Solving the 200-Year-Old Mystery of a Strange Eclipsing Star

[Judi Lynn]

By Nola Taylor Redd, Space.com Contributor | June 18, 2018 04:20 pm ET

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For nearly 200 years, astronomers have puzzled over the strange dimming process of the bright winter star Epsilon Aurigae. Now, thanks to precise distance measurements from the European Space Agency's Gaia satellite, scientists have pinned down the mass of the two stars involved in the process, and how their exchange of material has caused decades-long eclipses visible on Earth.

Every 27 years, Epsilon Aurigae dims for a two-year period. Scientists have speculated about what caused the eclipse: a cloud of meteors, a black hole, another star or a disk of material. Before the most recent eclipse, in 2010, astronomers began to suspect that the system contained two stars surrounded by a cloud of gas and dust. But the nature of the pair of stars remained a mystery.

"The debate for a long time — astronomers the likes of [Gerard] Kuiper and [Otto] Struve have weighed in on it — is, what the heck is this opaque, occulting thing," astronomer Robert Stencel of the University of Denver told the press during the 232nd annual meeting of the American Astronomical Society this month. Stencel and graduate student Justus Gibson, also of the University of Denver, used new data from Gaia to model stellar pairs that could produce the strange signals observed in the Epsilon Aurigae system. Thanks to Gaia, the pair found that the binary-star system is smaller than most previous estimates, and the exchange of material ongoing. [Photos: Gaia Spacecraft to Map Milky Way Galaxy]

"This is a pretty active system," Stencel said. "The F-star is boiling off, [and] the companion is grabbing material, producing a big dusty disk." F-type stars are slightly larger and slight warmer than the sun.

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