Astronomers have detected a giant “blinking” star toward the center of our galaxy, more than 25,000 light-years away.
The star, VVV-WIT-08, was observed using the VISTA (Visible and Infrared Survey Telescope for Astronomy) in Chile.
The scientists say its brightness dropped by a factor of 30 or 97 percent — meaning it almost completely disappeared from the sky — before returning to normal.
Many stars change in brightness because they pulse or are eclipsed by another star in a binary system (a solar system in which a few stars orbit each other).
However, the researchers say it is “exceptionally rare” for a star to dim and brighten over a period of several months.
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Artist impression of VVV-WHITE-08. An international team of astronomers saw VVV-WIT-08 decrease in brightness by a factor of 30, so that it almost disappeared from the sky. While many stars change brightness as they pulse or are eclipsed by another star in a binary system, it is exceptionally rare for a star to dim and then brighten over a period of several months.
VVV-WIT-08 may belong to a new class of “blinking giant” binary stars, where a giant star 100 times larger than the Sun is eclipsed once every few decades by a hitherto invisible orbital companion.
Possibly the companion, which could be another star or a planet, is surrounded by an opaque disk, covering the giant star, causing it to disappear and reappear in the sky.
‘Actually, the star was getting dimmer and fainter. And at its weakest point, it was 30 times less bright than at the beginning,” study co-author Dr. Sergey Koposov of the University of Edinburgh to MailOnline.
The star, VVV-WIT-08, was observed using the European Southern Observatory (ESO) VISTA telescope at Cerro Paranal Observatory in Chile
THE MILKY WAY
Our solar system is located in the Milky Way galaxy.
But our sun is only one of about 200 billion stars in the Milky Way.
And astronomers have discovered more than 3,200 other stars with planets orbiting them in the Milky Way.
The Milky Way is also just one of billions of galaxies in the universe.
‘Imagine you have a solar eclipse, but in such a way we can only do less than one-thirtieth of the solar disk.
“Another analogy: Imagine you have a light bulb that moves you 6 times farther away, which also makes you 30 times less bright.
“It is amazing that we have just seen a dark, large and elongated object pass between us and the distant star and we can only speculate as to its origin.”
VVV-WHITE-08 was found by the VISTA variables in the Via Lactea survey (VVV), a project using the British-built VISTA telescope in Chile and operated by the European Southern Observatory.
VISTA has been observing the same billion stars for nearly a decade, looking for examples of varying brightness in the infrared part of the spectrum.
“Occasionally we find variable stars that don’t fit into an established category, which we call ‘what-is-this?’ or WIT objects,” says co-leader of the project, Professor Philip Lucas of the University of Hertfordshire.
“We really don’t know how these blinking giants came to be. It is exciting to see such discoveries made by VVV after so many years of planning and collecting the data.’
The researchers say that VVV-WIT-08 reached its weakest in April 2012 and that the total duration of the event was a few hundred days.
The researchers say that VVV-WIT-08 reached its weakest in April 2012 and that the total duration of the event was a few hundred days
Nearly a decade later, the team reports their findings in a new paper published in the journal Monthly Notices from the Royal Astronomical Society.
There is a very good reason for this time difference, explains study leader Dr Leigh Smith of Cambridge’s Institute of Astronomy.
‘The research in which VVV-WIT-08 was found is based on about 200,000 observations spread over 10 years’, he tells MailOnline.
“Each sighting is 16 separate 4 megapixel images. This set contains hundreds of repeated observations of the same fields, like frames from a movie. This involves a total of about 15 terabytes of images.
‘Processing all these images, detecting stars and identifying individual stars between the ‘frames of the film’ takes an enormous amount of time and calculations.
‘We first identified VVV-WIT-08 about two years ago. Since then we’ve had to collect some extra data and develop and run the software needed to model the solar eclipse.’
Because the star is in a dense region of the Milky Way, the researchers considered whether an unknown dark object could have accidentally drifted in front of the giant star.
However, simulations showed that there would have to be an incredibly large number of dark bodies orbiting the galaxy for this scenario to be likely.
Another galaxy of this kind has been known for a long time. The giant star Epsilon Aurigae is partially eclipsed by a huge disk of dust every 27 years, but only eclipses by about 50 percent.
A second example, TYC 2505-672-1, was found a few years ago and holds the current record for the eclipsing binary star system with the longest orbital period – 69 years – a record for which VVV-WIT-08 is currently a contender.
The team found two more of these peculiar giant stars in addition to VVV-WIT-08, suggesting that these could be a new class of “blinking giant” stars for astronomers to investigate.
VISTA: THE WORLD’S LARGEST TELESCOPE SURVEY
Image of the European Southern Observatory (ESO)’s four-meter VISTA (Visible and Infrared Survey Telescope for Astronomy) at Cerro Paranal Observatory
VISTA – the Visible and Infrared Survey Telescope for Astronomy – is part of ESO’s Paranal Observatory in the Atacama Desert in northern Chile.
VISTA operates at near infrared wavelengths and is the world’s largest survey telescope.
The large mirror, wide field of view and highly sensitive detectors reveal a completely new view of the southern sky.
The main mirror of VISTA is 4.1 meters wide. In photographic terms, it can be seen as a 67 megapixel digital camera with a 13000mm f/3.25 mirror lens.
The heart of the telescope is a huge three-ton camera with 16 state-of-the-art infrared-sensitive detectors.
Photo of the housing of the four-meter VISTA telescope at the Cerro Paranal Observatory, taken on September 16, 2008 in Paranal, north of Santiago, Chile
VISTA’s observation time is spent systematically mapping the sky, and six major public surveys take up most of the telescope’s operating time.
Some study small patches of sky for long periods of time to detect extremely faint objects, and others survey the entire southern sky.
Using VISTA data, astronomers can create a three-dimensional map of about 5 percent of the entire observable universe.
Beyond that, VISTA is a powerful tool for discovering distant quasars and studying the evolution of galaxies and galaxy clusters.
VISTA was conceived and developed by a consortium of 18 universities in the United Kingdom, led by Queen Mary, University of London.
The telescope was provisionally accepted by ESO on December 10, 2009 and is now operated by ESO.