URANUS SYSTEM / SATELLITE DOSSIER

Portia

Portia is a small inner moon of Uranus, completing an orbit in just over twelve hours and still known mainly from distant observations.

Moon view ↗

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Artist’s impression of Portia

Portia is a small inner moon of Uranus, completing an orbit in just over twelve hours and still known mainly from distant observations.

Environment ↗

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DIAMETER / EARTH0.01×
EARTHPORTIA
ATMOSPHERE
No substantial atmosphere detectedEffectively airless
SURFACE TEMPERATURE
Cold exposed surface
SURFACE PRESSURE
Effectively airless
HABITABILITYNo life detected
UNPROTECTED HUMANSNot survivable

Interior ↗

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Portia interiorPortia's internal structure is unresolved.Unresolved

Moon system ↗

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Uranus moon orbitsSelected moons, ordered outward. Orbit sizes and positions are schematic; relative periods are preserved.URANUSCORDELIAOPHELIABIANCACRESSIDADESDEMONAJULIETPORTIAROSALINDCUPIDBELINDAPERDITAPUCKMABMIRANDAARIELUMBRIELTITANIAOBERON

Landscape ↗

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A speculative ground-level view on Portia. The crater, fragments and local relief are artistic reconstructions.
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Rotation ↗

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Portia rotationThe rotation period is unresolved. Static portrait, not an orientation prediction.PERIOD UNCERTAINNO UNIQUE PERIOD ADOPTED

Gravity ↗

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GRAVITY UNKNOWNMASS UNCERTAIN

Orbit ↗

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Portia orbitElliptical orbit viewed along the orbital axis, relative to Uranus. Motion is accelerated, not a live position. Distances are center to center.URANUSPORTIA≈ 66,101 km
Sources ↗
PORTIA

Instrument detail

THE SKY FROM PORTIA

Uranus, in perspective.

SHARED ANGULAR SCALE
Uranus compared with Luna in Earth's skyAt semimajor-axis distance, Uranus spans approximately 45.55 degrees, 87.94 times the apparent diameter of Luna at its mean distance from Earth. Both disks share one angular scale.URANUSOUR MOON≈ 0.52°
Idealized size study · full disks · decorative lighting · rings excluded
ANGULAR DIAMETER
45.55°
OUR MOON'S APPARENT DIAMETER
87.94 ×
CENTER-TO-CENTER DISTANCE
66,101 km

The viewpoint is on Portia’s nominal spherical surface, directly facing Uranus. The reference is Luna seen from Earth’s center at its mean distance. The reference distance is the orbit’s semimajor axis. Rounded body diameters and orbital elements set the disk sizes; terrain, phases, rings and the actual sky position are not modeled.

Explore Uranus ↗
Portia orbitElliptical orbit viewed along the orbital axis, relative to Uranus. Motion is accelerated, not a live position. Distances are center to center.URANUSPORTIA≈ 66,101 km
ONE ORBIT0.5132 Earth days around Uranus
Closest to Uranus
65,837 km
Farthest from Uranus
66,365 km

Portia circles Uranus. Distances are measured between the centers of the two bodies.

The adopted URA184 mean elements describe an approximate path. Inclination, precession and interactions with neighboring moons are omitted.

Portia rotationThe rotation period is unresolved. Static portrait, not an orientation prediction.PERIOD UNCERTAINNO UNIQUE PERIOD ADOPTED
ROTATION STATEUncertain

Rotation remains uncertain

The cited overview does not provide a measured spin period. This static portrait makes no fixed-rate or orientation assumption; uncertainty does not imply chaotic tumbling.

Satellite atlasMoons
Uranus moon orbitsSelected moons, ordered outward. Orbit sizes and positions are schematic; relative periods are preserved.URANUSCORDELIAOPHELIABIANCACRESSIDADESDEMONAJULIETPORTIAROSALINDCUPIDBELINDAPERDITAPUCKMABMIRANDAARIELUMBRIELTITANIAOBERON
FEATURED MOONS18
  1. 01Cordelia ↗0.3347 days
  2. 02Ophelia ↗0.3764 days
  3. 03Bianca ↗0.4347 days
  4. 04Cressida ↗0.4639 days
  5. 05Desdemona ↗0.4736 days
  6. 06Juliet ↗0.4931 days
  7. 07Portia0.5132 days
  8. 08Rosalind ↗0.5583 days
  9. 09Cupid ↗0.6125 days
  10. 10Belinda ↗0.6236 days
  11. 11Perdita ↗0.6382 days
  12. 12Puck ↗0.761833 days
  13. 13Mab ↗0.9229 days
  14. 14Miranda ↗1.41 days
  15. 15Ariel ↗2.5204 days
  16. 16Umbriel ↗4.1442 days
  17. 17Titania ↗8.7059 days
  18. 18Oberon ↗13.4632 days

Faint rings and a family of moons surround Uranus. Many of those moons take their names from characters in Shakespeare and Alexander Pope. One journey around the Sun lasts about 84 Earth years.

GRAVITY UNKNOWNMASS UNCERTAIN
SURFACE GRAVITYUnknown

Mass remains uncertain

No measured mass is adopted from the cited overview. A numerical surface gravity would require additional assumptions, so the jump comparison is not shown.

Portia interiorPortia's internal structure is unresolved.Unresolved

Beyond the surface

Portia’s interior is unresolved. Available observations do not establish distinct internal layers or a present-day ocean.

    Artist’s impression of Portia

    A Voyager find in the tilted system.

    Portia was discovered in January 1986 in images returned by Voyager 2 during its Uranus flyby. The brief encounter expanded the known family of small moons close to the planet.

    Large among the lesser satellites.

    NASA’s overview gives an approximate diameter of 140 kilometers. Portia remains poorly characterized, so the portrait is an artistic interpretation and the landscape studies invent local relief rather than reproducing mapped terrain.

    A year shorter than an Earth day.

    The adopted mean elements place Portia about 66,101 kilometers from Uranus’s center, with an orbital period of 0.5132 Earth days. The displayed ellipse omits inclination and interactions with neighboring satellites.

    A character carried into the outer solar system.

    Portia takes its name from the heroine of Shakespeare’s The Merchant of Venice. Its original designation was S/1986 U 1. No measured interior layering or habitable environment is established.

    DIAMETER / EARTH0.01×
    EARTHPORTIA
    EARTH
    12,742 km
    PORTIA
    140 km
    Mean diameters · circles share one scale

    140 km is the adopted approximate diameter. This rounded estimate follows NASA’s overview; the irregular outline is not a measured sphere.

    ATMOSPHERE
    No substantial atmosphere detectedEffectively airless

    Portia is effectively airless. No substantial atmosphere is known.

    SURFACE TEMPERATURE
    Cold exposed surface
    SURFACE PRESSURE
    Effectively airless
    HABITABILITYNo life detected

    No life has been detected, and a habitable environment has not been established.

    UNPROTECTED HUMANSNot survivable

    The exposed surface requires oxygen, pressure protection and thermal control.

    Planet and landscape images are artistic interpretations.

    • NASA ↗
      • Classification and orbital data
      • Mass and gravity constraints
      • Rotation model and synchronous or independent spin
      • Rotation and internal structure constraints
      • Size, physical data and atmospheric constraints
      • Natural conditions and human survival
      • Discovery
      • Scale
      • Name
    • NASA ↗
      • Parent-body diameter for the angular sky comparison
    • NASA / JPL ↗
      • Mean orbital dimensions; distances from parent center
      • Orbit
    A speculative ground-level view on Portia. The crater, fragments and local relief are artistic reconstructions.

    Inside an imagined hollow

    A speculative ground-level view on Portia. The crater, fragments and local relief are artistic reconstructions.

    An imagined landscape on Portia. Surface textures and illumination are not a spacecraft panorama.

    Along an uneven ridge

    An imagined landscape on Portia. Surface textures and illumination are not a spacecraft panorama.

    A low dark fractured slab whose fine dusty edge curves across the frame. An artistic reconstruction of Portia; local detail, lighting and viewpoint are imagined.

    Surface fragments in close view

    A low dark fractured slab whose fine dusty edge curves across the frame. An artistic reconstruction of Portia; local detail, lighting and viewpoint are imagined.