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TESS Shows Ancient North Star Undergoes Eclipses

11 Jan 2020, 09:53 UTC
TESS Shows Ancient North Star Undergoes Eclipses
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Astronomers using data from NASA's Transiting Exoplanet Survey Satellite (TESS) have shown that Alpha Draconis, a well-studied star visible to the naked eye, and its fainter companion star regularly eclipse each other. While astronomers previously knew this was a binary system, the mutual eclipses came as a complete surprise."The first question that comes to mind is 'how did we miss this?'" said Angela Kochoska, a postdoctoral researcher at Villanova University in Pennsylvania who presented the findings at the 235th meeting of the American Astronomical Society in Honolulu on Jan. 6. "The eclipses are brief, lasting only six hours, so ground-based observations can easily miss them. And because the star is so bright, it would have quickly saturated detectors on NASA's Kepler observatory, which would also mask the eclipses."The system ranks among the brightest-known eclipsing binaries where the two stars are widely separated, or detached, and only interact gravitationally. Such systems are important because astronomers can measure the masses and sizes of both stars with unrivaled accuracy.Alpha Draconis, also known as Thuban, lies about 270 light-years away in the northern constellation Draco. Despite its "alpha" designation, it shines as Draco's fourth-brightest star. Thuban's fame arises from a historical role it played ...

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