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Science Saturday Comet-like exoplanet cruises near stellar poles

Model of a stellar regatta around GJ436 and explanet GJ436b

Space boaters above the poles of the GJ436 have a breathtaking view of the entire planetary system, including the "hairy planet" with its comet tail (right)

(Denis Bajram - Creative Commons)

The GJ436b exoplanet follows an elliptical orbit over the poles of its star, researchers from the Swiss University of Geneva have discovered.

The exoplanet, known for its huge cloud of gas, also has a very special orbit, according to an article published in the prestigious Nature magazine earlier this month.

Instead of turning in the equatorial plane of the star, the planet passes almost above the stellar poles and unlike the planets of the solar system, it forms a flat ellipse.

“This planet is under enormous tidal forces because it is incredibly close to its star, barely three percent of the Earth-Sun distance,” Vincent Bourrier, researcher at the department of astronomy of Geneva University is quoted as saying in a press releaseexternal link.

“The star is a red dwarf whose lifespan is very long, the tidal forces it induces should have since circularised the orbit of the planet, but this is not the case,” he continues.

Bourrier is also the first author of the study and a member of the European project FOUR ACES under the EU’s Horizon 2020 research programme.

Massive and distant planet

The discovery about the orbital inclination of GJ436b is the latest piece of a puzzle that has apparently baffled astronomers for a decade.

The reasons for the circular orbit could be the existence of an unknown, more massive and distant planet, says Christophe Lovis, researcher and co-author of the study.

The calculations which measured the orbital inclinations also predict that the planet has not always been so close to its star, and the “evaporating planet” would not always have evaporated.

“Our next goal is to identify the mysterious planet that has upset this planetary system,” Bourrier is quoted as saying.

swissinfo.ch/ug

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