Comets Facts- 5 Cool Fact About Comets

FACT #1: There are LOTS of comets out there. Scientists so far have discovered about 4,000 comets, and evidence suggests there may be hundreds of millions more — perhaps trillions.

FACT #2: All comets orbit the sun. Comets come in different shapes and sizes, but all orbit the sun. “Short-period” comets come from the Kuiper belt, a disc-shaped region of icy bodies located beyond Neptune’s orbit, and take less than 200 years to make a full orbit. Long-period comets like ISON come from the Oort cloud, another swarm of objects that lies hundreds, maybe even thousands of times farther than the Kuiper belt, near the very edge of our solar system. These comets can take millions of years to complete an orbit. Rare hyperbolic comets may pass through the solar system only once before being flung out on a hyperbolic trajectory into interstellar space.

  

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FACT #3: Comets can strike our planet — and have. New research suggests that a comet smashed into the Sahara desert some 28 million years ago. Earlier this month, scientists reported that a tiny pebble found in Sahara — dubbed “Hypatia” — came from the comet’s icy core (nucleus).

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An artist’s rendition of the comet exploding in Earth’s atmosphere above Egypt.

FACT #4. Comets may have brought life to Earth — and filled our oceans. In 2009 a NASA space probe took a sample from comet Wild-2 and found that it contained the amino acid glycine — an essential building block of life. A recent study suggests that comet collisions may have brought 22 trillion pounds of organic material to Earth, and provided energy for the synthesis of more complex molecules.

In 2011 scientists also discovered that the water inside a comet had nearly the same chemical composition as the water in Earth’s oceans — suggesting that comets may have brought water to Earth billions of years ago.

FACT #5: Comets have been observed for millennia. Around 500 B.C., Greek philosophers coined the word “komotes” — literally, “long-haired” — to refer to the comets they observed in the sky.

The most famous comet ever observed, of course, is Halley’s comet. Its orbit brings it near Earth about once every 76 years. Some scholars say it was first recorded by Chinese astronomers in 239 B.C. Others argue that it was spotted in Greece around 467 B.C. In any case, it was Edmund Halley who first concluded in 1705 that three comet sitings from 1531, 1607 and 1682 were most likely observations of the same comet. Halley’s comet is set to appear next in July 2061.

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