by Astronomers have revealed a large number of hidden stars, including some violently erupting newborn protons as well as others that fall under an unexpected new category of red giant stars. they dubbed the last bodies “old wearers.”
These old smokers are at the center of the Milky Way, the team says, sitting quietly for years and decaying until they eventually disappear in huge clouds of smoke. The stars were discovered through a 10-year survey of the sky by the Visible and Infrared Survey Telescope (VISTA), located high in the Chilean Andes at the Cerro Paranal Observatory. This effort succeeded in tracking nearly 1 billion stars.
The same investigation, called VISTA Variables in the Via Lactea (VVV), revealed many of the erupting protons as the international team behind the study looked closely at 222 stars.
“About two-thirds of the stars were easy to classify as well-understood events of various types,” Phillip Lucas, team leader and professor at the University of Hertfordshire, said in a statement. “The rest was a bit more difficult, so we used the Very Large Telescope (VLT) to get spectra of many of them individually. A spectrum tells us how much light we can see spread out in wavelengths different, which gives a much clearer idea.” which we are looking at.”
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The stars the team saw were still hidden by the vast amount of gas and dust that blocks our view of the heart of the Milky Way.
This material is very effective at absorbing visible light — but less adept at absorbing and blocking infrared wavelengths of electromagnetic radiation. What that means is that VISTA, with its infrared eye on the cosmos, was able to look through those clouds of gas and dust to find unseen stars near the center of the Milky Way.
“Our main aim was to find rarely seen newborn stars, also known as protostars, undergoing spectacular outbursts that last for months, years, or even decades,” Zhen Guo, team member and scientist at Valparaiso University, said in the statement.
Protons in these young star systems undergo these dramatic outbursts as they gather enough mass from their natal envelope of gas to fuel hydrogen-to-helium fusion and become full-fledged stars, a process the team hoped would further learn about it.
“These outbursts occur in the slowly rotating disc of matter that is the new solar system. They help the newborn star in the center grow, but make it harder for the planets to form,” Guo said. “We still don’t understand why the discs become unstable like this.”
Astronomers say they saw 32 “screaming” star babies, which experienced brightness increases between 40 and 300 times their usual luminosity.
For many of these protostars, the explosive events that triggered such increases in brightness are still occurring, allowing the team to investigate how these eruptions change over time. which increase in brightness, reach a peak luminosity, and then fade.
Although this is what the astronomers were hunting for with VISTA, their study of the core of our galaxy turned up something completely unexpected: a star of a hitherto unknown type at the other end of the stellar life cycle.
Where are the ‘ex-smoking’ stars hanging out?
The VVV team found 21 red stars in the center of the Milky Way, showing changes in brightness over several years that were difficult to explain.
“We weren’t sure if these stars were protostars starting to erupt, or recovering from a dip in brightness caused by a disk or dust shell in front of the star – or if they were older massive stars throwing off material in the late stages. of her life,” said Lucas.
The team used light spectra from 7 of these stars to finally determine that they represent an entirely new type of red giant star that had sat quietly for years before suddenly and unexpectedly spewing clouds of smoke, and hence the name “ex-smokers”.
The old emitters are highly concentrated in the innermost region of the Milky Way’s core, known as the nuclear disk, where stars tend to have a much higher concentration of elements heavier than hydrogen and helium. Astronomers call these heavier elements “metals”.
Although the greater concentration of metals in these stars should help dust condense more easily from their outer layers of superheated gas, or plasma, it is not known how they cause smoke to be ejected.
The team thinks that solving this puzzle could help to better understand how the elements created by stars are distributed throughout the cosmos, as well as how they become the building blocks of the first generation another of the stars and planets.
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“Material ejected from old stars plays a key role in the life cycle of the elements, helping to form the next generation of stars and planets,” said Lucas. “This was thought to happen mainly in a well-studied type of star known as a Mira variable.
“However, the discovery of a new star that ejects matter may have wider implications for the distribution of heavy elements in the nuclear disk and metal-rich regions of other galaxies.”
The team’s research was published on Friday, January 26 across two papers in the journal Monthly Notices of the Royal Astronomical Society.
