Anastasios “Andy” Tsanidakis and James Davenport are self-admittedly interested in offbeat stars. When the Gaia survey alerted them to Gaia17bpp, astronomers at the University of Washington were looking for “strange behaving stars.” These studies showed that this star gradually increased in brightness over the course of 2 and a half years.

Tsanidakis recently reported at the 241st meeting of the American Astronomical Society that further analysis showed that Gaia17bpp itself did not undergo any changes. Instead, it is likely part of a unique binary system, and its apparent illumination was the completion of a multi-year eclipse caused by its unusual stellar partner.

“We believe this star is part of an extremely rare binary system between Gaia17bpp — a large, plump main star — and a small companion star surrounded by a large disk of dusty material,” said UW PhD Tsanidakis. D. student of astronomy. “According to our analysis, these two stars have been orbiting each other for an exceptionally long time – up to 1,000 years – so seeing this bright star overshadowed by its dusty companion is a once-in-a-lifetime opportunity.”

Since the Gaia spacecraft’s observations of the star were only made in 2014, Tsanidakis and Davenport, assistant professor of astronomy and deputy director of the DiRAC Institute, had to do some detective work to come to this conclusion. First, they combined Gaia’s observations of the star with observations from other missions since 2010, including Pan-STARRS1, WISE/NEOWISE and the Zwicky Transient Facility.

These observations, combined with the Gaia data, showed that Gaia17bpp had decreased by about 4.5 orders of magnitude, or about 63 times. The star remained dormant for nearly seven years, from 2012 to 2019. The brightness detected by the Gaia probe was the end of this seven-year eclipse.

No other stars near Gaia17bpp showed similar dimming behavior. Using the DASCH program, a digital catalog of over a hundred years of astrophotographic plates at Harvard, Tsanidakis, and Davenport analyzed observations of the star dating back to the 1950s.

“In 66 years of observational history, we found no other sign of this star dimming significantly,” Tsanidakis said.

They believe that Gaia17bpp is simply part of a rare binary star system with a dusty companion star.

“Based on the available data, this star appears to have a slow-moving companion surrounded by a large disk of material,” Tsanidakis said. Said. “If this material were in the Solar System, it would extend from the Sun to Earth’s orbit or beyond.”

During the eclipse, Davenport said the invisible companion blocked about 98% of Gaia17bpp’s light.

Several other similar “dusty” systems have been spotted over the years, most notably Epsilon Golden, a star in the constellation Auriga, which is overshadowed for two years by a relatively large, dim companion every 27 years. The system discovered by Tsanidakis and Davenport is unique among these few dusty binaries, having an eclipse period of around seven years, and is by far the longest. Unlike the Epsilon Aurigae binary, Gaia17bpp and its companion are so distant that it would take a century or more for an intelligent observer on Earth to witness another such eclipse.