[meteorite-list] First Binary Star Exoplanet Discovered

[Sterling K. Webb]

Numerous news stories that start like this:

> they have discovered Tatooine
> orbiting a binary pair.

Kepler-16b the very first exoplanet found around
(orbiting) a binary star (i.e., both of the stars). Hardly
Tatooine. Saturn sized and massed (core mass
40 to 60 Earths), with an orbital period of 229 
days (another news piece says 221 days, an
obvious typo frm one to another, but which?).

The binary stars, are 0.69 solar masses and 0.20
solar masses and are actually relatively cool. The
surface temperature of the planet is therefore
estimated to be a chilly -38 C.to -65 C (unless
the reporters wrote down -100 to -150 F when the
investigators actually said -100 to -150 C -- never 
trust a media source).

At any rate, that would be about 0.7 AU for the
distance of the planet from the common center of
gravity. The stars have a separation of 0.22  AU
and a period of mutual orbit of 41 days. It seems
that we are viewing the system right in its orbital
plane or local ecliptic. The planet's plane and the
two stars' plane are within 0.3 degrees of each
other. The planet orbits at the inner edge of the
stable zone surrounding the two stars.

A lucky discovery: the system's orbital plane shifts
position with time. Between 2018 and 2042, the
team calculates, Kepler 16-b's transit across the
largest star will vanish, while transits across the
smaller star will disappear for about 35 years
beginning in 2014.

"Theory" has long held that conventional planetary
systems cannot form around binary stars. So much
for theory... as usual. Now maybe we can get somebody
to look at alpha Centauri?

Please!


Sterling K. Webb
 ----------------------------------------------------------------------