An exceptional shot. Scientists from the European Southern Observatory (ESO) have managed to take a detailed image of a star in a galaxy other than our Milky Way, a first that will allow them to better study this star at the end of its life.
160,000 light years away, the star WOH G64 is located in the Large Magellanic Cloud, a small satellite galaxy of ours.
Nicknamed “the colossal star” by astronomers, it is approximately 2,000 times larger than our Sun and is classified among the red supergiants, one of the last stages in the evolution of massive stars before their explosion as a supernova.
“We discovered an egg-shaped cocoon that closely surrounds the star,” explains Keiichi Ohnaka, an astrophysicist at the Universidad Andrés Bello in Chile, in an ESO press release.
“The ovoid shape in the center represents material ejected from the central star and still surrounding it. Another oval ring can also be seen surrounding this ovoid shape. Although additional observations are needed to definitively confirm this, we believe that this ring is also made of the material ejected by the star,” he describes to Agence France Presse.
An elongated cocoon shape
Scientists had “indications” that the star’s surroundings were not spherical, but no images had been taken until now.
“Thanks to this image, we can create a better computer model of the star and study how it expels matter before disappearing,” explains the researcher, who led a study on these observations, published on Thursday in the journal Astronomy & Astrophysics.
This elongated cocoon, a sign that the star “ejects more material in certain directions than in others,” could be a consequence of its interaction with another star, according to Keiichi Ohnaka.
“Although we have not yet found a second star, such a companion could exist and remain difficult to detect if it is much fainter than the main star,” he says.
Captured using a sophisticated instrument.
Keiichi Ohnaka’s team has long been interested in this giant star. In 2005 and 2007, these astronomers used the interferometer on ESO’s Very Large Telescope (VLTI) in Chile to learn more about its characteristics. But at that time, the interferometer only combined light from two of the VLT’s telescopes.
To obtain the image published on Thursday, astronomers had to wait for the development of the Gravity instrument, which captures light from four glasses, creating very detailed cosmic images.
Comparing these new results with previous observations, they found that WOH G64 had become dimmer over the past decade.
“The rare opportunity to observe the life of a star”
It has “undergone a significant change over the past ten years, giving us a rare opportunity to observe the life of a star in real time,” says Gerd Weigelt, co-author of the study cited in the press release and professor of astronomy at the Max Institute. Planck in Bonn, Germany.
In their final stages of life, before exploding as a supernova, red supergiants lose their outer layers of gas and dust, in a process that can last hundreds of thousands of years.
Scientists who observed WOH G64 believe that the ejected material could be responsible for its dimming and that this could mean that the star has entered a new phase of its life cycle.
“Or it could return to its previous state after a while, although we do not know how long it could take. Precisely for this reason we believe that it is important to continue observing this star with different telescopes and instruments,” emphasizes Keiichi Ohnaka.
As the star dims, it becomes increasingly difficult to take more close-up images, even with VLTI. But planned upgrades to the telescope’s instruments could soon change that.
Source: BFM TV
