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058

asteroids

OLogy Series
astronomy
card
058

asteroids

OLogy Series
astronomy

Asteroids are space rocks that have existed since the formation of the planets over 4.6 billion years ago. Scientists believe that asteroids are pieces of rock that were never swept up into planets. Like the planets, asteroids are kept in orbit by the gravity of the Sun. Most of the asteroids in the solar system lie in the Asteroid Belt between the orbits of Mars and Jupiter.

The largest asteroid ever discovered measured:

over 300 feet in length

over 3,000 feet in length

over 3,000,000 feet in length

Are you right?

Correct!

Ceres is the largest and first asteroid ever found. In 1801, astronomer Giuseppe Piazzi discovered this gigantic asteroid that resembled a small planet.

"Asteroid" is a Greek word that means:

"starlike"

"rocklike"

"peanutlike"

Are you right?

Correct!

When looking at an asteroid through a telescope, it actually resembles a faint star. The difference is that it moves against the background stars from night to night as it follows its orbit around the Sun.

Mordecai-Mark MacLow, astrophysicist

Nearly every shooting star you see at night is a very small piece of an asteroid (the size of a grain of sand) broken off in a collision.

Astronomers are not very interested in studying asteroids.

Fact
or
Fiction
?

Fiction

In 1996, NASA sent the NEAR Shoemaker (Near Earth Asteroid Rendezvous) probe to study the surface of Eros, a 21-mile-long asteroid.

Number of asteroids: over 5,000 identified, millions more estimated to exist
Size: a few feet to thousands of feet across
Shape: irregular
Where: found in Asteroid Belt between Mars and Jupiter
Composition: metal, rock, or both
Significance: give scientists clues about the formation of the solar system

Image credits: Asteroid Gaspra's Best Face, courtesy of NASA, The Galileo Project; Mordecai-Mark MacLow: AMNH.