Dr Ellen Stofan, Nasa's chief scientist.
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Nasa chief scientist: 'I'm a bit sceptical about ninth planet'

Nasa's chief scientist says she is "sceptical" about the existence of a ninth planet in our Solar System.

American astronomers say they have strong evidence that the planet could exist, orbiting far beyond even the dwarf world Pluto.

Dr Ellen Stofan says the lack of direct observations to confirm its presence means that we can't know for sure it is there.

  • 20 Jan 2016
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