This diagram illustrates that mature planetary systems like our own might
be more common around twin, or binary, stars that are either really close
together, or really far apart.
NASA's Spitzer Space Telescope observed that debris disks, which are
signposts of mature planetary systems, are more abundant around the
tightest and widest of binary stars it studied. Specifically, the infrared
telescope found significantly more debris disks around binary stars that
are 0 to 3 astronomical units apart (top panel) and 50 to 500 astronomical
units apart (bottom panel) than binary stars that are 3 to 50 astronomical
units apart (middle panel). An astronomical unit is the distance between
Earth and the sun.
In other words, if two stars are as far apart from each other as the sun
is from Jupiter (5 astronomical units) or Pluto (40 astronomical units),
they would be unlikely to host a family of planetary bodies.
The Spitzer data also revealed that debris disks circle all the way around
both members of a close-knit binary (top panel), but only a single member
of a wide duo (bottom panel). This could explain why the intermediately
spaced binary systems (middle panel) can be inhospitable to planetary
disks: they are too far apart to support one big disk around both stars,
and they are too close together to have enough room for a disk around just
one star.
