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Object profile · URANUS

Uranus

Ice giant

A cold blue-green giant rotating almost on its side, with faint rings, long seasons and a deep interior known mostly through models.

Atlas data reviewed
Editorial stage
Published
Visibility
Public
Two Voyager views of Uranus side by side, one pale cyan in near-natural colour and one banded in strongly enhanced false colour.Direct observation
Voyager 2 composites from blue, green, orange, ultraviolet and violet filtered observations in January 1986.

Processed comparison. The left aims at human-eye colour; the right remaps ultraviolet, violet and orange data and strongly boosts contrast. Neither image is a size or distance scale.

NASA/JPL ↗
Vastward explanation

What this world is

Uranus is called an ice giant, but it is not a frozen ball. The name points to water, methane and ammonia components expected deep inside a hot, dense fluid mixture. Its rotation axis lies nearly sideways, so each pole can face decades of sunlight and darkness.

Why it looks this way now

A major early collision or a sequence of encounters may explain the extreme tilt, but that history is not settled. Methane removes red light from the reflected spectrum, while a surprisingly small internal heat output distinguishes Uranus from Neptune.

02

Where it sits

Uranus is the seventh planet from the Sun, averaging about 2.9 billion kilometres or 19 astronomical units away. One orbit lasts 84 Earth years.

How to read this mapPlanetary order · 7 of 8 from the Sun

Swipe sideways to inspect the full map

Planetary order · 7 of 8 from the SunEight compressed orbits surround the Sun. Orbit 7, belonging to Uranus, is highlighted in blue, with all planets ordered below.SunPosition 7 from the SunUranusMercuryVenusEarthMarsJupiterSaturnUranusNeptune
Blue marks the current planet

The blue orbit, marker and name locate Uranus without implying its live position today.

Neighboring worlds provide order context

Saturn is immediately inside; Neptune is immediately outside. The lower sequence preserves all eight positions.

The figure preserves the eight-planet order and orbital hierarchy; distances, orbit spacing, body sizes and marker positions are compressed for teaching rather than shown live.
03

Read the numbers

Reference values retain their units, context, evidence state and published uncertainty.

Physical measurements

Mean radiusglobal mean
25,362kmCalculated measurementAbout four Earth radii.

An atmospheric reference level, not solid ground.

Published uncertainty: ± 7 km

JPL tabulated uncertainty at an adopted atmospheric reference level.

Massglobal mean
8.68099E25kgCalculated measurementAbout 14.5 Earth masses.

Mass comes mainly from moon orbits and flyby tracking.

Published uncertainty: ± 4E21 kg

Converted from the uncertainty in the JPL 10^24 kilogram table.

Mean densityglobal mean
1.270g/cm³Calculated measurementSlightly denser than water and denser than Saturn.

Bulk density supports more heavy material than gas giants contain proportionally.

Published uncertainty: ± 0.001 g/cm³

Calculated from adopted mass and volume.

Reference gravityequatorial reference
8.87m/s²Calculated measurementAbout 90 percent of Earth's at the reference level.

There is nowhere solid to stand.

No uncertainty published in this source table

Reference gravity at an adopted atmospheric level; Uranus has no solid surface.

Temperaturevisible cloud level
-224.2°CCalculated measurementAmong the coldest measured planetary atmospheric temperatures.

A minimum near the tropopause, not the whole planet.

Approximate value

NASA's minimum atmospheric temperature near the tropopause; it is not a solid-surface value.

Temperaturedeep interior model
4,727°CScientific modelA modeled deep value, not a probe reading.

Pressure and composition profiles can trade off.

Approximate value

Representative modeled deep-interior temperature near 5,000 kelvin; composition and thermal profiles are uncertain.

Orbit and rotation

Average distancerelative to the Sun
2,900,000,000kmCalculated measurementAbout 19 times Earth's solar distance.

Sunlight is roughly one 360th as intense.

Approximate value

Rounded average distance, about 19 astronomical units.

Rotation periodrelative to distant stars
-0.71833Earth daysCalculated measurementAbout 17 hours 14 minutes, retrograde.

The sign records direction, and winds differ from bulk rotation.

No uncertainty published in this source table

Negative sign records retrograde rotation under the JPL convention; atmospheric winds rotate differently.

Orbital periodrelative to the Sun
84.016846Earth yearsCalculated measurementOne Uranus season lasts about 21 Earth years.

Its tilt makes seasonal lighting extreme.

No uncertainty published in this source table

Sidereal orbital period from astrometry and dynamical ephemerides.

04

Atmosphere and inside

Atmosphere

Hydrogen and helium dominate, with methane and traces of other gases. Methane contributes to the cyan colour. Cloud and haze layers hide the gradual transition to dense fluid below.

HydrogenRelative abundance described; exact fraction not listed
HeliumRelative abundance described; exact fraction not listed
Methane and trace gasesRelative abundance described; exact fraction not listed

Surface and interior

There is no solid surface. A light envelope, volatile-rich conducting mantle and denser core region are model layers constrained by sparse gravity, magnetic, thermal and composition data.

No solid surface: layers transition gradually as pressure and temperature rise.

  1. 1
    Small rocky core region

    Mass, radius and gravity permit a dense central region, but its size and boundary are not directly observed.

    Scientific model
  2. 2
    Hot volatile-rich fluid mantle

    Models place a deep electrically conducting mixture rich in water, methane and ammonia components above the core. Here ice giant describes composition, not frozen blocks.

    Scientific model
  3. 3
    Hydrogen-helium envelope

    A lighter outer envelope grades into dense fluid without a solid landing surface.

    Scientific model
  4. 4
    Methane clouds and haze

    Methane absorbs red light, contributing to the blue-green appearance. Enhanced images expose subtle bands hidden in near-natural colour.

    Direct observation
05

How we know

Voyager 2 provided the only close pass. Imaging, infrared spectra, radio tracking and occultations are combined with decades of telescope astrometry and atmospheric monitoring.

  1. 01

    Multifilter imaging

    Voyager 2 and telescopes record reflected light through filters to map colour, clouds, rings and the limb.

    Where this method stops

    The 1986 flyby sampled one season and hemisphere geometry; contrast enhancement can make subtle structure look stronger.

    Direct observation
  2. 02

    Astrometry and flyby radio tracking

    Long-term sky positions set the orbit, while Voyager Doppler and moon motions constrain mass and gravity.

    Where this method stops

    A single close flyby leaves the gravity field and rotation less precisely mapped than at orbited planets.

    Calculated measurement
  3. 03

    Infrared spectroscopy and radiometry

    Thermal and reflected spectra constrain atmospheric gases, clouds, temperature and emitted heat.

    Where this method stops

    Different wavelengths sense broad pressure ranges and retrievals rely on cloud and radiative-transfer models.

    Calculated measurement
  4. 04

    Interior and thermal-evolution modeling

    Mass, shape, gravity, magnetic field and weak heat output are tested against candidate compositions and histories.

    Where this method stops

    Sparse gravity data allow many layer boundaries, mixing states and formation histories.

    Scientific model
06

Evidence key

Direct observation
An instrument or sample recorded the phenomenon, with processing still disclosed.
Calculated measurement
Observed motion or signal is converted into a physical quantity using equations and reference constants.
Scientific model
A tested interpretation that fits observations but is not directly imaged or sampled.
Vastward explanation
Original beginner-facing synthesis, traceable to the source records but not itself a measurement.
Artist visualization
An interpretive image, not observational evidence.
07

Missions and instruments

Active

Voyager 2

The only spacecraft to visit Uranus, returning close images and measurements of its atmosphere, rings, moons, gravity, magnetic field and plasma environment.

Official mission ↗
Instruments
  • Voyager Imaging Science SubsystemFiltered visible-light images of the planet, clouds, rings and moons.
  • Voyager radio scienceDoppler motion and radio occultations used for gravity, atmosphere and ring structure.
  • Infrared Interferometer Spectrometer and RadiometerThermal spectra and energy balance of the atmosphere.
08

Official source trail

Links below are the exact records used for this profile. Access dates are retained with the content.

  1. 01

    NASA Jet Propulsion Laboratory, Solar System Dynamics · dataset

    Planetary Physical Parameters

    Source updated
    No source update date published
    Access checked
    2026-07-30
    Open official source ↗
  2. 02

    NASA Science · official-page

    Uranus Facts

    Source updated
    2025-06-26
    Access checked
    2026-07-30
    Open official source ↗
  3. 03

    NASA/JPL · image

    Uranus in True and False Color

    Source updated
    2025-09-03
    Access checked
    2026-07-30
    Open official source ↗
  4. 04

    NASA Science · official-page

    Voyager 2

    Source updated
    2026-01-07
    Access checked
    2026-07-30
    Open official source ↗
09

Continue exploring

Atlas is a starting point. Use these relationships to move into explanation, experiment and mission thinking.

Relationship reserved

Turn a planet sideways

Move through an 84-year orbit and track polar sunlight.

lab
Relationship reserved

Decode true and false colour

Remap filters and see which claims survive the palette.

lab
Relationship reserved

Fit more than one interior

Discover why sparse gravity data allow several hidden structures.

lab