Satellites of Uranus
ATLAS OF THE UNIVERSE
U
ranus, like all the giant planets, has an extensive
satellite family. The two outer members, Titania and
Oberon, were discovered by William Herschel in 1787.
Herschel also announced the discovery of four more satel-
lites, but three of these are non-existent and must have
been faint stars; the fourth may have been Umbriel, but
there is considerable doubt. Umbriel and Ariel were found
in 1851 by the English amateur William Lassell. All the
four first-discovered satellites are between 1100 and 1600
kilometres (700 to 1000 miles) in diameter, so that they
are comparable with the medium-sized icy satellites in
Saturn’s system, but their greater distance makes them
rather elusive telescopic objects.
During the 1890s W. H. Pickering (discoverer of
Phoebe, the outermost satellite of Saturn) searched for fur-
ther members of the system, but without success. The fifth
moon, Miranda, was discovered by G. P. Kuiper in 1948;
it is much fainter and closer-in than the original four.
Voyager 2 found another ten satellites, all moving insideSATELLITES OF URANUS Miranda. The innermost
of Uranus’ large satellites
is seen at close range in
this image from Voyager 2,
taken from a distance of
35,000 km (22,000 miles).
Scarps, ice-cliffs and craters
are visible.▲ Oberon.Voyager 2 took
this picture from around
660,000 km (413,000 miles),
with a resolution of 11 km
(7 miles). Note the high peak,
which is about 6 km high
(3.8 miles), projecting from
the lower left limb. Umbriel.The surface
of Umbriel is much darker
and more subdued than that
of Ariel. The largest crater,
Skynd, is 110 km (68 miles)
in diameter, with a bright
central peak. Wunda,
diameter 140 km (87 miles),
lies near Umbriel’s equator;
its nature is uncertain, but it
is the most reflective feature
on the satellite. (Remember
that owing to the pole-on
view, the equator lies round
the limb in this picture.)Name Distance from Orbital Orbital Orbital Diameter, Density, Escape Magnitude
Uranus, km period, days inclination, º eccentricity km water = 1 velocity, km/s
Cordelia 49,471 0.330 0.14 0.0005 26? very low 24.2
Ophelia 53,796 0.372 0.09 0.0101 32? very low 23.9
Bianca 59,173 0.433 0.16 0.0009 42? very low 23.1
Cressida 51,777 0.463 0.04 0.0001 62? very low 22.3
Desdemona 62,676 0.475 0.16 0.0002 54? very low 22.5
Juliet 64,352 0.493 0.04 0.0002 84? very low 21.7
Portia 66,085 0.513 0.09 0.0002 106? very low 21.1
Rosalind 69,941 0.558 0.08 0.0006 54? very low 22.5
Belinda 75.258 0.622 0.03 0.0001 66? very low 22.1
1986 U10 75.258 0.62 low low 40? very low 23
Puck 86,000 0.762 0.31 0.0001 154? very low 20.4
Miranda 129,400 1.414 4.22 0.0027 481 466 466 1.3 0.5 16.3
Ariel 191,000 2.520 0.31 0.0034 1158 1.6 1.2 14.2
Umbriel 256,300 4.144 0.36 0.0050 1169 1.4 1.2 14.8
Titania 435,000 8.706 0.014 0.0022 1578 1.6 1.6 13.7
Oberon 583,500 13.463 0.10 0.0008 1523 1.5 1.5 13.9
Caliban 7,170,000 579 140 0.082 60? very low 22.3
Stephano 7,940,000 676 141.5 0.146 30? very low 24
Sycorax 12,214,000 1203 153 0.51 120? very low 20.7
Prospero 16,110,000 1993 146.3 0.327 40? very low 23
Setebos 18,200,000 2202 148.8 0.494 40? very low 23D108- 151 UNIVERSE UK 2003CB 7/4/03 5:15 pm Page 126