Astrophysics (Index)About

moon

(a planet's natural satellite, such as Earth's)

A moon is a natural satellite of a planet. (A satellite is an object orbiting a planet, and can either be natural, like the Moon, or artificial, like HST.)

More specifically, the Earth's natural satellite is known as the Moon:

Current theory on the formation of the Moon favors the giant-impact hypothesis, that the Moon coalesced from orbiting debris from an impact between Earth and a Mars-sized planet, very early in solar system history. Characteristics of lunar material show a striking similarity to that of Earth in abundances and radioactivity, as compared to other planets such as Mars. This supports the giant impact hypothesis, yet it is too much like Earth, providing no evidence of different material from the presumed impacting planet.

The moon is equivalent to a rocky planet within the Sun's habitable zone but that hasn't led to its habitability. It essentially lacks water though some exists as ice in shadows and Moon surface material may contain a very small amount.

The Moon is thought to have a relatively small iron core and does not have the type of magnetic field that suggests a current dynamo and it is thought the Moon is internally solid (unlike Earth). The Moon's extant magnetic rocks might reveal its early thermal history, from before it cooled.

Tidal locking keeps the Moon's same face toward the Earth, and it rotates roughly perpendicular to the ecliptic, so valleys at its poles have shadows that never receive light from the Sun. Places cold enough to keep water ice frozen are called Lunar cold traps.

Other well-known solar-system moons:

Planet Well-known moons 11/2022 total
moon count
Mars Deimos, Phobos 2
Jupiter Io, Europa, Ganymede, Callisto (the Galilean Moons) 80
Saturn Titan, Mimas, Enceladus, Tethys, Dione, Rhea, Iapetus, Hyperion 83
Uranus Miranda, Ariel, Umbriel, Oberon, Titania 27
Neptune Triton 14
Pluto Charon 5

No moons are known for Mercury or Venus, but moons have been found for more than 400 minor planets (minor planet moons), e.g., minor planet Orcus.


(moon,object,object type,Earth)
Further reading:
https://en.wikipedia.org/wiki/Moon
https://en.wikipedia.org/wiki/Natural_satellite
https://en.wikipedia.org/wiki/Minor-planet_moon
https://solarsystem.nasa.gov/moons/earths-moon/overview/
https://solarsystem.nasa.gov/moons/overview/
RedshiftParsecs
/Distance
Lightyears
/Lookback Years
  
~0384402km~0lymoon

Referenced by pages:
47 Tucanae (47 Tuc)
abundances
aerosols
albedo
ammonia (NH3)
angular distance
apparent magnitude (m)
appulse
Arecibo Occultation Survey (AO)
astrobiology
astrometry
astronomical quantities
astronomical unit (AU)
atmosphere
atmospheric temperature profile
barycenter
basalt
bathymetry
Callisto
Carl Sagan Institute (CSI)
Cassini
Catalog of Circumpolar Stars (Groombridge)
celestial event
celestial mechanics
Ceres
chemical equilibrium (CE)
CIG
circular polarization ratio (CPR)
circumplanetary disk
cold trap
complex crater
corotation resonance
crustal magnetism
crustal plates
cryogenic spectroscopy
cryovolcano
destriping
disk
double transit
Dragonfly (NF4)
Dragonfly Telephoto Array
drogue chute
dwarf planet
dynamo
Earth
earthshine
eccentricity (e)
Enceladus
Enceladus Life Finder (ELF)
Enceladus Orbilander
ephemeris
escape velocity (Ve)
Europa
Europa Clipper
Europa Lander
EXOSAT
exosatellite
exosphere
facula
flyby
free-air anomaly
Galileo
Ganymede
general circulation model (GCM)
geochemistry
Goddard gravity model (GGM)
GRAIL
gravimetry
gravitational potential model
gravitational potential well
gravitationally bound
gravity
gravity anomaly
greenhouse effect
habitability
habitable zone (HZ)
Hadley cell
halo orbit
Haumea
High Energy Transient Explorer (HETE)
Hill radius
Hipparchus
humidity
hydrogen cyanide (HCN)
hydrology
Hyperion
impact
in situ
internal gravity wave (IGW)
International Cometary Explorer (ICE)
intertropical convergence zone (ITCZ)
Io
ion engine
ionosphere
irregular moon
isolation mass
J2
JUICE
Juno
Jupiter
Kepler's laws
Kozai mechanism (ZLK)
Lagrangian point
Laplace radius (rL)
late heavy bombardment (LHB)
LCROSS
LEDA
libration
limb darkening
Lindblad resonance
Love number
low Earth orbit (LEO)
Lunar Prospector
Lunar Reconnaissance Orbiter (LRO)
lunar swirl
lunar water
Lunar-based Ultraviolet Telescope (LUT)
Lyapunov time
magnetic anomaly
magnetic field
magnetic induction
magnetometer
Mars
mass
mass extinction
mass spectrometer
Mercury
meridian
meteorite
meteoroid
methane (CH4)
minor planet
MMX
moment of inertia factor
Moon formation
nebula
Neptune
neutron scattering
nutation
obliquity
occultation observations
orbital decay
orbital inclination
orbital period
orbital resonance
orbital speed
orrery
Other Worlds Laboratory (OWL)
paleomagnetism
particle spectrometer
phase angle
phase curve
pingo
planet
planet formation
planetary differentiation
planetary protection
planetary science
planetoid
Pluto
point source
polycyclic aromatic hydrocarbon (PAH)
porosity
precession
precession of the equinoxes
primary
Psyche
quake
quasi-satellite
radar
radioactive dating
radioactive heating
rare designator prefixes
Rayleigh scattering
reduced mass
regolith
retrograde orbit
Roche limit
ROCKE-3D
Roemer delay
rotation period
Saturn
seismic waves
SELENE
shepherd moon
sidereal
SMART-1
solar day
solar eclipse
solar mass (MSun)
solar system
solar system object (SSO)
Space Launch System (SLS)
SPACEWATCH
SSSB (SB)
standard gravitational parameter (μ)
stellar radius determination
subsatellite
substellar point
superrotating wind
surface brightness (SB)
synodic period
terminator
Terrestrial Time (TT)
THEMIS
theory of figures (TOF)
tidal force
tidal heating
tidal locking
tidal migration
tidal Q
tide
TiNy Titans (TNT)
Titan
trans-Neptune object (TNO)
transit
Triton
twinkling
ultraviolet astronomy
Uranus
USNO
Van Allen belts
Venus
visible light
XRISM
XZ Catalog of Zodiacal Stars (XZ)

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