Researchers have discovered nine new exoplanets, overturning a pillar of planetary theory. Previously, astronomers thought that all planets orbit their suns in the same direction as the suns rotate, but two of the new exoplanets have opposite, or retrograde, orbits.
Planets were thought to develop from dust and gas orbiting a young star, thus developing an orbit in the same direction as the star's rotation. The retrograde orbits, however, suggest that some developing planets could get caught in a long-term "gravitational tug-of-war" between other stars and planets, pushing the new planets into eccentric orbits around their transit stars. Such a development process would exclude the possibility of an Earth-like planet developing alongside the Jupiter-sized retrograde planets, since the latter's jerky movements would knock out smaller competition.
The new exoplanets are also notable for the way they were discovered. Scientists have found most of the 452 recorded exoplanets by noting their gravitational pull on their transit stars' light. Researchers found the newcomers, however, when the planets passed directly in front of their transit stars.
The same method recently disclosed another exoplanet, this one notable for its similarities to the members of our solar system: it resembles Jupiter in size but Mercury in orbit, giving it much lower temperatures than the gas giant. Since astronomers can learn more about this planet every 95 days, when it orbits past its sun, they will be able to conduct much more thorough research than if they had found it using traditional methods.
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