Two travelers from far beyond Neptune return home

TUCSON, Ariz. — Two visitors from the edge of the solar system appear to be returning to their birthplace. One is made of rock, the other slathered in organic compounds; neither looks like other bodies from the Oort cloud, the icy debris field that envelops the solar system. The objects may be relics from the solar system’s formative years, thrown to the Oort cloud while the planets were still forming over 4 billion years ago.

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A distant planet may lurk far beyond Neptune

Out beyond Neptune, the solar system resembles the deep ocean: dark, remote and largely unexplored. To an Earth-bound observer, even the brightest objects, such as Pluto, are 4,000 times as faint as what the human eye can see. An undiscovered planet could easily lurk out there unnoticed, a possible fo ... Read more »