This solar system planets guide is your complete tour of the cosmic neighbourhood we call home — a single star, the Sun, holding eight solar system planets, five officially recognised dwarf planets, hundreds of moons and countless asteroids and comets in its gravitational grip. It sits in an outer spiral arm of the Milky Way, and everything in it orbits the Sun. This guide covers the solar system planets in order from the Sun, the dwarf planets, the small-body populations, and the missions exploring them — with the latest facts for 2026. For more science explainers, explore our education guides.
The Sun: The Star at the Centre
Every journey through the solar system planets starts with the Sun — a G-type main-sequence star (G2V), about 4.6 billion years old with roughly 5 billion years of fuel remaining. The Sun holds 99.86% of all the mass in the solar system; the eight planets, their moons and every asteroid combined make up barely 0.14%.
It is enormous: about 1.39 million kilometres across (roughly 109 Earths side by side), with a surface temperature near 5,500°C. Its light takes 8 minutes and 20 seconds to reach Earth. The Sun is the engine of everything here — its gravity binds the planets in their orbits, its light warms every world, and its solar wind sculpts the plasma environment around the planets and moons. Learn more from NASA’s Sun overview.
The Rocky Solar System Planets: Mercury, Venus, Earth, Mars
The four inner solar system planets are small, dense and rocky — built mostly of rock and metal, each with a solid surface.
Mercury is the smallest planet and the closest to the Sun, racing around it in just 88 days. With almost no atmosphere to hold heat, it swings between scorching dayside temperatures and freezing nights — one of the most extreme ranges anywhere. It has no moons.
Venus, the second planet, is the hottest in the solar system — not Mercury. Its thick carbon-dioxide atmosphere traps heat in a runaway greenhouse effect, pushing the surface to about 465°C, hot enough to melt lead. Similar in size to Earth but wrapped in toxic clouds, Venus also spins backwards compared to most planets.
Earth, third from the Sun, is the only planet known to support life — with liquid-water oceans, an oxygen-rich atmosphere and exactly one moon. It completes its orbit in 365.25 days.
Mars, the fourth planet, is the famous red world; its colour comes from iron oxide — rust — coating its dusty surface. It hosts Olympus Mons, the tallest volcano in the solar system, and Valles Marineris, a canyon system that dwarfs anything on Earth. Mars has two tiny moons, Phobos and Deimos, and a year lasting 687 Earth days.
The Gas Giants: Jupiter and Saturn
Beyond Mars lies the asteroid belt, and beyond that the giant solar system planets — Jupiter and Saturn, made mostly of hydrogen and helium with no solid surface to stand on.
Jupiter is the largest planet: more than twice as massive as all the other planets combined. Its Great Red Spot is a storm wider than Earth that has raged for centuries. Jupiter’s four largest moons — Io, Europa, Ganymede and Callisto, discovered by Galileo in 1610 — are worlds in their own right; Ganymede is bigger than the planet Mercury. A year on Jupiter lasts 11.9 Earth years.
Saturn, sixth from the Sun, is famous for its spectacular ring system — billions of chunks of ice and rock from grains to house-sized boulders. Its largest moon, Titan, has a thick nitrogen atmosphere and lakes of liquid methane — the only moon with stable liquid on its surface. Saturn takes 29.5 Earth years to orbit the Sun.
The Ice Giants: Uranus and Neptune
The two outermost solar system planets are “ice giants” — built mostly of water, ammonia and methane ices around a rocky core.
Uranus is the oddball: tilted about 98 degrees, it essentially rolls around the Sun on its side. Methane in its atmosphere gives it a pale blue-green colour. One Uranian year lasts 84 Earth years.
Neptune, the farthest planet at 30 times Earth’s distance from the Sun, is a deep blue world with the strongest winds measured anywhere — over 2,000 km/h. Remarkably, it was found by mathematics before telescopes: astronomers predicted its position from Uranus’s orbit in 1846. Its year lasts about 165 Earth years.
Pluto and the Dwarf Planets
For 76 years, schoolchildren learned nine planets — until 2006, when the International Astronomical Union voted a formal definition: a planet must orbit the Sun, be massive enough for its own gravity to make it nearly round, and have cleared its orbital neighbourhood of debris.
Pluto — discovered in 1930 by Clyde Tombaugh — met the first two criteria but not the third, sharing its orbit with many icy Kuiper Belt bodies. So Pluto was reclassified as a dwarf planet. NASA still describes it as a complex dwarf planet completing one 248-year orbit of the Sun.
There are five officially recognised dwarf planets: Pluto, Eris (whose 2005 discovery triggered the debate — it is more massive than Pluto), Haumea, Makemake, and Ceres. Ceres is the odd one out, living in the asteroid belt between Mars and Jupiter; it was briefly considered a planet in the 1800s before asteroids were understood.
Asteroids, Comets, the Kuiper Belt and the Oort Cloud
Not everything orbiting the Sun is one of the solar system planets. The asteroid belt between Mars and Jupiter holds millions of rocky bodies — leftovers from the solar system’s formation that never assembled into a planet, partly due to Jupiter’s gravitational interference.
Beyond Neptune lies the Kuiper Belt, a vast donut-shaped region of icy bodies — Pluto’s neighbourhood, home to thousands of known objects. Far beyond that, astronomers theorise the Oort Cloud: a spherical shell of icy bodies never directly observed, thought to be the source of long-period comets taking thousands of years per orbit.
Comets are the wanderers — dirty snowballs of ice and dust. As a comet nears the Sun, heat vaporises its ice, creating the glowing coma and the famous tail that always points away from the Sun.
Moons: Worlds of Their Own
Astronomers have confirmed hundreds of moons around the solar system planets, and the count keeps rising — especially at Saturn and Jupiter, which hold most of them. Earth has one; Mars has two; Mercury and Venus have none. Some moons outshine planets for intrigue: Europa may hide a subsurface ocean, Enceladus sprays water geysers into space, and Triton orbits Neptune backwards — likely a captured Kuiper Belt object. The Earth–Moon system is special: the Moon sits about 384,400 km away, and all the other planets could fit side by side in that gap.
Exploring the Solar System Planets: Key Missions
Humans have never left the Earth–Moon system in person, but our robots have visited all eight planets:
- 1957–1969: The Space Age begins — Sputnik, then Apollo 11 lands the first humans on the Moon in 1969.
- 1977: Voyager 1 and 2 launch. Voyager 1 is now the farthest human-made object, in interstellar space since 2012 — still phoning home from over 15 billion miles away.
- 1990s–2000s: Mars rovers (Sojourner, Spirit, Opportunity, Curiosity, Perseverance) and orbiters transform Mars from a dot into a mapped world.
- 2015: NASA’s New Horizons flies past Pluto, revealing its heart-shaped glacier and stunning complexity.
- 2022: Artemis I sends an uncrewed Orion capsule around the Moon, testing hardware for humanity’s return.
- 2023: India’s Chandrayaan-3 lands near the Moon’s south pole — the first soft landing there; its Pragyan rover confirmed sulfur and measured dramatic subsurface temperature swings.
- 2024: NASA’s Parker Solar Probe flies closer to the Sun than any spacecraft before, skimming the solar corona.
- 2026: Artemis II completes a crewed lunar flyby — four astronauts loop the Moon, the first crewed voyage beyond low Earth orbit since Apollo. A crewed landing is targeted later this decade.
Frequently Asked Questions
What are the solar system planets in order?
From the Sun outward: Mercury, Venus, Earth, Mars (the rocky planets), then Jupiter, Saturn (gas giants), Uranus and Neptune (ice giants).
Which is the hottest of the solar system planets?
Venus, at about 465°C — not Mercury. Its thick carbon-dioxide atmosphere creates a runaway greenhouse effect.
Why is Pluto not counted among the solar system planets?
The IAU reclassified Pluto as a dwarf planet in 2006 because it hasn't cleared its orbital neighbourhood — it shares the Kuiper Belt with many other icy bodies.
Which solar system planets are visible to the naked eye?
Five: Mercury, Venus, Mars, Jupiter and Saturn. Venus is the brightest, often called the morning or evening star.
Will humans return to the Moon?
Yes — that is the goal of NASA's Artemis programme. Artemis I (uncrewed) flew in 2022 and Artemis II (crewed flyby) in 2026; a crewed landing is planned later this decade, though spaceflight timelines frequently shift.
The Bottom Line
The eight solar system planets form one vast, interconnected family with the Sun: four rocky worlds, two gas giants and two ice giants, plus dwarf planets, hundreds of moons and billions of smaller bodies. We have visited every planet with robots, landed humans on the Moon, and are preparing to go back — while robotic explorers push toward the Kuiper Belt and beyond. The next time you look up, remember: five of the eight solar system planets are visible to the naked eye, shining back at you across the dark. For more guides like this tour, browse our education section and the Mixarena homepage.
