A star is an object in the sky made of hot gases—so hot that they glow with light! 

The size of stars can appear larger if they are closer to Earth than other stars. Although the Sun appears much larger than the stars we see at night, it is not the largest star. The farther away a star is from Earth, the smaller it will appear. A star that is very far away from Earth will appear dimmer than a star that is closer to Earth. This is true even though the farther star may actually be the brighter star. The Sun is the closest star to Earth, which makes it appear to be the largest and the brightest.

Because stars are so far apart, we have a special unit of distance we use to measure them. The distance of a star from Earth is measured in light-years. A light-year is equal to the distance that light travels (through space) in 1 year. A light-year is equal to about 5,878,499,810,000 miles,