Double Star Systems May Be Hiding a Third Companion  Pairs of
stars with separations five hundred times the size of the solar
system could be triplets in disguise. New research indicates
that many of the known wide binaries (double star systems) may
have once contained three stars, and many could still harbor a
third.  Bound together by gravity, binary stars make a large
percentage of the universe. While most are close, some pairs can
orbit with separations thousands of times larger than the
distance between the Earth and the sun, known as an astronomical
unit. But the wide spread between the two stars means that they
couldn't have formed in the same cloud of dust and gas, leaving
astronomers to puzzle over how they formed.  "This has been a
long-time mystery about these very wide binaries," Bo Reipurth,
of the University of Hawaii at Manoa, told  When a binary
becomes a triple  Scientists estimate that as many as 10 percent
of stars in the universe are part of wide binaries. Close
examination of many of thes