Our solar system contains a single star, our sun. But about half the stars in the sky exist in binary star systems in which two stars orbit each other. In the “Star Wars” movies, Luke Skywalker’s home planet of Tatooine orbited the two suns of such a binary star system, what astronomers refer to as a circumbinary orbit. Astronomers worked out the orbital dynamics of such a system decades ago and have found multiple examples of circumbinary orbits.
Although
astronomers have discovered thousands of triple star systems, no circumtriple
planetary orbit was known before now. Recently, astronomers studying the young
triple star system GW Orionis detected a gap in the dust ring surrounding the
stars. Such a gap is considered evidence for the existence of a planet.
The
research team, led by Jeremy Smallwood, lead author and a recent Ph.D. graduate
in astronomy from UNLV, studied multiple possible scenarios for how such a gap
might have formed. The three stars can create gravitational torque on the dust
ring, causing gaps. A similar situation occurs in the rings of Saturn where
gravitational interactions with it dozens of moons cause warps and gaps in the
ring structure.
After
analyzing all possible scenarios, the team announced that the most likely
explanation for the gap is the presence of one or more massive, Jupiter-like
planets, whose gravity cleared out the dust. The group found no evidence of
smaller, Earth-like planets in the young triple star system.
According to Smallwood, current theory says that gas giants, like Jupiter and Saturn, should be the first planets to form in a star system. Smaller, rocky planets like Earth and Mars should form later. "It's really exciting because it makes the theory of planet formation really robust," said Smallwood. "It could mean that planet formation is much more active than we thought."
GW
Orionis may not be through forming planets. Who knows? Perhaps a one-up of a Tatooine-like
planet may still form in its dusty disk.
Each month, I write an astronomy-related column piece for
the Oklahoman newspaper. On the
following day, I post that same column to my blog page.
