Term Index (D)
Astrophysical terms and names of things beginning with the letter D.
D1
D2
D3
D4
D5
D6
DA
DB
DC
DD
DE
DF
DG
DH
DI
DJ
DK
DL
DM
DN
DO
DP
DQ
DR
DS
DT
DU
DV
DW
DX
DY
- D (deuterium): hydrogen isotope with one neutron
- D: see CFHTLS
- D: see rare designator prefixes
- D burning (deuterium burning): any fusion reaction starting with deuterium
- D lines: see sodium
- D orbital: see electron orbital
- D²: see DEEP2
- D-σ relation: see Faber-Jackson relation
- D-CIXS: see SMART-1
- D-type galaxy
- D/1993 F2 (Comet Shoemaker-Levy 9): comet that collided with Jupiter in 1994
- D1: see CFHTLS
- D2: see CFHTLS
- D3: see CFHTLS
- D3A
- D4: see CFHTLS
- D5
- D56: a target survey field of ACT telescope
- D56: a target survey field of ACT telescope
- D6
- D56: a target survey field of ACT telescope
- D2O: see deuterium
- DH: see Hubble constant
- DL (luminosity distance): distance to an object based upon the distance's effect on received flux
- dL (luminosity distance): distance to an object based upon the distance's effect on received flux
- Dp: see deuterium
- Db: see Big Bang nucleosynthesis
- DA (Dominion Observatory 1420 MHz Source Catalog): 1960s survey of northern-hemisphere radio sources
- DA: see Cassini
- DA: see double star designation
- Da (dalton): mass unit used on atomic scale
- Dall-Kirkham telescope: type of reflector telescope
- dalton: mass unit used on atomic scale
- dalton: see mass
- DAMA/LIBRA: dark matter detection experiment in Italy
- ANAIS-112: dark matter detection experiment in Spain
- COSINE-100: dark matter detection experiment in South Korea
- DAMA/NaI: see DAMA/LIBRA
- Damocles: see damocloid
- damocloid: minor planet with a comet-like orbit
- damocloid family: see damocloid
- damped Lyman alpha absorber: object producing broadened lines in a Lyman alpha forest
- damped wings: see damping profile
- damping
- damping profile: mathematical shape that models some types of spectral line broadening
- damping tail: see diffusion damping
- damping wing signature: see damping profile
- damping wings: see damping profile
- DAN: see Mars Science Laboratory
- DANCe (Dynamical Analysis of Nearby Clusters): survey of stars in stellar clusters
- Daniel K. Inouye Solar Telescope (DKIST): 4 m solar telescope at Haleakala Observatory
- Danish
- Danish 1.54-m telescope: see La Silla Observatory
- Danjon astrolabe: instrument to measure the position of stars
- Danjon prismatic astrolabe (Danjon astrolabe): instrument to measure the position of stars
- Danks: see rare designator prefixes
- DAO (Dominion Astrophysical Observatory): long-standing observatory in British Columbia
- DAOPHOT: 1980s CCD photometry software
- DAOPHOT: 1980s CCD photometry software
- DAOPHOT II: see DAOPHOT
- Daphnis: see shepherd moon
- Darcy velocity: see Darcy velocity field
- Darcy velocity field: vector field indicating a kind of seepage in a porous medium
- Darcy's law: see Darcy velocity field
- dark age: interval when the universe's hydrogen atoms were neutral
- dark ages (dark age): interval when the universe's hydrogen atoms were neutral
- dark burst: see gamma-ray burst
- dark cloud (dark nebula): cloud that obscures stars behind it
- dark current: see photodiode
- dark electron: see atomic dark matter
- dark energy: energy theorized to accelerate the expansion of the universe
- Dark Energy Camera
- Dark Energy Survey: survey aimed at mapping the universe's expansion
- DECaLS: survey imaging part of SDSS footprint with DECam
- dark energy density parameter: see Lambda-CDM model
- Dark Energy Space Telescope
- Dark Energy Spectroscopic Experiment
- Dark Energy Spectroscopic Instrument: new instrument for measuring red-shift of distant objects
- Dark Energy Spectroscopic Instrument: see Mayall 4m Telescope
- dark energy star: theoretical alternative to black holes
- Dark Energy Survey: survey aimed at mapping the universe's expansion
- dark flow: non-random patterns in peculiar velocity of galaxy clusters
- dark galaxy: gas and dark matter of a galaxy but with no stars
- dark halo (dark matter halo): hypothetical dark matter throughout and surrounding a galaxy
- dark matter: matter in galaxies and galaxy clusters suggested by their gravity
- dark matter annihilation: particle/antiparticle annihilation of WIMPs
- dark matter density parameter: see Lambda-CDM model
- dark matter detector: type of particle detector attempting to detect WIMPs
- dark matter dynamical friction: see dynamical friction
- dark matter equation of state (cosmological equation of state): equation of state of dark matter
- dark matter experiment (dark matter detector): type of particle detector attempting to detect WIMPs
- dark matter filament: hypothesized type of long, thin volume of dark matter
- cosmic web: hypothesized structure of the dark matter throughout the universe
- filament: linear volume of high molecular gas density within a galaxy
- dark matter halo: hypothetical dark matter throughout and surrounding a galaxy
- dark matter particle detector (dark matter detector): type of particle detector attempting to detect WIMPs
- dark matter star (dark star): theoretical star-like object heated by dark-matter annihilation
- exotic star: term for theoretical stars not made of atoms/ions
- dark matter web (cosmic web): hypothesized structure of the dark matter throughout the universe
- dark nebula: cloud that obscures stars behind it
- cloud: higher-density region of space
- LDN 1527: dark nebula in Taurus
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- nebula: cloud of dust and gas
- reflection nebula: nebula made visible by light it scatters from nearby stars
- dark night sky paradox (Olbers' paradox): argument using the dark of the sky regarding the nature of the universe
- dark photon: see atomic dark matter
- dark proton: see atomic dark matter
- dark radiation: see atomic dark matter
- dark sky: sky with limited light pollution
- dark star: theoretical star-like object heated by dark-matter annihilation
- exotic star: term for theoretical stars not made of atoms/ions
- dark-matter-free galaxy: galaxy showing signs of no dark matter
- dark-sky park: see dark sky
- dark-sky preserve: see dark sky
- dark-sky reserve: see dark sky
- dark-sky site: see dark sky
- DARPA
- Dartmouth College
- Dartmouth isochrone: see Dartmouth Stellar Evolution Database
- Dartmouth Stellar Evolution Database: database relating isochrones to stellar parameters
- Dartmouth Stellar Evolution Program (Dartmouth Stellar Evolution Database): database relating isochrones to stellar parameters
- Darwin: past plan for space telescopes acting as an interferometer
- DASCH: project to digitize Harvard astronomy plates
- DASH345: see Atacama Submillimeter Telescope Experiment
- DASI: 2000-2003 South Pole CMB telescope
- data
- data cube: three-dimensional array of numerical data
- data folding: locating periods in data by trial
- data release: publication or distribution of a set of data from a survey
- database
- datacube (data cube): three-dimensional array of numerical data
- daughter nuclide: see radioactive dating
- daughter nuclide: see radioactive decay
- DAV star
- David Dunlap Observatory: see David Dunlap Observatory Catalog
- David Dunlap Observatory Catalog: catalog of dwarf galaxies
- DAVINCI: planned NASA Venus orbiter
- DAVINCI+ (DAVINCI): planned NASA Venus orbiter
- DAW: see double star designation
- Dawes criterion: see angular resolution
- Dawes limit: see angular resolution
- Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
- day: see solar time
- solar day: length of a solar system planet or Moon's day
- DB (Dominion Observatory 10.03 MHz Source Catalog): 1960s survey of northern-hemisphere radio sources
- DB: see rare designator prefixes
- DBB: see rare designator prefixes
- DBMM: see brown dwarf
- DBSB: see rare designator prefixes
- DBSP: see Hale Telescope
- DBV star
- DC: see dark nebula
- DC: see rare designator prefixes
- DCAM3: see Hayabusa2
- DCAM5: see MMX
- DCBH (direct collapse black hole): theoretical means for quick formation of SMBHs
- DCEP: see Cepheid variable
- DCld: see dark nebula
- DCMF (dense core mass function): function describing range of masses of dense cores
- DCT (Lowell Discovery Telescope): 4.3 m telescope at Lowell Observatory, Arizona
- DD: see Type Ia supernova problem
- DD: see supernova progenitor
- DDO (David Dunlap Observatory Catalog): catalog of dwarf galaxies
- DDO 221 (Wolf-Lundmark-Melotte): irregular galaxy at edge of Local Group
- DDO classification (van den Bergh galaxy classification): galaxy classification variant including luminosity
- DDS: see Galileo
- DDT: see detonation
- dE: see dwarf galaxy classification
- de Broglie frequency: see de Broglie wavelength
- de Broglie wave: see de Broglie wavelength
- de Broglie wavelength: wavelength of a particle's matter wave
- de Broglie waves
- de Sitter precession
- de Sitter space: see anti-de Sitter space
- de Vaucouleurs' law (de Vaucouleurs' profile): relation between elliptical galaxy surface brightness and distance from center
- de Vaucouleurs' profile: relation between elliptical galaxy surface brightness and distance from center
- de-Sitter universe: see Einstein-de Sitter model
- dead zone: area within a disk where normal things don't happen
- DEBRA: see cosmic background radiation
- DEBRA: see extragalactic background light
- debris belt: see debris disk
- debris disk: circumstellar disk of dust and debris around a star
- disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
- Debye length: length scale of screening effects within a plasma
- dec (declination): direction coordinate above/below celestial equator
- decadal survey: periodic NASA effort to plan for future astrophysical research
- decadal survey: type of once-a-decade planning report from NASA and the NAS
- DECaLS: survey imaging part of SDSS footprint with DECam
- DECam: see Víctor M. Blanco Telescope
- Dark Energy Survey: survey aimed at mapping the universe's expansion
- DECaLS: survey imaging part of SDSS footprint with DECam
- GW170817: 2017 gravitational wave detection from a neutron star merger
- NOAO Source Catalog: catalog compiled from NOAO public data
- DECam Legacy Survey (DECaLS): survey imaging part of SDSS footprint with DECam
- deceleration parameter: measure of the Hubble expansion's deceleration
- Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO): proposed Japanese space mission to detect gravitational waves
- DECIGO: proposed Japanese space mission to detect gravitational waves
- decimal exponent (dex): a number or ratio's log base 10
- decision tree
- decision tree learning
- declination: direction coordinate above/below celestial equator
- decollimator: see collimator
- deconvolution: see convolution
- mixture: type of probability distribution resulting from two others
- deconvolution free: see DSA-2000
- decouple: see decoupling
- decoupling: some type of particle stops being destroyed as often as it is created
- freeze-out: particles existing long-term after a decoupling
- recombination: time when the universe's ionized hydrogen atoms neutralized
- decretion disk: disk around an astronomical body of its ejected material
- DEEP
- DEEP2: redshift survey of 60,000 galaxies
- deep atmosphere models: see Juno
- Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI): planned NASA Venus orbiter
- deep carbon cycle: see carbonate-silicate cycle
- deep CO2 cycle
- Deep Dish Development Array
- deep drilling: see deep field
- deep drilling field: see deep field
- Deep Ecliptic Survey: late 1990s/early 2000s survey for KBOs
- Deep Extragalactic Evolutionary Probe
- DEEP2: redshift survey of 60,000 galaxies
- Deep Extragalactic Visible Legacy Survey (DEVILS): visible-light spectrographic survey of 56k distant galaxies
- deep field: survey field subject to lengthy observation to identify distant galaxies
- survey field: portion of the celestial sphere where a survey's observations aim
- Deep Impact: mission to create and observe an impact with a comet
- EPOXI: mission using Deep Impact for further exploration
- Deep Impact Extended Investigation
- EPOXI: mission using Deep Impact for further exploration
- Deep Investigations of Neutral Gas Origins: see Australian Square Kilometre Array Pathfinder
- deep learning: description of machine learning using substantial neural networks
- Deep Lens Survey: investigating mass distribution of the universe
- deep Mars-crosser: see Mars crosser
- Deep Multicolor Survey: 1990s optical and infrared deep survey
- Deep Near Infrared Survey of the Southern Sky (DENIS): 1990s southern sky survey of two near-infrared bands
- Deep Space 1: 1998-2001 mission to fly by asteroid
- Deep Space Climate Observatory (DISCOVR): space weather satellite
- Deep Space Network (NASA Deep Space Network): NASA's world-wide radio communication setup
- Deep Spectroscopic High-redshift Mapper (DESHIMA): submillimeter spectrometer
- deep survey: survey using lengthy observation to identify distant galaxies
- Deep Synoptic Array 2000 (DSA-2000): array plan to detect radio transients
- Deep Underground Neutrino Experiment: neutrino experiment under construction
- deep water cycle: see hydrology
- DEEP-GSS: see DEEP2
- DEEP2: redshift survey of 60,000 galaxies
- AEGIS: early 2000s survey study of distant galaxies
- DEEP2 Redshift Survey (DEEP2): redshift survey of 60,000 galaxies
- DEEP2 Survey (DEEP2): redshift survey of 60,000 galaxies
- DEEP3
- DEEP2: redshift survey of 60,000 galaxies
- Deep5
- D56: a target survey field of ACT telescope
- Deep56 (D56): a target survey field of ACT telescope
- Deep6
- D56: a target survey field of ACT telescope
- deferent: see epicycle
- deflagration: see detonation
- deflagration to detonation transition: see detonation
- deformable mirror: mirror that can be flexed for fine control
- deg²: see solid angle
- DeGaS-MC: APEX survey of potential star formation regions in the Magellanic Clouds
- degeneracy: general word meaning a violation of normal rules
- degeneracy (degeneracy weight): number of quantum states with same energy level
- degeneracy pressure: see degeneracy
- degeneracy pressure: see electron degeneracy
- degeneracy weight: number of quantum states with same energy level
- degeneracy weighting (degeneracy weight): number of quantum states with same energy level
- degenerate dwarf (white dwarf): stellar remnant largely of electron degenerate matter
- degenerate electron pressure: see electron degeneracy
- degenerate energy levels: see degeneracy
- degenerate matter: see degeneracy
- degenerate matter: see electron degeneracy
- degenerate perturbation problem: see perturbation theory
- degenerate star: see compact object
- degree: see CMB anisotropies
- degree: see arcsecond
- degree: see spherical harmonics
- kelvin: unit of temperature scale starting at absolute zero
- Degree Angular Scale Interferometer (DASI): 2000-2003 South Pole CMB telescope
- degree of dissociation: see degree of ionization
- degree of ionization: fraction of material consisting of ions
- degrees: see arcsecond
- DeHt: see rare designator prefixes
- DEIA: abbreviation used for US government efforts
- DEIMOS: see Keck Observatory
- DEEP2: redshift survey of 60,000 galaxies
- SPLASH: survey of M31's Giant Stellar Stream
- Deimos
- Mars: well-explored planet in the solar system
- MMX: Japanese probe to bring back a sample of a Martian moon
- moon: a planet's natural satellite, such as Earth's
- delay time distribution: characterization of interval from star formation until some type of event
- delayed collapse: see neutron star merger
- delensing: see CMB lensing
- Delta
- Delta Cephei: see Cepheid variable
- Delta Cepheid Variable: see Cepheid variable
- Delta Scuti variable
- DEM: see rare designator prefixes
- democratic reionization: see epoch of reionization
- demographics: statistics of characteristics within a group
- DEN: see DENIS
- dendrogram: diagram of a "tree", i.e., of a graph without cycles
- DENIS: 1990s southern sky survey of two near-infrared bands
- DENIS-P: see DENIS
- dense cloud (molecular cloud): interstellar gas cloud that includes molecules
- dense cloud: see HII region
- dense core: dense molecular cloud
- dense core mass function: function describing range of masses of dense cores
- Dense Gas Survey of the Magellanic Clouds (DeGaS-MC): APEX survey of potential star formation regions in the Magellanic Clouds
- densitometer: see plate measuring machine
- density: see specific volume
- sound speed: speed at which compression waves traverse a gas
- density fluctuations
- density function
- density parameter: ratio of a density with the critical density
- density parameter: see critical density
- density scale height: see scale height
- density wave model: see spiral density wave
- density-morphology relation (morphology-density relation): a galaxy is more likely to be elliptical if surrounded by galaxies
- depth (survey depth): indication of how far a survey reaches
- DES (Dark Energy Survey): survey aimed at mapping the universe's expansion
- DES (Deep Ecliptic Survey): late 1990s/early 2000s survey for KBOs
- descending node: see orbital element
- DESHIMA: submillimeter spectrometer
- DESI (Dark Energy Spectroscopic Instrument): new instrument for measuring red-shift of distant objects
- DESI: see Mayall 4m Telescope
- DESI Legacy Imagine Surveys: see Dark Energy Spectroscopic Instrument
- Design Review: see MDR/SRR
- designation
- designator (survey-based designator): astronomical object designators based on name of survey
- Destiny
- destriping: removing streak-like noise from images
- destructive interference
- detached binary: see binary star
- detached binary: see contact binary
- detached object
- detached population
- detection
- red noise: noise tending toward lower frequencies
- detective quantum efficiency: measure of instrument's ability to create images
- detonation: ignition propelled by a shock wave
- deuterated hydrogen (hydrogen deuteride): hydrogen molecule with one deuterium atom
- deuterated methane: see methane
- deuterium: hydrogen isotope with one neutron
- 21-cm line: hydrogen line useful for determining redshift
- deuterium burning: any fusion reaction starting with deuterium
- H-alpha: hydrogen line for electrons settling from n = 3 to n = 2
- H-beta: hydrogen line for electrons settling from n = 4 to n = 2
- deuterium Balmer series: see Lyman series
- deuterium burning: any fusion reaction starting with deuterium
- hydrogen burning: any fusion reaction starting with hydrogen
- planet: round object orbiting a star that clears out its own orbital path
- deuterium fusion (deuterium burning): any fusion reaction starting with deuterium
- deuterium hydride (hydrogen deuteride): hydrogen molecule with one deuterium atom
- deuterium Lyman series: see Lyman series
- deuterium Rydberg constant: see Lyman series
- Deutsches Zentrum füaut;r Luft- und Raumfahrt (DLR): German's space and aerotautics research agency
- Devasthal Observatory
- DeVeny Spectrograph: see Lowell Discovery Telescope
- deviance information criterion: see Akaike information criterion
- DEVILS: visible-light spectrographic survey of 56k distant galaxies
- dewar: term used re cryogenics for vacuum-insulated containers
- dex: a number or ratio's log base 10
- DF (deep field): survey field subject to lengthy observation to identify distant galaxies
- DF2: see NGC 1052
- DF4: see NGC 1052
- DFG: see Magnetospheric Multiscale Mission
- DFMI: see Stardust
- DFT: see fast Fourier transform
- DG: see rare designator prefixes
- DG code
- DG method (discontinuous Galerkin method): computational method for PDEs handling discontinuities
- DGE: see Lunar Prospector
- DGL: see cosmic optical background
- DGL: see extragalactic background light
- DGP gravity: alternative theory of gravity addressing "dark energy"
- DGP model (DGP gravity): alternative theory of gravity addressing "dark energy"
- DGR: see gas-to-dust ratio
- DGRB (cosmic gamma ray background): gamma-ray radiation seen everywhere
- DH (hydrogen deuteride): hydrogen molecule with one deuterium atom
- DHK: see rare designator prefixes
- diagnostic: test or measurement that reveals something's characteristics
- diagnostic tool (diagnostic): test or measurement that reveals something's characteristics
- diagonalization: see eigen-decomposition
- diagram
- diagrams
- isophote: line on a diagram indicating a level of brightness
- diamond planet (carbon planet): theoretical planet type with more carbon than oxygen
- Dias: see rare designator prefixes
- DIB: see interstellar medium
- DIBs (diffuse interstellar bands): type of absorption bands seen in astronomical objects
- DIC: see Akaike information criterion
- DICE
- CASA-MIA: 1990s cosmic-ray detector in Utah
- Dickel-Wendker-Bieritz Catalog: list of HII regions in the Cygnus X star-forming region
- DID: see Giotto
- dielectric: insulator that responds to an electric field
- dielectric material (dielectric): insulator that responds to an electric field
- dielectric medium
- dielectric polarization: see dielectric
- difference equations
- differential cross section: see cross section
- differential equation: see partial differential equation
- differential equations
- differential photometry: see photometry
- differential reddening: see reddening
- differential rotation (zonal flow): east-west air circulation
- differential rotation: see rotation period
- differential rotation: see stellar rotation
- differential spectroscopy: analysis of the comparison of two spectrographs
- differentiated object: see hydrostatic equilibrium
- diffraction: an effect of the edge of an obstacle on a wave
- diffraction grating (grating): spectrometer component
- diffraction limited: telescope limited only by the laws of diffraction
- confusion limit: limit on telescope imaging due to too many sources in the same region
- diffraction spike: type of artifact in astronomical images of point sources
- diffractive interstellar scintillation: diffraction of star light by the ISM
- diffractive scintillation (diffractive interstellar scintillation): diffraction of star light by the ISM
- diffuse: see diffuse emission
- diffuse cloud: see HII region
- diffuse emission: electromagnetic radiation not confined to a point source
- diffuse emission nebula: see diffuse emission
- diffuse extragalactic background radiation: see cosmic background radiation
- diffuse extragalactic background radiation: see extragalactic background light
- diffuse galactic light: see cosmic optical background
- diffuse galactic light: see extragalactic background light
- diffuse gamma ray background (cosmic gamma ray background): gamma-ray radiation seen everywhere
- diffuse gamma ray emission (cosmic gamma ray background): gamma-ray radiation seen everywhere
- diffuse HI cloud (HI region): cloud of neutral atomic hydrogen
- diffuse interstellar band: see interstellar medium
- diffuse interstellar bands: type of absorption bands seen in astronomical objects
- diffuse ionized gas: see interstellar medium
- diffuse nebula: see diffuse emission
- diffusion: the spreading of particles toward an even distribution
- diffusion coefficient: see diffusion
- diffusion damping: a damping process within the plasma during recombination
- diffusion equation: see diffusion
- diffusion-limited escape: see atmospheric escape
- diffusivity: see diffusion
- DIG: see interstellar medium
- Digital Access to a Sky Century @ Harvard (DASCH): project to digitize Harvard astronomy plates
- digital image stabilization: see image stabilization
- Digitized Sky Survey: digitization of Palomar and UK Schmidt plates
- dimensionless: see nondimensionalization
- dimensionless Hubble parameter: see Hubble constant
- DINGO: see Australian Square Kilometre Array Pathfinder
- Dinkinesh
- Lucy: space probe to observe Jupiter Trojan asteroids
- Dione: see Saturn
- moon: a planet's natural satellite, such as Earth's
- dipole: field with two poles
- dipole: see multipole expansion
- dipole antenna: see dipole
- dipole magnetic field: see magnetic field
- dipole tilt: see magnetic field
- Dirac constant: see Planck constant
- DIRBE: see Cosmic Background Explorer
- direct collapse
- direct collapse black hole: theoretical means for quick formation of SMBHs
- direct detection (direct imaging): detection/observation of exoplanets by taking pictures of it
- direct imaging: detection/observation of exoplanets by taking pictures of it
- direct Urca process: see Urca process
- dIrr: see dwarf galaxy classification
- dIrr: see irregular galaxy
- dirty image: image that includes the distortions of the beam and sampling
- CLEAN: algorithm to extract usable images from interferometry-produced images
- DIS: see Galaxy Evolution Explorer
- discontinuous Galerkin method: computational method for PDEs handling discontinuities
- discontinuous shock: see shock wave
- Discovery 1 (NEAR Shoemaker): space mission to an asteroid
- Discovery 10 (Kepler Telescope): space telescope that watched stars for exoplanets
- Discovery 11 (GRAIL): 2011 NASA lunar orbiters to collect gravity data
- Discovery 12 (InSight): NASA Mars mission to study its interior
- Discovery 13 (Lucy): space probe to observe Jupiter Trojan asteroids
- Discovery 14 (Psyche): space mission on its way to asteroid Psyche
- Discovery 15 (VERITAS): planned NASA Venus orbiter
- Discovery 16 (DAVINCI): planned NASA Venus orbiter
- Discovery 2 (Mars Pathfinder): 1990s mission to Mars with rover
- Discovery 3 (Lunar Prospector): NASA 1998 lunar orbiter
- Discovery 4 (Stardust): space mission that collected and returned comet coma dust
- Discovery 5 (Genesis): NASA spacecraft that returned solar wind particles
- Discovery 6 (CONTOUR): failed 2002 NASA astroid flyby mission
- Discovery 7 (MESSENGER): Mercury probe launched by NASA in 2004
- Discovery 8 (Deep Impact): mission to create and observe an impact with a comet
- Discovery 9 (Dawn): explorer spacecraft sent to asteroids Vesta and Ceres
- Discovery Channel
- Discovery Channel Telescope (Lowell Discovery Telescope): 4.3 m telescope at Lowell Observatory, Arizona
- Lowell Observatory: Arizona observatory of long standing
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- Discovery Program
- DAVINCI: planned NASA Venus orbiter
- Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
- Deep Impact: mission to create and observe an impact with a comet
- Enceladus Life Finder: mission to search for life on Saturn moon Enceladus
- Genesis: NASA spacecraft that returned solar wind particles
- GRAIL: 2011 NASA lunar orbiters to collect gravity data
- InSight: NASA Mars mission to study its interior
- Kepler Telescope: space telescope that watched stars for exoplanets
- Lucy: space probe to observe Jupiter Trojan asteroids
- Lunar Prospector: NASA 1998 lunar orbiter
- Mars Pathfinder: 1990s mission to Mars with rover
- MESSENGER: Mercury probe launched by NASA in 2004
- NASA: includes space-based astronomy research
- NEAR Shoemaker: space mission to an asteroid
- Psyche: space mission on its way to asteroid Psyche
- Stardust: space mission that collected and returned comet coma dust
- VERITAS: planned NASA Venus orbiter
- DISCOVR: space weather satellite
- discrete Fourier transform: see fast Fourier transform
- Discrete Ordinates Radiative Transfer (DISORT): simulation of radiative transfer in an atmosphere
- discrete random variable: see probability density function
- discrete random variable: see probability mass function
- discrete spectrum: see continuous spectrum
- dish antenna
- disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
- disk (circumstellar disk): disk or ring shaped accumulation of matter around a star
- disk (galactic disk): the "disk" portion of a disk galaxy
- disk (protoplanetary disk): disk of dust and gas around a young star or protostar
- disk coupling: see final parsec problem
- Disk Detective: Zooniverse effort to find planets within protoplanetary disks
- disk galaxy: circular, relatively flat galaxy such as a spiral galaxy
- disk gap: empty radius-range within a disk separating it into rings
- disk heating: see heating
- disk instability model (gravitational instability model): model for the formation of giant planets
- disk instability model: see giant planet formation
- disk migration: see planetary migration
- Disk Substructures at High Angular Resolution Project (DSHARP): ALMA survey of imageable protoplanetary disks
- disk type
- disk wind: see jet
- disks
- cold mass accretion: stellar accretion through an accretion disk
- dead zone: area within a disk where normal things don't happen
- disk gap: empty radius-range within a disk separating it into rings
- DSHARP: ALMA survey of imageable protoplanetary disks
- eclipse mapping: using eclipse light curves to map surface features
- Lindblad resonance: resonant orbits within a disk due to a high-density portion
- line tomography: using double-peaked spectral lines to place constituents of a disk
- mass transport: transfer of mass from one part of a body/disk to another
- Orion Disks: protoplanetary disks visible in front of Orion Nebula
- radial drift: inward drift of objects within a protoplanetary disk
- RODEO: code for 2D disk simulation
- shearing box: method of simulating 3D MHD in disks
- spiral density wave: spiral structure that can form in disks
- streaming instability: type of interplay between disk gas and solids that brings solids together
- DISORT: simulation of radiative transfer in an atmosphere
- disperser: prism, grating, or grism within a spectrometer
- dispersing element (disperser): prism, grating, or grism within a spectrometer
- dispersion (velocity dispersion): statistical dispersion of velocities of a group of objects
- dispersion: see disperser
- dispersion: see velocity dispersion
- dispersion constant: see dispersion measure
- dispersion correction: see dispersion measure
- dispersion direction: see imaging spectrometer
- dispersion measure: to what degree an EMR signal's lower frequencies are delayed
- pulsar: type of astronomical body with EMR in regular cycles of seconds or less
- velocity dispersion: statistical dispersion of velocities of a group of objects
- dispersive delay: see velocity dispersion
- displacement: vector quantity showing the position of one point in relation to another
- DISR: see Cassini
- DISS (diffractive interstellar scintillation): diffraction of star light by the ISM
- dissipation function
- tidal Q: measure of orbital energy dissipated per orbit due to tidal forces
- dissociated: see photodissociation
- dissociation: see photodissociation
- dissociation front (molecular hydrogen dissociation front): point in a gas cloud where it is hot enough to dissociate hydrogen
- distance: magnitude of the displacement or length of a curve
- distance ambiguity: see kinematic distance
- distance modulus: apparent magnitude minus absolute magnitude
- distant
- AzTEC-3: very distant starburst galaxy
- GN-z11: distant galaxy with SMBH of interest
- HD1: very distant 2022 galaxy candidate
- HFLS3: very distant starburst galaxy
- distortion: aberration where the image is in focus but misshaped
- distributed
- disturbance
- disturbed galaxy: see galaxy merger
- dither: see hot pixel
- diurnal libration: see libration
- diurnal motion: see horizontal coordinate system
- divergence: see mathematical field
- divergence theorem: see finite volume method
- diversity (DEIA): abbreviation used for US government efforts
- Diviner: see Lunar Reconnaissance Orbiter
- DIXI
- EPOXI: mission using Deep Impact for further exploration
- Djorg: see rare designator prefixes
- Dju: see double star designation
- DKIST: 4 m solar telescope at Haleakala Observatory
- DLA (damped Lyman alpha absorber): object producing broadened lines in a Lyman alpha forest
- DLR: German's space and aerotautics research agency
- SOFIA: aircraft-based infrared observatory
- DLS (Deep Lens Survey): investigating mass distribution of the universe
- DM (dark matter): matter in galaxies and galaxy clusters suggested by their gravity
- DM (deformable mirror): mirror that can be flexed for fine control
- DM (dispersion measure): to what degree an EMR signal's lower frequencies are delayed
- DM: see Bonner Durchmusterung Catalog
- pulsar: type of astronomical body with EMR in regular cycles of seconds or less
- DM Tau: nearby T-Tauri star
- DM Tauri (DM Tau): nearby T-Tauri star
- DM-dominated dwarf spheroidals: see dwarf spheroidal galaxy
- DM-Ice: see COSINE-100
- DM-Ice17: see COSINE-100
- DM99: see rare designator prefixes
- DMDF: see dynamical friction
- DMR: see Cosmic Background Explorer
- DMR: see gas-to-dust ratio
- DMS (Deep Multicolor Survey): 1990s optical and infrared deep survey
- DN (Duus-Newell catalog): list of southern galaxies/clusters assembled in 1970s
- DN (dwarf nova): flash of a cataclysmic variable star
- DNS (binary neutron star): two neutron stars co-orbiting
- DO: see rare designator prefixes
- Do: see rare designator prefixes
- DoAr: see rare designator prefixes
- document
- DoDz (Dolidze-Dzimselejsvili Catalogue): list of 11 open clusters
- DOG: see hot DOG
- DOGS (Dwingeloo Obscured Galaxy Survey): radio survey of ZOA for 21-cm lines indicating galaxies
- doldrums (intertropical convergence zone): circulation pattern near equator where north and south Hadley cells meet
- Dolidze-Dzimselejsvili Catalogue: list of 11 open clusters
- Dolidze-Dzimselejsvili Open Clusters Catalogue (Dolidze-Dzimselejsvili Catalogue): list of 11 open clusters
- DOLoRes: see Telescopio Nazionale Galileo
- domain wall: see topological defect
- Dome A
- Dome C
- Dominion Astrophysical Observatory: long-standing observatory in British Columbia
- DAOPHOT: 1980s CCD photometry software
- Dominion Observatory 10.03 MHz Source Catalog: 1960s survey of northern-hemisphere radio sources
- Dominion Observatory 1420 MHz Source Catalog: 1960s survey of northern-hemisphere radio sources
- Dominion Radio Astrophysical Observatory: radio observatory in British Columbia, Canada
- Dominion Radio Astrophysical Observatory 10.03 MHz Telescope
- Dominion Radio Astrophysical Observatory 25.6m Telescope
- Don: see double star designation
- donor star: see mass transfer
- Doo: see double star designation
- Doppler
- Doppler beaming (relativistic beaming): directional relativistic effect on light from relativistic speeds
- Doppler boosting (relativistic beaming): directional relativistic effect on light from relativistic speeds
- Doppler broadening: broadening of spectral lines due to movement of the sources of photons
- Doppler effect (Doppler shift): wave frequency difference due to relative velocity difference with source
- Doppler imaging: see Doppler shift
- Doppler shift: wave frequency difference due to relative velocity difference with source
- Doppler broadening: broadening of spectral lines due to movement of the sources of photons
- Doppler spectroscopy (radial velocity method): method of detecting exoplanets and binary companions
- Doppler tomography: see tomography
- dormant SMBH: see supermassive black hole
- dormant supermassive black hole: see supermassive black hole
- Dorpat: see Struve Catalogs
- Dorpat Catalog: see Struve Catalogs
- Dorpat Observatory
- double beta decay: see neutrinoless double beta decay
- double bond: see hydrocarbon
- double degenerate model: see Type Ia supernova problem
- double degenerate model: see supernova progenitor
- double minor merger: see galaxy merger
- double neutron star (binary neutron star): two neutron stars co-orbiting
- double planet
- Pluto: dwarf planet formerly listed as one of the nine planets
- double star: two stars close together in the sky
- double star designation: systems and format of double star designators
- double star designator: see double star designation
- double stars
- double transit: star showing transits of two bodies
- double transit system: see double transit
- double-line spectroscopic binary: spectroscopic binary star where a specific line shows up at two different wavelengths
- double-lined spectroscopic binary (double-line spectroscopic binary): spectroscopic binary star where a specific line shows up at two different wavelengths
- double-peaked spectral line: see line tomography
- doubling time: see e-folding time
- down: see flavor
- down quark: see particle
- down quark: see quark
- downconversion
- downconverter: device that reduces the frequency of a signal
- dP/dt (period derivative): rate of change in the period of an orbit or rotation
- DPM: see High Altitude Observatory
- DPOSS: see Palomar Observatory Sky Survey
- DQ Herculis star: see variable star
- DQ Tau: young binary star system
- DQE (detective quantum efficiency): measure of instrument's ability to create images
- DR (data release): publication or distribution of a set of data from a survey
- DR: see atomic dark matter
- DR: see rare designator prefixes
- DR1: see data release
- DR2: see data release
- Draco Dwarf
- DraGMet: see Dragonfly
- DraGNS: see Dragonfly
- DragonCam: see Dragonfly
- Dragone design: see Dragone telescope
- Dragone telescope: off-axis reflector telescope type that preserves polarization
- Dragone-design telescope (Dragone telescope): off-axis reflector telescope type that preserves polarization
- Dragonfly: Titan flying rover under development
- Saturn: second largest planet in the solar system
- Dragonfly Telephoto Array: Canadian compact array of small visible-light telescopes
- Drake equation: estimate of advanced life in the Milky Way
- DraMS: see Dragonfly
- DRAO (Dominion Radio Astrophysical Observatory): radio observatory in British Columbia, Canada
- DRCG: see rare designator prefixes
- DRDF: "Director's Research and Development Fund"
- dredge-up: stellar convection bringing up fused material
- Dreyer: see New General Catalogue
- drift barrier (radial-drift barrier): the problem that forming planets would drift inward into the star
- barrier: challenging issue regarding planet formation
- radial drift: inward drift of objects within a protoplanetary disk
- drift scan: method of observing substantial sky with CCDs
- drogue
- drogue chute: parachute to slow something moving at high speed
- drogue chute: parachute to slow something moving at high speed
- drogue parachute (drogue chute): parachute to slow something moving at high speed
- dropout: means of identifying distant galaxies
- DRS: data reduction system
- DRT: see Mars Science Laboratory
- dry ice: see ice
- dS: see dwarf galaxy classification
- DS1 (Deep Space 1): 1998-2001 mission to fly by asteroid
- DSA-10: see DSA-2000
- DSA-110: see DSA-2000
- DSA-2000: array plan to detect radio transients
- DSCT
- DSE: see Stardust
- DSED (Dartmouth Stellar Evolution Database): database relating isochrones to stellar parameters
- DSED isochrone: see Dartmouth Stellar Evolution Database
- DSEP (Dartmouth Stellar Evolution Database): database relating isochrones to stellar parameters
- DSEP isochrone: see Dartmouth Stellar Evolution Database
- DSFG (submillimeter galaxy): galaxy that produces significant submillimeter radiation
- DSFG: see dusty galaxy
- MORA: high resolution 2-mm survey of a portion of the COSMOS field
- DSHARP: ALMA survey of imageable protoplanetary disks
- DSN (NASA Deep Space Network): NASA's world-wide radio communication setup
- dSph (dwarf spheroidal galaxy): spheroidally-shaped dwarf galaxy lacking star formation
- DSS (Digitized Sky Survey): digitization of Palomar and UK Schmidt plates
- DSS2: see Digitized Sky Survey
- DTD (delay time distribution): characterization of interval from star formation until some type of event
- du Pont Telescope: see Las Campanas Observatory
- du Pont telescope
- Dual Imaging Cherenkov Experiment
- CASA-MIA: 1990s cosmic-ray detector in Utah
- DUN (Dunlop Double Star Catalogue): 1829 catalog of double stars viewed from Australia
- DUNE (Deep Underground Neutrino Experiment): neutrino experiment under construction
- Dunlop: see Dunlop Double Star Catalogue
- Dunlop: see rare designator prefixes
- Dunlop Double Star Catalogue: 1829 catalog of double stars viewed from Australia
- dUrca: see Urca process
- Durchmusterung (Bonner Durchmusterung Catalog): well-known astrometric catalog from late 1800s
- Durham
- DUST: see Ulysses
- dust (cosmic dust): dust in space such as interstellar dust
- dust cloud: see interstellar medium
- dust coagulation: see planet formation
- dust devil: small whirlwind visible from dust it collects
- dust echo: the glow of dust heated by a transient
- dust extinction: see extinction
- dust grain: see cosmic dust
- dust map: see cosmic dust
- dust particle: see cosmic dust
- dust polarimetry: see polarimetry
- dust tail: see comet
- dust trap: protoplanetary disk mechanism that gathers dust
- dust-obscured galaxy: see hot DOG
- dust-to-gas ratio: see gas-to-dust ratio
- dust-to-metals ratio: see gas-to-dust ratio
- DustEM: code to calculate dust extinction and emission
- dusty galaxy: galaxy including substantial dust
- dusty galaxy: see submillimeter galaxy
- dusty star-forming galaxy (submillimeter galaxy): galaxy that produces significant submillimeter radiation
- dusty star-forming galaxy: see dusty galaxy
- MORA: high resolution 2-mm survey of a portion of the COSMOS field
- duty cycle: percent of time when activity is recurring
- Duus-Newell catalog: list of southern galaxies/clusters assembled in 1970s
- DV: see rare designator prefixes
- DW: see rare designator prefixes
- dwarf elliptical galaxy: see dwarf galaxy classification
- dwarf galaxies
- dwarf galaxy: small galaxy with up to a few billion stars
- dwarf galaxy classification: terms for of dwarf galaxy types
- dwarf galaxy problem: theories have more dwarf galaxies than are observed
- dwarf irregular galaxy: see dwarf galaxy classification
- dwarf nova: flash of a cataclysmic variable star
- dwarf planet: round like a planet, only smaller
- Ceres: dwarf planet and largest asteroid
- Haumea: dwarf planet discovered in 2004
- Pluto: dwarf planet formerly listed as one of the nine planets
- dwarf planets
- dwarf spheroidal (dwarf spheroidal galaxy): spheroidally-shaped dwarf galaxy lacking star formation
- dwarf spheroidal galaxy: spheroidally-shaped dwarf galaxy lacking star formation
- dwarf spiral galaxy: see dwarf galaxy classification
- dwarf star (main sequence star): star burning hydrogen into helium in its center
- DWB (Dickel-Wendker-Bieritz Catalog): list of HII regions in the Cygnus X star-forming region
- DWE: see Cassini
- Dwingeloo: see Dwingeloo Obscured Galaxy Survey
- Dwingeloo Obscured Galaxy Survey: radio survey of ZOA for 21-cm lines indicating galaxies
- Dwingeloo Radio Observatory
- DXS: see UKIDSS
- dynamic capture: see tidal capture
- dynamic instability (dynamical instability): situation where a perturbation makes itself larger
- dynamic mass: see mass
- Dynamical Analysis of Nearby Clusters: survey of stars in stellar clusters
- dynamical friction: drag produced by gravitational interaction with surrounding objects
- dynamical heating: see heating
- dynamical instability: situation where a perturbation makes itself larger
- dynamical instability region (instability region): region around an object where orbits cannot persist
- dynamical systems
- chaos theory: theory of systems highly sensitive to initial conditions
- dynamical timescale: see free-fall time
- dynamical timescale: see timescale
- dynamically nested sampling: see dynesty
- dynamics: see mechanics
- dynamo: mechanism for generating magnetic fields around astronomical bodies
- dyne
- dynesty: code for comparing the applicability of multiple models
- Dysnomia
Index