Exploring our solar system
The Solar System consists of the Sun with planets in orbit around it. Most planets have at least one satellite in orbit around them. Gravity provides the centripetal force needed to keep objects in orbit.
We can explore space using manned or unmanned spacecraft.
The Universe contains:
A star is a huge ball of gas, mostly hydrogen and helium. Nuclear fusion reactions inside the star release enormous amounts of energy. Stars are very hot and give off their own light. This is why we can see the Sun during the day, and distant stars in the night sky.
A galaxy is a large group of many millions of stars. Our Sun is just one of at least 200 billion stars in our galaxy, the Milky Way. The observable universe contains around 80 billion galaxies.
A black hole cannot be seen because light is unable to escape from it. A black hole forms when a large star collapses in on itself because of gravity.
A planet is a large rocky or gaseous object that orbits a star. Planets are large enough to sweep away any smaller objects in their orbit. Their orbits are almost circular.
Comets are balls of ice and dust. They are much smaller than planets and their orbit around a star is very elongated, rather than circular.
Meteors are small rocks. They burn up if they enter a planet’s atmosphere, forming a ‘shooting star’.
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