Uranus

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.

J2000 Equatorial Sky Chart & Culmination Altitude

The chart below plots Uranus — Ice Giant Orbital & Physical Data at RA 03h 18m 00.00s, Dec +17° 55′ 00.0″ within Aries, 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

While sweeping the stars of Gemini with a homemade 6.2-inch reflecting telescope from his garden in Bath, England, on March 13, 1781, William Herschel noticed a pale blue-green disk that crept slowly against the background stars—doubling the known span of the Solar System overnight. Orbiting at 19.19 astronomical units with a period of 84.02 years, Uranus has a mass of 14.54 Earth masses and an equatorial diameter of 51,118 kilometers. Unlike the hydrogen-dominated gas giants Jupiter and Saturn, roughly 80 percent of Uranus's mass resides in a hot, dense fluid mantle of water, ammonia, and methane 'ices' surrounding a small rocky core.

Uranus is unique among the planets in having its rotational axis tipped 97.77 degrees relative to its orbital plane, meaning it effectively rolls around the Sun on its side while its 13 dark narrow rings and 28 known moons (led by Titania, Oberon, Umbriel, Ariel, and Miranda) orbit in its equatorial plane. Each pole endures 42 consecutive Earth years of sunlight followed by 42 years of darkness. Voyager 2 thermal measurements in 1986 also revealed that Uranus radiates almost no excess internal heat beyond what it absorbs from the Sun, giving it the coldest planetary tropopause in the Solar System at 49 K.

Trace methane (~2.3 percent) in the upper hydrogen-helium atmosphere strongly absorbs red and near-infrared sunlight, giving Uranus its characteristic pale cyan-aquamarine tint in eyepiece views.

Practical Visual Observing Guide

• At opposition magnitude V ~ 5.6, Uranus is dimly visible to the unaided eye under dark rural skies and effortless to spot in any binoculars.
• Magnifications of 150x or higher in a 4-inch+ telescope cleanly resolve its 3.7-arcsecond pale blue-green non-stellar disk.
• Its two brightest moons, Titania (V ~ 13.9) and Oberon (V ~ 14.1), can be glimpsed in 10-inch to 14-inch amateur telescopes at 250x–350x.

Catalog Cross-Identifications & Aliases

Common Aliases: Georgium Sidus · 34 Tauri · Sol VII

Related Objects, Comparisons & Guides

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