Astronomers have discovered an unusual star in the central part of the Milky Way, the brightness of which gradually decreases, then increases again. Scientists believe they are dealing with a new type of binary star system, which they have called the “flashing giant”. The research results are published in the Monthly Notices of the Royal Astronomical Society.
It all began with the fact that astronomers noticed that the brightness of the star VVV-WIT-08, located in the center of the Galaxy, at a distance of more than 25,000 light years from us, decreased 30 times, so that it almost disappeared from the sky. Many stars in binary systems change their brightness or pulsate due to the fact that they are periodically obscured by a passing companion star. The uniqueness of the VVV-WIT-08 was that it slowly faded over several months and then brightened again.
The researchers believe that the “blinking giant” they discovered belongs to a new class of binary star systems, where a giant star, hundreds of times larger than the Sun, is eclipsed every few decades by an invisible orbiting satellite – a smaller star or a large planet surrounded by an opaque disk.
“We observed a dark, large and elongated object passing between us and a distant star, and we can only assume its origin,” – quoted in a press release from the University of Cambridge, the words of one of the authors of the study, Sergei Koposov from the University of Edinburgh.
Since the star is located in the densest region of the Milky Way, the researchers initially suggested that some unknown dark object was just passing in front of the giant star by chance. However, simulations have shown that there must be an incredibly large number of coincidences to implement this scenario.
Another similar star system has been known for a long time – the giant star Epsilon Auriga is partially eclipsed by a huge disk of dust every 27 years, but its brightness is reduced by only half. The second example is the binary star system TYC 2505-672-1, discovered several years ago. It has a record long eclipse period of 69 years.
Also known are half a dozen star systems where giant stars are periodically eclipsed by large, opaque disks. The authors propose to single out the giant “blinking” stars in a separate class and purposefully study them.
“The challenge is to figure out what these hidden satellites are and how they ended up surrounded by disks, even though they are orbiting so far from the giant star,” said study leader Dr. Leigh Smith of the University of Cambridge’s Astronomy Institute. “This way we can learn something new about how such systems develop.”
The “flashing giant” VVV-WIT-08 was discovered by scientists working in the VISTA Variables in the Via Lactea survey (VVV), an infrared survey of the central part of the Milky Way with the VISTA telescope of the Paranal Observatory in Chile, operated by the European Southern Observatory (ESO). The VISTA telescope has observed how the brightness of one billion stars changes over ten years in the infrared range.
The fact that the brightness of the star VVV-WIT-08 changes in the visible part of the spectrum was confirmed by scientists at the University of Warsaw in the framework of the experiment on optical gravitational lensing (OGLE).