Hot Jupiter WASP-103b is orbiting extremely close to its star and is experiencing such strong tidal forces that it has deformed into the shape of an elongated rugby ball.
Observations by Europe's Cheops Space Telescope have revealed that hot jupiter WASP-103b is being pulled so strongly by tidal forces from its star that it has become elongated rather than spherical. This is the first evidence of such deformed exoplanets, as scientists report in an article published in Astronomy & Astrophysics. Their work is also described in a press release from the European Space Agency (ESA).
Sun-like star WASP-103 is located about 1,500 light-years away, in the constellation Hercules. Its exoplanet WASP-103b was discovered in 2014. It's an 'ultra-hot Jupiter' - a gas giant orbiting so close to its star that it takes just 22 hours to complete a full revolution and its temperature rises above 2500 Kelvin (more than 2200 degrees Celsius). That's as close as it gets: calculations show that if the orbit of WASP-103b were only slightly smaller, the planet would be destroyed by tidal forces.
These forces arise from the movement of sufficiently large bodies in a heterogeneous gravitational field. They create tides in Earth's oceans, deform and heat Jupiter's satellites, and in the vicinity of black holes can reach such magnitude that they easily stretch and tear entire stars. And with WASP-103b in a tight orbit, the tidal force is powerful enough to deform the entire planet, giving it the shape of a flattened rugby ball.
To find this out, scientists have used data from the U.S. Hubble and Spitzer telescopes, as well as Europe's Cheops exoplanet hunter, which searches for distant worlds by transiting - recording faint changes in a star's brightness during periods when planets pass between it and us. The nature and shape of these variations make it possible to estimate the size and mass of an exoplanet. In the case of WASP-103b, the extreme precision of Cheops has allowed it to observe that the light curve changes in a slightly peculiar way, indicating a deformation.
WASP-103b weighs about one and a half times as much as Jupiter and is as large as Jupiter. This makes the planet 'loose' enough for the tidal forces of the star to change its entire geometric shape. According to scientists, this is the first known case of such a deformation of an exoplanet, although it has yet to be definitively confirmed. To do so, they hope to make additional observations on Cheops, as well as the new James Webb Space Telescope.
