An unusually bright star is attracting attention as a stellar oddity

An unusually bright star is attracting attention as a stellar oddity
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Astronomers may have solved the mystery behind an unusually bright star.

Anastasios Tzanidakis, a graduate student at the University of Washington, and James Davenport, an assistant professor of astronomy, were looking for “stars that are behaving strangely” when they received a warning from the Gaia spacecraft about a possible stellar oddity.

Launched in 2013 by the European Space Agency, the space observatory has a mission to create the most accurate 3D map of the Milky Way to date. Astronomers focused on Gaia17bpp, a star that had gradually increased in luminosity over a period of 2.5 years.

The star announced the results of their investigation and analysis on 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 who is responsible for what researchers are calling a “seven-year photobomb.”

“We believe this star is part of an exceptionally rare binary system, between a large, bloated older star – Gaia17bpp – and a small companion star surrounded by an extensive 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 – up to 1,000 years. So it’s a unique opportunity to catch this bright star eclipsed by its dusty companion.”

The Gaia spacecraft began observing the star in 2014. The researchers merged all of Gaia’s observations of the star and tracked down other observations of Gaia17bpp made by the Pan-STARRS1 telescope in Hawaii, NASA’s WISE/NEOWISE mission and the Zwicky transient facility in California since 2010.

The star Gaia17bpp, circled in red, was captured in this image by the Pan-STARRS1 telescope.

By comparing the images of Gaia17bpp, the researchers found that the star’s brightness was dimmed by 4.5 magnitudes, or 67 times. It stayed that way for 7 years, from 2012 to 2019.

The astronomers happened to observe the star at the end of a year-long solar eclipse.

No other star near Gaia17bpp has shown an eclipse of this magnitude. The team also searched a digital catalog of astrophotographic plates at Harvard University, dating back to the 1950s.

“In the 66 years of observational history, we have found no other evidence of a significant dimming of 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 disc of material,” Tzanidakis said. “If this material were in the solar system, it would extend from the sun to Earth’s orbit or beyond.”

Although Gaia17bpp is unique in having such a long eclipse, it is not the only binary to show dimming behavior. Astronomers are also intrigued by Epsilon Aurigae, a star that experiences an eclipse from a large companion every two years out of 27 – but the actual identity of the companion remains a mystery.

The giant star Betelgeuse also caught astronomers’ attention when it dimmed dramatically in late 2019, fueling speculation that it would explode in a supernova. Instead the old had a dusty tantrum.

For Gaia17bpp, the dust-producing stellar companion could be a small dead star called a white dwarf, but they’re not exactly sure what might be contributing to the debris disk surrounding it.

Whatever the identity of his companion, Gaia17bpp and his mysterious cosmic partner are so far apart that another solar eclipse is centuries away.

“It was an accidental discovery,” Tzanidakis said. “If we had had a couple of years off, we would have missed it. It also indicates that these types of binaries could be much more common. If so, we must theorize how this type of mating came about in the first place. It’s definitely an oddity, but it could be a lot more common than anyone thought.”

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