Mysterious ‘elongated object’ that made giant star disappear puzzles scientists

The strange object is circling a star 25,000 light years away

(Amanda Smith, University of Cambridge)

A star in the centre of our galaxy keeps blinking in and out of existence, and scientists have not been able to work out why.

In the middle of the Milky Way galaxy, 25,000 light years away, is the mysterious star VVV-WIT-08. Many stars change in brightness because they pulsate, or are eclipsed by another star, but this one is exceptionally rare because it becomes fainter over a several months – then suddenly brighter again.

Astronomers believe that VVV-WIT-08 is a new class of ‘blinking giant’ binary star system, where the giant mass of gas is blocked every few decades.

Scientists still don’t know what could be hiding the planet, though; the companion object, which could be another star or planet, is surrounded by an opaque disc, covering the star.

"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,” Professor Philip Lucas from the University of Hertfordshire said.

It is possible that some unknown, dark object could have drifted in front of the giant star by chance, but it is incredibly unlikely. Simulations indicate there would have to be a ridiculously large number of dark bodies floating in the Milky Way for such an occurrence to happen by chance.

"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 co-author Dr Sergey Koposov from the University of Edinburgh.

One other star system similar to VVV-WIT-08 has been known for some time: the giant star Epsilon Aurigae, which is partially eclipsed by a massive dust disk every 27 years. Even then, however, it is only dimmed by 50 per cent. Two more of these strange stars have been found in addition to this one, implying that even more may be out there.

"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 Leigh Smith from Cambridge’s Institute of Astronomy.

The study is published in Monthly Notices of the Royal Astronomical Society