Astronomers spot giant ‘blinking’ star

Scientists observed that the enormous star, which lies 25,000 light years away, almost disappeared from the sky before slowly returning to its former brightness.  

Many stars in the Galaxy change in brightness because they pulsate or they are eclipsed by another orbiting star.

However, it’s exceptionally rare for a star to become fainter over a period of several months and then brighten again, experts say.

Twinkle twinkle

Researchers believe the star, known as VVV-WIT-08, might belong to a new class of ‘blinking giant’ star system, where a huge star is eclipsed once every few decades by an as-yet unseen orbital companion.

The partner, which may be another star or planet, is surrounded by an opaque disc that covers the giant star, causing it to disappear and reappear in the sky.

As the blinking star is located in a dense region of the Milky Way, scientists considered whether an unknown dark object could have simply drifted in front of the giant star by chance.

However, simulations showed that there would have to be an implausibly large number of dark bodies floating around the galaxy for this scenario to be likely.

Researchers from the University’s School of Astronomy and Physics collaborated on the discovery with experts from the University of Cambridge’s Institute of Astronomy, who led the study, the University of Hertfordshire, the University of Warsaw in Poland and Universidad Andres Bello in Chile.

VISTA telescope

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

ESO has been observing the same one billion stars for nearly a decade to search for those with varying brightness.

While VVV-WIT-08 was discovered using VVV data, the dimming of the star was observed by the Optical Gravitational Lensing Experiment, a long-running observation campaign run by the University of Warsaw.

Shining brightly

Edinburgh’s astronomers worked on the scientific modelling of the changes in the brightness of the star.

Specifically they tried to understand the shape, opacity and velocity of the giant star’s orbital companion, through their analysis of the variations in VVV-WIT-08’s brightness.

Scientists hope that future observations of the giant star, in different parts of the electromagnetic spectrum, may shed some light on the nature of its mysterious companion.

The discovery of this rare star is very exciting not only because the object itself is a bit of a mystery, but also because it tells us what discoveries can be made when we can access not only one single image of the sky, but when we’re able to observe its evolution with time. Essentially we are able to look at the movies of the sky as opposed to single photographs and this opens up a lot of opportunities for new discoveries.

Dr Sergey Koposov

 

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

 

There now appear to be around half a dozen potential known star systems of this type, containing giant stars and large opaque discs. “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. In doing so, we might learn something new about how these kinds of systems evolve.

Dr Leigh Smith

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

Related links

Journal paper    

School of Physics and Astronomy   

Institute for Astronomy