Astrophysics (Index)About

atmosphere

(envelope)
(gas surrounding astronomical object)

An atmosphere is basically any gas surrounding a celestial body such as a star or a planet. It is sometimes referred to as an envelope around the body. (For planets, the term envelope has also been used for the solid material above the core, a common usage in discussions of planet formation and early life, in which case the term is sometimes qualified to distinguish the intent, e.g., gaseous envelope.) A stellar atmosphere is essentially the external gas that we can see through, i.e., transmits visible light, but that of a planet or moon may include opaque portions, such as that of Venus or Jupiter, as well as the Earth's clouds. (The rest of this page is essentially about planet and moon atmospheres except that the comments regarding spectroscopy might apply to stars.)

A planet or moon atmosphere may be a significant portion of its mass, e.g., a gas giant, or nearly nothing, e.g., the Moon.

bodyfraction which is gas
Jupiter>95%
Uranus and Neptune~10%
Venus0.01%
Earth1/1,000,000
Moon3×10-19

The body's atmosphere is of interest in itself as well as the hints it provides regarding the character of the body, and also as a factor in habitability and biosignatures. Emitted EMR and transmission spectroscopy are hints to its makeup, and any evidence of chemical mixtures that should not last, i.e., out of chemical equilibrium, indicates something replenishing the mixture, e.g., a reaction with the surface, or a emission from inside the planet, or life. Atmospheric models and climate models (e.g., one dimensional climate models or tailored general circulation models) are created to study and explain planetary atmospheres.

The Earth's atmosphere serves as a well-studied example of a planetary atmosphere. Its effects on astronomical observation (atmospheric windows and seeing) have motivated analysis also useful for understanding other atmospheres.

Atmospheric retention and its lack (atmospheric escape) are of interest, both to explain observations of a body's atmosphere (or its lack) and to establish that an atmosphere is being replenished, if it ought to be gone. Its temperature, the body's gravity, and the mass of the molecules determine if some molecules reach escape velocity and are lost: for example, hydrogen molecules are sufficiently light that the Earth's temperature assured they haven't remained. Photodissociation can break molecules into smaller units, affecting retention, as can gravitational separation, i.e., chemical differentiation, stratification of the atmosphere by molecular weight.

The phrase bulk atmosphere (and similar phrases, such as bulk planetary atmosphere) refers to the entire atmosphere, e.g., when speaking of its composition, it can indicate you're speaking of components of the entire atmosphere rather than what is at some particular portion.


(planets,stars,Sun,gas)
Further reading:
https://en.wikipedia.org/wiki/Atmosphere
https://en.wikipedia.org/wiki/Stellar_atmosphere
https://en.wikipedia.org/wiki/Extraterrestrial_atmosphere
https://solarsystem.nasa.gov/news/436/10-things-planetary-atmospheres/
https://www.britannica.com/science/atmosphere/The-atmospheres-of-other-planets
https://www.planetary.org/space-images/the-atmospheres-of-the-solar-system
https://www.psi.edu/epo/faq/atmosphere.html
https://www.oxfordreference.com/display/10.1093/oi/authority.20110803100530873

Referenced by pages:
51 Eridani b
abiotic oxygen
ablation
absorption
absorption line
acetylene (C2H2)
adaptive mesh refinement (AMR)
adaptive optics (AO)
admittance
advection
aerosols
AGILE
air shower
airglow
airmass
albedo
ALMACAL
antimatter
apparent magnitude (m)
ARGOS
ARIEL
astrometry
atm
ATMO
atmosphere formation
atmospheric escape
atmospheric model
atmospheric temperature profile
atmospheric tide
atmospheric window
aurora
autoconversion rate
Autonomous Space Transport Robotic Operations (ASTRO)
bar
baroclinicity
binary neutron star (BNS)
biosignature
black hole merger
Black Widow Pulsar (B1957+20)
bow shock
brown dwarf (BD)
Brunt-Väisälä frequency
BT-Settl
carbon dioxide (CO2)
carbon star (C)
carbonate system
carbonate-silicate cycle
Cassini
chemical equilibrium (CE)
Cherenkov detector
Cherenkov radiation
Cherenkov Telescope Array (CTA)
chopping mirror
chromosphere
CMB anisotropies
cold trap
Colossus Telescope
comet
core collapse supernova (CCSN)
Coriolis force
cosmic rays (CR)
CUTE
DAVINCI
deformable mirror (DM)
differential spectroscopy
diffraction limited
diffractive interstellar scintillation (DISS)
DISORT
Dragonfly (NF4)
drogue chute
dust devil
dynamical instability
Earth
Earth analog
earthshine
eccentricity (e)
eclipse mapping
emission
emission coefficient (j)
emission line
equation of radiative transfer (RTE)
ethylene (C2H4)
European Space Research Organisation (ESRO)
EUSO-SPB
evaporation
ExoCTK
exoplanet eclipse light curve
exosphere
extinction
extreme ultraviolet (EUV)
fluorescence
focal plane tilt
forbidden line
forward model
Fraunhofer lines
Fred Young Submillimeter Telescope (FYST)
free streaming
Fulton gap
G-CLEF
Galileo
Galileo Observatory
gamma rays (GR)
gas flow
Gemini Observatory
general circulation model (GCM)
geosignature
giant planet
giant planet formation
GJ 1132 b
GJ 1214 b
gravity wave
gray atmosphere
greenhouse effect
habitability
Hadley cell
HD 80606 b
helium 1083 nm line
helium planet
helium rain
High Elevation Antarctic Terahertz Telescope (HEAT)
High-altitude Water Cherenkov Observatory (HAWC)
high-resolution imaging
Hisaki
HITEMP
HITRAN
homopause
Hope Probe
humidity
hydrodynamic equations
hydrodynamic escape
hydrodynamics
hydrology
hydrostatic equilibrium
image stabilization
inertial wave
infrared (IR)
Infrared Telescope Maffei (ITM)
intensity interferometer
internal gravity wave (IGW)
intertropical convergence zone (ITCZ)
ion engine
ionosphere
James Webb Space Telescope (JWST)
Jeans escape
Jeans parameter (λ)
jet stream
Juno
Jupiter
K2-18b
Kelvin waves
Kelvin-Helmholtz instability (KHI)
Kepler-79
Kuiper Airborne Observatory (KAO)
lattice Boltzmann method (LBM)
light curve
light pollution
limb
limb darkening
line blanketing
liquid planet
Lorentz force
low Earth orbit (LEO)
lucky imaging
lunar water
Lyman alpha (Ly-α)
Lyman-break galaxy (LBG)
M dwarf
magnetohydrodynamics (MHD)
magnetometer
Mars
Mars 2020
Mars Express
mass density
mass extinction
mass spectrometer
Mauna Kea
MAVEN
Mercury
meridional flow
MESSENGER
metallicity (Z)
meteorite
meteoroid
methane (CH4)
microwave
Mie scattering
millimeter astronomy
mini-Neptune
MITgcm
mixing length theory
mixing ratio
molecular hydrogen dissociation front (H2 dissociation front)
MUSCLES
natural astronomical telescopes
near infrared (NIR)
Neptune
neutron spectrometer
nitrogen (N)
nova (N)
number density (n)
numerical weather prediction (NWP)
observational astronomy
occultation
one dimensional climate model
optical depth (τ)
orbital decay
Orbiting Wide-angle Light Collectors (OWL)
OSIRIS-REx
PAH emissions
PanCET
parts per million (PPM)
passive dust
phase curve
PHOENIX stellar model
phosphorus (P)
photoevaporation
photometry
PICASO
Pioneer Venus Orbiter (PVO)
plane wave
plane-parallel atmosphere
planet formation
planet structure
planetary boundary layer (PBL)
planetary differentiation
planetary protection
planetary science
plasma wave
POEMMA
pointing error (PE)
post-common-envelope binary (PCEB)
precipitable water vapor (PWV)
radial velocity method
radial-drift barrier
radiation pressure
radiative forcing (RF)
radiative transfer (RT)
radiative transfer code (RT code)
radioactive dating
ram pressure
RASCALL
Rayleigh scattering
red noise
reducing atmosphere
refraction
regolith
retrieval
Reynolds decomposition
Reynolds number (Re)
Richardson number (Ri)
Roche lobe
rocky planet
Rossby number (Ro)
Rossby radius of deformation
Rossby waves
scale height (H)
SCAP
scintillator
seeing
SELENE
shift-and-add
signal-to-noise ratio (SNR)
silicate weathering feedback
sky subtraction
solar constant
Solar Dynamics Observatory (SDO)
sounder
sounding rocket
speckle imaging
spectral energy distribution (SED)
spectroscopy
stationkeeping
stellar atmosphere
stellar structure
stellar temperature determination
strewn field
Subaru Telescope
subgrid-scale physics
sublimation
submillimeter astronomy
Sun surface features
super-Earth
SuperBIT
supercritical fluid (SCF)
superrotating wind
surface gravity (g)
surface reaction
surface temperature
Suzaku
TAM
Tau-REx
Taylor-Proudman theorem
technosignature
telescope
Telescope Array Project (TA)
telluric line
telluric star
thermal wind
Thorne-Żytkow object (TZO)
three dimensional model
tidal capture
tidal migration
tide
time-ordered data (TOD)
TIMED
timescale (t)
tip of the red-giant branch (TRGB)
Titan
titanium (Ti)
tomography
Trace Gas Orbiter (TGO)
transit spectroscopy
transiting planet
transition region
transmission spectroscopy
turbulence
twinkling
two-stream approximation
Ultimate Spitzer Phase Curve Survey (USPCS)
ultraviolet (UV)
Upper Atmosphere Research Satellite (UARS)
Uranus Orbiter and Probe
Venus
Venus Express
very-high-energy gamma rays (VHEGR)
visible light
volatile material
vortex
WASP-43b
water (H2O)
water lines
water vapor planet
water world
weathering
Wide Field Infrared Explorer (WIRE)
X-ray
zonal flow
zone

Index