Weighing Atoms: A Race Odyssey

Walk on the Wild Side

This is one wild and crazy comet – aren't they all! Read on to get to know it a little better.

• The “Wild” in Comet Wild 2 is actually pronounced “Vilt.” It references not the celestial body’s feral nature, but Swiss astronomer Paul Wild, who discovered it in 1978. The comet is also known as 81P.
• Wild 2 used to orbit the sun between Jupiter and Uranus. But in 1974, a close encounter with Jupiter altered its orbit; since then its orbit intersects that of Mars.
• Prior to 1974, Wild 2 circled the sun about every 40 years. Now one complete orbit takes about 6.4 years. To see exactly where Wild 2 is today, or where it will be in a few years, click here.
• Wild 2 is one of more than 800 known comets in our solar system, though scientists believe there are trillions.
• Wild 2 is about 5 kilometers (3.1 miles) in diameter – a typical size for a comet, though small compared to Halley’s comet, which measures about 8 x 16 kilometers.
• The nucleus of a comet is made up of ice and rocky dust particles, often referred to as “a dirty snowball.” The ice is mostly frozen water but may also include other frozen materials.
• Most comets we see from Earth originated in the Kuiper Belt, which extends far beyond Pluto’s orbit. They’re called short-term (or periodic) comets, and orbit the sun at least once every 200 years. Much greater quantities of comets are believed to reside in the Oort Cloud, a vast spherical region well beyond Pluto but encompassing the vast majority of the space of our solar system. One of these comets can take more than a million years to orbit the sun.

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