Seven-year photobomb: A star emerging from an unusual seven-year eclipse has the astronomers in awe

Seven-year photobomb: A star emerging from an unusual seven-year eclipse has the astronomers in awe

The star hasn't changed, but it has a strange companion responsible for what researchers call a “seven-year photobomb.”

An alert about a potential stellar oddity from the Gaia spacecraft might have solved the mystery behind an unusually brightening star. University of Washington doctoral student Anastasios Tzanidakis and research assistant professor of astronomy James Davenport, who were searching for “stars behaving strangely”, had been focussing on Gaia17bpp, a star that had gradually increased in luminosity over a 2.5-year period.

The two made their probe public at the 241st meeting of the American Astronomical Society in Seattle on Wednesday. They revealed that the star hasn't changed, but it has a strange companion responsible for what researchers call a “seven-year photobomb.”

“We believe that this star is part of an exceptionally rare type of binary system, between a large, puffy older star, Gaia17bpp, and a small companion star that is surrounded by an expansive disk of dusty material,” said Tzanidakis in a statement.

Seven-year photobomb: A star emerging from an unusual seven-year eclipse has the astronomers in awe
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“Based on our analysis, these two stars orbit each other over an exceptionally long period of time, as much as 1,000 years. So, catching this bright star being eclipsed by its dusty companion is a once-in-a-lifetime opportunity.”

The Gaia spacecraft was launched by the European Space Agency in 2013 and aims to create the most precise 3D map of the Milky Way galaxy to date. It started observing the star in 2014.

Gaia’s observations of the star put together with other observations of Gaia17bpp taken by Pan-STARRS1 telescope in Hawaii, the NASA WISE/NEOWISE mission and the Zwicky Transient Facility in California going back to 2010, led to the final results.

The astronomers simply happened to catch the star at the end of a years-long eclipse. Its brightness dimmed by 4.5 orders of magnitude, or 45,000 times, for seven years, from 2012 to 2019. None of the other stars near it displayed a similar activity.

“Over 66 years of observational history, we found no other signs of significant dimming in this star,” Tzanidakis said.

“Based on the data currently available, this star appears to have a slow-moving companion that is surrounded by a large disk of material,” Tzanidakis said. “If that material were in the solar system, it would extend from the sun to Earth’s orbit, or farther.”

There are other binary star systems that show a similar behaviour. A star in the Epsilon Aurigae experiences an eclipse for two out of every 27 years by a large unknown companion.

The giant star Betelgeuse also became the centre of attraction for astronomers when it dramatically dimmed in late 2019. Experts thought that it will explode into a supernova, but instead it experienced a titanic surface mass ejection, wherein it lost a substantial part of its visible surface.

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