A Waterfall of Planets: The Mystery of the Vanishing Water Worlds ⚡ экспресс
A new study explains the mysterious “radius valley” of exoplanets. Scientists built a Bayesian model combining rocky and water worlds without hydrogen-helium envelopes. It turns out water planets with hot steam atmospheres neatly reproduce the gap at around 2 Earth radii. Their typical mass is 7 Earth masses, and water makes up 41% of their bulk. Rocky planets, by contrast, weigh half as much. But for bigger sub-Neptunes (over 3 Earth radii), water alone doesn’t cut it: at least 20% of them contain a dash of light gases. The number of planets plunges at this threshold like a waterfall—hence the name of the effect.
The Kepler telescope William Borucki's caught the faint twinkling of distant stars and discovered thousands of planets around other suns. Among them gapes a gap: almost no worlds sized between rocky balls and puffy water giants. This 'radius valley' was explained by a new model: planets initially divide into rocky and water ones. Water worlds with a steam atmosphere fill the gap, but at three times Earth's size they abruptly cut off — like a stream plunging over a waterfall.
Upon reaching a critical mass, such a planet captures hydrogen and helium and becomes a gas giant. Large water worlds simply don't get a chance to appear — they transform earlier. But inside them lies a surprise: water under immense pressure turns into hot ice — solid but scorching. Light measurements from Kepler show that the oceans there have no bottom. And although such water worlds are common in the galaxy, our Solar System is just one possible recipe.
🎯 On water planets, water turns into hot ice under incredible pressure — a solid substance that remains red-hot. So the oceans there can be liquid on top and icy deep down at the same time.
🎬 In 'Interstellar,' the characters visit Miller's planet, covered by a shallow ocean. But real water worlds are more like giant droplets without a solid surface, far deeper than any Earthly seas.