Planets shine because they reflect sunlight. Unlike stars, planets do not produce their own natural light. Their close proximity to Earth allows them to reflect enough sunlight to make many of them visible in the night sky.
Stars produce their own light through a constant process of nuclear fusion, where hydrogen atoms fuse to form helium. Nuclear fusion produces energy emitted as photons, which makes the stars shine. Stars are quite large but appear small because of their great distance from Earth. Planets appear the same size as stars in the night sky because they are much smaller than stars and much closer to Earth. Both stars and planets shine, but planets are close enough to Earth to reflect a steady, flat light that originates from the sun, while stars twinkle because of disturbances in Earth's atmosphere.
Mercury, Venus, Mars, Jupiter and Saturn shine the brightest and are known as naked eye planets because they are visible to people without the assistance of a telescope. The planets are visible throughout the year, except when they are too close to the sun. Planets are distinguishable from stars in the sky because they change position from night to night while stars remain stationary.