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Astronomers have found two warm Saturn-sized planets that weigh differently and likely formed under different conditions.
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NASA's TESSspace telescope monitors thousands of stars, catching the moment when a planet crosses its star's disk — the star's light dims slightly. That's how astronomers spotted two planets orbiting stars similar to our Sun. One, TOI-883 b, completes an orbit in ten days; the other, TOI-899 b, takes nearly thirteen. Both are hot: their temperatures reach about 800 degrees Celsius, like a ceramic kiln.
Ground-based telescopes then took over, measuring how each planet's gravity makes its star wobble — a method akin to a heavy child on a swing making the whole frame vibrate. It turns out both planets are lighter than Saturn: one weighs as much as 39 Earths, the other 68. But here's the twist: despite nearly identical masses and similar host stars, the planets differ in size. The first is just over half of Jupiter's radius, while the second is nearly Jupiter-sized. That means their interiors have different compositions.
Why the difference? Perhaps one planet accumulated more heavy elements, rock and metal, while the other stayed fluffy and gas-rich. It's like two pies of equal weight: one dense, packed with nuts and dried fruit, the other a light sponge cake.
Such a difference under similar birth conditions is puzzling. Maybe the planets formed in different parts of the protoplanetary disk, or one suffered a collision that reshaped its interior. Now both planets serve as excellent laboratories: their atmospheres can be studied as they transit their stars, and the gas composition may reveal where and how they formed.
