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The other eclipse: University of Cambridge astronomers probe mystery of giant ‘blinking’ star 25,000 light years away

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While we’ve all been enjoying the spectacle of a partial solar eclipse, astronomers have been trying to solving the mystery of a giant ‘blinking’ star more than 25,000 light years away towards the centre of the Milky Way.

The international team, led by Dr Leigh Smith from Cambridge’s Institute of Astronomy, observed the star VVV-WIT-08 decreasing in brightness by a factor of 30 – meaning it nearly disappeared from the sky.

An artist's impression of the binary star VVV-WIT-08. Picture: Amanda Smith
An artist's impression of the binary star VVV-WIT-08. Picture: Amanda Smith

Many stars change brightness because they pulsate, or are eclipsed by another star in a binary system, but it is very rare for a star to become fainter over a period of several months and then brighten again.

The researchers believe VVV-WIT-08 belongs to a new class of ‘blinking giant’ binary star system. In this, a giant star – 100 times larger than the Sun – is eclipsed once every few decades by an as-yet unseen orbital companion, which may be another star or planet.

This companion is surrounded by an opaque disc, covering the giant star and causing it to disappear and reappear in the sky.

Half a dozen star systems that could be of this type have now been identified.

“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 Dr Smith. “In doing so, we might learn something new about how these kinds of systems evolve.”

The study’s co-author, Dr Sergey Koposov, from the University of Edinburgh, said: “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.”

VVV-WIT-08 was found by the VISTA Variables in the Via Lactea survey (VVV), which is a project using the British-built VISTA telescope in Chile and operated by the European Southern Observatory.

Prof Philip Lucas, the project’ co-leader from the University of Hertfordshire, added: “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. It’s exciting to see such discoveries from VVV after so many years planning and gathering the data.”

The dimming of the star was also observed by the Optical Gravitational Lensing Experiment (OGLE), run by the University of Warsaw.

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