Betelgeuse During Great Dimming” June 16, 2021 Nature..
DOI: 10.1038 / s41586-021-03546-8

The team consists of M. Montargès (LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris France). [LESIA] And Astronomy Institute, KU Ruben, Belgium [KU Leuven]), E. Canon (KU Ruben), E.La Gadeck (University of the Cote d’Azur, Cote d’Azur Observatory, CNRS, Laboratoire Lagrange, Nice, France [OCA]), A. deKoter (Anton Pannekoek Institute for Astronomy, University of Amsterdam, Netherlands, KU Leuven), P.M. Kervella (LESIA), J. Sanchez-Bermudez (Max Planck Institute for Astronomy, Heidelberg, Germany) [MPIA] And Instituto de Astronomía, Universidad Nacional Autóno made México, Mexico City, Mexico), C. Paladini (Southern Europe Observatory, Santiago, Chile) [ESO-Chile]), F. Cantalloube (MPIA), L. Decin (KU Leuven and School of Chemistry, University of Leeds, UK), P. Scicluna (ESO-Chile), K. Kravchenko (Max Planck Institute for Extraterrestrial Physics, Germany), AK Dupree (Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA), S. Ridgway (NSF NOIRLab, Tucson, AZ, USA), M. Wittkowski (European Southern Observatory, Garching bei Munchen, Germany) [ESO-Garching]), N. Anugu (Steward Observatory, University of Arizona, Tucson, Arizona, USA, Faculty of Physics and Astronomy, University of Exeter, UK) [Exeter]), R. Norris (New Mexico Institute for Mining Technology, Socorro, USA), G. Rau (NASA Goddard Space Flight Center, Exoplanet and Stellar Astronomical Physics Laboratory, Greenbelt, Maryland, USA) [NASA Goddard] And Department of Physics, Catholic University USA, Washington DC, USA), G. LESIA, A. Chiavassa (OCA), S. Klaus (Exeter), JD Monnier (University of Michigan, Faculty of Astronomy, Ann Arbor), MI, USA [Michigan]), F. Millour (OCA), J.-B. Le Bouquin (Univ. GrenobleAlpes, CNRS, IPAG, Grenoble, France and Michigan), X. Haubois (ESO-Chile), B. Lopez (OCA), P. Stee (OCA), and W. Danchi (NASA Goddard).

ESO is Europe’s most important intergovernmental astronomy organization and the world’s most productive terrestrial observatory. There are 16 member countries: Austria, Belgium, Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, Netherlands, Poland, Portugal, Spain, Sweden, Switzerland, United Kingdom, and host country Chile and as a strategic partner With Australia. ESO has an ambitious program focused on the design, construction and operation of powerful ground-based observation facilities that enable astronomers to make important scientific discoveries. ESOs also play a leading role in facilitating and organizing cooperation in astronomical research. ESO operates three unique world-class observation sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates two research telescopes: the Extremely Large Telescope and its world-leading Extremely Large Telescope Interferometer, and VISTA, which operates with infrared and visible VLT Survey Telescopes. The Paranal ESO will also host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner of Chajnantor’s two facilities, APEX and ALMA. ALMA is the largest astronomical project in existence. In Cerro Armasonez, near Paranal, ESO is building a 39-meter ultra-large telescope ELT. This will be “the world’s largest sky eye”.



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