Lunar Fact Sheet

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Lunar Fact Sheet

(glossary entry)


Description

Students of the Moon's surface features are often interested in additional facts related to distances and times. How large is it? How fast does it spin? etc.
 
  What appears to be an up-to-date and authoritative source of such information is the National Space Science Data Center's Moon Fact Sheet.

Additional Information

  • For comparison, here are the (often rather technical) lunar constants currently being used by the equally authoritative JPL Horizons on-line ephemeris system:


Revised: Mar 11, 1998 Moon / (Earth) 301

PHYSICAL PROPERTIES:
Radius = 1737.53+-0.03 km
Mass = 734.9x10^20 kg
Density = 3.3437 gm cm^-3
Geometric albedo = 0.12
V(1,0) = +0.21
GM = 4902.798+-.005 km^3/s^2
Earth/Moon mass ratio = 81.300587
Surface gravity = 1.62 m s^-2
Nearside crust. thick.= 58+-8 km
Farside crust. thick. = ~80 - 90 km
Heat flow, Apollo 15 = 3.1+-.6 mW/m^2
Heat flow, Apollo 17 = 2.2+-.5 mW/m^2
Mean crustal density = 2.97+-.07 g/cm^3
k2 = 0.0302+-.0012
Induced magnetic mom. = 4.23x10^22 Gcm^3
Magnetometer moment = 435+-15

DYNAMICAL CHARACTERISTICS:
Mean angular diameter = 31'05.2" [0.5181 deg = 1865.2 arc-sec]
Orbit period = 27.321582 d
Obliquity to orbit = 6.67 deg
Eccentricity = 0.05490
Semi-major axis, a = 384400 km
Inclination = 5.145 deg
Mean motion, rad/s = 2.6616995x10^-6
Nodal period = 6798.38 d
Apsidal period = 3231.50 d
Mom. of inertia C/MR^2= 0.3935+-.0011
beta (C-A/B), x10^-4 = 6.31(72+-15)
gamma (B-A/C), x10^-4 = 2.278(8+-2)

  • And here is a much older, but more observer-oriented list of (slightly out-dated) facts compiled by Elger and published as an appendix to his 1895 book. Metric and decimal equivalents of some of the numbers have been added in square brackets, but his basic data has not been altered or updated.


LUNAR ELEMENTS

  • Moon's mean apparent diameter - 31 min. 8 sec. [0.5189 deg = 1868 arc-sec]
  • Moon's maximum apparent diameter - 33 min. 33.20 sec. [0.5592 deg = 2013.2 arc-sec]
  • Moon's minimum apparent diameter - 29 min. 23.65 sec. [0.4899 deg = 1763.65 arc-sec]
  • Moon's diameter, in miles - 2163 miles. [3481 km]
  • Volume (earth's = 1) - 1/49.20 or 0.02033.
  • Mass (earth's = 1) - 1/81.40 or 0.0128.
  • Density (earth's = 1) - 0.60419, or 3.444 the density of water (water being unity).
  • Surface area, about 14,600,000 square miles (earth's surface area, 196,870,000 miles) [37,800,000 / 316,830,000 sq km]
  • Earth's surface area = 1, moon's - About 2/27 or 0.07407.
  • Action of gravity at surface - 0.16489 or 1/6.065 of the earth's.
  • Surface of moon never seen - 0.4100.
  • Surface of moon seen at one time or another - 0.5900.
  • Synodical revolution, or interval from new moon to new moon (commonly called a lunation) - 29 d. 12 h. 44 m. 2.684 s. - 29.5305887 days.
  • Sidereal revolution, or time taken in passing from one star to the same star again - 27 d. 7 h. 43 m. 11.545 s. - 27.3216614 days.
  • Tropical revolution, or time taken in passing from "the first point of Aries" to the same point again - 27 d. 7 h. 43 m. 4.68 s. - 27.321582 days.
  • Anomalistic revolution, or time taken in passing from perigee to perigee - 27 d. 13 h. 18 m. 37.44 s. - 27.55460 days.
  • Nodical revolution, or time taken in passing from rising node to rising node - 27 d. 5h. 5m. 35.81 s. - 27.21222 days.
  • Distance (mean) in terms of the equatorial radius of the earth - 60.27.
  • Distance in miles (mean) - 238,840 miles. [384,376 km]
  • Distance, maximum - 252,972 miles. [407,119 km]
  • Distance, minimum - 221,614 miles. [356,653 km]
  • Mean excentricity of moon's orbit - 0.05490807.
  • Inclination of moon's orbit to the ecliptic (mean) - 5 deg. 8 min. 39.96 sec. [5.144433 deg]
  • Inclination of moon's axis to the ecliptic - 87 deg. 27 min. 51 sec. [87.4642 deg]
  • Inclination of moon's equator to the ecliptic - 1 deg. 32 min. 9 sec. [1.5358 deg]
  • Maximum libration in latitude - 6 deg. 44 min. [6.73 deg]
  • Maximum libration in longitude - 7 deg. 45 min. [7.75 deg]
  • Maximum total libration from earth's centre - 10 deg. 16 min. [10.27 deg]
  • Maximum diurnal libration - 1 deg. 1 min. 28.8 sec. [1.02467 deg]
  • Angle subtended by one degree of selenographical latitude and longitude at the centre of the moon's disc, when at its mean distance - 16.566 sec.
  • Length of a degree under these conditions - 18.871 miles. [30.370 km]
  • Selenographical arc at the centre of the moon's surface, subtending an angle of one second of arc - 3 min. 37.31 sec. [0.060364 deg]
  • Miles at the centre of the moon's disc, subtending an angle of one second of arc - 1.139 [1.833 km]
    • [It must be remembered that this value is increased, in departing from the centre, in the proportion of the secants of the angular distance from the centre.]
  • Period of similar phase - 59 d. 1h. 28m. = 2 lunations.
    • Or, more accurately - 442 d. 23 h. = 15 lunations.



LPOD Articles


Bibliography

See also:
  • Colgrove, W. G. 1930. The Moon - A Concise Summary. Journal of the Royal Astronomical Society of Canada, Vol. 24, p. 409.
  • Roncoli, Ralph B. 2005. Lunar Constants and Models Document. JPL Technical Document D-32296. (PDF file with facts compiled for use by planners associated with NASA's upcoming lunar reconnaisance missions of the next few years -- heavy on things affecting orbital dynamics and positioning)



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