NASA Astronomers Discover Thuban Eclipses

NASA astronomers discover ancient Star eclipses.
This animation illustrates a preliminary model of the Thuban system, now known to be an eclipsing binary thanks to data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The stars orbit every 51.4 days at an average distance slightly greater than Mercury’s distance from the Sun. (Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA))

NASA astronomers have discovered that an ancient star pair undergoes eclipses using Transiting Exoplanet Survey Satellite (TESS), a space telescope whose purpose is to seek for exoplanets.

The star pair named Thuban, may have been the North Star, the one closest to the northern pole of Earth’s spin axis. Researches believe it may have guided ancient Egyptians in constructing the pyramids, and other historical events that transpired some 4,700 years ago.

However, due to changes in the Earth’s spin axis, an event known as precession that happens over a 26,000-year cycle, the North Star is Polaris.

As the pair, the bigger star is more than four times larger than our sun and 70 per cent hotter with a surface temperature around 17,500 degrees Fahrenheit. The smaller of the pair is five times fainter, than the bigger star and about half its size.

The two stars orbit one another at an average distance of about 38 million miles and complete a full circle every 51 days. Astronomers had never found any evidence that the stars eclipse one another in those orbital paths until now, because, the eclipses are brief, lasting only six hours, so ground-based observations can easily miss them, according to Angela Kochoska, a postdoctoral researcher at Villanova University in Pennsylvania,

“And because the star is so bright, it would have quickly saturated detectors on NASA’s Kepler observatory, which would also mask the eclipses,” she said.

Based on the discovery, astronomers have learnt that Thuban and its partner are among the brightest “eclipsing binaries” pairs of stars that pass in front of one another, leaving the other in shadow. In this case, the two stars never completely conceal one another, but portions of them become shrouded from view.

Kochoska, who presented the findings at the 235th meeting of the American Astronomical Society in Honolulu on January 6, is planning a follow-up study to look into additional eclipses that TESS can see.


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