Skip to main content

This weird exoplanet is shaped like a rugby ball

Exoplanets come in many sizes, and sometimes they also come in unusual shapes. The European Space Agency’s CHEOPS exoplanet-hunting telescope has discovered a planet the shape of a rugby ball, pulled into that form by extreme gravitational forces.

The planet, named WASP-103b and located in the constellation of Hercules, experiences epic tidal forces due to orbiting so close to its star, with a year that lasts just one day. The planet is big, at twice the size of Jupiter, and with one and a half times its mass. “Because of its great proximity to its star, we had already suspected that very large tides are caused on the planet. But, we had not yet been able to verify this,” explained study co-author Yann Alibert, professor of astrophysics at the University of Bern, in a statement.

Artist impression of planet WASP-103b and its host star.
Artist impression of planet WASP-103b and its host star: ESA’s exoplanet mission Cheops has revealed that an exoplanet orbiting its host star within a day has a deformed shape more like that of a rugby ball than a sphere. The planet, known as WASP-103b is located in the constellation of Hercules. ESA

Using CHEOPS, the team was able to verify the tidal deformation of the planet by looking at its transits. When the planet passes between its star and Earth, in an event called a transit, the team could measure the dip in brightness from the star and learn about the planet. “After observing several such so-called “transits”, we were able to measure the deformation. It’s incredible that we were able to do this — it’s the first time such an analysis has been done,” said co-author Babatunde Akinsanmi.

As well as measuring its odd shape, the researchers were also able to learn about the planet’s interior by seeing how it was deformed. “The resistance of a material to deformation depends on its composition,” explained Akinsanmi. “We can only see the tides on Earth in the oceans. The rocky part doesn’t move that much. Therefore, by measuring how much the planet is deformed, we can determine how much of it is made up of rock, gas, or water.”

The findings suggest that the planet is similar internally to Jupiter, though it is twice the size. The researchers therefore think the planet has been inflated, perhaps due to heating from the nearby star.

The research is published in the journal Astronomy & Astrophysics.

Editors' Recommendations