A star is a giant ball of gas. Hydrogen is by far the most abundant element in most stars. The Sun is the closest star to Earth. Our Sun is a medium-sized star, and there are bigger stars and smaller stars than the Sun.

Except for the Sun, stars are so far away that they look like pinpoints of light. A light-year is the distance that light travels in one year. Proxima Centauri is the nearest star to the Sun. As of November 2026, it is about 4.24 light-years away.

Stars come in different colors, such as red, orange, yellow, white and blue. A star's color tells about its temperature. Blue-white stars are much hotter than the Sun, and red stars are cooler.

Stars twinkle because we see their light through Earth's air. Seen from the Moon, where there is no air, stars do not twinkle at all. Planets twinkle less than stars do. They tend to glow with a steady light.

Some names in the sky can fool you. A shooting star is not a star. It is a streak of light from a meteoroid burning up in Earth's atmosphere. Polaris is not the brightest star in the sky. Sirius is the brightest star in the night sky.

Words to know

• hydrogen: lightest gas
• Sirius: brightest star
• meteoroid: space rock bit
• temperature: how hot