Newly discovered exoplanets are not alone

Astronomers from a Canadian university have given a clearer understanding on a class of exoplanets known as Warm Jupiters, that often have unexpected planetary companions.

The researchers have strong evidence of two distinct types of Warm Jupiters and how they formed. Warm Jupiters are large, gas-giant exoplanets that 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.

These exoplanets are warmer than the cold gas giants in our Solar System but not as warm as Hot Jupiters which are closer to their parent stars than Mercury is to ours. Hot Jupiters, the other type of exoplanets, lack companions and are likely to have migrated to their current orbits.

Chelsea Huang, lead author from the University of Toronto, said: “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.”

This study challenges previously held theories that Warm Jupiters didn’t form where they can be observed as they are too close to their parent stars to have amassed large, gas giant like atmospheres. Researchers believed they formed in the outer reaches of their planetary systems and migrated inwards, with a possibility they could become Hot Jupiters.

It was assumed that these Warm Jupiters would have disturbed neighbouring or companion planets while travelling due to their gravitational pull, by ejecting them on their journey. But the scientists found 11 of the 27 planets they studied have companions that range in size from Neptune to Earth-like.

Huang said that more analysis was to come; leading to the number of Warm Jupiters with smaller neighbours possibly increasing. The scientists used four years of Kepler space telescope observations to conduct this study.

The research was published in the Astrophysical Journal.