Solar System Exploration
Join us as we explore our solar system.
10 THINGS about our solar system
1. Many Worlds
Our solar system has eight planets, and five dwarf planets.
2. Small Worlds, Too
About 1.4 million asteroids, and about 4,000 comets are in our solar system.
3. Lots of Moons
Our solar system has more than 200 planetary moons.
4. Meet Me in the Milky Way
Our solar system is in one of the Milky Way galaxy’s spiral arms called the Orion Spur.
5. A Long Way Around
Our solar system takes about 230 million years to orbit the galactic center.
6. Spiraling Through Space
The Milky Way is a barred spiral galaxy.
7. Room to Breathe
Our solar system has many worlds with many types of atmospheres.
8. Ring Worlds
The four giant planets – and at least one asteroid – have rings.
9. Getting Out There
More than 300 robotic spacecraft have left Earth's orbit, and 24 U.S. astronauts have traveled to the Moon.
10. Life as We Know It
So far, Earth is the only place we've found life in our solar system.
Solar System Overview
Our solar system has one star, eight planets, five officially named dwarf planets, hundreds of moons, thousands of comets, and more than a million asteroids.
About the Planets
Learn about the planets in our solar system.
The solar system has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are five officially recognized dwarf planets in our solar system: Ceres, Pluto, Haumea, Makemake, and Eris.
Get the Facts
Which Planet is Biggest
Which planet is smallest? What is the order of the planets as we move out from the Sun?
This is a simple guide to the sizes of planets based on the equatorial diameter – or width – at the equator of each planet. Each planet’s width is compared to Earth’s equatorial diameter. There's also a handy list of the order of the planets moving away from our Sun.
Size Up the Planets
What’s the Weather Like Out There?
We mean waaaay out there in our solar system – where the forecast might not be quite what you think.
Let’s look at the mean temperature of the Sun, and the planets in our solar system. The mean temperature is the average temperature over the surface of the rocky planets: Mercury, Venus, Earth, and Mars. Dwarf planet Pluto also has a solid surface. But since the gas giants don’t have a surface, the mean is the average temperature at what would be equivalent at sea level on Earth.
Get the Forecast
Skywatching Resources
Hubble's Night Sky Challenge
Do you have a telescope? Each month in 2025, the Hubble team will release a new set of objects for you to explore. Compare your view to Hubble’s, then submit your observations to the Astronomical League to earn recognition for your achievement.
Featured Missions
Europa Clipper
NASA's Europa Clipper is the first mission that will conduct a detailed science investigation of Jupiter's moon Europa. The spacecraft launched Oct. 14, 2024.
Psyche
Psyche is traveling to a unique metal-rich asteroid with the same name, orbiting the Sun between Mars and Jupiter. The spacecraft will arrive at the asteroid in August 2029.
NEO Surveyor
Near-Earth Object (NEO) Surveyor is the first space telescope designed to hunt asteroids and comets that may be potential hazards to Earth. It will launch no earlier than June 2028.
VERITAS
VERITAS, and another mission called DAVINCI, will be the first NASA spacecraft to explore Venus since the 1990s. VERITAS will launch no earlier than 2031.
Go Beyond Our Solar System
Hubble Sees a Celestial Cannonball
The spiral galaxy in this NASA/ESA Hubble Space Telescope image is IC 3225. It looks like it could have been launched from a cannon, speeding through space like a comet with a tail of gas streaming from its disk behind it. IC 3225 is about 100 million light-years away from Earth.
Hubble Explores Alien Atmospheres
For the past 30 years the Hubble Space Telescope has continued its important mission of uncovering the mysteries of the universe. One of those mysteries that Hubble has helped us understand are exoplanets.
Discover the Universe
Learn about the history of the cosmos, what it's made of, and so much more. The origin, evolution, and nature of the universe have fascinated and confounded humankind for centuries. New ideas and major discoveries made during the 20th century transformed cosmology – the term for the way we conceptualize and study the universe – although much remains unknown. Here is the history of the universe according to cosmologists’ current theories.
