also via NG, a University of Hawaii astronmer has discovered a very unusual double binary system in the constellation Aquarius 166 light years from our solar system. The four stars all reside within an area smaller than the orbit of Jupiter in our own system.
"University of Hawaii researcher Evgenya Shkolnik reported another odd finding: a unique quadruple star system that packs four stars into a region smaller than the orbit of Jupiter. The stars are grouped into two closely spaced pairs, 12 and 50 million miles (20 and 80 million kilometers) apart, respectively.
"It's really quite amazing that four stars all orbit each other at this distance," Shkolnik said. It's not possible for all four stars to have formed that closely together, she said. Rather, they must have formed at greater distances and then spiraled together as interstellar gas slowed their orbits."
While certainly very rare, the system isn't one of a kind. In my trip to Kitt Peak observatory in 2006, we observed a similar double binary system in the constellaiton Lyra, but the two pair of stars in that system are much further apart. This system's stars probably drifted together into their uniquely close paired cosmic gravity dance within 100,000 years of forming.