Diameter
3,032 miles
0.38× Earth’s diameter
Eight worlds · one planetary system
Solar System Explorer
Compare the eight planets using NASA data for size, average distance, gravity, rotation, and orbital period. For giant planets, gravity is calculated at an atmospheric reference level, not a solid surface. Select a world to compare the details with Earth.
NASA / ESA planetary photography · sizes and distances are not shown to scale · image credits shown with each world
Planet 1 of 8
Terrestrial
No rings
Mercury
The smallest planet and the closest to the Sun.
Average distance from Sun
36.0 million miles
0.39 AU
Surface gravity
12.1 ft/s²
0.38× Earth gravity
Approximate surface measurement from NASA's planetary facts.
Rotation period
58.7 Earth days
Prograde rotation
Orbital period
88 Earth days
0.24 Earth years
Region
Inner planet
Planetary group is descriptive, not a strict visual scale.
A physical distance you can feel
How long does sunlight take?
Light needs time to cross space, even at its maximum speed of about 186,282 miles per second.
Approximate one-way travel time from the Sun to this planet using its average orbital distance. Actual travel time changes as the planet moves along its orbit.
Source: NIST speed of light ↗Why observers care
Planet families
Rocky worlds, gas giants, and ice giants.
The eight planets are not simply different-sized versions of the same world. Their bulk composition, atmospheres, formation histories, and locations divide them into broad planetary families.
Mercury · Venus · Earth · Mars
Terrestrial planets
Relatively compact worlds dominated by rock and metal, with solid surfaces and much higher average densities than the giant planets.
Jupiter · Saturn
Gas giants
Enormous planets dominated by hydrogen and helium, with deep atmospheres and no ordinary solid surface where a spacecraft could stand.
Uranus · Neptune
Ice giants
Giant planets containing a larger proportion of heavier volatile compounds and interior materials than Jupiter and Saturn, while still possessing deep gaseous envelopes.
Compare all eight
A solar system of extremes.
Scale reality
The real solar system does not fit on this screen.
If the planet disks were drawn to the same physical scale as the distances between their orbits, the worlds would be tiny and separated by enormous stretches of empty space. Educational diagrams compress distance and enlarge planets so the system can be understood visually.
Distance unit
1 astronomical unit ≈ Earth’s average distance from the Sun
StarStation uses about 93 million miles as the Earth-distance reference when showing AU comparisons on this page.
Retrograde rotation
Venus and Uranus rotate in the opposite sense from most planets.
Rotation labels here call that out directly instead of displaying a negative period from the underlying fact sheet.
Moon counts
Not used as a headline comparison.
Planetary satellite counts can change as additional moons are discovered or confirmed. This explorer emphasizes more stable planetary measurements instead.
Keep exploring
Turn planetary facts into observing context.
Terms
Astronomy Glossary
Learn opposition, conjunction, elongation, transit, phase, retrograde motion, and other planetary vocabulary.
Observe
Tonight's Sky
Check observing weather, Sun/Moon timing, and current skywatching context.
News and missions
Solar System News
Follow new discoveries, missions, planetary science, asteroids, comets, and exploration.
Sources
Source Desk
Go from StarStation context to primary NASA, JPL, ESA, and mission-source material.
Primary data
Built from NASA planetary facts.
Planet diameters, average solar distances, surface gravity, rotation periods, and orbital periods are based on NASA/NSSDC planetary fact-sheet data. Classification context follows NASA’s Solar System exploration material.