But some giant stars, such as Aldebaran, are 20 to 100 times as big. Supergiants are vast. Aurigae double-star system 3000 million km across. If this star were a football, the Sun would be a grain of salt. There are also tiny stars.
Some dwarf stars are smaller than the Earth.
Neutron stars may be only 15km across - yet contain as much matter as the Sun. They are so dense, a spoonful of their matter would weigh several tons. Starlight Stars are so far away that they look like points of light even through the most powerful telescopes. But we can find out more about them by studying their colour. If the light from a star is passed through a prism, it splits into a rainbow of colours called a spectrum.