Astronomers spot a ‘blinking giant’ near Milky Way

The Milky Way blazes above the European Southern Observatory (ESO) facilities at Mount Paranal in northern Chile’s Atacama Desert. Paranal hosts the world’s most advanced ground-based astronomical observatory, the Very Large Telescope (VLT), and is home to two new telescopes for large imaging surveys currently under construction, the VLT Survey Telescope (VST) and the Visible and Infrared Survey Telescope for Astronomy (VISTA). Both are expected to “take up duty” in the 2009-2010 timeframe. This photograph shows an edge-on view of the Milky Way’s glowing plane slicing across the night sky, laced by bands of dust and dark gas. Taken with a digital camera using a three-minute exposure, the photograph also reveals a bit of action on the ground. To the left, a vehicle with its parking lights on stops lets out a passenger. Though bathed by the light of the Milky Way, the high-altitude desert remains quite dark. To illuminate the rightward path to the underground entrance ramp of the ‘Residencia’, where staff and visitors stay, the passenger takes along a small flashlight, seen as a squiggly bright line. In the lower right, the glass dome on the Residencia’s roof reflects the starry sky overhead. One of our Milky Way’s galactic satellites, the Large Magellanic Cloud, is seen hanging above the Residencia in the lower right corner of the image.

London, June 11 (IANS) An international team of astronomers has spotted a giant ‘blinking’ star towards the centre of the Milky Way, more than 25,000 light years away.

The star, VVV-WIT-08, decreased in brightness by a factor of 30, so that it nearly disappeared from the sky. While many stars change in brightness because they pulsate or are eclipsed by another star in a binary system, it is exceptionally rare for a star to become fainter over a period of several months and then brighten again, the team said.

The researchers believe that VVV-WIT-08 may belong to a new class of “blinking giant” binary star system, where a giant star 100 times larger than the Sun is eclipsed once every few decades by an as-yet unseen orbital companion.

The companion, which may be another star or a planet, is surrounded by an opaque disc, which covers the giant star, causing it to disappear and reappear in the sky. The study is published in Monthly Notices of the Royal Astronomical Society.

“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 Sergey Koposov from the University of Edinburgh.

Since the star is located in a dense region of the Milky Way, the researchers considered whether some 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.

One other star system of this sort has been known for a long time. The giant star Epsilon Aurigae is partly eclipsed by a huge disc of dust every 27 years, but only dims by about 50 per cent. 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 UK-based team has also found two more of these peculiar giant stars in addition to VVV-WIT-08, suggesting that these may be a new class of “blinking giant” stars for astronomers to investigate.

There now appear to be around half a dozen potential known star systems of this type, containing giant stars and large opaque discs.

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