TIC 168789840

TIC 168789840, also known as TYC 7037-89-1, is a stellar system with six stars. Three pairs of binary stars circle a common barycenter. 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 the Earth lies approximately on their planes of rotation.

Discovery

The Transiting Exoplanet Survey Satellite 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 giant star 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 and the three lettered pairs, as groups, have been resolved. From A pair to C pair is calculated to be apart, which means this gap should be resolvable using speckle interferometry which has not yet been achieved.
Note, the three binaries A, B, and C are resolved only as systems, the pairs being just , , and apart, respectively.
According to Jeanette Kazmierczak of NASA's Goddard [Space Flight Center]:

Stellar characteristics

The primary stars of all three close binaries are slightly hotter and brighter than the Sun, 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, while the less massive and longer-lived secondaries are all still firmly on the main sequence and fusing hydrogen in their cores.