Sunday, 29 May 2011

Wandering Planets Without a Sun?

An artist’s impression of a wandering giant planet. Image courtesy of NASA/JPL-Caltech/R. Hurt.

Joel Kontinen

Astronomers think that they have found ten giant planets that either orbit extremely far from their sun or do not orbit at all but instead roam freely in interstellar space.

Two research teams who used gravitational microlensing to find exoplanets recently reported on their discovery in the journal Nature.

According to Nature news, “Microlensing involves measuring changes in the brightness of distant, background stars as a passing planet's gravity bends and magnifies the starlight. As a result, the star brightens and fades in a pattern distinct from random twinkling, and the duration of brightening indicates the mass of the magnifying object.”

Takahiro Sumi, an astrophysicist at Osaka University, who was a co-author of the paper in Nature, says that while planet formation theories predicted the existence of free-roaming planets, their number is a surprise.

However, other astronomers would still need more data before they are willing to accept the claims of Sumi and colleagues. After all, the planets could actually be brown dwarf stars.

The discovery challenges naturalistic views of the origin of solar systems at least to some extent and emphasises the uniqueness of our solar system.


Drake, Nadia. 2011. So many lonely planets with no star to guide them. Nature News. (18 May).

Wambsganss, Joachim. 2011. Bound and unbound planets abound. Nature 473 (7347), 289-291.