An Exo-Neptune Beat the Odds and Kept its Atmosphere

An artist impression of exoplanet LTT9779b orbiting its host star. Credit: Ricardo Ramírez Reyes (Universidad de Chile)

As planet-hunting scientists find more and more planets, they’ve encountered some puzzles. One of them concerns the lack of Neptune-size worlds orbiting close to their stars. Astronomers think that these planets aren’t massive enough to retain their atmospheres in the face of their stars’ powerful radiation, which strips it away.

But at least one of these planets has retained its atmosphere. How?

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