Some time ago, astronomers discovered that the strange behavior of the red giant Betelgeuse was caused by the presence of an invisible companion, named Siwarha. However, it had not been possible to see it directly until now. Thanks to the Hubble Space Telescope, this has now been achieved.
Companion of Betelgeuse
Using new observations from NASA’s Hubble Space Telescope and ground-based observatories, astronomers have tracked the influence of recently discovered companion Siwarha on the gas surrounding Betelgeuse. Research conducted by scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) has detected a trail of dense, swirling gas in Betelgeuse’s vast, expanded atmosphere, shedding light on why the giant star’s brightness and atmosphere have changed in strange and unusual ways.
Detection of Siwarha’s trail
The team discovered Siwarha’s trail by carefully tracking changes in the star’s light over nearly eight years. These changes reveal the influence of a previously unconfirmed companion breaking through Betelgeuse’s outer atmosphere. This discovery solves one of the greatest mysteries about the giant star, helping scientists explain how it behaves and evolves, and opens up new opportunities for understanding other massive stars nearing the end of their lives.
Located approximately 650 light-years from Earth in the constellation Orion, Betelgeuse is a red supergiant star so large that it could contain more than 400 million Suns. Due to its enormous size and proximity, Betelgeuse is one of the few stars whose surface and surrounding atmosphere astronomers can observe directly, making it an important and accessible laboratory for studying how giant stars age, lose mass, and explode as supernovae.
Using NASA’s Hubble Space Telescope and ground-based telescopes at the Fred Lawrence Whipple Observatory and Roque de Los Muchachos Observatory, the team was able to see a pattern of changes in Betelgeuse, providing clear evidence of the long-suspected companion star and its influence on the outer atmosphere. These include changes in the spectrum of the star (specific colors of light emitted by different elements) and the speed and direction of gases in the outer atmosphere due to the trail of denser material. This trail appears immediately after the companion passes in front of Betelgeuse every six years, or approximately 2,100 days, confirming theoretical models.
Ancient mysteries and new evidence
For decades, astronomers have been tracking changes in Betelgeuse’s brightness and surface features, hoping to figure out why the star behaves this way. Curiosity intensified after the giant star seemed to “burp” in 2020 and unexpectedly dimmed. Two distinct periods of change in the star particularly puzzled scientists: a short 400-day cycle, recently linked to pulsations within the star itself, and a long 2,100-day secondary period.
Previously, scientists had considered all possible options: from large convection cells and dust clouds to magnetic activity and the possibility of a hidden companion. Recent studies have concluded that the prolonged secondary period is best explained by the presence of a low-mass companion orbiting deep within Betelgeuse’s atmosphere, and another group of scientists has reported the possible detection of such a companion. However, until now, astronomers had no evidence to support their hypothesis. Nowadays, for the first time, they have compelling evidence that the companion disrupts the atmosphere of this supergiant star.
“The idea that Betelgeuse had an undetected companion has been gaining in popularity for the past several years, but without direct evidence, it was an unproven theory,” said Andrea Dupree, lead author of the study. “With this new direct evidence, Betelgeuse gives us a front-row seat to watch how a giant star changes over time. Finding the wake of its companion means we can now understand how stars like this evolve, shed material, and eventually explode as supernovae.”
Since Betelgeuse is currently eclipsing its companion from our perspective, astronomers are planning new observations for its subsequent appearance in 2027. This breakthrough may also help explain similar mysteries involving other giant and supergiant stars.
According to phys.org
