Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2000 January 2
Explanation: There, that faint dot in the centre - that's the largest rock known. It is larger than every known asteroid, moon, and comet nucleus. It is larger than any other rocky planet. (Nobody knows for sure what size rocks lie at the cores of Jovian planets, or orbit other stars.) The Voyager 1 spacecraft took this picture 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. Yesterday, this rock started 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.
Authors & editors:
Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U.