In 2012, a giant star some 25,000 light years away blinked at Earth, and we looked back, a little confused.
Astronomers using the VISTA telescope in Chile observed the star’s luminosity decrease dramatically, then re-ignite over a period of about 200 days. The team has a hunch that a large object, orbiting the giant star, briefly obscured our view of it – but the nature of the obscuring object is uncertain. They nicknamed the event VVV-WIT-08.
“It’s amazing that we just observed a dark, tall and elongated object pass between us and the distant star and we can only speculate on its origin,” said Sergey Koposov, astronomer at the University of Edinburgh. and co-author of the new study.
The study, published in the journal Monthly Notices of the Royal Astronomical Society, suggests a few possibilities, but the drop doesn’t appear to be due to inherent characteristics of the star itself – it must be a related companion. to gravity.
The event was discovered in the VISTA variables of the Via Lactea (VVV) survey. The acronym WIT which stands for “What is this?” and is used when astronomers are unsure why these giant stars might be blinking.
A number of WIT objects have been discovered before, with a handful of explanations: violent quasars, star collisions, and novas. The team states that this one is almost certainly an occultation event – something happened in front of the star from our point of view in the universe – and it must be faint, over 23 million thick. miles (or about a quarter of the distance between the Earth and the Sun).
They considered a number of different objects, excluding a fortuitous object wandering the cosmos passing just in front of the star. Huge disks of debris around white dwarfs and neutron stars are also unlikely to have caused the occultation, although the team says a cloud of dusty and messy gas and debris around a hole black – a “black hole rescue disk” – may be to blame. .
The team also identified two other candidate events, VVV-WIT-10 and VVV-WIT-11, suggesting that there may be more of these “flashing giants” to be discovered and described.
“There is certainly more to be found, but the challenge now is to determine what the hidden companions are and how they were surrounded by discs, despite their orbit so far from the giant star,” said Leigh Smith, astronomer at Institute of Cambridge Astronomy and first author of the study.