Known as VVV-WIT-08, the star dimmed so much that it almost disappeared from view as astronomers observed it over time.
It's not uncommon for a star's brightness factor to change. Some stars pulsate, or one star within a stellar pair, called a binary, can be eclipsed by another. But it is incredibly rare for a star to grow faint and brighten again, or blink.
The observation of this star has led researchers to believe that it may belong to a new class: a "blinking giant" binary star system. This class includes giant stars a hundred times larger than our sun being eclipsed every few decades or so by an unseen companion, which could be a planet or another star.
This companion is likely surrounded by a disk of material that cloaks the giant star, causing the blinking pattern witnessed by astronomers.
The study published Friday in the Monthly Notices of the Royal Astronomical Society.
The center of our galaxy is a dense region that includes a supermassive black hole, superclusters of stars, streams of gas and magnetic filaments.
"It's amazing that we just observed a dark, large and elongated object pass between us and the distant star, and we can only speculate what its origin is," said Sergey Koposov, study coauthor and reader in observational astronomy at the University of Edinburgh, in a statement.
At first, the researchers speculated that an unknown dark object passed in front of the giant star, but that 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 brighten, or showcase this blinking pattern, helped the researchers determine that a new class of blinking giant stars may exist and need to be investigated. So far, it appears there are around six such systems.
The star system in this study was found using the VISTA Variables in the Via Lactea, or VVV survey. This project, utilizing the VISTA telescope at the European Southern Observatory in Chile, has observed 1 billion stars for almost a decade to see how they vary in brightness.
"Occasionally we find variable stars that don't fit into any established category, which we call 'what-is-this?', or 'WIT' objects," said Philip Lucas, VISTA project lead and professor at the University of Hertfordshire, in a statement. "We really don't know how these blinking giants came to be. It's exciting to see such discoveries from VVV after so many years planning and gathering the data."
The star's dimming was also observed using the Optical Gravitational Lensing Experiment, or OGLE, a sky survey run by the University of Warsaw. The data sets from both surveys showed that the star dimmed equally in both infrared and visible light.
Astronomers will continue to search for more of these giant blinking star systems to learn more about them.
"There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star," said Leigh Smith, discovery lead and research associate in the University of Cambridge's Institute of Astronomy, in a statement. "In doing so, we might learn something new about how these kinds of systems evolve."
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