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Have you ever taken a cup of tea at a state fair? If so, you might get a little taste of life in a swirling sixfold and eclipsing sixfold star system.
“Sextuply-eclipsing the six-fold star system” is the astronomer-speak for a system with six stars all orbiting each other and all regularly eclipsing each other from the perspective of Earth – and astronomers just found one called TIC 168789840.
This six-star system is quite far from Earth (just under 2,000 light years) that telescopes cannot resolve its individual stars, which merge into a single point of light. Instead, astronomers were able to spot this brightening and dimming point of light in an unusual pattern, thanks to the stars’ penchant for regularly slipping away.
These eclipses are visible thanks to a lucky point: the stars of TIC 168789840 orbit on a plane perfectly aligned with the Earth, so each time one of the stars crosses another, it creates an eclipse visible to the terrestrial telescopes. From a different point of view, the stars would never block and the system would be just another point of light in space.
This is not the first sextuple system ever discovered, astronomers noted in an article published Jan.12 at arXiv database (not yet peer reviewed) But the star system joined a club with only three other members, including Castor, a famous system discovered in 1920.
Related: 12 trippy objects hidden in the zodiac
Castor, known since ancient times as one of the stars of the constellation Gemini, was identified as a binary system in 1719 by English pastor and astronomer James Pound. Just 51 light years from Earth, the system revealed itself to Pound through a telescope as two points of light dancing around each other. In 1905, astronomers realized that these two points were in fact two pairs of stars orbiting each other and encircling a common center; and in 1920, another team spotted a third pair of stars circling the four interiors, making it a six-star system.
There are other ways for six-star systems to organize themselves. The ADS 9731, for example, has four light spots surrounding a common center. Two of those bright spots are tight binaries, making this a sixfold system.
But “TIC 168789840 is very similar to the famous Castor system,” the authors wrote.
There are two inner pairs of stars that each rotate in tight circles. (The first pair completes a binary orbit every 31 hours, the second every 38 hours.) And these binaries – the “inner quadruple” – complete a circuit around a common center about once every 3.7 years.
Compared to internal couples, the two stars in the external binary are less comfortable with each other, only rotating a binary orbit once every 197 hours. And the binary pair only completes its circuit of the whole system once every 2000 years or so.
Identifying the distant and faint TIC 168789840 was a high-tech undertaking as James Pound’s telescope observations of near and bright Castor. Researchers used NASA’s Discover supercomputer to dig years of data from the Transiting Exoplanet Survey Satellite (TESS), which is tuned to look for changes in starlight all over the sky.
The researchers trained a “neural network” – a type of artificial intelligence – running on Discover to look for gradation and brightening patterns that could indicate complex systems. But most of what turned out was boring binaries. However, careful study of TIC 168789840 revealed something unusual and follow-up observations confirmed the presence of six stars.
Researchers are still not sure exactly how complex multi-star systems form, the authors wrote in the article. This discovery provides essential data to address this problem. And more data may soon be on the way.
“TESS has enabled us to find well over 100 candidate multi-star systems to date, with the analysis of another sixfold system… to be followed in the near future,” they wrote.
Originally posted on Live Science.
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