Term Index (D)
- D:
- 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-CIXS:
- SMART-1: Swedish lunary orbiter operational 2004-2008
- D-type galaxy:
- D1:
- CFHTLS: surveys of transients and stars
- D2:
- CFHTLS: surveys of transients and stars
- D3:
- CFHTLS: surveys of transients and stars
- D3A:
- D4:
- CFHTLS: surveys of transients and stars
- D56: a target survey field of ACT telescope
- DH:
- dL:
- Dp:
- deuterium (D,2H): hydrogen isotope with one neutron
- Db:
- DA:
- Dall-Kirkham telescope: type of reflector telescope
- dalton (Da,u): mass unit used on atomic scale
- mass: object's quality that determines the effects of forces and gravity
- damocloid: minor planet with a comet-like orbit
- damping tail:
- DAN:
- Danks:
- 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 burst:
- gamma-ray burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- dark cloud:
- dark current:
- photodiode: class of solid state device to detect EMR
- 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:
- 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 galaxy: gas and dark matter of a galaxy but with no stars
- dark halo:
- dark matter: matter suggested by gravity in galaxies and galaxy clusters
- 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 dynamical friction:
- dark matter filament: hypothesized type of long, thin volume of dark matter
- cosmic web: hypothesized structure of the dark matter throughout the universe
- dark matter halo: hypothetical dark matter throughout and surrounding a galaxy
- dark matter star:
- exotic star: term for theoretical stars not made of atoms/ions
- dark nebula: cloud that obscures stars behind it
- 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 sky: sky with limited light pollution
- dark star:
- exotic star: term for theoretical stars not made of atoms/ions
- dark-sky park:
- dark sky: sky with limited light pollution
- dark-sky preserve:
- dark sky: sky with limited light pollution
- dark-sky reserve:
- dark sky: sky with limited light pollution
- dark-sky site:
- dark sky: sky with limited light pollution
- DARPA:
- Darwin: past plan for space telescopes acting as an interferometer
- DASCH: project to digitize Harvard astronomy plates
- DASH345:
- DASI: 2000-2003 South Pole CMB telescope
- data:
- data cube: "table" of numerical data covering three dimensions
- data release (DR): publication or distribution of a set of data from a survey
- FITS: IAU standard for data such as images
- 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 concept using velocity as one of the three dimensions
- templates: mechanism to help classify many survey objects or events
- time-ordered data (TOD): observation data arranged by the time it was received
- virtual observatory (VO): online database of astronomical data
- data cube: "table" of numerical data covering three dimensions
- data folding: locating periods in data by trial
- data release (DR): publication or distribution of a set of data from a survey
- database:
- daughter nuclide:
- DAV star:
- David Dunlap Observatory:
- David Dunlap Observatory Catalog (DDO): catalog of dwarf galaxies
- DAW:
- Dawes:
- Dawes criterion:
- Dawes limit:
- Dawn: explorer spacecraft sent to asteroids Vesta and Ceres
- day:
- solar time: time based upon the position of the Sun in the Earth's sky
- DB:
- DBMM:
- brown dwarf (BD): star-like object with less mass than a star
- DBSP:
- DBV star:
- DC:
- DCAM5:
- MMX: Japanese probe to bring back a sample of a Martian moon
- DCBH:
- DCEP:
- DCld:
- DCMF:
- DCT:
- DDO:
- DDO 221:
- DDS:
- Galileo: circa 1990s space mission to Jupiter
- dE:
- de Broglie frequency:
- de Broglie wave:
- de Broglie wavelength: wavelength of a particle's matter wave
- de Broglie waves:
- de Sitter space:
- de Vaucouleurs' law:
- de Vaucouleurs' profile: relation between elliptical galaxy surface brightness and distance from center
- de-Sitter universe:
- dead zone: area within a disk where normal things don't happen
- DEBRA:
- debris disk: circumstellar disk of dust and debris around a star
- disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
- 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:
- deconvolution free:
- DSA-2000: array plan to detect radio transients
- decouple:
- decoupling: some type of particle stops being destroyed as often as it is created
- 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:
- deep CO2; cycle:
- Deep Dish Development Array:
- 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 Investigations of Neutral Gas Origins:
- Deep Lens Survey (DLS): investigating mass distribution of the universe
- deep Mars-crosser:
- Mars crosser (MC,MCA): asteroid with an orbit that crosses that of Mars
- Deep Near Infrared Survey of the Southern Sky:
- DENIS: 1990s southern sky survey of two near-infrared bands
- Deep Space 1 (DS1): 1998-2001 mission to fly by asteroid
- Deep Space 2:
- Deep Space Network:
- deep survey: survey using lengthy observation to identify distant galaxies
- Deep Synoptic Array 2000:
- DSA-2000: array plan to detect radio transients
- 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:
- degeneracy weight: number of quantum states with same energy level
- degeneracy weighting:
- degenerate dwarf:
- white dwarf (WD): stellar remnant of mostly electron degenerate matter
- degenerate electron pressure:
- degenerate energy levels:
- degeneracy: general word meaning a violation of normal rules
- degenerate matter:
- degenerate perturbation problem:
- degenerate star:
- compact object (CO): dense astronomical body such as white dwarf or denser
- degree:
- Degree Angular Scale Interferometer:
- DASI: 2000-2003 South Pole CMB telescope
- degree of ionization: fraction of material consisting of ions
- degrees:
- arcsecond (arcsec,sec,second of arc): a 3600th of an angular degree
- DeHt:
- 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 Cepheid Variable:
- 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
- DENIS-P:
- 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:
- density wave model:
- density-morphology relation:
- depth:
- DES:
- descending node:
- DESI:
- Design Review:
- MDR/SRR: planning step for a NASA mission
- designation:
- designator:
- Destiny:
- destriping: removing streak-like noise from images
- destructive interference:
- detached binary:
- detached object:
- detached population:
- detection:
- red noise: noise tending toward lower frequencies
- deuterated methane:
- methane (CH4): compound of one carbon and 4 hydrogen atoms
- deuterium (D,2H): hydrogen isotope with one neutron
- 21-cm 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:
- deviance information criterion:
- 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
- DFG:
- DFMI:
- Stardust: space mission that collected and returned comet coma dust
- 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
- Dias:
- DIB:
- DIBs:
- DIC:
- Dickel-Wendker-Bieritz Catalog (DWB): list of HII regions in the Cygnus X star forming region
- DID:
- Giotto: 1980s space mission carrying out a Comet Halley flyby
- dielectric: insulator that responds to an electric field
- dielectric material:
- dielectric: insulator that responds to an electric field
- dielectric medium:
- difference equations:
- differential cross section:
- differential equation:
- differential equations:
- differential photometry:
- photometry: studying starlight through bandpass filters
- differential reddening:
- reddening: red appearance of astronomical objects because blue light is attenuated by dust
- differential rotation:
- differential spectroscopy: analysis of the comparison of two spectrographs
- differentiated object:
- diffraction: effect of an obstacle on a wave
- diffraction grating:
- 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
- diffractive interstellar scintillation (DISS): diffraction of star light by the ISM
- diffractive scintillation:
- 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 radiation:
- diffuse galactic light:
- diffuse HI cloud:
- HI region (HI): cloud of neutral atomic hydrogen
- diffuse interstellar band:
- 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 damping: a damping process within the plasma during recombination
- 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
- dimensionless:
- dimensionless Hubble parameter:
- DINGO:
- Dione:
- moon: a planet's natural satellite, such as Earth's
- Saturn: second largest planet in the solar system
- dipole: field with two poles
- dipole antenna:
- 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
- 51 Eridani b: Jupiter-like planet discovered in 2015
- Beta Pictoris b (β Pic b): super Jupiter discovered in 2008
- PALMS: survey to find exoplanets for direct imaging
- dIrr:
- DIS:
- discontinuous Galerkin method: computational method for PDEs handling discontinuities
- discontinuous shock:
- shock wave: abrupt propagating disturbance in a fluid
- Discovery 1:
- NEAR Shoemaker (NEAR): space mission aiming to return a sample of an asteroid
- Discovery 14:
- Psyche: planned space mission to orbit an asteroid
- Discovery Channel:
- 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:
- dish antenna:
- disk: rotating disk-shaped object such as disk galaxy or circumstellar disk
- disk coupling:
- disk galaxy: galaxy shaped like a flat circle
- disk heating:
- heating: increasing the velocity of particles
- disk instability model:
- disk migration:
- disk type:
- disk wind:
- jet: stream of matter from an astronomical body
- disks:
- DISORT: simulation of radiative transfer in an atmosphere
- dispersion:
- dispersion measure (DM): to what degree an EMR signal's lower frequencies are delayed
- spectroscopy: measurement of light with various electromagnetic wavelengths
- velocity dispersion (σ): statistical dispersion of velocities of a group of objects
- dispersion constant:
- dispersion direction:
- dispersion measure (DM): to what degree an EMR signal's lower frequencies are delayed
- pulsar (PSR): type of astronomical body with EMR in regular cycles of seconds or less
- DISR:
- Cassini: explorer spacecraft sent to Saturn
- DISS:
- dissociated:
- dissociation:
- dissociation front:
- distance:
- distance ambiguity:
- distance modulus (μ): apparent magnitude minus absolute magnitude
- distortion: aberration where the image is in focus but misshaped
- distributed:
- disturbance:
- disturbed galaxy:
- dither:
- hot pixel: CCD pixel that shows more brightness than it should
- 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
- Djorg:
- Dju:
- DLR:
- SOFIA: aircraft-based infrared observatory
- DLS:
- DM:
- DM-dominated dwarf spheroidals:
- DM99:
- DMDF:
- DMR:
- DN:
- DNS:
- Do:
- DoDz:
- DOG:
- hot DOG: high-energy galaxy with a lot of dust
- DOGS:
- doldrums:
- Dolidze-Dzimselejsvili Catalogue (DoDz): list of 11 open clusters
- Dolidze-Dzimselejsvili Open Clusters Catalogue:
- DOLoRes:
- domain wall:
- Dome C:
- 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:
- Don:
- Doo:
- 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 imaging:
- Doppler shift: wave frequency difference due to relative velocity difference with source
- Doppler spectroscopy:
- Doppler tomography:
- tomography: observation of sections of a 3D object
- Dorpat:
- Dorpat Catalog:
- Dorpat Observatory:
- double bond:
- hydrocarbon (HC): any compound of just carbon and hydrogen
- double neutron star:
- 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 stars:
- double transit: star showing transits of two bodies
- double transit system:
- double-line spectroscopic binary (SB2): spectroscopic binary star where a specific line shows up at two different wavelengths
- spectroscopic binary (SB): binary star detected by movement indicated by Doppler shifts in the spectrum
- double-lined spectroscopic binary:
- down quark:
- downconverter: device that reduces the frequency of a signal
- dP/dt:
- DPM:
- DPOSS:
- DQ Herculis star:
- DQ Tau: young binary star system
- DR:
- 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
- Draco:
- DraGMet:
- DraGNS:
- DragonCam:
- Dragone design:
- Dragone telescope: off-axis reflector 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:
- dredge-up: stellar convection bringing up fused material
- Dreyer:
- drift barrier:
- barrier: challenging issue regarding planet formation
- radial drift: inward draft of objects within a protoplanetary disk
- radial-drift barrier: the problem that forming planets would drift inward into the star
- 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
- DRT:
- dry ice:
- ice: solid state of water
- dS:
- DS1:
- DSA-10:
- DSA-2000: array plan to detect radio transients
- DSA-110:
- DSA-2000: array plan to detect radio transients
- DSA-2000: array plan to detect radio transients
- DSCT:
- DSE:
- Stardust: space mission that collected and returned comet coma dust
- 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 cloud:
- 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:
- dust tail:
- comet: Sun-orbiting object with coma and possible tail
- dust-obscured galaxy:
- hot DOG: high-energy galaxy with a lot of dust
- DustEM: code to calculate dust extinction and emission
- dusty galaxy:
- dusty star-forming galaxy:
- duty cycle: percent of time when activity is recurring
- Duus-Newell catalog (DN): list of southern galaxies/clusters assembled in 1970s
- dwarf elliptical galaxy:
- dwarf galaxies:
- dwarf galaxy: small galaxy with 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:
- dwarf nova (DN): flash of a cataclysmic variable star
- dwarf planet: round like a planet, only smaller
- Ceres: dwarf planet and largest asteroid
- Pluto: dwarf planet formerly listed as one of the nine planets
- dwarf planets:
- minor planet: lesser solar system body without comet characteristics
- dwarf spheroidal:
- dwarf spheroidal galaxy (dSph): spheroidally-shaped dwarf galaxy lacking star formation
- dwarf spiral galaxy:
- dwarf spiral spiral galaxy:
- dwarf star:
- DWB:
- DWE:
- Cassini: explorer spacecraft sent to Saturn
- Dwingeloo:
- Dwingeloo Obscured Galaxy Survey (DOGS): radio survey of ZOA for 21-cm 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 heating:
- heating: increasing the velocity of particles
- 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:
- Dysnomia:
Index