ThE UnIvErSe

Refresh What can you observe when you look at the sky?

Galaxies are a collection of nebulae and millions of stars.

• Nebulae are huge clouds of gas and dust. Stars come from nebulae.

• Stars are very large, hot balls of gas. They produce light and heat.

Our galaxy, the Milky Way, also has: satellites planets dwarf planets asteroids comets a) The Big Bang created the Milky Way / the Universe. b) Stars are very large, hot / cold balls of gas. c) Stars don’t emit / emit light and heat.

The Big Bang was a huge explosion that created the universe billions of years ago.

Nebulae produce stars.

1 Choose the correct option to complete the sentences.

2 Why is our galaxy called the Milky Way?

3 Other celestial bodies

• Planets are spherical, rocky and gaseous. They revolve around a star.

• Dwarf planets are also spherical, but they are smaller than planets.

• Satellites revolve around a planet. The Moon is Earth’s satellite.

• Asteroids are rocky objects that travel through space or revolve around a star or a planet.

• Meteorites are asteroids that collide with planets or satellites.

Small meteorites that disintegrate in the Earth’s atmosphere are called shooting stars.

• Comets are balls of dust and ice. They have tails of steam that shine when they get closer to stars. The most famous comet is Halley’s Comet.

3 a) What is the difference between an asteroid and a comet? b) How are asteroids, meteorites and shooting stars related?

Answer the questions.

4 4 Listen to the de nitions. Write the celestial bodies. satellites shooting stars comets planets

5 Look at pictures a-d. What types of celestial bodies do they show?

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6 What type of celestial body is Pluto? Give reasons for your answer.

The comparative Dwarf planets are smaller than planets.