Facts About Stars
Our Sun is a star. If anyone asks you which is the closest star to us, the technically correct answer is the Sun.
You can see a few thousand stars on a clear dark night.
Stars come in a variety of colours except green.
Blue stars are the hottest, red stars are the coolest.
Stars burn by fusing hydrogen atoms into helium atoms. When a star's fuel runs out, it dies.
Stars twinkle because their light gets disrupted passing through Earth's atmosphere. Stars near the horizon twinkle more because their light passes through more atmosphere than those overhead.
How a star lives and dies depends largely on how massive it is.
Stars are born from clouds of cold molecular hydrogen that collapse under their own gravity. Eventually, when there is enough mass, the gravity is strong enough to squeeze atoms together and begin nuclear fusion.
What keeps a star going is the balance between nuclear fusion throwing stuff outwards, and gravity pulling it back in. Although there is a net loss over time, the balance is good enough to keep stars burning for billions of years.
Our Sun is a "lone star" but many stars come in pairs. In fact it looks likely that at least half of all stars are part of a binary system. You can also have star systems with three or more stars although these are less common.
The biggest, most massive stars live hard and die young. Smaller stars are more sedate and last much longer.
When the original Star Wars movie was made, astronomers didn't know if it was possible for a planet to have two suns (like Tatooine). We now know that they can, and we've even found several examples.
Neutron stars can spin at a rate of 700 rotations per second.
The core of a star can reach 167 million °C.
Throughout the observable Universe, 275 million new stars are born every day.
There are more stars in the Universe than grains of sand on the Earth.