Unusual exoplanet with Jupiter-like mass discovered orbiting giant star

10 Aug 2017

Illustration of an exoplanet orbiting a star. Image: BabyRhino/Shutterstock

A planet similar in size to Jupiter, seemingly hidden to astronomers, has been found after an exhaustive search.

An international team of astronomers has discovered a Jupiter-mass alien world circling a giant star (HD 208897), thanks to some breakthrough techniques of stargazing.

At a distance of 210 light years away from Earth, the star is about five times larger than our sun, equal to approximately 1.25 solar masses. Encircling it is a planet with 1.4 Jupiter masses.

Future Human

Located at a distance of about 1.05 astronomical units from the star – each unit being the same distance from Earth to the sun – the planet circles its host every 353 days, similar to Earth but with an unusual orbit.

Publishing its findings in a recent paper, the team said that HD 208897 is believed to be metal-rich and was discovered as part of an extensive observational campaign carried out from 2007 to 2017 to search for substellar companions and planets around 50 stars.

The team, led by Ankara University’s Mesut Yilmaz, then discovered 13 targets – including HD 208897 – which all showed significant radial velocity variations.

By observing the star for a long period of time, the team found a periodic signal from the surrounding region, suggesting the presence of an unseen and possibly low-mass planet.

Will help us find planets

The study was a major breakthrough as it suggests that it is possible to detect such lower-mass planets in the range of Jupiter, even around giant stars, if long-term observations are carried out.

“This discovery will be important in understanding the planet formation around metal-rich intermediate-mass stars and the effect of stellar evolution on the planetary system configuration,” the team said in its paper.

This comes just a few days after a gas giant planet called WASP-121b was discovered. The planet is similar to Jupiter but has five times the mass as well as a boiling atmosphere of close to 2,500 degrees Celsius.

What makes WASP-121b particularly unique is that it also has a stratosphere, similar to our own planet.

Colm Gorey was a senior journalist with Silicon Republic