New observations have shown that Betelgeuse, a red giant located in the constellation of Orion, is acting strangely, prompting some astronomers to suggest the star is about to go supernova. According to reports, not only has the star been dimming abruptly, but astronomers have revealed that the shape of the star has also changed.
Betelgeuse is considered the eleventh-brightest star in the night sky and, after Rigel, the second-brightest in the constellation of Orion.
Classified as a red supergiant, Betelgeuse is one of the most massive stars visible to the naked eye.
If it were located at the center of our solar system, its surface would extend beyond the asteroid belt, and it would engulf the orbits of planets Mercury, Venus, Earth, Mars, and possibly even Jupiter.
In October 2019, astronomers noted something strange was happening with Betelgeuse: it began to dim noticeably.
Astronomical observations in January 2020 saw its brightness drop by a factor of around 2.5, from magnitude 0.5 to 1.5.
Betelgeuse had been a beacon in the night sky for astronomers for thousands of years. Now, something strange is happening with Betelgeuse leaving experts stumped. As of writing, Betelgeuse is about 36% of its normal brightness, a change noticeable even to the naked eye.
To find out more about the unprecedented dimming, a group of scientists led by Miguel Montargès, an astronomer at KU Leuven in Belgium, had been watching the star with ESO’s Very Large Telescope since December 2019, with the aim of understanding why its brightness has reduced so abruptly.
Among the first observations that came out of his campaign is a surprising new image of the surface of Betelgeuse, taken at the end of last year with the SPHERE instrument.
The team also observed the star with SPHERE in January 2019, before it started to dim abruptly, giving us a before and after image of the star.
Taken in visible light, the images highlight the changes that occur in the star both in brightness and in apparent form, the ESO (European Southern Observatory) reports in a statement.
Many astronomy enthusiasts wondered if Betelgeuse’s attenuation meant the star was about to explode. Like all red supergiants, Betelgeuse will one day become a supernova, but astronomers don’t believe this is happening now.
They have other hypotheses to explain what exactly is causing the change in shape and brightness of the star, seen in SPHEREs images.
“The two scenarios we are working on are cooling of the surface due to exceptional stellar activity or dust ejection towards us,” explained Montargès.
“Of course, our knowledge of red supergiants remains incomplete, and this is still a work in progress, so a surprise can still happen.”
To understand more about the changes in brightness and apparent change in shape, Montargès, and his team needed the VLT at Cerro Paranal in Chile to study the star, which is more than 700 light-years away and gather clues about its dimming.
“The ESO Paranal Observatory is one of the few facilities capable of obtaining images of the Betelgeuse surface,” the researchers revealed.
The instruments on ESO’s VLT allow observations from the visible to the middle infrared, which means that astronomers can see both the surface of Betelgeuse and the material around it.
“This is the only way we can understand what is happening to the star.”
Another new image, obtained with the VISIR instrument on the VLT, shows the infrared light emitted by the dust surrounding Betelgeuse in December 2019:
The result of the observations, above visible, were explained by Pierre Kervella of the Paris Observatory in France, whose team led the survey using the VISIR instrument.
“the wavelength of the image is similar to that detected by heat cameras. The clouds of dust, which resemble flames in the VISIR image, are formed when the star sheds its material back into space.”
Although experts don’t believe— as of now— that the star will explode, if it does, it will shine as bright as the half-moon— nine times fainter than the full moon— for more than three months.