Giant Star Obscured By Mysterious "Dark, Large, Elongated" Object Spotted By Astronomers

Artist's impression of the binary star VVV-WIT-08. Image Credit: Amanda Smith

VVV-WIT-08 is a giant star located more than 25,000 light-years away, and is about 100 times larger than the Sun. This would be enough to make it pretty interesting but what makes it unique is that it disappears for a while behind something "dark, large and elongated", and astronomers are still not sure what that is.

As reported in Monthly Notices of the Royal Astronomical Society, this "blinking" happens every few decades. This usually indicates some kind of transit. When we look at an object like a star or planet from Earth and its light dips, it means something has passed in front of it. If this happens regularly, it's likely something is orbiting it. This star is a peculiar type of eclipsing binary and something is making its brightness drop by a factor of 30. This unseen companion could be a planet or another star surrounded by a vast disk causing the eclipsing event.

"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," co-author Dr Sergey Koposov from the University of Edinburgh said in a statement.

VVV-WIT-08's light dimmed by a factor of 30. Image credit: VISTA Variables in the Via Lactea survey team, ESO

The team believes that this star is not alone but part of a new class of long-period eclipsing binary systems. Several other stars also appear to be occulted by something like a large disk of material. In the case of VVV-WIT-08, the disk obscures both visible light and infrared.   

"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," explained lead author Dr Leigh Smith from Cambridge's Institute of Astronomy. "In doing so, we might learn something new about how these kinds of systems evolve."


Two other stars similar to VVV-WIT-08 are well known. Epsilon Aurigae is partly eclipsed by a huge disk of dust every 27 years, dimming by about half. TYC 2505-672-1 is the eclipsing binary with the longest orbital period of 69 years, although VVV-WIT-8 might turn out to be longer than that.

If you are curious about the name, the discovery comes from the VISTA Variables in the Via Lactea survey that gives the VVV to the name. The WIT part of its name has a fun story, too.

"Occasionally we find variable stars that don't fit into any established category, which we call 'what-is-this?', or 'WIT' objects. We really don't know how these blinking giants came to be," explained project co-leader Professor Philip Lucas from the University of Hertfordshire, UK. "It's exciting to see such discoveries from VVV after so many years planning and gathering the data."


 This Week in IFLScience

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