Planet Information including orbital & rotational times and velocities, mass, etc.
 

0
Sun
1
Mercury
2
Venus
3
Earth
4
Mars
5
Jupiter
6
Saturn
7
Uranus
8
Neptune
9
Pluto
  Luna
(Our Moon)

"The universe is there for us to see, but it cannot be understood without learning its language - mathematics."
- Galileo Galilei



SUN   (Click here for index of all planet data)

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PHYSICAL PROPERTIES:
    Diameter of photosphere = 1.392x10^6 km = 8.649x10^5 miles ≈ 4 times the distance from Earth to the Moon!
    Mass = 1.99x10^30 kg
    Mean density = 1.408 g/cc

Escape velocity = 617.7 km/s = 1,381,756 miles/hr   ≈ 55 times the escape velocity of Earth
Surface gravity = 274.0 m/s = 899 ft/s
Solar constant at 1 AU = 1367.6 W/m for a total output of 3.846x10^26 watts
Solar luminosity = 3.85x10^33 erg/s
Mass-energy conversion rate = 4.3x10^12 gm/s
Effective temperature = 5778 K
Surface temperature of the photosphere = 6600 K (bottom)
Surface temperature of the photosphere = 4400 K (top)
Photospheric depth ≈ 400 km
Chromospheric depth ≈ 2500 km
Sunspot cycle = 11.4 yr

Rotation:
The period of actual rotation is approximately 25.6 days at the equator and 33.5 days at the poles.

However, due to Earth's orbit around the Sun,
the period of apparent rotation is approximately 28 days at the equator and 35.9 days at the poles
.

Motion relative to nearby stars:
    speed: 19.4 km/s = 0.0112 AU/day ≈ 43,397 miles/hr
Motion relative to 2.73K BB:
    speed: 369 11 km/s ≈ nearly one million miles/hr (!)

Comparisons:
    Radius: largest solar system body, 109 times Earth, 9.7 times Jupiter
    Mass: largest solar system body, 333000 times Earth, 1048 times Jupiter
    Over 99.8% of the total mass of the solar system.
    Density: 25.5% of Earth, 106% of Jupiter

Notes:
    Composition by mass: about 75% Hydrogen, 25% Helium
    Composition by atoms: 92.1% Hydrogen, 7.8% Helium, 0.1% other
    Period of rotation: 25.38 days at equator up to 36 days at the poles
    Approximate Age: 4.5 billion years
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MERCURY   (Click here for index of all planet data)

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GEOPHYSICAL DATA:
    Mean radius = 2440(1) km (Spherical) = 1516 miles (diameter = 3032 miles)
    Equatorial radius, Re = 2440 km
    Core radius ≈ 1600 km
    Mass = 3.30x10^23 kg
    Density = 5.427 g/cc
    Volume = 6.09x10^10 km
ROTATIONAL & ORBITAL DATA:
    Sidereal Rotational Period: 58.6462 d (2/3 of orbital period)
    Rotation Rate = 0.124001x10^5 s
    Mean solar day = 175.9421 d
    Obliquity to orbit ≈ 0.1
    Sidereal Orbital Period: 0.2408445 y = 87.968435 d
    Average Orbital Velocity: 47.8725 km/s = 107,088 miles/hr

Max. angular diam. = 11.0"
Maximum visual magnitude: -1.9
Visual mag. V(1,0) = -0.42
Geometric albedo = 0.106

Escape velocity = 4.435 km/s
Equ. gravity = 3.701 m/s
Mom. of Inertia = 0.33
GM = 22032.09 km/s
GM 1-sigma = 0.91 km/s
Mass ratio (sun/plnt) = 6023600

Planetary Solar Const = 9936.9 Wm

Orbital Data:
    Perihelion, q: 0.30749951 AU
    Semimajor axis, a: 0.38709893 AU
    Aphelion, Q: 0.46669835 AU
    Eccentricity, e: 0.20563069
    Inclination, i: 7.00487

Comparisons:
    Radius: 38.3% of Earth, 11th largest body (Titan > Mercury > Callisto) 92.6% of Ganymede, 94.8% of Titan, 140.4% of Luna
    Mass: 5.5% of Earth, 9th largest body (Mars > Mercury > Ganymede) 2.2 times Ganymede, 2.5 times Titan, 4.5 times Luna
    Density: 98% of Earth, 2nd largest (Earth > Mercury > Venus)
    Surface gravity: 38% of Earth
    Magnetic field: 1% of Earth
    Atmosphere: None
    Satellites: Mercury as no moons

Viewing:
    Mercury is often visible with binoculars or the naked eye, but is always close to the sun and difficult to see
        in the twilight sky. A telescope will show phases on Mercury, like the phases of the Moon.
    From time to time, Mercury, like Venus, will pass between the earth and sun, and a transit will occur.
         During a transit, Mercury appears as a very small dot crossing the disk of the sun.
             Click here for an image of the May 7, 2003 transit of Mercury
         These events happen infrequently.  The first was observed in 1631.  The next will occur on May 9, 2016.

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VENUS   (Click here for index of all planet data)

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GEOPHYSICAL DATA:
    Mean radius = 6051.8(41) km (Spherical) = 3,760 miles (diameter = 7520 miles)
    Equatorial radius, Re = 6051.893 km
    Core radius ≈ 3200 km
    Mass = 48.69x10^23 kg
    Density = 5.204 g/cc
    Volume = 92.84x10^10 km

ROTATIONAL & ORBITAL DATA:
    Sidereal Rotational Period:  -243.0185 d (Retrograde, 108% of orbital period)
    Rotational Rate = -0.029924x10^5 s
    Mean solar day = 116.7490 d
    Obliquity to orbit = 177.3
    Sidereal Orbital Period: 0.6151826 y = 224.695434 d
    Average Orbital Velocity: 35.0214 km/s = 78,341 miles/hr

Max. angular diam. = 60.2"
Maximum visual magnitude: -4.4
Visual mag. V(1,0) = -4.40
Geometric albedo = 0.65

Escape velocity = 10.361 km/s
Equ. gravity = 8.870 m/s
Mom. of Inertia = 0.33
Potential Love # k2 ≈ 0.25
Grav spectral fact u = 1.5
Topo. spectral fact t = 23
Fig. offset (Rcf-Rcm) = 0.1901
Offset (lat./long.) = 11/102 dg/dg
GM = 324858.63 km/s
GM 1-sigma = 0.04 km/s
Mass ratio (sun/plnt) = 408523.61

Atmos. pressure = 90 bar
Mean Temperature = 735 K ≈ 900 F
Planetary Solar Const = 2613.9 Wm

Orbital Data:
    Perihelion, q: 0.71843270 AU
    Semimajor axis, a: 0.72333199 AU
    Aphelion, Q: 0.72823128 AU
    Eccentricity, e: 0.00677323 (Most circular of any planet)
    Inclination, i: 3.39471

Comparisons:
    Radius: 94.9% of Earth, 7th largest body (Earth > Venus > Mars)
    Mass: 81.5% of Earth, 7th largest body (Earth > Venus > Mars)
    Density: 95% of Earth, 3rd largest (Earth > Mercury > Venus)
    Surface gravity: 91% of Earth
    Magnetic field: None
    Atmosphere: 90 times denser than Earth, 96.5% carbon dioxide
    Satellites: Venus as no moons

Notes:
    In many ways, Venus would appear to be a twin to the Earth; it has roughly the same diameter,
        a slightly lower mass, and should be a little hotter due to being closer to the sun.
    The density is close enough to earth's to lead one to think it might be composed of much the same materials.
    The main difference is caused by a thick atmosphere, about 90 times denser than our own. 96.5% of it is carbon dioxide,
        which tends to trap most incoming solar energy; so instead of just being a little hotter than Earth, Venus has a surface
        temperature of about 500C (900F).

Viewing:
    Venus is the brightest object in the sky after the Sun and Moon. A small telescope will show phases on Venus,
         like the phases of the moon.
    From time to time, Venus (like Mercury) will pass between the earth and sun, and a transit will occur.
         Click here to see an image of the last transit on June 8, 2004
         During a transit, Venus appears as a small dot crossing the disk of the sun.
         These events are rare.  The first was observed in 1639, and others have/will occur as detailed below:
               Dec 4, 1639
               Jun 3, 1769
               Dec 9, 1874
               Dec 6, 1882
               Jun 8, 2004
               Jun 5, 2012
               Dec 12, 2117
               Dec 8,  2125
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EARTH   (Click here for index of all planet data)

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GEOPHYSICAL DATA:
   Mean radius: 6,371.0 km = 3,959 miles (diameter = 7918 miles)
   Equatorial radius: 6,378.1 km
   Polar radius: 6,356.8 km
   Flattening: 0.0033528
   Circumference: 40,075.02 km (equatorial)
   Surface area:
        510,072,000 km Total
        148,940,000 km land (29.2 %)
        361,132,000 km water (70.8 %)
   Volume 1.08x10^12 km
   Mass 5.97 E24 kg
   Mean density: 5.5153 g/cm
   Equatorial Surface Gravity: 9.780327 m/s = 0.99732 g = 32.08759 ft/s
   Escape velocity: 11.186 km/s = 25,022 miles/hr
   Axial tilt 23.439281
Albedo 0.367
Surface temp min mean max
Kelvin  184 K 287 K 331 K
Celsius -89 C 14 C   58 C
Fahrenheit -128 F 57 F 136 F

ROTATIONAL & ORBITAL DATA:
   Sidereal Rotation Period:  0.99726968 d = 23h 56m 4.100s
   Equatorial Rotation Velocity: 1,674.4 km/h (465.1 m/s) = 1040 miles/hr
   Sidereal Orbital Period: 1.0000175 yr = 365.256366 days
   Average Orbital Velocity: 29.783 km/s = 66,622 miles/hr

Satellites: Earth has one moon, Luna, the Moon

Orbital Data:
   Aphelion: 1.0167103335 AU = 152,097,701 km
   Perihelion: 0.9832898912 AU = 147,098,074 km
   Semi-major axis: 1.0000001124 AU = 149,597,887.5 km
   Eccentricity: 0.016710219
   Inclination: 1.57869 to Invariable plane
   Longitude of ascending node: 348.73936
   Argument of perihelion: 114.20783

Atmosphere:
   Surface pressure 101.3 kPa (MSL)
   Composition 78.08% Nitrogen (N2)
   20.95% Oxygen (O2)
   0.93% Argon
   0.038% Carbon dioxide
   ~1.0% water vapor (varies with climate)
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MARS   (Click here for index of all planet data)

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GEOPHYSICAL DATA:
   Mean radius: 3389.9(+2/-4) km = 2,106 miles (diameter = 4212 miles, just over of Earth's)
   Equatorial radius: 3394.0 km
   Semimajor axis: 3397(4) km
   Flattening, f: 1/154.409
   Core radius ≈ 1700 km
   Mass: 6.42x10^23 kg
   Density: 3.933(5+-4) g/cc
   Volume: 16.32x10^10 km

ROTATIONAL & ORBITAL DATA:
   Sidereal Rotational Period = 24.622962 hr
   Rotation Rate = 7.088218x10^5 s
   Mean solar day = 1.0274907 d
   Obliquity to orbit = 25.19
   Sidereal Orbital Period = 1.8807115 y = 686.92971 d
   Average Orbital Velocity: 24.1309 km/s = 53,979 miles/hr

Maximum angular diameter = 25.10"  (See Viewing Mars section below)
Maximum visual magnitude = -2.9      (See Viewing Mars section below)
Visual magnitude V(1,0) = -1.52
Geometric albedo = 0.150

Escape velocity = 5.027 km/s
Polar gravity = 3.758 m/s
Equ. gravity = 3.690 m/s
Mom. of Inertia = 0.366
Potential Love # k2 ≈ 0.14
Grav spectral fact u = 14x10^5
Topo. spectral fact t = 96x10^5
Fig. offset (Rcf-Rcm) = 2.50(0.07) km
Offset (lat./long.) = 62 / 88
GM = 42828.3 km/s
GM 1-sigma = 0.1 km/s
Mass ratio (sun/plnt) = 3098708(9)

Atmos. pressure = 0.0056 bar
Mean Temperature = 210 K
Mag. mom (gauss Rp3) = < 1x10^-4

Orbital Data:
   Perihelion, q: 1.38133346 AU
   Semimajor axis, a: 1.52366231 AU
   Aphelion, Q: 1.66599116 AU
   Eccentricity, e: 0.09341233
   Inclination, i: 1.85061

Comparisons:
Radius: 53.1% of Earth, 8th largest body (Venus > Mars > Ganymede)
1.95 times the radius of our Moon
Mass: 10.7% of Earth, 8th largest body (Venus > Mars > Mercury)
Density: 71% of Earth
Surface gravity: 38% of Earth
Surface area: Approximately equal to the land area of Earth
Magnetic field: None/minimal
Atmosphere: Average pressure <1% of Earth, 95.3% carbon dioxide, 2.7% nitrogen,
1.6% argon, 0.15% oxygen, 0.03% water
Satellites: Mars has two moons: Phobos and Deimos (both, most likely, captured asteroids)

Viewing Mars:
Mars is easily visible with the naked eye. Its apparent size and brightness vary greatly as its distance from Earth changes. The following table lists opposition dates for Mars from 1969 to 2052, and the distance between Mars and Earth on those dates, in km and miles as well as the apparent size of Mars, in arcseconds, as seen from Earth. You'll notice that Mars comes particularly close in 1971, 1988, 2003, 2018, 2035 and 2050. This is part of a roughly 15.8-year cycle of favorable oppositions.  Click on any of the dates in the table below to see the relative position of the Earth and Mars on that date.
 

Date   ~Distance
(in km)
  ~Distance
(in miles)
  App size
(in arcsecs)
  Brightness
{Magnitude)
5/31/1969  

72,600,000

 

45,100,000

  19.24   -2.2
8/10/1971  

55,900,000

 

34,700,000

  24.89   -2.9
10/25/1973  

66,000,000

 

41,000,000

  21.20   -2.5
12/15/1975  

85,200,000

 

52,900,000

  16.43   -1.8
1/22/1978  

97,700,000

 

60,700,000

  14.30   -1.3
2/25/1980  

101,200,000

 

62,900,000

  13.81   -1.2
3/31/1982  

95,300,000

 

59,200,000

  14.67   -1.4
5/11/1984  

80,400,000

 

50,000,000

  17.40   -1.9
7/10/1986  

60,600,000

 

37,700,000

  23.02   -2.7
9/28/1988  

59,100,000

 

36,700,000

  23.64   -2.7
11/27/1990  

78,200,000

 

48,600,000

  17.94   -2.0
1/07/1993  

93,800,000

 

58,300,000

  14.91   -1.5
2/12/1995  

100,900,000

 

62,700,000

  13.85   -1.2
3/17/1997  

98,700,000

 

61,300,000

  14.16   -1.3
4/24/1999  

87,200,000

 

54,200,000

  16.02   -1.7
6/13/2001  

68,100,000

 

42,300,000

  20.50   -2.4
8/28/2003  

55,500,000

 

34,400,000

  25.10   -2.9
11/07/2005  

70,300,000

 

43,700,000

  19.92   -2.3
12/24/2007  

88,600,000

 

55,000,000

  15.80   -1.6
1/29/2010  

99,400,000

 

61,800,000

  14.08   -1.3
3/03/2012  

100,800,000

 

62,600,000

  13.88   -1.2
4/08/2014  

92,800,000

 

57,700,000

  15.05   -1.5
5/22/2016  

76,200,000

 

47,300,000

  18.35   -2.1
7/27/2018  

57,800,000

 

35,900,000

  24.23   -2.8
10/13/2020

 

62,700,000

 

39.000,000

  22.37   -2.6
12/08/2022  

82,200,000

 

51,000,000

  17.03   -1.9
1/15/2025  

96,300,000

 

59,800,000

 

14.54

 

-1.4
2/19/2027  

101,400,000

 

63,000,000

 

13.80

 

-1.2
3/25/2029  

97,100,000

 

60,000,000

 

14.42

 

-1.3
5/4/2031  

83,600,000

 

52,000,000

 

16.74

 

-1.8
6/27/2033  

63,900,000

 

39,700,000

 

21.89

 

-2.5
9/15/2035  

57,100,000

 

35,500,000

 

24.51   -2.8
11/19/2037  

74,700,000

 

46,400,000

 

18.73

 

-2.2
1/2/2040  

91,800,000

 

57,000,000

 

15.25

 

-1.5
2/6/2042  

100,500,000

 

62,500,000

 

13.93

 

-1.2
3/11/2044  

99,900,000

 

62,100,000

 

14.01

 

-1.3
4/17/2046  

89,900,000

 

55,900,000

 

15.56

 

-1.6
6/3/2048  

71,800,000

 

44,600,000

 

19.50

 

-2.2
8/14/2050  

56,000,000

 

34,800,000

 

25.01

 

-2.9
10/28/2052   66,800,000   41,500,000   20.96   -2.5

Angular diameter, close opposition: 25 arcseconds
Angular diameter, distant opposition: 14 arcseconds
Angular diameter, Earth/Mars dist = 1.5 AU: 6.2 arcseconds

Click the image below for an animated graphic showing the orbits of the Earth and Mars as seen from a point in space far above the plane of the ecliptic.  A separate image was created for each of the dates in the table (above) when Earth and Mars are closest together.  The eccentric (non-circular) orbits of Mars and the Earth generate the large variations in how large and bright Mars appears during different occultations.  These events occur approximately every 25.7 months.  Watch for the relative positions on 8/27/2003, when Mars was the closest to Earth in at least the past 50,000 years.  When seen from above, as in this graphic, all the planets in the Solar System revolve around the Sun in a counter-clockwise direction.


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JUPITER   (Click here for index of all planet data)

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PHYSICAL DATA:
   Equat. radius @ 1 bar = 71492(4) km
   Polar radius = 66854(10) km
   Volumetric mean radius = 69911(6) km
   Flattening = 0.06487
   Mass = 1898.6x10^24 kg
   Rocky core mass (Mc/M) = 0.0261
   Density = 1.326 g/cc

ROTATIONAL & ORBITAL DATA:
   Rotation period = 9h 55m 27.3s (9.92425 hours, longer near the poles)
   Rotation rate = 1.75853x10^-4 rad/s
   Obliquity to orbit = 3.12
   Sidereal Orbital Period: 11.856523 yr = 4330.595 d
   Average Orbital Velocity: 13.0697 km/s = 29,236 mile/hr
   Mean daily motion = 0.0831294 /d

Vis. mag. (opposition) = -2.70
Visual magnitude V(1,0)= -9.40
Geometric albedo = 0.52

Escape velocity = 59.5 km/s
Equ. grav, ge = 23.12(0.01) m/s
Pol. grav, gp = 27.01(0.01) m/s
m = w2a3/GM = 0.089195
Hydrostatic flat., fh = 0.06509
Inferred rot. period = 9.894(0.02) hr
ks = 3*J2/m = 0.494
Mom. of inert. I/MRo2 = 0.254
I/MRo2 (upper bound) = 0.267
GM = 126,686,537 km/s
GM 1-sigma = 100 km/s

Y factor (He/H ratio) = 0.18(0.04)
Atmos. temp. @ 1 bar = 165(5) K
Heat flow/mass = 15x10^7 erg/gm*s
Planetary Solar Const = 50.5 W/m
Mag.dip.mom(gauss-Rp3) = 4.2
Dipole tilt/offset = 9.6/0.1Rp
Aroche(ice)/Rp = 2.76

Orbital Data:
   Perihelion, q: 4.95155843 AU
   Semimajor axis, a: 5.20336301 AU
   Aphelion, Q: 5.45516759 AU
   Eccentricity, e: 0.04839266
   Inclination, i: 1.30530

Comparisons:
Radius: 11 times Earth, 2nd largest body (Sun > Jupiter > Saturn) 10.3% of Sun, 119% of Saturn.
   Jupiter's radius is about as large as a gas giant's radius can be. Additional mass would be compressed
   by gravity so much that there would be little increase in radius. Stars become larger because of their
   nuclear heat source, but Jupiter would have to be over 80 times more massive to be a star.
Mass: 318 times Earth, 2nd largest body (Sun > Jupiter > Saturn) 1/1048 of Sun, 3.3 times Saturn.
   Jupiter contains over twice the mass of all the other planets combined.
Density: 24% of Earth
Surface gravity: 2.55 times Earth
Magnetosphere: extends over 650 million km. If it were visible, it would appear about the size of our Moon.
Atmosphere: Interior pressure may be 100 million times the surface pressure of Earth
Satellites: Jupiter has at least 63 known moons, and more are discovered with each space probe sent.
                   Of these 63 moons, only 16 measure at least 6 miles (10 kilometers) in diameter.

Viewing:
Jupiter is normally the fourth brightest object in the sky (after the Sun, Moon, Venus, and sometimes Mars)
    and is easily spotted with the naked eye.
Some or all of its four large Galilean moons (Io, Europa, Ganymede, and Callisto) can be seen easily with
    binoculars. A few bands and the Great Red Spot are visible in a small telescope.

Data on the four Galilean moons, from the closest to Jupiter to the farthest:

Moon

Orbital Period

in Earth days in Earth hours
Io 1.769138 42.459312
Europa 3.551810 85.243440
Ganymede 7.154553 171.709272
Callisto 16.689018 400.536432

Io
SATELLITE PHYSICAL PROPERTIES:
    Radius 
  = 1821.3(+-0.2) km  (Radius: 1830.0 x 1818.7 x 1815.3 km)
    Mass      = 893.3(+-1.5)E+20 kg
    Density  
 = 3.530(+-.006) g/cc
    Maximum visual magnitude: 5.0
    Geometric albedo   = 0.61
SATELLITE ORBITAL DATA:
    Rotational period  = Synchronous rotation
    Orbital period     = 1.769138 d  (Orbital velocity: 17.34 km/s)
    Semimajor axis, a = 421.6E+3 km  (Ave dist: 5.9 Jupiter radii)
    Eccentricity, e    = 0.041
    Inclination, i     = 0.040 deg
Comparisons:
    Radius: 105% of Luna, 13th largest body (Callisto > Io > Luna)
    Mass: 122% of Luna, 13th largest body (Callisto > Io > Luna)
    Density: 106% of Luna, densest of Galilean moons
    Magnetic field: Weak
    Atmosphere: Thin sulfur dioxide, sulfur, and oxygen
    Surface gravity: 18.3% of Earth
    Escape velocity: 2.56 km/s
    Core: Molten iron and iron sulfide, radius at least 900 km (half its total)
    Mantle: Partially molten silicate rock, extends to the surface
    Surface: Sulfur and frozen sulfur dioxide, little or no water, no craters
Notes:
    Io is the inner most and third largest of Jupiter's four large Galilean moons.
    It orbits in resonance with Europa and Ganymede (4 orbits of Io and 2 orbits of Europa for every 1 orbit of Ganymede).
    The strong tidal forces from Jupiter and these moons drive the volcanic activity on Io.

Europa
SATELLITE PHYSICAL PROPERTIES:
    Radius 
  = 1565(+-8) km  (Spherical)
    Mass      = 479.7(+-1.5)E+20 kg
    Density  
 = 2.99(+-0.05) g/cc
    (Greatest elongation: 3' 40")
    (Maximum visual magnitude: 5.3)
    Geometric albedo   = 0.64  (5 times brighter than Luna)
SATELLITE ORBITAL DATA:
    Rotational period  = Synchronous rotation
    Orbital period     = 3.551810 d  (Orbital velocity: 13.74 km/s)
    Semimajor axis, a = 670.9E+3 km  (Ave dist: 9.5 Jupiter radii)
    Eccentricity, e    = 0.0101
    Inclination, i     = 0.470 deg
Comparisons:
    Radius: 90% of Luna, 15th largest body (Luna > Europa > Triton)
    Mass: 65% of Luna, 15th largest body (Luna > Europa > Triton)
    Density: 89.4% of Luna
    Magnetic field: Weak, approx 1/4 of Ganymede, varying
    Atmosphere: Very thin (1E-11 bar), oxygen
    Surface gravity: 13.5% of Earth
    Escape velocity: 2.02 km/s
    Core: Iron-sulfur, smaller than Io's
    Mantle: Primarily silicate rock
    Surface:  White and brownish tinted water ice, no features higher than 1 km
    -260 deg F at surface, but possibly liquid or "slushy" water beneath
    total thickness 80-170 km (50-106 miles), 100 km (62 miles) most likely
Notes:
    Europa is the 2nd inner most and smallest of Jupiter's four large Galilean moons.
    It orbits in resonance with Io and Ganymede (4 orbits of Io and 2 orbits of Europa for every 1 orbit of Ganymede).

Ganymede
SATELLITE PHYSICAL PROPERTIES:
    Radius    = 2634(+-10) km  (Spherical)
    Mass      = 1482(+-1)E+20 kg
    Density   = 1.94(+-0.02) g/cc
    (Greatest elongation: 5' 48")
    (Maximum visual magnitude: 4.6)
    Geometric albedo   = 0.42
SATELLITE ORBITAL DATA:
    Rotational period  = Synchronous rotation
    Orbital period     = 7.154553 d  (Orbital velocity: 10.9 km/s)
    Semimajor axis, a = 1070E+3 km  (Ave dist: 15.1 Jupiter radii)
    Eccentricity, e    = 0.0015
    Inclination, i     = 0.195 deg
Comparisons:
    Radius: 1.5 times Luna, 9th largest body (Mars > Ganymede > Titan)  41% of Earth, larger than Mercury (by radius) and Pluto
    Mass: 2.0 times Luna, 10th largest body (Mercury > Ganymede > Titan)
    Density: 58% of Luna
    Magnetic field: Yes
    Atmosphere: Very thin, oxygen
    Surface gravity: 14.5% of Earth
    Escape velocity: 2.74 km/s
    Core: Molten iron or iron/sulfur, 400-1200 km (250-800 miles)
    Mantle: Silicate rock, ice rich crust
    Surface: 50% ice (dirty ice), darker than Europa, impact craters
Notes:
    Ganymede is the largest moon in the solar system.
    It is the third inner most of Jupiter's four large Galilean moons.
    It orbits in resonance with Io and Europa (4 orbits of Io and 2 orbits of Europa for every 1 orbit of Ganymede).
Viewing:
    Ganymede is easily seen with binoculars, and is noticeably brighter than the other Galilean moons.

Callisto
SATELLITE PHYSICAL PROPERTIES:
    Radius    = 2403(+-5) km  (Spherical)
    Mass      = 1076(+-1)E+20 kg
    Density   = 1.851(+-.004) g/cc
    (Greatest elongation: 10' 13")
    (Maximum visual magnitude: 5.6)
    Geometric albedo   = 0.20
SATELLITE ORBITAL DATA:
    Rotational period  = Synchronous rotation
    Orbital period     = 16.689018 d  (Orbital velocity: 8.21 km/s)
    Semimajor axis, a = 1883E+3 km  (Ave dist: 26.6 Jupiter radii)
    Eccentricity, e    = 0.007
    Inclination, i     = 0.281 deg
Comparisons:
    Radius: 138% of Luna, 12th largest body (Mercury > Callisto > Io)
    Mass: 146% of Luna, 12th largest body (Titan > Callisto > Io)
    Density: 55% of Luna
    Magnetic field: No global, see Galileo spacecraft below
    Atmosphere: Very thin carbon dioxide
    Surface gravity: 12.7% of Earth
    Escape velocity: 2.45 km/s
    Core: Minimal core, only partially differentiated
    Composition: Fairly uniform mixture of 40% compressed ice and 60% rock/iron,
        but increasing percentage of rock toward the center
    Surface: 20% ice (dirty ice), much darker than Europa, very heavily cratered
Notes:
   Callisto is the outermost of Jupiter's large Galilean moons.
    Its orbit is close to, and gradually approaching resonance with Io, Europa, and Ganymede -
        8 orbits of Io, 4 orbits of Europa, and 2 orbits of Ganymede will take the same time as 1 orbit of Callisto.

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SATURN   (Click here for index of all planet data)

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PHYSICAL DATA:
Equat. radius @ 1 bar = 60268(4) km
Polar radius = 54364(10) km
Volumetric mean radius = 58232(6) km
Flattening = 0.09796
Mass = 568.46x10^24 kg
Rocky core mass (Mc/M) = 0.1027
Density = 0.6873 g/cc

ROTATIONAL & ORBITAL DATA:
   Sidereal Rotation Period: 10h 39m 22.4s
   Rotation rate = 1.63785x10^-4 rad/s
   Obliquity to orbit = 26.73
   Sidereal Orbital Period: 29.423519 yr = 10746.940 d
   Average Orbital Velocity: 9.6624 km/s = 21,614 miles/hr
   Mean daily motion = 0.0334979 /d

Vis. mag. (opposition) = +0.67
Visual magnitude V(1,0)= -8.88
Geometric albedo = 0.47

Escape velocity = 35.5 km/s
Equ. grav, ge = 8.96(0.01) m/s
Pol. grav, gp = 12.14(0.01) m/s
m = w2a3/GM = 0.15481
Hydrostatic flat., fh = 0.09829
Inferred rot. period = 10.61(0.02) hr
ks = 3*J2/m = 0.317
Mom. of inert. I/MRo2 = 0.210
I/MRo2 (upper bound) = 0.231
GM = 37,931,187 km/s
GM 1-sigma = 100 km/s

Atmos. temp. @ 1 bar = 134(4) K
Heat flow/mass = 15x10^7 erg/gm*s
Planetary Solar Const = 15.04 W/m
Mag.dip.mom(gauss-Rp3) = 0.21
Dipole tilt/offset = 0.0/0.0Rp
Aroche(ice)/Rp = 2.71

Orbital Data:
   Perihelion, q: 9.02063224 AU
   Semimajor axis, a: 9.53707032 AU
   Aphelion, Q: 10.0535084 AU
   Eccentricity, e: 0.05415060
   Inclination, i: 2.48446

Comparisons:
Radius: 9.4 times Earth, 3rd largest body (Jupiter > Saturn > Uranus)
Mass: 95 times Earth, 3rd largest body (Jupiter > Saturn > Uranus)
Density: 12% of Earth, least dense planet, less dense than water
Surface gravity: 125% of Earth
Magnetic field: Strong, minimal tilt & offset
Atmosphere: 75% Hydrogen, 25% Helium, traces of water, methane, ammonia
Satellites: Saturn has 62 confirmed moons as of 2010, 53 have been named.
                   Of these 62, only 25 measure at least 6 miles (10 kilometers) in diameter.
Viewing:
    Saturn is easily visible with the naked eye, but not as bright as Jupiter.
    Its rings and larger moons are visible in a small telescope. Many smaller moons are visible with
         medium sized telescopes - see the info sheet on each moon.
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URANUS   (Click here for index of all planet data)

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Discovered in 1781 by William Herschel

PHYSICAL DATA:
   Equat. radius @ 1 bar = 25559(4) km
   Polar radius = 24973(20) km
   Volumetric mean radius = 25362(12) km
   Flattening = 0.02293
   Mass = 86.832x10^24 kg
   Rocky core mass (Mc/M) = 0.0012
   Density = 1.318 g/cc

ROTATIONAL & ORBITAL DATA:
   Sidereal Rotation Period: 17.24(0.01) hr
   Rotation Rate: 1.012x10^-4 rad/s
   Obliquity to orbit = 97.86
   Mean daily motion = 0.0117690 /d
   Sidereal Orbital Period: 83.747407 yr = 30588.740 d
   Average Orbital Velocity: 5.4778 km/s = 12,254 miles/hr

Vis. mag. (opposition) = +5.52
Visual magnitude V(1,0)= -7.19
Geometric albedo = 0.51

Escape velocity = 21.3 km/s
Equ. grav, ge = 8.69(0.01) m/s
Pol. grav, gp = 9.19(0.02) m/s
m = w2a3/GM = 0.02954
Hydrostatic flat., fh = 0.01987
Inferred rot. period = 17.14(0.9) hr
ks = 3*J2/m = 0.357
Mom. of inert. I/MRo2 = 0.225
I/MRo2 (upper bound) = 0.232
GM = 5,793,947 km/s
GM 1-sigma = 23 km/s

Y factor (He/H ratio) = 0.262(.048)
Atmos. temp. @ 1 bar = 76(2) K
Planetary Solar Const = 3.71 W/m
Mag.dip.mom(gauss-Rp3) = 0.23
Dipole tilt/offset = 58.6dg/0.3Rp
Aroche(ice)/Rp = 2.20

Orbital Data:
   Perihelion, q: 18.2860560 AU
   Semimajor axis, a: 19.19126393 AU
   Aphelion, Q: 20.0964719 AU
   Eccentricity, e: 0.04716771
   Inclination, i: 0.76986

Comparisons:
    Radius: 3.98 times Earth, 4th largest body (Saturn > Uranus > Neptune)
    Mass: 14.5 times Earth, 5th largest body (Neptune > Uranus > Earth)
    Density: 24% of Earth
    Surface gravity: 92% of Earth
    Magnetic field: Strong, off center and tilted 58.6 from rotation axis
    Atmosphere: 83% hydrogen, 15% helium, 2% methane

Satellites: As of 2009, Uranus has 27 known moons and are named after characters
                   from the works by William Shakespeare and Alexander Pope.

Viewing:
Uranus is sometimes visible with the naked eye, and easily visible with binoculars. A small disk is visible with a small telescope.
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NEPTUNE   (Click here for index of all planet data)

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Discovered in 1846 by Adams and Le Verrier

PHYSICAL DATA:
Equat. radius @ 1 bar = 24766(15) km
Polar radius = 24342(30) km
Volumetric mean radius = 24624(21) km
Flattening = 0.0171
Mass = 102.43x10^24 kg
Density = 1.638 g/cc

ROTATIONAL & ORBITAL DATA:
   Sidereal Rotation Period: 16.11(0.01) hr
   Rotation Rate = 1.083x10^-4 rad/s
   Obliquity to orbit = 29.56
   Mean daily motion = 0.0060200 /d
   Sidereal Orbital Period: 163.72321 yr = 59799.900 d
   Average Orbital Velocity: 4.7490 km/s = 10,623 miles/hr

Vis. mag. (opposition) = +7.84
Visual magnitude V(1,0)= -6.87
Geometric albedo = 0.41

Escape velocity = 23.5 km/s
Equ. grav, ge = 11.00(0.05) m/s
Pol. grav, gp = 11.41(0.03) m/s
m = w2a3/GM = 0.02609
Hydrostatic flat., fh = 0.01804
Inferred rot. period = 16.7(1.4) hr
ks = 3*J2/m = 0.407
I/MRo2 (upper bound) = 0.239
GM = 6,835,107 km/s
GM 1-sigma = 15 km/s

Y factor (He/H ratio) = 0.235(.040)
Atmos. temp. @ 1 bar = 72(2) K
Heat flow/mass = 2x10^7 erg/gm*s
Planetary Solar Const = 1.47 W/m
Mag.dip.mom(gauss-Rp3) = 0.133
Dipole tilt/offset = 47/0.55Rp
Aroche(ice)/Rp = 2.98

Orbital Data:
   Perihelion, q: 29.8107953 AU
   Semimajor axis, a: 30.06896348 AU
   Aphelion, Q: 30.3271317 AU
   Eccentricity, e: 0.00858587
   Inclination, i: 1.76917

Comparisons:
Radius: 3.86 times Earth, 5th largest body (Uranus > Neptune > Earth)
Mass: 17.2 times Earth, 4th largest body (Saturn > Neptune > Uranus)
Density: 30% of Earth
Surface gravity: 137% of Earth
Magnetic field: Weakest of gas giants, off center and tilted 47
Atmosphere: Mostly hydrogen & helium with some methane
Satellites: Neptune has thirteen known moons as of 2010, five of those thirteen discovered in 2002 and in 2003

Viewing:
Neptune can be seen with binoculars, but a large telescope is needed to see
more than a tiny disk.
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PLUTO (Dwarf Planet aka Asteroid 134340)  (Click here for index of all planet data)

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Discovered in 1930 by Clyde Tombaugh

PHYSICAL DATA:
    Radius of Pluto, Rp = 1137( 8) km
    Mass Pluto = 1.27(0.02)x10^22 kg
    Density = 2.06 g/cc
    Mass ratio (Mc/Mp) = 0.12

ROTATIONAL & ORBITAL DATA:
    Sidereal Rotation Period: 6.39 days retrograde, synchronous rotation with Charon
    Tilt: Almost 90
    Sidereal Orbital Period: 248.0208 yr
    Average Orbital Velocity: 4.749 km/s = 10,623 miles/hr

Maximum visual magnitude: 13.6
Albedo (blue & var.) = 0.43 - 0.60

Surface gravity = 65.5 cm/s
GM (system) = 947(13) km/s

Orbital Data:
    Perihelion, q: 29.6583407 AU
    Semimajor axis, a: 39.48168677 AU
    Aphelion, Q: 49.3050329 AU
    Eccentricity, e: 0.24880766
    Inclination, i: 17.14175

Comparisons:
    Radius: 65% of Luna, 17th largest body after all planets plus Ganymede, Titan, Callisto, Io, Luna, Europa, and Triton
        (4 planets have a moon larger than Pluto)
    Mass: 17% of Luna, 17th largest body
    Density: 62% of Luna
    Magnetic field: Unknown
    Atmosphere: Thin near perihelion, freezes out near aphelion
    Satellites: Pluto has three known moons: Charon (the largest, about half Pluto's size), Hydra, and Nix (both very small).

Notes:
    Pluto's moon, Charon, has a diameter of about 1,300 km. They orbit each other once every 6.39 days, at a distance
         of about 12,000 km. They each keep the same face toward the other, much as the moon always shows the same
         face to the earth.
    Pluto's orbit is in 3:2 resonance with Neptune's (Pluto orbits the sun twice for every 3 orbits of Neptune).
    Their orbits cross, but there is no chance of collision because of this resonance. Pluto was closer to the sun than
         Neptune from February 7, 1979 to February 11, 1999. It will remain the most distant planet for 228 years.

Spacecraft:
    Pluto is the only planet that has not been visited by a spacecraft (except for long distance observations
        with the Hubble telescope). The New Horizons mission was launched in 2006 but will take 9 years to
        arrive in 2919 - and it's traveling at 36,000 m/h!

Viewing:
    A large telescope is required to see Pluto visually, but many amateurs with CCD imagers can detect it.
    The Hubble telescope can only resolve the largest surface features.
    Pluto is the second most contrasty body in the solar system, after Iapetus.
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LUNA (The Moon)  (Click here for index of all planet data)

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PHYSICAL PROPERTIES:
  Radius = 1737.53(0.03) km (Spherical)
  Mass = 734.9x10^20 kg
  Density = 3.3437 gm/cc
  Earth/Moon mass ratio = 81.300587
  Maximum visual magnitude: -12.7
  Geometric albedo = 0.12

Surface gravity = 1.62 m/s = 5.31 ft/s (~1/6 that of Earth)
Escape velocity: 2.37 km/s = 5301.54 miles/hr
Nearside crust. thick.= 58(8) km
Farside crust. thick. ≈ 80 - 90 km
Mean crustal density = 2.97(.07) g/cc
GM = 4902.798(.005) km/s
Heat flow, Apollo 15 = 3.1(.6) mW/m
Heat flow, Apollo 17 = 2.2(.5) mW/m
k2 = 0.0302(.0012)
Induced magnetic mom. = 4.23x10^22 Gcm
Magnetometer moment = 435(15)

DYNAMICAL CHARACTERISTICS:
  Mean angular diameter = 31' 05.2"

ROTATIONAL & ORBITAL DATA:
   Sidereal Rotational Period: 27.321582 d (tidally locked to Earth)
   Rotation Velocity: 10.35 miles/hr
   Mean motion = 2.6616995x10^-6 rad/s
   Sidereal Orbital Period: 27.321582 d
   Average Orbital Velocity: 1.0 km/s = 2237 miles/hr

Orbit Data:
   Synchronous rotation
   Obliquity to orbit = 6.67
   Semimajor axis, a = 384400 km (Ave dist: 60.3 Earth radii)
   Eccentricity, e = 0.05490
   Inclination, i = 5.145
   Nodal period = 6798.38 d
   Apsidal period = 3231.50 d

Mom. of inertia C/MR2 = 0.3935(.0011)
beta (C-A/B) = 6.31(7215)x10^-4
gamma (B-A/C) = 2.278(82)x10^-4

Comparisons:
Radius: 27% of Earth, 14th largest body (Io > Luna > Europa)
Mass: 1/81.2 of Earth, 14th largest body (Io > Luna > Europa)
Density: 61% of Earth
Magnetic field: None globally, localized residual fields.
Atmosphere: None
Surface gravity: 16% of Earth
Temperature: The temperature on the moon varies from -387 Fahrenheit (-233 Celsius) at night,
to 253 Fahrenheit (123 Celsius) during the day. Because the moon has no atmosphere to
protect it from some of the sun's rays or to help trap heat at night, its temperature varies greatly
between day and night.
Mean surface temperature (day) 107 C
Mean surface temperature (night) -153 C
Maximum surface temperature 123 C
Minimum surface temperature -233 C

Name:
Known as Luna by the Romans; Selene and Artemis by the Greeks.

Spacecraft:
The Soviet Luna 2 was the first spacecraft to visit the Moon in 1959, with
many other orbiters and landers to follow. The Apollo landings from 1969 to
1972 are the only visits by human beings to an extraterrestrial body. The
Moon is also the only body from which samples have been returned to Earth
(until Stardust returns with a sample of comet Wild-2 in 2006, hopefully!).
The first lunar polar orbiter, Clementine, mapped the surface extensively in
1994. Lunar Prospector obtained detailed gravity maps and found strong
evidence for water ice in shadowed craters of both poles.

Viewing:
The moon is the only solar system body with surface features visible with
the naked eye and small binoculars. Try viewing near quarter phase to see
well defined craters and mountains.
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