The star Gaia17bpp slowly changes brightness, fading and brightening again over several years. This strange behavior may be due to the presence of its neighbor, a small star surrounded by a vast cloud of dust.
The Gaia Space Observatory makes astrometric observations, tracking the positions and luminosities of billions of distant stars with high accuracy. One of them, Gaia17bpp, has attracted the attention of scientists by its unusual behavior: over several years, it gradually becomes brighter and brighter. Anastasios Tzanidakis and James Davenport were able to explain this feature of Gaia17bpp. They presented their findings at the ongoing 241st meeting of the American Astronomical Society (AAS). A summary of the work is described in a press release from the University of Washington.
To better track Gaia17bpp's behavior, the scientists used not only Gaia data but also earlier observations from the Pan-STARRS1, WISE/NEOWISE and ZTF telescopes. The work showed that between 2010 and 2012, the star lost a lot of luminosity, then within seven years remained darkened, and after 2019 began to sharply gain brightness. Astronomers had never seen anything like this before. Then Tsanidakis and Davenport turned to even earlier archival data, going all the way back to observations from the 1950s. It turned out that Gaia17bpp hardly changed during this period.
This allowed us to attribute the star's strange behavior not to its peculiarities, but to the presence of an unusual neighbor. "We believe Gaia17bpp is part of an extremely rare double system, which includes the star itself, a large and old star, and a smaller partner surrounded by a vast disk of dust," Tsanidakis said. - Our analysis showed that the two stars rotate very slowly, making a complete revolution around each other in a thousand years.
According to scientists, only a few such twins are known so far, including Epsilon of Ascendant, which is eclipsed every 27 years by a partner carrying a vast opaque disk of dust. The nature of such systems, however, remains a matter of debate. Their strange behavior may well find other explanations, as suggested, for example, for the eclipsing star in the constellation of the Lesser Leo.