From planets close to home to worlds orbiting alien stars, we now turn to the planet WASP-103b. This Jupiter-massed world orbits its star once per Earth day and is so close to its star that it is inflated by heat, and the star even raises tides of gas the way our Moon raises tides of water. The overall effect is a world that is more oval than round.

And we can see this weird shape in the data. As the planet passes in front of the star, we receive less and less light until the planet is completely in front of the star; we then get the same amount of less light until it begins to exit, and the light we receive increases again. The shape of this light curve can tell us a lot about the shape of the planet, and in this case, what we see is best explained by a planet distorted by tides. 

From space, you can’t see the few feet the tides rise here on Earth, but if you could, you’d see the ocean rising up both on the side facing the Moon, where gravity is strongest, and on the opposite side, where gravity is least. In a lot of textbook examples, they’ll show the Earth distorted to look more like a rugby ball or less pointy football. This planet is that tidally distorted world made real.

Moral of the story? If you get too close to your star, you’ll get bloated up to 1.5 times your normal size and distorted into an oval.

This work appears in Astronomy & Astrophysics and was led by SCC Barros.

More Information

ESA press release

“Detection of the tidal deformation of WASP-103b at 3 σ with CHEOPS,” S. C. C. Barros et al., 2022 January 11, Astronomy & Astrophysics