Mercury orbits the Sun 248 times for every one orbit of Pluto. A ‘year’ on Pluto is 248 Earth-years long.
How to Play: Guess if the body on the right takes LONGER or SHORTER to orbit the Sun than the one on the left.
Name A
Name B
Top 10 Longest Solar System Orbital Periods
Orbital period scales with distance from the Sun — Kepler’s third law. Outer planets take dramatically longer than inner ones.
| # | Name | Orbital Period (Earth years) | Unit |
|---|---|---|---|
| 1 | Comet Hyakutake | 70,000 | years |
| 2 | Sedna | 11,400 | years |
| 3 | Comet Hale-Bopp | 2,533 | years |
| 4 | Eris (dwarf planet) | 557 | years |
| 5 | Makemake | 310 | years |
| 6 | Haumea | 284 | years |
| 7 | Pluto | 248 | years |
| 8 | Neptune | 165 | years |
| 9 | Uranus | 84 | years |
| 10 | Halley's Comet | 75.30 | years |
Kepler's Laws of Orbits
Orbital period^2 = orbital radius^3 (in appropriate units). This is Kepler’s third law. Planets farther from the Sun take exponentially longer.
Pluto’s 248-year orbit means it has orbited the Sun only ~150 times since dinosaurs went extinct. It crosses Neptune’s orbit but they never collide due to a 2:3 resonance.
Sedna at 11,400 years has the longest known orbit of any solar system body — its existence raises questions about Planet Nine theories.
Frequently Asked Questions
Longest orbital period?
Sedna at ~11,400 years. We’ve only observed a tiny fraction of one orbit.
How long is a Pluto year?
248 Earth years. Pluto was discovered in 1930 and has only orbited 1/3 of its way around the Sun since.
Is Earth's year exactly 365 days?
Earth’s orbital period is 365.256 Earth-days — a ‘sidereal year’ relative to stars. Calendar years use 365 + leap-day adjustments.
How fast does Earth move around the Sun?
About 30 km/sec average — fast enough that Earth covers its diameter in seconds.
Note: Orbital periods in Earth years per NASA/JPL Horizons data.
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