Stars. Computer artwork showing a combination of stars of different colours,sizes and brightness. The colour of a star will depend on several of its properties,including its chemical composition,but in general a high-mass star is hot and blue,while a low-mass star is cool and red. Medium- mass stars,like the Sun,will be yellow. A star's appearance also changes during its lifetime,as it can expand and form a red giant star,and then contract to form a white dwarf star. The apparent brightness of a star will depend upon its distance,its luminosity (how much light it emits per unit area) and its size |