Astronomers have noticed a large ‘blinking’ star in the direction of the centre of the Milky Way, greater than 25,000 gentle years away.
An worldwide group of astronomers noticed the star, VVV-WIT-08, lowering in brightness by an element of 30, in order that it almost disappeared from the sky. While many stars change in brightness as a result of they pulsate or are eclipsed by one other star in a binary system, it is 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 could belong to a brand new class of ‘blinking large’ binary star system, the place a large star — 100 occasions bigger than the Sun — 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 enormous star, inflicting it to vanish and reappear within the sky. The examine is revealed in Monthly Notices of the Royal Astronomical Society.
The discovery was led by Dr Leigh Smith from Cambridge’s Institute of Astronomy, working with scientists on the University of Edinburgh, the University of Hertfordshire, the University of Warsaw in Poland and Universidad Andres Bello in Chile.
“It’s wonderful that we simply noticed a darkish, massive and elongated object move between us and the distant star and we will solely speculate what its origin is,” stated co-author Dr Sergey Koposov from the University of Edinburgh.
Since the star is positioned in a dense area of the Milky Way, the researchers thought of whether or not some unknown darkish object might have merely drifted in entrance of the enormous star by probability. However, simulations confirmed that there must be an implausibly massive variety of darkish our bodies floating across the Galaxy for this state of affairs to be doubtless.
One different star system of this type 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 couple 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 presently a contender.
The UK-based group has additionally discovered two extra of those peculiar large stars along with VVV-WIT-08, suggesting that these could also be a brand new class of ‘blinking large’ stars for astronomers to research.
VVV-WIT-08 was discovered by the VISTA Variables within the Via 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.
Project co-leader Professor Philip Lucas from the University of Hertfordshire stated, “Occasionally we discover variable stars that do not match into any established class, which we name ‘what-is-this?’, or ‘WIT’ objects. We actually do not understand how 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 info.”
While 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 commentary marketing campaign run by the University of Warsaw. OGLE makes extra frequent observations, however nearer to the seen a part of the spectrum. These frequent observations have been key for modelling VVV-WIT-08, and so they confirmed that the enormous star dimmed by the identical quantity in each the seen and infrared gentle.
There now seem like round half a dozen potential recognized star programs of this kind, containing large stars and enormous opaque discs. “There are actually 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 enormous star,” stated Smith. “In doing so, we’d be taught one thing new about how these sorts of programs evolve.”