Mercury, Venus, Mars, Jupiter and Saturn can be seen with the naked eye if one knows when and where to look. They are visible for much of the year, except for short periods of time when they are too close to the Sun to observe. All of the planets will not normally be visible on a single night, however.The planets can be distinguished from the stars because their position changes slightly against the background stars from one night to the next, and their brightness varies in a regular cycle over a period of time. Stars are so distant they appear as points of light in the night sky, and they appear to twinkle. The planets, on the other hand, appear as a sizeable (but nonetheless tiny) disk in the night sky and when they are well above the horizon, they shine with a more steady light than the stars.