快猫短视频

WHEN Luke Skywalker鈥檚 uncle forbids him to join the Space Academy in Star
Wars, Luke storms out of the house shielding his eyes against the glare of
two setting suns. But can planets form in binary star systems? Yes, say two
researchers who claim that such planets are more than science fiction.

When dust particles in the disc around a young star collide, they stick
together, eventually forming objects about a kilometre across. Such
鈥減lanetesimals鈥� can then merge, but only if their relative velocities are low.
If they are too fast, the planetesimals break up into smaller pieces when they
collide. 快猫短视频s had thought that the gravity of the second star in a binary
system would disrupt the orbit of planetesimals, keeping their relative
velocities high.

But Hans Scholl at the C么te d鈥橝zur Observatory in Nice and Francesco
Marzari at the University of Padua in Italy say this view ignores recent
observations of gas in the dust discs of binary systems. They found that the gas
and dust exert drag on the planetesimals, slowing them down and easing them into
stable orbits. And the second star鈥檚 gravity creates a zone in which the orbits
of the planetesimals come into alignment, favouring gentle collisions. 鈥淧eople
were surprised,鈥� says Scholl.

Their claim has led to renewed interest in the binary Alpha Centauri, our
nearest stellar neighbour. In this system, there would be a zone of stable
orbits as far away from one of the stars as the Earth is from the Sun. This
suggests that Earth-like planets could reside there. 鈥淪o maybe now we should be
looking for them,鈥� says Paul Wigert, an astrophysicist at York University in
Toronto.