Europa (Jupiter II)
Orbital parameters (3.551 d around Jupiter in 1:2:4 Laplace resonance), magnitude 5.29, icy shell & subsurface ocean, and observing guide for Europa.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Opposition visual magnitude (V) | 5.29 mag | ± 0.05 mag | JPL planetary satellite photometry (geometric albedo = 0.67) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Orbital period around Jupiter | 3.551181 d | ± 0.000001 d | Galilean 1:2:4 Laplace resonance ephemeris (semi-major axis = 671,100 km / 9.39 R_Jup) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Mean solid radius | 0.245 R⊕ | ± 0.0002 R⊕ | Galileo spacecraft limb imaging (1,560.8 ± 0.5 km, 90% of Moon's radius) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Satellite mass | 0.008035 M⊕ | ± 0.000001 M⊕ | Galileo & Juno flyby radio-Doppler tracking (4.7998 × 10^22 kg) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Europa (Jupiter II Subsurface Ocean World) at RA 06h 00m 07.20s, Dec +23° 00′ 00.0″ within Jupiter System (Ecliptic), alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Europa (Jupiter II), the smallest of the four Galilean moons discovered by Galileo Galilei in January 1610, has a diameter of 3,121.6 kilometers (slightly smaller than Earth's Moon) and orbits Jupiter every 3.5512 days at a distance of 671,100 kilometers. Locked in a 1:2:4 Laplace orbital resonance with inner Io (1.769 days) and outer Ganymede (7.155 days), Europa's orbit is forced into a non-zero eccentricity (e = 0.009), flexing its interior through continuous tidal dissipation.
With a geometric albedo of 0.67, Europa's water-ice surface is one of the brightest and smoothest solid surfaces in the Solar System, crisscrossed by dark reddish-brown lineae (fractures) and chaotic ice-raft terrains while virtually devoid of large impact craters—indicating a surface geologic age of only 40 to 90 million years. During the late 1990s, the Galileo spacecraft detected an induced magnetic field inside Europa as Jupiter's tilted magnetosphere swept past it, providing the strongest geophysical evidence for a global liquid saltwater ocean ~60 to 150 kilometers deep containing roughly twice the liquid water volume of all Earth's oceans combined.
In 2023 the James Webb Space Telescope's NIRSpec instrument mapped Europa's surface and discovered that crystalline and amorphous carbon dioxide (CO2) ice is concentrated inside Tara Regio, a geologically young 'chaos terrain' where warm subsurface ocean brines have recently upwelled through the ice shell—proving that Europa's internal ocean contains bio-essential carbon.
Practical Visual Observing Guide
- At visual magnitude 5.29, Europa is theoretically bright enough to see with the naked eye if it were not lost in the glare of magnitude −2.8 Jupiter (maximum elongation ~3.5 arcminutes).
- Any 7×50 or 10×50 binocular splits Europa from Jupiter near eastern or western elongation, and any 60–150 mm telescope at 120×–200× lets you watch Europa transit across Jupiter's disk, cast its crisp black shadow onto the clouds, and disappear into Jupiter's shadow during eclipses.
Catalog Cross-Identifications & Aliases
Common Aliases: Jupiter II
| Catalog Authority | Identifier |
|---|---|
| WIKIDATA | Q3143 |
Related Objects, Comparisons & Guides
Jupiter (Gas Giant & Galilean Moons)
JPL orbital parameters (5.2038 AU, 11.862 yr), opposition magnitude −2.94, 50.1″ angular disk, Galilean moons, and observing guide for Jupiter.
Titan (Saturn VI Nitrogen-Atmosphere Moon)
Orbital parameters (15.945 d around Saturn), visual magnitude 8.4, 1.45-bar N2/CH4 atmosphere, hydrocarbon lakes, and observing guide for Titan.
Saturn (Ringed Giant & Cassini Division)
JPL orbital parameters (9.5826 AU, 29.457 yr), ring tilt cycle, Cassini Division resolution, and telescope observing guide for Saturn.
TRAPPIST-1 e (Temperate Terrestrial World)
Coordinates, Gaia distance (12.47 pc), 6.10-day orbital period, mass 0.692 M⊕, radius 0.920 R⊕, and JWST transit spectroscopy for TRAPPIST-1 e.
Solar System Planets & Moons Opposition Guide
How to observe Jupiter, Saturn, Mars, Titan, and Europa around opposition using high magnification, atmospheric dispersion control, and transit timing.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
Scientific Sources & Dataset Provenance
- NASA/JPL Solar System Dynamics & Planetary Fact Sheets (DE441 (2021/2026)): Park, R. S., et al. 2021, AJ, 161, 105 (The JPL Planetary and Lunar Ephemerides DE440 and DE441) — NASA Jet Propulsion Laboratory / GSFC
- JWST / MAST Science Archive & Mission Documentation (Cycle 1–4 Public Releases (2022–2026)): Rigby, J., et al. 2023, PASP, 135, 048001 (The Science Performance of JWST as Characterized in Commissioning) — NASA / ESA / CSA / STScI