Lesson 7: Spot the planets

Planets look like bright stars to your eyes alone. In your telescope they turn into tiny disks, and some of them bring company.

How to find a planet

• Check your app to see which planets are up tonight. Some appear in the evening and others before sunrise, and it changes over the year.
• Look for a steady light. Stars twinkle more than planets do. A planet's light comes from a tiny disk instead of a single point, so the air makes it shimmer less.
• Search along the path the Sun and Moon take across the sky. The planets travel along it too.
• Over weeks, a planet moves against the background stars. The word planet comes from a Greek word that means wanderer.

Jupiter and its four big moons

Jupiter is the biggest planet in our solar system. Through your telescope it looks like a small, bright disk. On steady nights you may see two dark stripes across it, which are bands of clouds.

Jupiter and its Great Red Spot, a storm wider than Earth.

Photo: NASA · Source

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Look for up to four tiny points of light in a line beside Jupiter. They're its largest moons, Io, Europa, Ganymede, and Callisto. Galileo spotted them in 1610. They were the first moons anyone found circling another planet, and they showed that Earth isn't the center of everything in the sky.

Jupiter's four big moons, Io, Europa, Ganymede, and Callisto.

Photo: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · Source

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A page of Galileo's notes from January 1610. At the bottom, he drew Jupiter's moons night after night.

Photo: Galileo Galilei · Source

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The moons move every night. Sometimes one passes in front of Jupiter or behind it, and you'll count three, or even two. Ganymede is the biggest moon in the solar system. It's even wider than the planet Mercury.

Ganymede, the biggest moon in the solar system, photographed by NASA's Juno spacecraft.

Photo: NASA /JPL · Source

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Saturn and its rings

Saturn, photographed by NASA's Cassini spacecraft.

Photo: NASA / JPL / Space Science Institute · Source

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From a spacecraft

NASA's Cassini spacecraft orbited Saturn for 13 years and took close-up pictures like this one.

Photo: NASA / JPL / Space Science Institute

Saturn photographed through a backyard telescope.

Image: Stub Mandrel, CC BY-SA 4.0 · Source

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From a backyard telescope

Through a small telescope, Saturn looks tiny, but the rings are easy to see. Seeing them yourself is a thrill.

Image: Stub Mandrel, CC BY-SA 4.0

Titan, Saturn's biggest moon, wrapped in orange haze. Photo from NASA's Cassini spacecraft.

Photo: Justin Cowart · Source

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Titan

Saturn's biggest moon. In your telescope it's a faint dot near the planet.

Photo: Justin Cowart

Saturn's rings are made of countless chunks of ice and rock. At low power, Saturn looks like a tiny oval with a bump on each side. Galileo thought those bumps were ears. Switch to higher power and the rings separate from the planet. Look for a faint dot nearby too. That's Titan, Saturn's biggest moon.

Saturn's rings tilt toward us by different amounts over the years. In 2025 they lined up edge-on with Earth and almost disappeared from view. They'll open a little wider each year until about 2032.

Other planets to try

Venus goes through phases like the Moon as it circles the Sun.

Photo: NASAImage modified by Jcpag2012 · Source

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Venus

The brightest planet. It goes through phases like the Moon, so your telescope may show it as a tiny crescent. Look for it after sunset or before sunrise, once the Sun is out of the sky.

Photo: NASAImage modified by Jcpag2012

Mars, photographed by Hubble in 2003, when it came closer to Earth than it had in about 60,000 years.

Photo: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) · Source

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Mars

A small orange-red dot. It looks biggest about every two years, when Earth passes it as both planets go around the Sun.

Photo: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)