While mapping out the location of a type of stars that vary in brightness, researchers using the VISTA telescope at the ESO’s Paranal Observatory in Chile have discovered a never-before-seen component of the Milky Way: a thin disc of young stars located in the central bulge.
As part of the Vista Variables in the Vía Láctea Survey, astronomers led by Istvan Dékány of the Pontificia Universidad Católica de Chile were mapping out the locations of a class of star known as Cepheids when they spotted this previously unknown feature hidden behind thick dust clouds.
“The central bulge of the Milky Way is thought to consist of vast numbers of old stars. But the VISTA data has revealed something new – and very young by astronomical standards,” Dékány, lead author of the new study published in The Astrophysical Journal Letters, said in a statement.
Survey found over 600 candidate variable stars
He and his fellow researchers used data collected by the VISTA telescope from 2010 to 2014 in their work, and found 655 candidate Celpheids—variable stars that expand and contract periodically and undergo significant changes in brightness during these periods.
Cepheids, the ESO explained, can take anywhere from a few days to several weeks to complete one of these cycles, and more time is needed for the more luminous ones to brighten and fade again than for the duller ones. These variable stars are said to be one of the best ways to measure the distances to and determine the positions of distant objects in the solar system.
However, there are actually two different classes of Cepheids, the study authors noted. One is far younger than the others. Among the new stars identified by the survey team were 35 identified as classical Cepheids—younger bright stars that are far different than older, more typical stars within the Milky Way’s central bulge. They collected data on the brightness and pulsation length of the stars, which helped determine their ages, and also calculated their distances.
“All of the 35 classical Cepheids discovered are less than 100 million years old,” second author Dante Minniti from the Universidad Andres Bello in Santiago, Chile, explained. “The youngest Cepheid may even be only around 25 million years old, although we cannot exclude the possible presence of even younger and brighter Cepheids.”
Disc of young stars could shed new light on galactic evolution
By determining precisely how young these classical Cepheids actually are, Minniti, Dékány and their fellow astronomers collected evidence that a previously unconfirmed, steady supply of new stars have been produced in the central part of our galaxy over the past 100 million years.
Furthermore, by mapping the new Cepheids, they were able to trace a completely new kind of feature in the Milky Way—a thin disc of young stars across the galactic bulge. The disc went undetected for so long because it was obscured by thick clouds of dust, and the researchers noted that its discovery helps demonstrate the incredible power of the VISTA telescope.
Dékány called their work “a powerful demonstration of the unmatched capabilities of the VISTA telescope for probing extremely obscured galactic regions that cannot be reached by any other current or planned surveys,” while Minnitti added that this region of the galaxy was “completely unknown” before they observed it in five near-infrared bands as part of the VVV survey.
Additional research will be required to determine if these Cepheids were born near their current location, or if they originated from more distant regions of space, the authors said. Determining their fundamental properties, the way they interact with other objects, and how they evolve may shed new light on the evolution of the Milky Way (and other galaxies, for that matter).
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Feature Image: ESO/Microsoft WorldWide Telescope
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