Io
Moon of JupiterMajor moon
The most volcanically active body known, kneaded continuously by Jupiter's tides.
Where it is right now
Io is in Cancer, 6.30 AU away.
Computed for 2 August 2026, 17:00 UTC, and recomputed at least hourly. This page is cached, so treat the line above as accurate to the hour rather than to the second. The map shows the live position.
Position from astronomy-engine's VSOP87-derived series, accurate to about an arcsecond.
Facts
Every line carries the source it came from.
- Mean radius
- 1821.5 kmSource: NASA/JPL Planetary Satellite Physical Parameters
- Orbits
- Jupiter, 421,800 km out on averageSource: NASA/JPL Planetary Satellite Mean Elements
- Orbital period
- 1.76 daysSource: NASA/JPL Planetary Satellite Mean Elements
- Orbit shape
- eccentricity 0.0040, inclined 0.00 degrees to Jupiter's Laplace planeSource: NASA/JPL Planetary Satellite Mean Elements
- Discovered
- 1610 by GalileoSource: NASA/JPL Planetary Satellite Discovery Circumstances
- Volcanoes
- over 400 active, more than the rest of the solar system combinedSource: NASA/JPL Galileo mission results
Physical size
- Mean radius
- 1,821 km
- Diameter
- 3,643 km across
Orbit
Elements are relative to Jupiter.
- Average distance from Jupiter
- 421,800 km
- Eccentricity
- 0.0040, almost perfectly circular
- Inclination to Jupiter's reference plane
- 2.21 degrees
- Orbital period
- 42.3 hours
- Longitude of ascending node
- 338.23 degrees
- Argument of periapsis
- 69.14 degrees
- Mean anomaly at J2000.0
- 330.90 degrees
Family
Orbits Jupiter.
Claim this body
Catalog id io. 3,172 objects on the map, of which 171 are hand-authored with sourced facts.