Indy's Object Catalog
Solar System Objects
The Sun and Solar System were formed approximately 4.6 billion years ago in the inner rim of the Orion Arm of the Milky Way Galaxy, between the larger Perseus and Sagittarius arms of the galaxy. Our Solar System consists of objects that circle the Sun in a nearly flat disc called the ecliptic plane, including Planets, Asteroids, Moons, Etc. The Sun orbits the center of the Milky Way galaxy every 250 million years at a distance of approximately 25,000 light years from the galactic center, taking the Earth and other solar system objects along with it.

To get an idea of the scale of the solar system, consider that it takes 6.84 hours for light to travel from the Sun to Pluto at it's farthest point from the Sun. At almost 4.5 billion miles from Earth, Pluto is so distant that it takes 248 years to complete one orbit of the Sun.

The Sun: Our Sun is a main sequence star composed of 98% hydrogen and helium, generating its energy by nuclear fusion of hydrogen nuclei into helium. The remaining 2% is trace quantities of other elements, including iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium, and chromium. The Sun is 1 au ( 93 million miles ) from the earth and is over 109 times the diameter of the Earth. At almost 865,000 miles in diameter, the Sun is so large that It's volume equals 1,300,000 planets the size of Earth. In the image above, the Sun is to scale.

The Planets:
Most of the mass of the objects circling our Sun is contained within eight relatively isolated planets whose orbits are almost circular.

The four small inner terrestial planets; Mercury, Venus, Earth, and Mars, are primarily composed of dense rock and metal. In fact, the Earth is the densest planet in the solar system.

The four outer gas giants, or Jovian planets; Jupiter, Saturn, Uranus, and Neptune, are composed largely of low density hydrogen and helium, owing their great mass to their giant size. At 11.2 times the diameter of Earth, it is estimated that 1,321.3 planets the size of Earth would equal the volume of space occupied by Jupiter, yet Jupiter's density is so low that it only masses 317.89 times that of Earth. The planet with the lowest density is Saturn, which is only half as dense as Jupiter.

Dwarf Planet: Although originally classified as a planet, Pluto's status as the ninth planet has been downgraded to Dwarf Planet, putting it in a class with some of the major asteroids. This change in classification upset many astronomers used to considering Pluto a planet, and actually created the new verb "to pluto", defining "to pluto" as "to demote or devalue someone or something". The reason for the change makes sense because unlike the major planets, Pluto's orbit is 17 outside the plane of the ecliptic and highly eccentric causing it sometimes to be just inside the orbit of Neptune. Smaller than Earth's moon and about half the size of Mercury, Pluto is believed to be composed of rock and ice, and it's size and unusual orbit suggest that the pluto system may possibly be stray moons or asteroids that were captured or created in a chance encounter.

Sideways Planet: The majority of the planets have an axis of rotation or polar inclination that is relatively perpendicular to and vertical with the plane of the ecliptic, ranging from -2 to as much as 29, sort of like a bunch of spinning tops. Uranus is unusual in that it rotates sideways fashion with an axis of rotation of over 97 that is relatively horizontal and parallel to the ecliptic plane. Excluding normal precession of Uranus's polar axis over long periods of time, the orientation it's axis doesn't change as it orbits the Sun, so once in 84 years one pole faces the sun, 42 years later the other pole. Twice in between those times in Uranus's orbit, the sun falls on it's equatorial regions.

Moons: Counting asteroid moons and satellites of Trans-Neptunian objects, there are currently 335 known natural satellites of planets, dwarf planets, and minor planets, that are formally classified as moons. These include 167 moons orbiting six of the eight planets, and 3 orbiting the dwarf planet Pluto. There are no known moons that have natural satellites of their own, probably due to the orbital instabilities that would exist in such a system.

True to the definition of planets, the inner system is pretty much cleaned out. Of the inner planets, Mercury and Venus have no moons at all and Earth only has one large satellite, known as the Moon. Mars has two tiny moons, Phobos and Deimos that are not much more than big rocks; with Phobos the largest of the two at only 6.9 miles in diameter.

The outer system of large gas giants has extensive systems of moons, including six moons similar in size to Earth's moon. Jupiter's Ganymede is the largest moon in the solar system. The Solar System's second largest moon, Titan, is Saturn's largest moon, and is the only moon in the Solar System known to possess a significant atmosphere. Both Ganymede and Titan are larger than Mercury, and almost large enough to be comparable in size to Mars.

Even tiny Pluto has three known moons, the largest of which is Charon which is 750 miles in diameter. The Pluto-Charon system is unusual in that the center of mass lies in open space between the two, a characteristic of a double planet system.

In the table below, only a selected few moons (24) are listed.
Return to Catalog Index
Object Image Solar
Distance
Solar
Orbit
Dia
(km)
Rotation Polar
Inclination
Earth
Masses
Density Escape
Velocity
Surface
Gravity
Magnitude

Sun
N/A N/A 109.125
(1,392,000)
25.380
days
7 15' 332,946 1.409 617.5
km/sec
27.9
g
M -26.8

Mercury

0 Moons
0.39 au 0.24
years
0.382
(4,880)
58.65
days
0 0.055 5.5 4.3
km/sec
0.38
g
M 0.0

Venus
0 Moons
0.72 au 0.62
years
0.949
(12,100)
-243.01
days
(Retro)
-2 0.815 5.25 10.36
km/sec
0.9032
g
M -4.4

Earth

1 Moon
1 au 1
year
1.0
(12,756)
23.9345
hours
23.45 1 5.517 11.18
km/sec
1
g
N/A

Moon
1 au 1
year
0.272
(3,476)
27.322
days
1 21' 0.0203 3.342 2.38
km/sec
0.1653
g
M -12.7

Mars
2 Moons
1.52 au 1.88
years
0.532
(6,790)
24.6229
hours
23.98 0.1074 3.94 5.03
km/sec
0.3799
g
M -2.0
Phobos 0.00087
(11.1)
Deimos 0.00048
(6.2)
Object Image Solar
Distance
Solar
Orbit
Dia
(km)
Rotation Polar
Inclination
Earth
Masses
Density Escape
Velocity
Surface
Gravity
Magnitude

Jupiter

63 Moons
5.2 au 11.86
years
11.209
(142,200)
9.841
hours
3.08 317.89 1.33 60.22
km/sec
2.643
g
M -2.6
Io 0.286
(3,642)
Europa 0.245
(3,138)
Ganymede 0.413
(5,268)
Callisto 0.378
(4,820)

Saturn

61 Moons
9.54 au 29.46
years
9.449
(119,300)
10.233
hours
29 95.17 0.706 36.25
km/sec
1.159
g
M 0.7
Mimas 0.031
(396)
Enceladus 0.040
(512)
Tethys 0.083
(1,066)
Dione 0.088
(1,123)
Rhea 0.1197
(1,528)
Titan 0.404
(5,152)
Hyperion 0.0211
(270)
Iapetus 0.1152
(1,470)
Phoebe 0.0167
(213)

Uranus

27 Moons
19.22 au 84.01
years
4.007
(47,100)
-15.5
hours
(Retro)
97.92 14.54 1.19 21.22
km/sec
1.11
g
M 5.5
Miranda 0.0369
(471)
Ariel 0.0907
(1,158)
Umbriel 0.0916
(1,169)
Titania 0.1235
(1,576)
Oberon 0.1193
(1,522)

Neptune

13 Moons
30.06 au 164.8
years
3.883
(49,500)
15.8
hours
28.8 17.23 1.66 23.6
km/sec
1.12
g
M 7.8
Triton 0.2116
(2,700)
Nereid 0.0266
(340)

Pluto
3 Moons
29.7 au
to
49.3 au
248.09
years
0.19
(2,300)
-6.39
days
(Retro)
? 0.0017 0.6-1.7? 5.3?
km/sec
0.44?
g
M 14.9
Charon 0.0946
(1,207)
Object Image Solar
Distance
Solar
Orbit
Dia
(km)
Rotation Polar
Inclination
Earth
Masses
Density Escape
Velocity
Surface
Gravity
Magnitude
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Exception: The Pluto and Scale Images are Artist Renditions by Indigotide.
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