14 DAY TRIAL // Astronomers thought that they managed to unlock the secrets of planetary formation many years ago, but new data comes to challenge those beliefs. Recently, nine new transiting exoplanets were found, and their discovery reported at the RAS National Astronomy Meeting (NAM2010), in Glasgow, Scotland. When this dataset was combined with previous observations, it was demonstrated that six planets out of a larger set of 29 orbited their stars backwards, opposite to the direction in which their “parent” spun. This poses some intricate questions, which existing theories on how planets form cannot explain, ESO reports.
Such instances are not visible in our Solar System, where all of the planets spin in the exact same direction as the Sun. The discovery of the six exoplanets poses a serious challenge for existing ideas, and astronomers are taking it very seriously. All the new celestial bodies that were observed tended to be members of the “hot Jupiter” class, and this fact has two implications. First, it may be that this kind of planet forms differently than theories now suggest. Secondly, some have proposed that star systems containing hot Jupiters are highly unlikely to contain Earth-like planets.
“This is a real bomb we are dropping into the field of exoplanets,” explains Geneva Observatory PhD student Amaury Triaud. For the discovery of the nine planets, the team behind the study used data from the Wide Angle Search for Planets (WASP) observatory for detection, and from a number of other instruments for validation. The La Silla, Chile-based 3.6-meter telescope, operated by the European Southern Observatory (ESO), made its HARPS spectrograph available for the work. The Swiss Euler telescope, which is also located at the Chilean facility, was used for the investigation as well.
Current planetary formation models show that planets emerge from the protoplanetary disk that forms around stars when the cosmic fireballs themselves appear. The disk naturally rotates in the same direction as the star does, and so all objects coming out of it should do the same. But the team found that the six peculiar exoplanets did not follow this rule. “The new results really challenge the conventional wisdom that planets should always orbit in the same direction as their stars spin,” explained University of St. Andrews expert Andrew Cameron, who presented the findings at NAM2010.