How to Find Planets in the Night Sky (and Tell Them from Stars)

Planets are among the easiest things to find in the night sky. They are bright, they don’t need a dark site, and several of them can be seen from the middle of a city. The trick is knowing where along the sky to look and how to tell them apart from the thousands of stars around them.

Which planets can you see?

Five planets are visible to the unaided eye: Mercury, Venus, Mars, Jupiter and Saturn. People have watched them for thousands of years. The other two are much harder:

• Uranus is around magnitude 5.7, at the limit of what eyes can see. The British Astronomical Association describes it as technically naked-eye but needing a dark, clear sky and good eyesight. Binoculars show it easily as a starlike point.
• Neptune, near magnitude 7.8, is never visible without optics and looks like a faint star in binoculars.

Magnitude is astronomers’ brightness scale. Lower numbers are brighter, and the brightest objects have negative numbers. On that scale Venus can reach about −4.8 and Jupiter about −2.9, according to NASA’s fact sheets, while Uranus at 5.7 sits near the limit of the eye.

Planet or star? Four clues

The Morehead Planetarium at the University of North Carolina gives a few simple ways to tell a planet from a star.

Brightness

The bright planets are often brighter than any star. NASA’s skywatching FAQ notes that Venus is the brightest planet, and that Jupiter at its brightest nearly matches Venus at its faintest. If you see a very bright “star” low in the west after sunset or in the east before dawn, it is very likely Venus. Mars varies a lot: near its closest approaches it can rival Jupiter, but far from Earth it fades to a modest reddish star.

Steady light

Stars twinkle; planets usually don’t. James Lattis of the University of Wisconsin–Madison explains why. A star is so far away that its light reaches us as a single point, and turbulence in the air bends that thin beam back and forth, making the star flicker. A planet is close enough to show a tiny disk. Light from different parts of the disk is bent in different ways, and the flickering averages out.

There’s an exception. Close to the horizon, where you look through much more air, even planets can twinkle.

Location on the ecliptic

The planets orbit the Sun in nearly the same flat plane as Earth. From the ground, that means they always appear along one line across the sky, the ecliptic. It is the same path the Sun follows during the day, and the Moon stays close to it too. The constellations along it are the zodiac: Taurus, Gemini, Leo, Scorpius, Sagittarius and the others.

So if a bright point lies on the line that joins the Sun’s setting point with the Moon, it’s a good candidate for a planet. A bright point far from that line, near the Big Dipper or Orion’s head, is a star.

Color

Mars has a clear orange-red tint, which helps pick it out. But color can mislead: the Morehead Planetarium notes that Antares, a reddish star in Scorpius, is often taken for Mars. Check its position against a planet chart before deciding.

When to look for each planet

Planets fall into two groups, and they behave very differently.

Mercury and Venus: twilight only

Mercury and Venus orbit closer to the Sun than Earth does. From our point of view, they never stray far from the Sun, so NASA’s FAQ notes they are seen only near sunrise or sunset. Look low in the west after sunset or low in the east before dawn.

The best times are near greatest elongation, when the planet is at its farthest angle from the Sun. Mercury never gets very far, so it’s always low in bright twilight and needs a clear, flat horizon. Venus climbs much higher and can shine for hours after sunset or before sunrise.

Mars, Jupiter and Saturn: best at opposition

The outer planets can appear at any hour of the night, depending on the time of year. They are at their best around opposition, when Earth passes between the planet and the Sun. At opposition, the planet rises at sunset, is up all night and is at its closest and brightest, as NASA and the Hong Kong Observatory explain. According to NASA’s planetary fact sheets, Jupiter returns to opposition about every 13 months, Saturn every year and about two weeks, and Mars only about every 26 months.

Around conjunction, each planet sits on the far side of the Sun and is lost in its glare for several weeks.

How to use our planet pages

You don’t have to work out any of this by hand. Our planets page shows which planets are up tonight from your location: when each one is visible, the best time to look, its direction and height at that time, its brightness and the constellation it’s in. Each planet’s own page, like Jupiter, shows month by month when it’s visible in the evening or morning, plus its opposition, elongation and conjunction dates.

A simple routine:

1. Open the planets page, and note which planets are up and in which direction.
2. Check the time each one is highest. A planet high in the sky looks sharper than one near the horizon, because you see it through less air.
3. Go outside, face the right direction and look for the brightest steady point near the ecliptic.
4. Use your hand to measure. NASA’s FAQ notes that a fist held at arm’s length covers about 10 degrees of sky, and your little finger about 1 degree. If a planet is listed as 20 degrees up, look about two fists above the horizon.

The Moon is a good signpost. Because it travels along the ecliptic too, it passes near each visible planet once a month, which shows you exactly where to look.

What to expect through binoculars and telescopes

Even small optics show something extra:

• Jupiter: binoculars show one or more of its four big moons as tiny points beside it. A small telescope shows its cloud bands.
• Saturn: binoculars don’t show its rings, but even a small telescope does.
• Mars: a tiny disk that shows detail only near its closest approaches, when it appears largest.

Our guide to binoculars and telescopes covers what to buy.