Astronomers have noticed an enormous ‘blinking’ star in direction of the middle of the Milky Means, greater than 25,000 mild years away.
A world staff of astronomers noticed the star, VVV-WIT-08, reducing in brightness by an element of 30, in order that it almost disappeared from the sky. Whereas many stars change in brightness as a result of they pulsate or are eclipsed by one other star in a binary system, it’s exceptionally uncommon for a star to turn out to be fainter over a interval of a number of months after which brighten once more.
The researchers imagine that VVV-WIT-08 might belong to a brand new class of ‘blinking big’ binary star system, the place an enormous star — 100 instances bigger than the Solar — is eclipsed as soon as each few many years by an as-yet unseen orbital companion. The companion, which can be one other star or a planet, is surrounded by an opaque disc, which covers the large star, inflicting it to vanish and reappear within the sky. The examine is revealed in Month-to-month Notices of the Royal Astronomical Society.
The invention was led by Dr. Leigh Smith from Cambridge’s Institute of Astronomy, working with scientists on the College of Edinburgh, the College of Hertfordshire, the College of Warsaw in Poland and Universidad Andres Bello in Chile.
“It’s superb that we simply noticed a darkish, massive and elongated object go between us and the distant star and we are able to solely speculate what its origin is,” mentioned co-author Dr Sergey Koposov from the College of Edinburgh.
For the reason that star is situated in a dense area of the Milky Means, the researchers thought of whether or not some unknown darkish object may have merely drifted in entrance of the large star by likelihood. Nonetheless, simulations confirmed that there must be an implausibly massive variety of darkish our bodies floating across the Galaxy for this situation to be probably.
One different star system of this kind has been recognized for a very long time. The large star Epsilon Aurigae is partly eclipsed by an enormous disc of mud each 27 years, however solely dims by about 50%. A second instance, TYC 2505-672-1, was discovered a number of years in the past, and holds the present file for the eclipsing binary star system with the longest orbital interval — 69 years — a file for which VVV-WIT-08 is at present a contender.
The UK-based staff has additionally discovered two extra of those peculiar big stars along with VVV-WIT-08, suggesting that these could also be a brand new class of ‘blinking big’ stars for astronomers to analyze.
VVV-WIT-08 was discovered by the VISTA Variables within the By way of Lactea survey (VVV), a undertaking utilizing the British-built VISTA telescope in Chile and operated by the European Southern Observatory, that has been observing the identical one billion stars for almost a decade to seek for examples with various brightness within the infrared a part of the spectrum.
Undertaking co-leader Professor Philip Lucas from the College of Hertfordshire mentioned, “Sometimes we discover variable stars that don’t match into any established class, which we name ‘what-is-this?’, or ‘WIT’ objects. We actually don’t know the way these blinking giants got here to be. It’s thrilling to see such discoveries from VVV after so a few years planning and gathering the information.”
Whereas VVV-WIT-08 was found utilizing VVV information, the dimming of the star was additionally noticed by the Optical Gravitational Lensing Experiment (OGLE), a long-running statement marketing campaign run by the College of Warsaw. OGLE makes extra frequent observations, however nearer to the seen a part of the spectrum. These frequent observations had been key for modeling VVV-WIT-08, they usually confirmed that the large star dimmed by the identical quantity in each the seen and infrared mild.
There now look like round half a dozen potential recognized star programs of this sort, containing big stars and huge opaque discs. “There are definitely extra to be discovered, however the problem now could be in determining what the hidden companions are, and the way they got here to be surrounded by discs, regardless of orbiting so removed from the large star,” mentioned Smith. “In doing so, we’d study one thing new about how these sorts of programs evolve.”
Reference: 11 June 2021, Month-to-month Notices of the Royal Astronomical Society.