After analysing Kepler space telescope data, astronomers from the University of Toronto, Canada, have found a clear understanding yet of a class of exoplanets called 'Warm Jupiters', showing that many have unexpected planetary companions.
The analysis provides strong evidence of the existence of two distinct types of 'Warm Jupiters', each with their own formation and dynamical history.
The two types include those that have companions and thus, likely formed where we find them today and those with no companions that likely migrated to their current positions.
"Our findings suggest that a big fraction of 'Warm Jupiters' cannot have migrated to their current positions dynamically and that it would be a good idea to consider more seriously that they formed where we find them," said Chelsea Huang, a Dunlap Fellow at the Dunlap Institute for Astronomy and Astrophysics, University of Toronto.
Warm Jupiters are large, gas-giant exoplanets -- planets found around stars other than the Sun.
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They are comparable in size to the gas-giants in our solar system.
But unlike the Sun's family of giant planets, "Warm Jupiters" orbit their parent stars at roughly the same distance that Mercury, Venus and the Earth circle the Sun.
They take 10 to 200 days to complete a single orbit.
Because of their proximity to their parent stars, they are warmer than our system's cold gas giants -- though not as hot as "Hot Jupiters" which are typically closer to their parent stars than Mercury.
Instead of finding "lonely", companion-less "Warm Jupiters", the team found that 11 of the 27 targets they studied have companions ranging in size from Earth-like to Neptune-like.
"The number of 'Warm Jupiters' with smaller neighbours may be even higher. We may find that more than half have companions," Huang noted in a paper published in the Astrophysical Journal.
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