- Solar-Stellar Connections
- Solar and Stellar Atmospheres
- Spectroscopy
- Stellar Structure and Evolution
The star Betelgeuse became visibly darker in 2019 and 2020, puzzling astronomers. New images show that the star was partially concealed by a cloud of dust, solving the mystery of the "Great Dimming" of Betelgeuse.
Cambridge, MA - 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 today 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.
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.
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!"
About the Center for Astrophysics | Harvard & Smithsonian
The Center for Astrophysics | Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask—and ultimately answer—humanity's greatest unresolved questions about the nature of the universe. The Center for Astrophysics is headquartered in Cambridge, MA, with research facilities across the U.S. and around the world.
Media Contact:
Nadia Whitehead
Public Affairs Officer
Center for Astrophysics | Harvard & Smithsonian
nadia.whitehead@cfa.harvard.edu
617-721-7371
Related News
Astronomers Discover New Building Blocks of Complex Organic Matter
NASA Media Call on Upcoming Air Quality Satellite Launch
Media Advisory: New Space Instrument To Deliver Near Real-Time Air Pollution Data
Air Pollution Sensor Integrated and Tested with Commercial Satellite Host
First Rocky Exoplanet Confirmed with NASA's JWST
A Leading Light in Atmospheric Science
New from JWST: An Exoplanet Atmosphere as Never Seen Before
Astronomers Warn of Risk of Misinterpreting JWST Planetary Signals
New Grant Supports Teen Air Quality Studies
Astronomers Detect Carbon Dioxide on Planet for the First Time with JWST
Projects
AstroAI
AtomDB
GMACS
For Scientists
HITRAN and HITEMP Database
Sensing the Dynamic Universe
SDU Website