NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a rare six-star system with stars that flicker in and out of brightness, piquing the interest of researchers.
Most star systems discovered by TESS are three- or four-star systems. Six-star systems are very rare. NASA’s Brian Powell, the study’s first author, said, “The record through June 2020 shows that 17 six-star systems were discovered before this system was found.”
But this system, TIC 168789840, is unusual in that it consists of three pairs of cross-eclipsing binary star systems, the first such system discovered to date.
A binary system is a system in which one star rotates around another star. The eclipsing binary system is a special type of system, because of its position, from the Earth’s perspective, one of the stars will occasionally block the light from the other star during its orbital period, resulting in periodic changes in the brightness of one star, similar to the solar and lunar eclipses seen on Earth, hence the name eclipsing binary, or light-varying binary.
This system is about 1,900 light-years from Earth, and is located in the constellation Eridanus. The system is complex, with two inner pairs of cross-eclipsing binary systems, systems A and C, and a third pair of binary systems, B, on the periphery, rotating around the inner two systems.
The researchers write, “Our analysis shows that the three pairs of binary systems each have orbital periods of 1.57 days (system A), 1.3 days (system C), and 8.2 days (system B), respectively, with systems A and C orbiting each other in the inner circumference and forming another four-star subsystem with a period of about 4 years; finally, system B rotates around the inner four-star in the outer circumference again with a period of about is about 2000 years.”
Another feature of this six-star system is that the three pairs of binary systems within it are highly similar, as if they were “triplets,” meaning that they have similar masses, orbital radii, and temperatures.
The mass of the primary star of these three binary systems is 1.23 to 1.3 times that of the Sun; the radius is 1.46 to 1.69 times that of the Sun; and the mass of the companion stars in the three systems is 0.56 to 0.66 times that of the Sun, and the radius is 0.52 to 0.62 times that of the Sun.
The researchers estimate that the four inner stars are unlikely to have any planets around them because the “quartet” is so close that any planets orbiting them would be thrown out of the system or swallowed up. The outer binary systems are farther away and could have planets around them.
The study was published in early January on arXiv, and has been accepted for publication in The Astronomical Journal.
Recent Comments