Astronomers have discovered a massive ‘blinking’ star near the Milky Way’s centre, more than 25,000 light-years away. A multinational team of astronomers observed the star VVV-WIT-08 dimming by a factor of 30 to the point where it nearly vanished from the sky. While many stars undergo brightness changes as they pulsate or are eclipsed by another star in a binary system, it is extremely rare for a star to dim over several months before brightening again.
VVV-WIT-08, the researchers believe, may be a new type of ‘blinking giant’ binary star system, in which a giant star 100 times the size of the Sun is eclipsed every few decades by an as-yet-unseen orbital companion. The companion, which could be another star or a planet, is encircled by an opaque disc that obscures the giant star, causing it to vanish and reappearance in the sky. The study was published in the Royal Astronomical Society’s Monthly Notices.
Dr Leigh Smith of Cambridge’s Institute of Astronomy led the discovery, which involved scientists from the University of Edinburgh, the University of Hertfordshire, the University of Warsaw in Poland, and Chile’s Universidad Andres Bello. “It’s incredible that we just witnessed a dark, large, and elongated object pass between us and a distant star, and we can only speculate on its origin,” co-author Dr Sergey Koposov of the University of Edinburgh said.
Due to the star’s location in a dense region of the Milky Way, the researchers considered the possibility that an unknown dark object drifted in front of the giant star by chance. However, simulations indicated that this scenario would require an implausibly large number of dark bodies floating around the Galaxy.
Another similar star system has been known for a long period of time. Every 27 years, the giant star Epsilon Aurigae is partially eclipsed by a massive disc of dust, but only dims by about 50%. A second example, TYC 2505-672-1, was discovered a few years ago and currently holds the record for the longest orbital period of an eclipsing binary star system — 69 years — a record for which VVV-WIT-08 is a contender.
Additionally to VVV-WIT-08, the UK-based team discovered two more of these strange giant stars, implying that these may represent a new class of ‘blinking giant’ stars for astronomers to investigate. VVV-WIT-08 was discovered by the VISTA Variables in the Via Lactea Survey (VVV), a project that has been observing the same one billion stars for nearly a decade in search of examples with varying brightness in the infrared region of the spectrum.
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Professor Philip Lucas of the University of Hertfordshire, the project’s co-leader, stated, “Occasionally, we discover variable stars that defy classification, which we refer to as ‘what-is-this?’ or ‘WIT’ objects. We truly have no idea how these blinking titans came to be. It’s exciting to see such breakthroughs from VVV after years of planning and data collection.”
While VVV-WIT-08 was discovered using VVV data, the star’s dimming was also observed by the OGLE, a long-running observation campaign run by the University of Warsaw. OGLE collects data more frequently, but in the visible region of the spectrum. These frequent observations were critical in developing a model for VVV-WIT-08, as they demonstrated that the giant star dimmed equally in visible and infrared light.
There now appear to be approximately a half-dozen known potential star systems of this type, which contain giant stars and large opaque discs. “There are undoubtedly more to be discovered, but the challenge now is determining what the hidden companions are and how they ended up surrounded by discs despite orbiting such a great distance from the giant star,” Smith explained. “By doing so, we may gain new insight into how these types of systems evolve.”
What is a blinking start?
There are variable stars, whose luminosity varies with time. But you need quite posh instruments and lots of photography to detect them.
What you describe has traditionally been called ‘twinkling’, and what scientists (who never let a chance for a long word go by unchallenged) call ‘scintillation’. It is caused by minute interactions in the intervening atmosphere on the very last bit of the trip the light makes to your eye. The light rays wriggle around by refraction because our atmosphere is not homogeneous, and just occasionally get bent enough to miss your eyeball.
This explanation used to be one of the regular science titbit’s in newspapers or almanacs, and led my Grandfather to make copious notes in an attempt to decide if more twinkling meant better weather was coming or worse. He came to the conclusion that in Britain any starlit night meant worse weather was coming, because it would soon be clouding over. – Robert Harvey, lived in Lincolnshire, UK
source: HT via ANI
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