TIC 168789840, also known as TYC 7037-89-1, is a

stellar system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a ''star cluster'' or ''galaxy'', although, broadly speaking, ...

with six stars. Three pairs of

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

s circle a common

barycenter In astronomy, the barycenter (or barycentre; ) is the center of mass of two or more bodies that orbit one another and is the point about which the bodies orbit. A barycenter is a dynamical point, not a physical object. It is an important conc ...

. While other systems with three pairs of stars have been discovered, this was the first system where the stars can be observed eclipsing one another, as their planes of rotation point approximately towards the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

Discovery

The

Transiting Exoplanet Survey Satellite Transiting Exoplanet Survey Satellite (TESS, Explorer 95 or MIDEX-7) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the ''Kepler' ...

identified that the star system consisted of six eclipsing stars. The discovery was announced in January 2021. It is approximately from Earth, in the constellation Eridanus, west of the river asterism's sharpest bend, Upsilon2 Eridani, often called Theemin. To be seen the group needs strong magnification from Earth as is much fainter than

red clump Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...

giant star A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moo ...

Theemin and is about nine times further away.

Orbits

Two sets of the binaries co-orbit relatively closely, while the third pair of stars takes 2,000 years to orbit the entire system barycenter. The inner A pair and C pair orbit each other in 3.7 years. These are, as taken from the paired B stars, about away (specifically the mean telescopic separation is ) and the three lettered pairs, as groups, have been resolved (the three gaps made out). From A pair to C pair is calculated to be () apart, which means this gap should be resolvable using

speckle interferometry Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("''i ...

which has not yet been achieved. Note, the three binaries (here close pairs) A, B, and C are resolved only as systems, the pairs being just (), (), and () apart, respectively. According to Jeanette Kazmierczak of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...

Stellar characteristics

The primary stars of all three close binaries are slightly hotter and brighter than the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, while the secondary stars are much cooler and dimmer. Because the two closely bound pairs are so close, only the third, more distant pair could have planets. The primaries are all beginning to evolve away from the

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

, while the less massive and longer-lived secondaries are all still firmly on the main sequence and fusing hydrogen in their cores.

References

{{Stars of Eridanus 6 Astronomical objects discovered in 2021 Eridanus (constellation) Eclipsing binaries

Discovery

Orbits

Stellar characteristics

See also

References