NASA’s exoplanet-hunting satellite, Transiting Exoplanet Survey Satellite (TESS), has discovered that one of the brightest stars in the night sky is sometimes unexpectedly eclipsed! While it was known that the Alpha Draconis was part of a binary system along with a fainter companion star, the stars were found to regularly eclipse each other.

Thuban or Alpha Draconis is located 270 light-years away from the Earth in the constellation of Draco. The star is visible to the naked and even served as the North Star about 4,700 years ago. At the time, it was the closest star located near the North Pole of Earth’s spin axis. But sometime later, the Earth underwent a change in the spin axis that made Polaris closest to the North Pole.

In 2004, the star was seemingly found to be pulsating as small periodic changes in the brightness of the star were observed. Astronomers wanted to investigate the case of Alpha Draconis and found that it was not pulsating at all. Instead, they found that the binary system of stars would eclipse each other as they danced along with each other. The findings were presented at the 235th meeting of the American Astronomical Society.

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Astronomers using data from NASA’s TESS were surprised to find that Alpha Draconis, a star visible to the naked-eye, undergoes mutual eclipses with its fainter companion star. The brief six-hour eclipses were easy for ground-based observatories to miss. 327 6:25 AM – Jan 7, 2020 Twitter Ads info and privacy

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Alpha Draconis is about 4.3 times bigger and 70% hotter compared to the Sun, while the five times fainter companion star is about half its size and 40% hotter than the Sun. The stars orbit every 51.4 days and due to the three degree tilted view of the orbital plane, the stars don’t completely eclipse each other.

One of the presenters of the observations, Angela Kochoska from Villanova University explained, “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.”

Image Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA)/ NASA Video(YouTube)


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