Saturn
JPL orbital parameters (9.5826 AU, 29.457 yr), ring tilt cycle, Cassini Division resolution, and telescope observing guide for Saturn.
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) | 0.4 mag | -0.55 to 1.17 mag | JPL ephemeris photometry (varies strongly with ring tilt angle from −0.55 wide-open to +0.8 edge-on) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Orbital semi-major axis | 9.5826 AU | ± 0.0002 AU | JPL DE441 planetary ephemeris (e = 0.0565) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Sidereal orbital period | 10759.22 d | ± 0.05 d | JPL DE441 ephemeris (29.457 Julian years; synodic period = 378.09 d) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Planetary mass | 95.159 M⊕ | ± 0.001 M⊕ | Cassini spacecraft radio-Doppler tracking (5.6834 × 10^26 kg) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
| Equatorial 1-bar radius | 9.449 R⊕ | ± 0.001 R⊕ | Cassini radio occultations (60,268 km equatorial vs 54,364 km polar) | definitive | NASA/JPL Solar System Dynamics & Planetary Fact Sheets |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Saturn (Ringed Giant & Cassini Division) at RA 23h 30m 00.00s, Dec -05° 00′ 00.0″ within Ecliptic (Zodiac), 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
Saturn, orbiting at a mean heliocentric distance of 9.58 AU (1.43 billion kilometers) with a period of 29.46 years, is the second-largest planet in the Solar System and the least dense of all planets: with 95.16 Earth masses inside an equatorial radius of 60,268 kilometers (9.45 Earth radii), its mean bulk density is just 0.687 g/cm³—nearly 30% less dense than liquid water. Rapid 10-hour 33-minute rotation flattens Saturn's globe by 9.8%, the largest oblateness of any planet.
When Galileo first observed Saturn in July 1610, his 32× refractor showed mysterious lateral 'ears' or companion globes that vanished completely in 1612 when the rings turned edge-on; in 1655–1659 Christiaan Huygens deduced that Saturn is surrounded by a thin, flat ring nowhere touching the planet, and in 1675 Giovanni Domenico Cassini discovered the dark 4,800-kilometer Cassini Division cleared between the outer A Ring and brighter inner B Ring by a 2:1 orbital resonance with the moon Mimas.
NASA's Cassini orbiter (2004–2017) proved that Saturn's main rings are composed of >99% pure water-ice particles (ranging from micron dust to 10-meter boulders) with a vertical thickness of only 10 to 30 meters, and weighed the rings' total mass during its Grand Finale dives at ~40% the mass of Mimas—suggesting the bright rings may have formed only 100 to 400 million years ago from a tidally disrupted icy moon.
Practical Visual Observing Guide
- To the naked eye Saturn shines with a calm, steady yellowish-cream light between magnitude +0.8 and −0.5, moving eastward along the ecliptic by ~12° per year.
- Any telescope of 50 mm aperture or larger at 40×–60× resolves Saturn's rings; because Saturn passed through a ring-plane crossing in March 2025, the rings appear as a razor-thin needle in 2025–2026 before gradually opening wider each year toward their next 27° maximum in 2032.
- When the rings are open by more than ~8°–10°, a 100–150 mm telescope at 150×–250× resolves the dark Cassini Division in the ring ansae, the translucent inner Crepe (C) Ring, the planet's crisp shadow on the rings, and up to five moons (Titan, Rhea, Dione, Tethys, and Iapetus).
Catalog Cross-Identifications & Aliases
Common Aliases: Sol VI
| Catalog Authority | Identifier |
|---|---|
| WIKIDATA | Q193 |
Related Objects, Comparisons & Guides
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.
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.
Mars (Terrestrial Planet & Opposition Cycle)
JPL orbital parameters (1.5237 AU, 686.98 d), 780-day synodic opposition cycle, 25.1″ maximum disk, and telescope observing guide for Mars.
WASP-39 b (JWST Benchmark Saturn Exoplanet)
Coordinates, Gaia DR3 distance (213 pc), 4.055-day period, 0.28 M♃ mass, 1.27 R♃ radius, and JWST CO2/SO2 photochemical spectrum of WASP-39 b.
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.
Suburban & Urban Light-Pollution Targets Guide
Practical observing guide to high-surface-brightness targets—planets, double stars, open clusters, and planetary nebulae—that cut through Bortle 6–8 skyglow.
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