4 stars within 6 AU

The universe keeps throwing neat stuff up for our telescopes to look at. A team lead by Evgenya Shkolnik (University of Hawaii), has observed a tight system of 4 stars crammed within 6 AU of one another - If located in our solar system, all four stars would fit within the orbit of Jupiter! The system consists of 2 tight binaries, with the two binary systems orbiting the center of mass for all 4 stars. There is less than a 1 in 2000 percent chance that stars of this type could form in this 4-star type of a system, and this is the first time a system like this has been found.

The two sets of binaries are very tight. One pair orbits a point between the two stars (their center of mass) with a separation of 0.06 AU, and the other set has a maximum separation of 0.56 AU. For perspective, Callista orbits Jupiter at a distance of 0.01 AU and Mercury orbits the Sun at a distance of 0.46 AU.

This is a system that is neat to model. While brown dwarfs live a long long long long time, as these stars (someday many 10s of billions of years in the future) evolve, the orbits in the system will change, material may exchange between stars, and who knows what else. This is a discovery announcement, and I can’t wait to see what the theorists do with their knowledge that these things can form!

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