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Birthday · January 1, 2006

The Largest Rock in the Solar System

January 1, 2006

The night sky on your birthday is never quite the same twice — the planets shift, the constellations drift, the Moon wears a different phase.

The Largest Rock in the Solar System

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APOD published January 1, 2006. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.

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The Largest Rock in the Solar System

Original APOD · January 1, 2006

There, that faint dot in the center - that's the largest rock known in our Solar System. It is larger than every known asteroid, moon, and comet nucleus. It is larger than any other local rocky planet. (Nobody knows for sure what size rocks lie at the cores of Jovian planets, or orbit other stars.) It used to be the largest rock of any type known until earlier last year. The Voyager 1 spacecraft took the above picture of the giant space rock in 1990 from the outer Solar System. This rock is so large its gravity makes it nearly spherical, and holds heavy gases near its surface. Today, this rock starts another orbit around its parent star, for roughly the 5 billionth time, spinning over 350 times during each trip. Happy Gregorian Calendar New Year to all the human inhabitants of this rock we call Earth.

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