Unusually glowing star draws attention like a stellar oddity
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Astronomers may have solved the mystery behind an unusually bright star.
University of Washington doctoral student Anastasios Tzanidakis and research assistant professor of astronomy James Davenport were looking for “stars behaving strangely” when they received a warning about a possible stellar oddity from the Gaia spacecraft.
Launched by the European Space Agency in 2013, the space observatory is on a mission to create the most accurate 3D map of the Milky Way galaxy yet. The astronomers focused on Gaia17bpp, a star that had gradually increased in brightness over a period of 2.5 years.
The results of their research and analysis of the star, shared on the Tuesday 241st Meeting of the American Astronomical Society in Seattle revealed that the star itself did not change. Instead, the star has a strange companion responsible for what the researchers estimate to be a “seven-year photobomb.”
“We believe this star is part of an exceptionally rare type of binary system, between a large, swollen older star – Gaia17bpp – and a small companion star surrounded by a vast disk of dusty material,” Tzanidakis said in a statement.
“Based on our analysis, these two stars orbit each other for an exceptionally long period of time – as long as 1,000 years. So capturing this bright star eclipsed by its dusty companion is a once-in-a-lifetime opportunity.”
The Gaia spacecraft began observing the star in 2014. The researchers collected all the observations of Gaia from the star and tracked other observations of Gaia17bpp made by the Pan-STARRS1 telescope in Hawaii, the NASA WISE/NEOWISE mission and the Zwicky Transient Facility in California dating back to 2010.
By comparing the images of Gaia17bpp, the researchers determined that the star’s brightness decreased by 4.5 magnitudes, or 67 times. This continued for 7 years, from 2012 to 2019.
The astronomers happened to see the star at the end of an eclipse that lasted for years.
No other star in the vicinity of Gaia17bpp has experienced an eclipse of this magnitude. The team also searched a digital catalog of astrophotographic plates at Harvard University from the 1950s.
“During 66 years of observational history, we have not found any other signs of significant dimming in this star,” Tzanidakis said.
So what happened to Gaia17bpp? “Based on the data currently available, this star appears to have a slow-moving companion 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 beyond.”
While Gaia17bpp is unique in having such a long eclipse, it’s not the only binary star system to exhibit dimming behavior. Astronomers are also intrigued by Epsilon Aurigae, a star that experiences an eclipse by a large companion for two of its 27 years — but the companion’s actual identity remains a mystery.
The giant star Betelgeuse also caught astronomers’ attention when it dimmed dramatically in late 2019, sparking speculation that it might explode into a supernova. Instead, the star had a dusty tantrum.
For Gaia17bpp, the dust-forming stellar companion could be a small dead star called a white dwarf, but they’re not entirely sure what could be contributing to the disk of debris surrounding it.
Whatever the identity of its companion, Gaia17bpp and its mysterious cosmic partner are so far apart that another solar eclipse is centuries away.
“This was an accidental discovery,” Tzanidakis said. “If we had been away for a few years, we would have missed it. It also indicates that these types of binaries may be much more common. If so, we need to come up with theories about how this kind of linking even came about. It’s definitely an oddity, but it may be much more common than anyone has realized.
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