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Baby Planet Puzzles Astronomers - Universe Today
In June, researchers from the University of Rochester discovered a planet around a star so young that it shouldn't exist according to existing theories of planetary formation. Further observations have backed up the discovery; there's definitely a planet there which is only 100,000 to 500,000 years old. This is much too young for either of the established theories of planetary formation. In the "core accretion" model, larger and larger chunks of rock smash together for 10 million years until a large planet is formed. In the "gravitational instability" model, a cloud of material pulls together into a planet by its own gravity; this is faster, but still not fast enough to explain how the planet got there.