In 2012, a giant star some 25,000 light-years away flickered toward Earth, and we stared back, a bit confused.
Astronomers using the VISTA telescope in Chile saw the star drastically dimmer and then brighten again over a period of about 200 days. The team has a hunch that a large object, orbiting the giant star, briefly obscured our view, but the nature of the hidden object is uncertain. They have dubbed the event VVV-WIT-08.
“It is surprising that we have just observed a large, elongated dark object passing between us and the distant star and we can only speculate what its origin is,” said Sergey Koposov, an astronomer at the University of Edinburgh and a co-author of the new study.
The study, published in the Monthly Notices of the Royal Astronomical Society, suggests a couple of possibilities, but the drop doesn’t appear to be due to inherent characteristics of the star itself – it must be a gravitationally bound companion.
The event was discovered in the VISTA Variables in the Milky Way survey (VVV). The acronym WIT which stands for “What is this?” and is used when astronomers are unclear about why these giant stars may be blinking.
Several WIT objects have been discovered before, with a handful of explanations: violent quasars, star collisions, and novae. The team states that this is almost certainly an occultation event: something has passed in front of the star from our view in the universe, and it must be faint, with a thickness greater than 23 million miles (or about a quarter of the distance). ). between the Earth and the sun).
They considered a number of different objects, ruling out a random object that wandered the cosmos simply by passing in front of the star. Huge debris disks around white dwarfs and neutron stars are also unlikely to have caused the occultation, though the team says a dusty, messy cloud of gas and debris around a black hole, a “black hole recoil disk. “may be the culprit.
The team has also identified two other candidate events, VVV-WIT-10 and VVV-WIT-11, suggesting that there may be more of these “blinking giants” to discover and describe.
“Certainly there is more to find, but the challenge now is to discover what the hidden companions are and how they came to be surrounded by disks, despite orbiting so far from the giant star,” said Leigh Smith, an astronomer at the Cambridge Institute of Astronomy. and first author of the study.