How to tell a planet from a star
Planets shine steadily, sit along one line in the sky and wander from week to week. Here is how to spot them.
Five planets are easy naked-eye objects: Mercury, Venus, Mars, Jupiter and Saturn. Three clues give them away.
- They do not twinkle much. Stars are points, so the turbulent air makes them flicker. Planets are tiny discs, and their light averages out into a steady glow, especially high in the sky.
- They sit on the ecliptic. The Sun, Moon and planets all move along the same band, through the zodiac constellations. If a bright “star” lines up with the Moon and the sunset point, it is probably a planet.
- They move. Over a week or two a planet shifts against the background stars. Planet comes from the Greek for wanderer.
Who is who
- Venus: dazzling white, never far from the Sun, only in the evening or morning twilight.
- Jupiter: bright cream-white, up for much of the night around opposition. Binoculars show its four big moons.
- Mars: orange-red, brightness varies a lot; best every 26 months at opposition.
- Saturn: steady pale yellow, fainter than Jupiter. A small telescope shows the rings.
- Mercury: low in bright twilight, only for a few weeks at a time.
The planets page tells you which are up from your place right now.