The 'frontier of the Solar System'
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Ultima Thule: The 'frontier of the Solar System'

Alan Stern, chief scientist on Nasa's New Horizons probe, looks forward to the flyby of Ultima Thule. The 30km-wide, icy object is some 6.5 billion km from Earth, making the encounter the most distant exploration yet of a Solar System body. Prof Stern spoke with our science correspondent Jonathan Amos.

  • 30 Dec 2018