In the twilight of their existence, stars go unnoticed before releasing a cloud of gas and dust that earns them the nickname “old smokers,” according to astronomers who reported the discovery of these stars in the heart of the Milky Way on Friday.
• Also read: After historic mission, NASA's Mars helicopter will no longer fly
• Also read: Water vapor observed in the atmosphere of a small exoplanet
“These ancient stars sit still for years or decades before bursting out like clouds of smoke, completely unexpectedly,” explains Dante Minniti of Chile’s Andrés Bello University in a press release.
They are so pale and red “that sometimes we can't see them at all,” said this professor, co-author of the study published in the Monthly Notices of the British Royal Astronomical Society.
Their “singular” behavior has never been observed before, astrophysicist Philip Lucas, lead author of the study and professor at Britain's University of Hertfordshire, told AFP.
The international team of astronomers initially searched for young stars as part of a ten-year observation program and discovered numerous protostars (forming stars).
AFP
With the discovery of at least 21 “old smokers”, he also offered them a “nice surprise”, says Professor Lucas.
They are located at the center of the Milky Way, in a region called the stellar core disk, which is home to a large concentration of stars.
New species of red giant
The “old smokers” would be a new type of red giant star, stars at the end of their lives that reach large sizes and low surface temperatures at this stage.
“The surprising thing about this discovery is observing stars standing still without doing anything,” comments Professor Lucas. And then its apparent brightness suddenly decreased 40 to 100 times until it was almost undetectable to telescopes. A few years later and without warning, they return to their original brightness.
AFP
“Everything we have been able to learn about them suggests that these stars emit plumes of smoke (…) for reasons unknown to us,” said Professor Lucas.
These clouds, made up of gas and dust, would be responsible for the decrease in the star's luminosity and would obscure it from an observer's eyes.
Their activity occurs in a region of the galaxy rich in heavy elements, to which these stars may contribute.
“The matter ejected from old stars plays a key role in the life cycle of elements and contributes to the formation of new generations of stars and planets,” explains Professor Lucas. In this case, the matter emitted and distributed by the “old smokers” should enrich the interstellar medium in which new stars are formed.
But scientists don't yet have a definitive answer to this, emphasizes Professor Lucas. “So far we’re trying to figure out what would make the most sense.”