The end of life on Earth?
Part 3

After the Chelyabinsk meteorite, scientists are now monitoring potential hazards even more carefully but, as far as they know, there is no danger in the foreseeable future.

Types of space rocks

• Comet – a ball of rock and ice that sends out a tail of gas and dust behind it. Bright comets only appear in our visible night sky about once every ten years.
• Asteroid – a rock a few feet to several kms in diameter. Unlike comets, asteroids have no tail. Most are too small to cause any damage and burn up in the atmosphere. They appear to us as ‘shooting stars’.
• Meteoroid – part of an asteroid or comet.
• Meteorite – what a meteoroid is called when it hits Earth.

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