Scientists find signs exoplanet was born ‘far away from current location’

Jamie Harris, PA Science Technology Reporter
·2-min read

Scientists believe a transiting exoplanet deep in space may have actually been born further away from its current spot.

Six different chemicals detected in the planet’s atmosphere – hydrogen cyanide, methane, ammonia, acetylene, carbon monoxide and low amounts of water vapour – suggest that it must have been formed at a greater distance from its star than it is at present.

Researchers say it is the first time that so many molecules have been measured, and points to an atmosphere with more carbon present than oxygen, leaving a “chemical fingerprint” of its past.

This would confirm previous thinking that the exoplanet – officially known as HD 209458b – has moved to its current position after forming, a mere seven million kilometres from its sun.

Dr Siddharth Gandhi, from a team at the University of Warwick which took part in the study, said: “The key chemicals are carbon-bearing and nitrogen-bearing species.

“If these species are at the level we’ve detected them, this is indicative of an atmosphere that is enriched in carbon compared to oxygen.

“We’ve used these six chemical species for the first time to narrow down where in its protoplanetary disc it would have originally formed.

“There is no way that a planet would form with an atmosphere so rich in carbon if it is within the condensation line of water vapour.

“At the very hot temperature of this planet, if the atmosphere contains all the elements in the same proportion as in the parent star, oxygen should be twice more abundant than carbon and mostly bonded with hydrogen to form water or to carbon to form carbon monoxide.

“Our very different finding agrees with the current understanding that hot Jupiters like HD 209458b formed far away from their current location.”

The study is published in the Nature journal.