NASA will make the most distant fly-by of any solar system object ever on New Year's Day.
That's when its spacecraft New Horizons will take images of Ultima Thule.
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Ultima Thule is about the size of Oakland and San Jose combined.
It's an object that sits in what's called the Kuiper Belt.
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"The Kuiper Belt objects formed in the outer part of the solar system - early on - and we think they've mostly been sitting there - in deep freeze - and so we are really excited to see this type of object because it may be a piece of the early solar system we can study," New Horizons Co-Investigator Kelsey Singer said.
Ultima is about a billion miles from Pluto. NASA said it is likely icy with a little bit of rock as well.
Mysterious streak of light seen in sky above California