Term Index (D)
- D:
- CFHTLS: surveys of transients and stars
- deuterium (D): hydrogen isotope with one neutron
- D burning:
- D lines:
- sodium (Na): metal, Na, atomic number 11
- D orbital:
- D²:
- DEEP2: redshift survey of 60,000 galaxies
- D-σ relation:
- D-type galaxy:
- D1:
- CFHTLS: surveys of transients and stars
- D2:
- CFHTLS: surveys of transients and stars
- D3:
- CFHTLS: surveys of transients and stars
- D4:
- CFHTLS: surveys of transients and stars
- dL:
- luminosity distance (dL, DL): distance to an object based upon the distance's effect on received flux
- Dp:
- deuterium (D): hydrogen isotope with one neutron
- DA:
- Dall-Kirkham telescope: type of reflecting telescope
- dalton (Da,u): mass unit used on atomic scale
- mass: object's quality that determines the effects of forces and gravity
- DAN:
- Daphnis:
- Darcy velocity:
- Darcy velocity field: vector field indicating a kind of seepage in a porous medium
- Darcy's law:
- 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 energy: energy theorized to accelerate the expansion of the universe
- Dark Energy Camera:
- Dark Energy Survey (DES): survey aimed at mapping the universe's expansion
- DECaLS: survey imaging part of SDSS footprint with DECam
- dark energy density:
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- Dark Energy Space Telescope:
- WFIRST: proposed space observatory
- Dark Energy Spectroscopic Instrument (DESI): new instrument for measuring red-shift of distant objects
- Dark Energy Survey (DES): survey aimed at mapping the universe's expansion
- dark flow: non-random patterns in peculiar velocity of galaxy clusters
- dark halo:
- dark matter: matter hypothesized to provide galaxies with mass that can't be viewed
- axion (A0): proposed light, electrically neutral elementary particle
- cold dark matter (CDM): one of three types of "dark matter" theory
- Cosmic Evolution Survey (COSMOS): investigation of dark matter and the universe's large scale structure
- dark matter annihilation: particle/antiparticle annihilation of WIMPs
- dark matter halo: hypothetical dark matter throughout and surrounding a galaxy
- DECaLS: survey imaging part of SDSS footprint with DECam
- galactic halo: spherical region around a galaxy with gas, dark matter, etc.
- galaxy bias: degree to which galaxy density fails to correspond to dark matter density
- halo abundance matching (HAM): method of comparing observed galaxies with cosmology models
- halo mass function: mass of distribution of dark matter
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- LasDamas: simulations of large scale evolution of dark matter and galaxies
- MACHO: proposed astronomical objects comprising dark matter
- MACHO Project: survey searching out microlensing that could indicate a MACHO
- MOA: search for microlensing
- Navarro-Frenk-White profile (NFW profile): a dark matter spatial mass distribution function
- neutralino: proposed type of particle that might include wimps
- OGLE: survey searching for microlensing transients
- RHAPSODY: simulation of galaxy cluster dark-matter halos
- VIRMOS-VLT Deep Survey (VVDS): spectroscopic survey of 100,000 high-redshift galaxies
- WIMP: proposed particle comprising dark matter
- dark matter annihilation: particle/antiparticle annihilation of WIMPs
- dark matter density:
- Lambda-CDM model (ΛCDM,LCDM): Big-Bang cosmological model with a cosmological constant and cold dark matter
- dark matter halo: hypothetical dark matter throughout and surrounding a galaxy
- dark nebula: cloud that obscures stars behind it
- LDN 1689: dense core within the Rho Ophiuchi Cloud Complex
- 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 sky:
- DARPA:
- Darwin: past plan for space telescopes acting as an interferometer
- DASCH: project to digitize Harvard astronomy plates
- DASH345:
- data:
- data cube: "table" of numerical data covering three dimensions
- data release (DR): publication or distribution of a set of data from a survey
- Galaxy Zoo: crowdsourcing website to identify galaxy types from surveys
- Galaxy Zoo 2 (GZ2): crowd-sourced classification of hundreds of thousands of galaxies
- IRSA: archive center for infrared data from NASA missions
- LAMBDA: NASA archive center re CMB data
- Planet Hunters (PH): crowdsourcing website to identify galaxy types from surveys
- position-position-velocity space (PPV): 3d space using velocity as one of the three dimensions
- virtual observatory (VO): online database of astronomical data
- data cube: "table" of numerical data covering three dimensions
- data release (DR): publication or distribution of a set of data from a survey
- database:
- HITEMP: spectroscopic parameters for modeling gas optics
- HITRAN: spectroscopic parameters for modeling atmospheric optics
- NASA/IPAC Extragalactic Database (NED): a database of galaxies and other objects outside the Milky Way
- SIMBAD: online database of astronomical objects
- daughter nuclide:
- David Dunlap Observatory:
- David Dunlap Observatory Catalog (DDO): catalog of dwarf galaxies
- Dawn:
- day:
- solar time: time based upon the position of the Sun in the Earth's sky
- DB:
- DBSP:
- DCAM5:
- MMX: Japanese probe to bring back a sample of a Martian moon
- DCBH:
- DCMF:
- DCT:
- DDO:
- de Broglie frequency:
- de Broglie wavelength: wavelength of a particle's matter wave
- de Broglie waves:
- de Sitter universe:
- de Vaucouleurs' law:
- de Vaucouleurs' profile: relation between elliptical galaxy surface brightness and distance from center
- dead zone: area within a disk where normal things don't happen
- DEBRA:
- debris disk: circumstellar disk of dust and debris around a star
- dec:
- declination (dec): direction coordinate above/below celestial equator
- DECaLS: survey imaging part of SDSS footprint with DECam
- DECam:
- DECam Legacy Survey:
- DECaLS: survey imaging part of SDSS footprint with DECam
- deceleration parameter:
- decimal exponent:
- dex: a number or factor's log base 10
- decision tree:
- decision tree learning:
- declination (dec): direction coordinate above/below celestial equator
- decollimator:
- deconvolution:
- 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:
- deep CO2; cycle:
- deep drilling:
- deep field (DF): survey field subject to lengthy observation to identify distant galaxies
- deep drilling field:
- deep field (DF): survey field subject to lengthy observation to identify distant galaxies
- 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 (DF): survey field subject to lengthy observation to identify distant galaxies
- Deep Impact:
- EPOXI: mission using Deep Impact for further exploration
- Deep Impact Extended Investigation:
- EPOXI: mission using Deep Impact for further exploration
- Deep Lens Survey (DLS): investigating mass distribution of the universe
- Deep Near Infrared Survey of the Southern Sky:
- DENIS: 1990s southern sky survey of two near-infrared bands
- Deep Space Network:
- deep survey: survey using lengthy observation to identify distant galaxies
- deep water cycle:
- DEEP-GSS:
- DEEP2: redshift survey of 60,000 galaxies
- DEEP2: redshift survey of 60,000 galaxies
- DEEP2 Redshift Survey:
- DEEP2: redshift survey of 60,000 galaxies
- DEEP2 Survey:
- DEEP2: redshift survey of 60,000 galaxies
- deferent:
- epicycle: small circular motion around a large circular motion
- deformable mirror (DM): mirror that can be flexed for fine control
- DeGaS-MC: GBT survey of potential star formation regions in the Magellanic Clouds
- degeneracy: general word meaning a violation of normal rules
- degeneracy pressure:
- electron degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- degeneracy weight: number of quantum states with same energy level
- degeneracy weighting:
- degenerate dwarf:
- white dwarf: stellar remnant of mostly electron-degenerate matter
- degenerate energy levels:
- degeneracy: general word meaning a violation of normal rules
- degenerate matter:
- degeneracy: general word meaning a violation of normal rules
- electron degeneracy: the condition of electrons supported solely by the Pauli exclusion principle
- degenerate perturbation problem:
- degenerate star:
- degree:
- arcsecond (arcsec,sec): a 3600th of an angular degree
- degree of ionization: fraction of material consisting of ions
- degrees:
- arcsecond (arcsec,sec): a 3600th of an angular degree
- Deimos:
- DEEP2: redshift survey of 60,000 galaxies
- Keck Observatory: observatory in Hawaii with two 10-meter reflectors
- Mars: well-explored planet in the solar system
- moon: a planet's natural satellite, such as Earth's
- delensing:
- Delta:
- Space Launch System (SLS): launch rocket in development, e.g., for future astronomical projects
- Delta Cephei:
- Delta Scuti variable:
- demographics: statistics of characteristics within a group
- DEN:
- DENIS: 1990s southern sky survey of two near-infrared bands
- dendrogram: diagram of a "tree", i.e., of a graph without cycles
- DENIS: 1990s southern sky survey of two near-infrared bands
- dense cloud:
- dense core: dense molecular cloud
- dense core mass function (DCMF,CMF): function describing range of masses of dense cores
- Dense Gas Survey of the Magellanic Clouds:
- DeGaS-MC: GBT survey of potential star formation regions in the Magellanic Clouds
- densitometer:
- density:
- density fluctuations:
- density parameter:
- density scale height:
- depth:
- DES:
- descending node:
- DESI:
- Design Review:
- MDR/SRR: planning step for a NASA mission
- designation:
- Destiny:
- WFIRST: proposed space observatory
- detached binary:
- detection:
- red noise: noise tending toward lower frequencies
- deuterated methane:
- methane (CH4): compound of one carbon and 4 hydrogen atoms
- deuterium (D): hydrogen isotope with one neutron
- 21cm line: hydrogen line useful for determining redshift
- deuterium burning: any fusion reaction starting with hydrogen
- H-alpha (Ha,Hα, H-α): hydrogen line for electrons settling from n = 3 to n = 2
- deuterium burning: any fusion reaction starting with hydrogen
- deuterium fusion:
- DeVeny Spectrograph:
- DEVILS: visible-light spectrographic survey of 56k distant galaxies
- dex: a number or factor's log base 10
- DF:
- deep field (DF): survey field subject to lengthy observation to identify distant galaxies
- DFT:
- DG code:
- DG method:
- DGL:
- DGP gravity: alternative theory of gravity addressing "dark energy"
- DGP model:
- DGP gravity: alternative theory of gravity addressing "dark energy"
- diagram:
- diagrams:
- isophote: line on a diagram indicating a level of brightness
- diamond planet:
- carbon planet: theoretical planet type with more carbon than oxygen
- DIBs:
- Dickel-Wendker-Bieritz Catalog (DWB): list of HII regions in the Cygnus X star forming region
- dielectric: insulator that responds to an electric field
- dielectric material:
- dielectric: insulator that responds to an electric field
- dielectric medium:
- difference equations:
- differential equation:
- differential equations:
- differential rotation:
- differential spectroscopy:
- diffraction: effect of an obstacle on a wave
- diffraction grating:
- diffraction limited: telescope limited only by the laws of diffraction
- diffractive interstellar scintillation (DISS): diffraction of star light by the ISM
- diffuse:
- diffuse cloud:
- HI region (HI): cloud of neutral atomic hydrogen
- HII region (HII): cloud of partially-ionized atomic hydrogen
- diffuse emission: electromagnetic radiation not confined to a point source
- diffuse emission nebula:
- diffuse extragalactic background light:
- diffuse galactic light:
- diffuse HI cloud:
- HI region (HI): cloud of neutral atomic hydrogen
- diffuse interstellar bands (DIBs): type of absorption bands seen in astronomical objects
- diffuse nebula:
- diffusion: the spreading of particles toward an even distribution
- diffusion coefficient:
- diffusion: the spreading of particles toward an even distribution
- diffusion equation:
- diffusion: the spreading of particles toward an even distribution
- diffusion-limited escape:
- diffusivity:
- diffusion: the spreading of particles toward an even distribution
- Digital Access to a Sky Century @ Harvard:
- DASCH: project to digitize Harvard astronomy plates
- digital image stabilization:
- Digitized Sky Survey (DSS): digitization of Palomar and UK Schmidt plates
- dilute core:
- metal: in astrophysics, any element more massive than helium
- Dione:
- moon: a planet's natural satellite, such as Earth's
- Saturn: second largest planet in the solar system
- dipole:
- dipole magnetic field:
- dipole tilt:
- Dirac constant:
- DIRBE:
- direct collapse black hole (DCBH): theoretical means for quick formation of SMBHs
- direct imaging: detection/observation of exoplanets by taking pictures of it
- PALMS: survey to find exoplanets for direct imaging
- dIrr:
- discontinuous Galerkin method: computational method for PDEs handling discontinuities
- discontinuous shock:
- shock wave: abrupt propagating disturbance in a fluid
- Discovery Channel:
- Discovery Channel Telescope (DCT): 4.3m telescope at Lowell Observatory, Arizona
- NEWS: planned near-infrared spectrometer on Discovery Channel Telescope
- Discovery Program:
- Enceladus Life Finder (ELF): mission to search for life on Saturn moon Enceladus
- NASA: includes space-based astronomy research
- Psyche: planned space mission to orbit an asteroid
- discrete Fourier transform:
- Discrete Ordinates Radiative Transfer:
- DISORT: simulation of radiative transfer in an atmosphere
- discrete random variable:
- discrete spectrum:
- disk:
- disk galaxy: galaxy shaped like a flat circle
- disk migration:
- disk wind:
- jet: stream of matter from an astronomical body
- disks:
- DISORT: simulation of radiative transfer in an atmosphere
- dispersion:
- spectroscopy: measurement of the strengths of different electromagnetic wavelengths
- velocity dispersion (σ): statistical dispersion of velocities of a group of objects
- dispersion direction:
- dispersion measure:
- pulsar (PSR): astronomical body whose electromagnetic radiation displays a cycle
- DISR:
- Cassini: explorer spaceship sent to Saturn
- DISS:
- dissociated:
- dissociation:
- dissociation front:
- distance:
- distance ambiguity:
- distance modulus (u): apparent magnitude minus absolute magnitude
- distributed:
- disturbance:
- diurnal libration:
- libration: oscillating motion of orbiting bodies relative to each other
- diurnal motion:
- divergence:
- divergence theorem:
- Diviner:
- DIXI:
- EPOXI: mission using Deep Impact for further exploration
- DLR:
- SOFIA: aircraft-based infrared observatory
- DLS:
- DM:
- DMR:
- DoDz:
- DOGS:
- doldrums:
- Dolidze-Dzimselejsvili Catalogue (DoDz): list of 11 open clusters
- Dolidze-Dzimselejsvili Open Clusters Catalogue:
- DOLoRes:
- domain wall:
- Dominion Observatory 10.03 MHz Source Catalog (DB): 1960s survey of northern-hemisphere radio sources
- Dominion Observatory 1420 MHz Source Catalog (DA): 1960s survey of northern-hemisphere radio sources
- Dominion Radio Astrophysical Observatory (DRAO): radio observatory in British Columbia, Canada
- Dominion Radio Astrophysical Observatory 10.03 MHz Telescope:
- Dominion Radio Astrophysical Observatory 25.6m Telescope:
- Doppler:
- Doppler beaming:
- Doppler boosting:
- Doppler broadening: broadening of spectral lines due to velocities of the photon sources
- Doppler effect:
- Doppler shift: wave frequency difference due to relative velocity difference with source
- Doppler shift: wave frequency difference due to relative velocity difference with source
- double bond:
- hydrocarbon (HC): any compound of just carbon and hydrogen
- double planet:
- Pluto: dwarf planet formerly listed as one of the nine planets
- double star: two stars close together in the sky
- double stars:
- double transit: star showing transits of two bodies
- double transit system:
- double-line spectroscopic binary: spectroscopic binary star where a specific line shows up at two different wavelengths
- double-lined spectroscopic binary:
- down quark:
- downconverter: device that reduces the frequency of a signal
- DPOSS:
- DQ Herculis star:
- DQ Tau: young binary star system
- DR:
- data release (DR): publication or distribution of a set of data from a survey
- DR1:
- data release (DR): publication or distribution of a set of data from a survey
- DR2:
- data release (DR): publication or distribution of a set of data from a survey
- DraGMet:
- DraGNS:
- DragonCam:
- Dragone design:
- Dragone telescope: off-axis reflecting telescope type that preserves polarization
- Dragone-design telescope:
- Dragonfly: plan for Titan flying rover
- Drake equation: estimate of advanced life in the Milky Way
- DraMS:
- DRAO:
- Dreyer:
- drift barrier:
- 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
- DRT:
- dry ice:
- ice: solid state of water
- DSFG:
- DSN:
- dSph:
- DSS:
- DSS2:
- du Pont Telescope:
- DUN:
- Dunlop:
- Dunlop Double Star Catalogue (DUN): 1829 catalog of double stars viewed from Australia
- Durchmusterung:
- Durham:
- dust:
- dust extinction:
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- dust grain:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- dust map:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- dust particle:
- cosmic dust: cosmic dust is dust in space such as interstellar dust
- dust polarimetry:
- dusty star-forming galaxy:
- duty cycle: percent of time when activity is recurring
- dwarf galaxies:
- dwarf galaxy: small galaxy with a few billion stars
- dwarf nova: flash of a cataclysmic variable star
- dwarf planet: round like a planet, only smaller
- Pluto: dwarf planet formerly listed as one of the nine planets
- dwarf spheroidal galaxy (dSph): spheroidally-shaped dwarf galaxy lacking star formation
- dwarf star:
- DWB:
- DWE:
- Cassini: explorer spaceship sent to Saturn
- Dwingaloo Radio Observatory:
- Dwingeloo:
- Dwingeloo Obscured Galaxy Survey (DOGS): radio survey of ZOA for 21cm lines indicating galaxies
- Dwingeloo Radio Observatory:
- DXS:
- UKIDSS: five-part infrared survey using UKIRT
- dynamic capture:
- tidal capture: bodies entering orbit through dissipation of energy by tides
- dynamic instability:
- dynamic mass:
- mass: object's quality that determines the effects of forces and gravity
- dynamical friction: drag produced by gravitational interaction with surrounding objects
- dynamical instability: situation where a perturbation makes itself larger
- dynamical systems:
- chaos theory: theory of systems highly sensitive to initial conditions
- dynamical timescale:
- free-fall time: time it would take a body to collapse if unopposed
- timescale (t,τ): general length of time something takes
- dynamics:
- dynamo: mechanism for generating magnetic fields around astronomical bodies
- dyne:
index