What are stars made of?
- stars are balls of gas, mainly hydrogen and helium.
- nuclear reactions in the heart of stars, such as those in nuclear bombs, generate enormous energy, which the stars send out as heat and light.
- heart of a star reaches 16 million°C.
- a grain of sand this hot could kill someone 100 miles away.
- gas in stars is in a special hot state called plasma, which is made of atom stripped of electrons.
- in the core of star, hydrogen nuclei fuse (join together) to form helium – this nuclear reaction is called a proton-proton chain.
Large stars are hot and white/blue, and smaller stars are cool and red.
A large star can make energy faster and get much hotter than a smaller star.
Medium-sized stars Sun, look yellow.
- stars twinkle because they are seem through the Earth’s atmosphere.
- astronomers work out the size of a star from its brightness and its temperature.
- the size and brightness of a star depends on its mass – how much gas it is made of. The Sun is a medium-sized star. No star has more than 100 more times the Sun’s mass or less than 6-7 percent of its mass.
- the coolest star, such as Arcturus and Antares, glow reddest.
- the hotter stars are yellow and white.
- the hottest are blue-white, like Rigel and Zeta Puppis.
- the blue supergiant, Zeta Puppis, has surface temperature of 40,000°C, while Rigel’s is 10,000°C.
- A swarm, or large cluster of stars known as Messier 80 (M80 or NGC 6093), from the Milky Way.
- This swarm, 28,000 light years from Earth, contains hundreds of thousand of stars, ‘attracted’ to each other by gravity.
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