Astronomy: Solar System & Space Rocks

What is an asteroid?

A rocky or metallic fragment from the inner solar system, generally larger than 1 meter in diameter that orbits the sun

What is a comet?

An icy remnant from the outer solar system as it approaches the Sun, ice vaporizes and creates a coma and tails

Which direction does a comet's gas tail point?

Away from the Sun, regardless of the comet's direction of travel due to solar wind and solar radiation pressure

What is a meteoroid?

A small piece of solid matter in space, less than about 1 meter across

What is a meteor?

The glowing streak produced when a meteoroid heats up and vaporizes in Earth's atmosphere; often called a shooting star

What is a meteorite?

A fragment that survives its passage through the atmosphere and reaches the ground

What causes meteor showers?

Earth passes through trails of dust left behind by comets

Where do short-period comets come from?

The Kuiper Belt and scattered disk beyond Neptune; they have orbital periods under 200 years

Where do long-period comets come from?

The distant Oort Cloud; they can have orbital periods of thousands to hundreds of thousands of years.

Put the main solar-system regions in order from the Sun outward.

Terrestrial planets, asteroid belt, jovian planets, kuiper belt, oort cloud

What do meteorites tell us about the solar system?

They are ancient building blocks left over from its formation; the oldest are about 4.57 billion years old