Known as VVV-WIT-08, the star attenuated so much that it almost disappeared from view when astronomers observed it over time.
It is not uncommon for a star ‘brightness factor to change. Some stars pulsate, or a star in a star pair, called binary, may be obscured by another. But it is incredibly rare for a star to fade and shine again or flash.
The observation of this star has led scientists to believe that it may belong to a new class: a “flashing giant” binary star system. This class includes giant stars that are a hundred times larger than our sun is overshadowed every few decades or so by an unseen companion who could be a planet or another star.
This companion is probably surrounded by a disk of material obscuring the giant star, causing the flashing pattern that astronomers are witnessing.
The center of our galaxy is a dense area that includes a supermassive black hole, superclusters of stars, gas streams, and magnetic filaments.
“It is astonishing that we have just observed a dark, large and elongated object pass between us and the distant star, and we can only wonder what its origin is,” said Sergey Koposov, student co-author and reader in observational astronomy at the University. of Edinburgh, in a statement.
At first, scientists speculated that an unknown dark object passed in front of the giant star, but this would only be possible if there were a large number of these objects in the galaxy, which is unlikely.
A study of other such unique star systems, including giant stars that dim and light up or exhibit this flashing pattern, helped scientists determine that a new class of flashing giant stars may exist and need to be investigated. So far, there appear to be about six such systems.
The star system in this study was found using the VISTA variables in the Via Lactea or the VVV study. This project, which uses the VISTA telescope at the European Southern Observatory in Chile, has been observing 1 billion stars for almost a decade to see how they vary in brightness.
“Occasionally we find variable stars that do not fit into any established category that we call ‘what-is-this?’ Or ‘WIT’ objects, “said Philip Lucas, VISTA project manager and professor at the University of Hertfordshire, in a statement. “We really do not know how these flashing giants came to be. It is exciting to see such discoveries from VVV after so many years of planning and collecting data.”
The attenuation of the star was also observed using the Optical Gravitational Lensing Experiment, or OGLE, a sky study conducted by the University of Warsaw. The datasets from both studies showed that the star dimmed alike in both infrared and visible light.
Astronomers will continue to search for more of these giant flashing star systems to learn more about them.
“There’s definitely more to find, but the challenge now is to find out what the hidden companions are and how they came to be surrounded by disks, despite orbiting so far from the giant star,” Leigh said. Smith, discovery leader and research assistant at the University of Cambridge Institute of Astronomy, in a statement. “That way, we might learn something new about how these kinds of systems evolve.”