Astrophysics (Index)About

planet

(round object orbiting a star that clears out its own orbital path)

The term planet is used for major objects orbiting stars other than binary-star companions. Detected extra-solar planets are so-far sufficiently large that there is no need to consider whether they qualify as "major". For the solar system, the IAU distinction is that the object be sufficiently massive that gravity draws it into a spherical shape and also massive enough to dynamically clear any planetesimals out of the path of its own orbit. This latter distinction (termed clearing the neighborhood) distinguishes it from a dwarf planet, and is what disqualified Pluto from being a "normal planet" (and incidentally disqualifies Ceres, also once considered a planet), leaving the solar system with eight known planets out of the hundreds of thousands of objects known to orbit the Sun.

The object must also not be so massive as to trigger fusion and thus qualify as a star. The IAU considers an object above 13 Jupiter-masses to be a brown dwarf companion, that mass being an adopted round number of the mass that could trigger deuterium fusion. (This threshold is likely to be revised as astronomers debate the natural line between the two object types.)


(solar system,object type)
Further reading:
http://en.wikipedia.org/wiki/Planet

Referenced by pages:
abiotic oxygen
abundances
accretion
accretion rate
aerosols
airglow
albedo
Automated Planet Finder (APF)
appulse
asteroid
asteroid belt
astrobiology
astrometry
astronomical object
astronomical quantities
atmosphere
atmosphere formation
atmospheric escape
atmospheric model
atmospheric temperature profile
atmospheric tide
aurora
axisymmetric
Black Widow Pulsar (B1957+20)
baroclinicity
barrier
basalt
Bayer designation
BepiColombo
biofluorescence
biosignature
black body (BB)
blended spectra
binary minor planet (BMP)
Bohr model
bow shock
brown dwarf (BD)
Brunt-Väisälä frequency
bulk density
carbon (C)
carbonate-silicate cycle
carbon planet
Cassini
chemical equilibrium (CE)
celestial mechanics
centaur
Ceres
chemodynamics
CHEOPS
chirp
chondrite
CIG
circumbinary planet
circumplanetary disk
circumstellar disk
California-Kepler Survey (CKS)
cosmic microwave background (CMB)
carbon dioxide (CO2)
cold trap
comet planet
coronagraph
COROT
corotation torque
crustal magnetism
crustal plates
cryogenic spectroscopy
cryovolcano
Carl Sagan Institute (CSI)
dark matter
dead zone
debris disk
demographics
destriping
dipole
direct imaging
double-line spectroscopic binary (SB2)
double star
double transit
Drake equation
drogue chute
Deep Space 1 (DS1)
NASA Deep Space Network (NASA DSN)
dwarf planet
dynamical instability
dynamo
Earth
Earth analog
earthshine
eccentricity (e)
exoplanet eclipse light curve
eclipse mapping
ecliptic
effective temperature (Teff)
electron orbital
electrostatic barrier
ephemeris
epicycle
EPOXI
equatorial coordinate system
equilibrium condensation model
equilibrium temperature (Teq)
escape velocity (Ve)
ESO 3.6m Telescope
Europa
event horizon (EH)
exoearth
extra-solar planet
facula
failed binary
falling evaporating body (FEB)
field
51 Eridani b
51 Pegasi b (51 Peg b)
fixed star
Flamsteed designation
fluorescence
fractionation
fragmentation barrier
Fulton gap
fusion
Gal
gas giant
gas planet
general circulation model (GCM)
geochemistry
gravitational instability (GI)
giant planet
giant planet formation
giant star
Gemini Planet Imager (GPI)
gravimetry
gravitational instability model
gravitational lensing
gravity
gravity anomaly
gravity sounding
greenhouse effect
molecular hydrogen dissociation front (H2 dissociation front)
habitability
habitable zone (HZ)
Hadley cell
HARPS
HARPS-N
HCI
HD 189733 b
HD 209458 b
heliocentric system
helium planet
Hobby-Eberly Telescope (HET)
Hill stability
hot Jupiter (HJ)
HR 8799
humidity
hydrodynamic escape
hydrology
hydrostatic equilibrium
International Astronomical Union (IAU)
ice giant
impact
inflated radii
infrared (IR)
instability region
internal gravity wave
Io
ion engine
ionosphere
interplanetary medium (IPM)
irregular moon
isolation mass
isophote
isostasy
isothermal core
intertropical convergence zone (ITCZ)
J1407
J2
epoch J2000.0
JUICE
Jupiter
Kapteyn's Star
K-type star (K)
KELT
Kelvin waves
Kepler Telescope
Kepler-16b
Kepler-186f
Keplerian disk
Keplerian orbit
Kepler radius
Kepler's laws
kilometer size barrier
Keck Planet Finder (KPF)
Keck Planet Imager and Characterizer (KPIC)
Kuiper Belt (K Belt)
Lagrange stability
Lagrangian point
Laplace-Lagrange secular theory
late heavy bombardment (LHB)
Lindblad torque
line broadening
liquid planet
long-period comet
MACHO
MACHO Project
Magellan Telescopes
magma ocean
magnetic anomaly
magnetic energy spectrum
magnetic field
magnetic induction
magnetometer
Mars
Mars crosser (MC)
mass
mass extinction
mass ratio (μ)
mass spectrometer
maximum iron fraction
M dwarf
mega-Earth
Mercury
meridian
meridional flow
metallicity (Z)
gravitational microlensing
minimum mass (m sin i)
mini-Neptune
minor planet
MITgcm
MMRTG
moment of inertia factor
moon
Moon formation
Minor Planet Center (MPC)
Microlensing Planet Search (MPS)
NASA
N-body problem
N-body simulation
nebula
nebular hypothesis
Neptune
neutron scattering
Nice model
NIRPS
normal mode
obliquity
occultation
occultation observations
oligarch
opposition
orbital inclination
orrery
Other Worlds Laboratory (OWL)
polycyclic aromatic hydrocarbon (PAH)
paleomagnetism
PALMS
particle spectrometer
planetary boundary layer (PBL)
Planet Crossing Asteroid Survey (PCAS)
phase angle
phase curve
photoevaporation
Planet Nine
planetary differentiation
planetary embryo
planetary migration
planetary protection
planetary science
planetary system
planet demographics
planetesimal
planet formation
Planet Hunters (PH)
planetoid
planet structure
planet type
PLATO
Pluto
planetary mass object (PMO)
planetary nebula (PN)
point source
polar cyclone
protoplanetary nebula (PPN)
precession
protected region
protoplanet
protoplanetary disk (PPD)
provisional designation
PSR 1257+12
pulsar timing array (PTA)
vortensity (PV)
Q factor
radar
radial velocity (RV)
radioactive heating
Rayleigh scattering
red dwarf
reducing atmosphere
regolith
retrograde hot Jupiter
retrograde orbit
radiative forcing (RF)
ring system
Laplace radius (rL)
Rossby number (Ro)
Roche limit
ROCKE-3D
rocky planet
RODEO
Rossby waves
rotation period
radial velocity method
Rossby wave instability (RWI)
Saturn
scale height (H)
scattering
secondary eclipse
secular
seismic waves
search for extraterrestrial intelligence (SETI)
shepherd moon
signatures of formation
Space Launch System (SLS)
solar system
sounder
SPACEWATCH
spectral signature
spectropolarimetry
SPECULOOS
spherical harmonics
star formation (SF)
stellar radius determination
subsatellite
super-Earth
superionic ice
superrotating wind
surface brightness (SB)
surface gravity
surface reaction
surface temperature
survey-based designator
Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS)
synodic period
Taylor-Proudman theorem
terminator
Transiting Exoplanet Survey Satellite (TESS)
thermal runaway
three dimensional model
tidal capture
tidal force
tidal locking
tidal Q
timescale (t)
Titius-Bode law
Telescopio Nazionale Galileo (TNG)
theory of figures (TOF)
transit
transiting planet
transitional disk
transit method
transit spectroscopy
transmission spectroscopy
terrestrial time (TT)
twinkling
ultraviolet (UV)
Uranus
Venus
visible light
volatile material
vortex
Voyager
vegetation red edge (VRE)
WASP
water-ice planet
water vapor planet
water world
wide binaries (WB)
weathering
Yarkovsky effect
Y-type star (Y)
zonal flow
zone

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