A six-star system unlike any other known to science.
Binary and even trinary star systems have long been considered rather common. Planets under two or three suns are also becoming less uncommon. However, systems that include six stars at once remain very rare. Until recently, only 17 such objects were known, and now TIC 168789840 became the 18th. This was reported in an article by American astronomers, accepted for publication in The Astronomical Journal.
TIC 168789840 lies in the constellation Eridani, approximately 1900 light-years away. It includes gravitationally bound pairs of stars, two of which (A and C) form the “core” of the system, and the third (B) revolves around them in a distant orbit.
The stars of the binary system A go around each other in 1.6 days, the system C – in 1.3 days, and B – in 8.2. In turn, systems A and C themselves revolve around each other in about four Earth years, and system B bypassing them – in 2000 years.
NASA astrophysicist Brian Powell and his colleagues discovered TIC 168789840 using the TESS space telescope, noting that such a structure resembles the already known multiple stars with six components, for example, Castor in the constellation Gemini.
However, the three pairs of TIC 168789840 are strikingly more similar to each other: they all include a larger star as well as its small companion.
Binary stars A and C are too close to each other, creating such strong gravitational anomalies that it is impossible to imagine that planets could form and survive near them. However, scientists suggest that the relatively distant system B may well have exoplanets. The authors plan to continue observing TIC 168789840 and possibly discover such a strange distant world.
This work will help to understand exactly how unusual systems are formed, including so many stars at once. It is assumed that they may appear as triple stars, formed together – in a common “cradle”. However, further, passing through the gas and dust cloud, each of the participants in the system acquired a new neighbor, becoming a double one.
Scientists were really fortunate to locate this new system with six stars. It was only possible because the orbital plane of the stars falls almost exactly on our line of sight on Earth. This allows scientists to observe the eclipses which occur between the partnering stars. If their orbital plane was different, the six-star system would have appeared as nothing more than a bright light in the cosmos.
The six-star system TIC 168789840 will remain under observation but there is also a lot of collected data that is yet to be analyzed. The scientific team has expressed their motivation for more discoveries and they have even suggested that there may be systems with even more than six suns yet to be found in the database.
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• Andrews, R. (2021, January 23). Six Stars, Six Eclipses: ‘The Fact That It Exists Blows My Mind’.
• Letzter, R. (2021, January 22). ‘Sextuply-eclipsing sextuple star system’ discovered whirling through the Milky Way.
• O’Callaghan, J. (2021, January 21). Astronomers spot amazing six-star system with three sets of eclipses.
• Powell, B., Kostov, V., Rappaport, S., Borkovits, T., Zasche, P., Tokovinin, A., . . . Villasenor, J. (2021, January 09). TIC 168789840: A Sextuply-Eclipsing Sextuple Star System.
• Robitzski, D. (2021, January 26). Astronomers discover solar system with six stars.