Term Index (E)
- E:
- E and B Experiment:
- EBEX: balloon-based CMB polarization survey
- E mode:
- EBEX: balloon-based CMB polarization survey
- E ring:
- Enceladus: Saturn moon considered possible carrier of life
- E-CDFS:
- MIGHTEE: radio survey of four established deep fields
- e-e bremsstrahlung:
- bremsstrahlung: photon emission when a charged particle is decelerated
- E-ELT:
- e-folding:
- e-folding time: time to increase by a factor of e
- e-ion bremsstrahlung:
- bremsstrahlung: photon emission when a charged particle is decelerated
- e-MERLIN:
- MERLIN: VLBI array spread across England
- E-mode:
- E-THEMIS:
- e-VLBI:
- Eh:
- EA:
- EA Observatory:
- EAGLE: simulation of galaxy formation and evolution
- EAGLE Project:
- EAGLE: simulation of galaxy formation and evolution
- EAO:
- early:
- early galaxies:
- first galaxies: targeted highest red-shift galaxies showing little or no metal
- early M dwarf:
- M dwarf: small, cool main-sequence star in stellar class M
- Early Release Science:
- early universe: from the Big Bang to recombination
- early-type galaxy:
- galaxy: gravitationally-bound group of stars
- early-type nitrogen-rich Wolf-Rayet:
- early-type star:
- spectral class: overall classification of stars based upon spectral features
- spectral type: classification of stars based upon spectral features
- Earth: third solar system planet from the Sun
- Earth analog: plant with characteristics of Earth
- Earth atmospheric pressure:
- Earth mass:
- mass: object's quality that determines the effects of forces and gravity
- Earth rotation aperture synthesis:
- Earth rotation synthesis: using the Earth's rotation to observe with various interferometry baselines
- Earth term:
- Earth-crossing asteroid:
- Earth-sized VLBI: ground-based VLBI with near-maximal baseline
- Earths:
- earthshine: reflected and emitted electromagnetic radiation from Earth
- East Asian Observatory (EAO): operator of JCMT
- EB:
- Ebb:
- GRAIL: 2011 NASA lunar orbiters to collect gravity data
- EBEX: balloon-based CMB polarization survey
- EBHIS:
- EBL:
- EBLM:
- eBOSS:
- EC:
- ECA:
- eccentric anomaly:
- mean anomaly: angle describing an object's position within an elliptical orbit
- eccentric Jupiter:
- eccentricity (e): degree to which an orbit is non-circular
- comet: Sun-orbiting object with coma and possible tail
- DQ Tau: young binary star system
- EXOSAT: 1980s European space X-ray telescope
- Haumea: dwarf planet discovered in 2004
- HD 80606 b: hot Jupiter discovered in 2001
- orbital element: parameters describing an orbit
- Planet Nine: theoretical planet beyond Neptune
- Pluto: dwarf planet formerly listed as one of the nine planets
- Sedna: distant solar system planetoid discovered in 2003
- Solar Orbiter (SolO): Sun-observing satellite in development
- eccentricity-type resonance:
- orbital resonance: tendency of orbits of multiple bodies to remain in a simple pattern
- ECDFS:
- echelette grating:
- echelle grating:
- grating: spectrometer component
- HARPS: high-precision spectrograph for exoplanet searches
- immersion grating: grating where light is within the material
- eclipse:
- eclipse mapping: using eclipse light curves to map surface features
- eclipse timing offset:
- eclipsing Algol:
- eclipsing Beta Lyrae:
- eclipsing binary (E): binary star system detected by variations in magnitude
- ecliptic: path of the Sun on the celestial sphere as seen from Earth
- ecliptic coordinate system: celestial coordinate system system based upon Earth's orbital plane
- ecliptic latitude:
- ecliptic longitude:
- ecliptic plane:
- ecliptic: path of the Sun on the celestial sphere as seen from Earth
- Ecliptic Plane Input Catalog:
- K2: second Kepler mission that worked around failed equipment
- ECSN:
- Eddington accretion rate:
- accretion: enlargement of an astronomical body by gravitationally attracting additional mass
- accretion rate: rate of addition of mass to an object
- Eddington luminosity: maximum luminosity at which radiation force overcomes gravity
- Eddington approximation: approximation of a star's internal EMR's divergence from isotropic
- Eddington bias: selection bias from mistaking something common for something rare
- Eddington limit:
- Eddington luminosity: maximum luminosity at which radiation force overcomes gravity
- Eddington valve:
- kappa mechanism (κ-mechanism): stellar instability caused by opacity increasing with temperature
- Eddington-Barbier relation:
- source function (S): measure indicating the effect of a material on EMR passing through
- eddy:
- EDG:
- Edgeworth-Kuiper Belt:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- Edgeworth-Kuiper Belt object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- EDI:
- EDM:
- EE:
- EE cosmic rays:
- EECR:
- EECRs:
- EELG:
- EF Eridani: binary star including a substellar object
- EF Eridani B:
- EF Eridani: binary star including a substellar object
- effective elastic thickness:
- elastic thickness (Te): measure of the thickness of a sagging layer of a planet surface
- effective field theory (EFT): type of useful simplification of a field theory
- effective number of neutrinos:
- neutrino (ν): light, electrically neutral elementary particle
- effective radius (Re): radius of a galaxy within which 1/2 the light is emitted
- effective temperature (Teff,Teff): temperature of an equivalent black body in terms of total radiation
- Effelsberg 100-m Radio Telescope: German large single-dish radio telescope
- Effelsberg Radio Telescope:
- Effelsberg-Bonn HI Survey:
- effusion:
- EFI:
- THEMIS: set of satellites studying the Earth's magnetic field
- EFOSC2:
- EFT:
- EGB:
- EGCR:
- cosmic rays (CR): very-high-energy particles from beyond the solar system
- EGG:
- EGGR:
- EGM:
- EGO:
- EGP:
- egress duration:
- EGRET:
- EGS:
- EH:
- event horizon (EH): surface-shape around a black hole through which light cannot escape
- EHB:
- horizontal branch (HB): a second "giant" stage in the evolution of some main sequence stars
- EHB star:
- horizontal branch (HB): a second "giant" stage in the evolution of some main sequence stars
- EHe:
- EHT:
- EIE Group:
- eigen-basis:
- eigen-decomposition: useful type of factoring a matrix into the product of three
- eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- eigenmode decomposition:
- eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- eigenmode expansion:
- eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- eigenvector:
- eigenvalue (λ): ratio between a vector and a linear transformation of that vector
- Einstein angle:
- Einstein Observatory:
- HEAO-2: 1978 X-ray observatory space mission
- Einstein parallax:
- Einstein radius:
- Einstein ring:
- Einstein Telescope: concept for a larger LIGO-like GW detector
- Einstein's field equation:
- Einstein-Boltzmann equation:
- CMBFAST: software to calculate CMB anisotropies
- Einstein-de Sitter model: universe tuned to the smallest expansion that continues forever
- Einstein-de Sitter universe:
- Einstein-Rosen bridge:
- wormhole: connection between two regions in a curved space
- EIS:
- EIT:
- ejection: forcing or throwing something out
- EKBO:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- El Niño:
- Kelvin waves: pressure and gravity waves formed by Coriolis force and a barrier
- ELAIS:
- ELAIS-N1:
- ELAIS-N2:
- ELAIS-N3:
- ELAIS-S1:
- ELAIS-S2:
- elastic scattering:
- elastic thickness (Te): measure of the thickness of a sagging layer of a planet surface
- electric:
- electric field (E): electric force as distributed over a space
- electric potential:
- electric thruster:
- electricity:
- electromagnetic induction:
- electromagnetic radiation (EMR): radiation such as light, radio, X-rays
- electromagnetic spectrum: spectrum of EMR
- electromagnetism (EM): electricity and magnetism and their interaction
- electromotive force (EMF): force that drives an electric current
- electron:
- electron capture: combination of an electron with a proton
- electron capture supernova:
- electron degeneracy: electrons set free of atoms by the Pauli exclusion principle
- electron degeneracy pressure:
- degeneracy: general word meaning a violation of normal rules
- electron degeneracy: electrons set free of atoms by the Pauli exclusion principle
- electron pressure: the electron contribution to pressure within a plasma
- neutron star (NS): stellar remnant consisting entirely of solar masses of neutrons
- electron degenerate matter (EDM): dense matter such as that in white dwarf
- electron excitation:
- electron fraction:
- ionization fraction: a substance's ratio of unattached electrons to nuclei
- r-process: synthesization of elements through neutron capture faster than beta decay
- electron neutrino:
- electron orbital: a nucleus's "locations" where an electron can orbit
- electron pressure: the electron contribution to pressure within a plasma
- electron relaxation:
- electron scattering: any process that changes the course of an electron
- electron screening: reduction of effective charge of a nucleus by nearby electrons
- electron shell: radius-level around an atomic nucleus at which electrons can orbit
- electron volt (eV): very small unit of energy
- photon: quantum of light, i.e., light as a particle
- photon energy: the energy carried by a single photon
- electron-ion bremsstrahlung:
- bremsstrahlung: photon emission when a charged particle is decelerated
- electron-positron plasma:
- Faraday rotation: rotation of optical polarization by a medium in a magnetic field
- electron-volt:
- gamma rays (GR): electromagnetic radiation, wavelength 10 picometers and less
- X-ray: electromagnetic radiation, wavelength 0.01 to 10 nanometers
- electronegativity:
- oxidation state: number of electrons loaned out by an atom in an ionic bond
- electronic:
- electronic very-long-baseline interferometry (e-VLBI): real-time VLBI using electronic links
- electronics:
- electrons:
- Cooper pair: pair of electrons sharing a particular type of bond
- Fermi sea: electrons sitting at the outer edge when the atom is least excited
- spark chamber: type of ion detector
- electrostatic barrier: the problem that dust grains will repel and not join to form planet seeds
- barrier: challenging issue regarding planet formation
- electrostatic bond:
- ice: solid state of water
- electroweak: single conception including both electromagnetic and weak forces
- electroweak force:
- electroweak: single conception including both electromagnetic and weak forces
- WIMP: proposed particle comprising dark matter
- element: class of atom based on its number of protons
- calcium (Ca): element, Ca, atomic number 20
- carbon (C): element, C, atomic number 6
- helium (He): non-metallic element, He, atomic number 2
- hydrogen (H): most prominent element, atomic number 1
- iron (Fe): metal, Fe, atomic number 26
- lithium (Li): metal, Li, atomic number 3
- magnesium (Mg): element, Mg, atomic number 12
- neon (Ne): element, Ne, atomic number 10
- nickel (Ni): metal, Ni, atomic number 28
- nitrogen (N): metal, N, atomic number 7
- oxygen (O): element, O, atomic number 8
- silicon (Si): metal, Si, atomic number 14
- sodium (Na): metal, Na, atomic number 11
- sulfur (S): metal, S, atomic number 16
- elements:
- fusion: formation of an atomic nucleus nuclei from multiple smaller nuclei
- elevation range: measure of how high and low a telescope can be pointed
- ELF:
- ELG:
- ELHC:
- Elias:
- Elias 2-27: much-studied YSO
- ELIRG:
- eLISA:
- ellipse:
- elliptical:
- elliptical galaxies:
- elliptical galaxy: ellipsoidal-shaped galaxy
- ellipticity:
- ELODIE:
- 51 Pegasi b (51 Peg b): first exoplanet found orbiting a main sequence star
- HD 189733 b: hot Jupiter orbiting an orange dwarf
- HD 209458 b: hot Jupiter discovered in 1999
- elongation:
- ELT:
- ELT-CAM:
- ELT-HARMONI:
- HARMONI: spectrograph planned for E-ELT
- ELT-HIRES:
- ELT-IFU:
- ELT-MIDIR:
- ELT-MOS:
- EM:
- EM radiation:
- embedded cluster:
- embedded lens:
- embryo:
- EME:
- eigenmode: vibration mode of an oscillator where all parts move at the same frequency
- emergent gravity:
- EMF:
- EMIR:
- EMIR Multi-line Probe of the ISM Regulating Galaxy Evolution:
- Emirates Mars Mission:
- EMIRS:
- emission: addition of photons to a beam of EMR
- emission band:
- emission coefficient (j): measure of how much light a substance emits
- emission line: narrow frequency-region of a spectrum with higher intensity
- emission line galaxy (ELG): a galaxy type characterized by emission lines
- emission line tomography:
- line tomography: using double-peaked spectral lines to place constituents of a disk
- emission nebula: nebula that emits light such as an HII region or PN
- emission redshift:
- redshift (z): change to longer wavelengths due to Doppler effects
- emission spectroscopy:
- emissivity: measure of a material's efficiency at radiating thermal radiation
- emissivity index:
- spectral index (α): power by which an object's flux depends on frequency
- EMP:
- EMPIRE Survey: survey of gas in M51a to follow up PAWS
- EMR:
- 21-cm experiment: search for redshifted 21-cm hydrogen emission lines
- AB system: monochromatic magnitude calibration based upon absolute values
- absolute magnitude (M): magnitude as would be seen from 10 parsecs
- absorption: removal of photons from a beam of EMR
- absorption coefficient: measure of how much light a substance absorbs
- active galactic nucleus (AGN): central region of a galaxy with extremely high luminosity
- airglow: glow from a planet's atmosphere
- albedo: measure of reflectance
- anomalous cosmic rays (ACR): cosmic rays with unexpectedly low energies
- aperture: opening through which light passes
- aperture synthesis: interferometry to simulate a larger aperture telescope
- apparent magnitude (m): magnitude as seen from Earth adjusted for Earth atmosphere
- atmospheric window: frequency bands within which the atmosphere passes EMR
- Auger effect: mechanism by which ions emit an electron after receiving one
- aurora: light produced by atmosphere and solar wind
- B: photometric filter for blue light
- bandwidth: number of hertz between minimum and maximum frequencies
- beam: portion of a sky that a radio telescope is viewing
- black body (BB): idealized object that reflects no light
- black-body radiation: EMR due to the temperature of a body with a characteristic spectrum
- bolometer: instrument measuring heat produced by radiation
- bolometric correction: difference between an object's bolometric and visible magnitudes
- bolometric luminosity (LBol): total luminosity of an object at all wavelengths
- bolometric magnitude (Mbol,Mbol): absolute magnitude of all wavelengths
- bremsstrahlung: photon emission when a charged particle is decelerated
- brightness temperature (TB): temperature of an equivalent black body in terms of intensity
- broad-line region (BLR): region in center of active galaxy where spectral lines are broad
- cavity-enhanced absorption spectroscopy (CEAS): passing a beam through a gas multiple times to amplify absorption lines
- CCD: electronic device to detect light
- Cherenkov radiation: radiation from the shock of a charged particle passing through a medium
- chirp: burst of signal rising or falling in frequency
- circular polarization ratio (CPR): ratio of circular polarization handedness in reflected radar signal
- CMB lensing: gravitational lensing of the CMB
- color index: a number that characterizes the color of an object
- color temperature (TC): temperature-measure of a source based on a color index
- color-period diagram: means of comparing periods of stars at various wavelengths
- column density: measure of the matter through which EMR is passing
- Compton reflection: recognizable emission due to a gas or plasma's Compton scattering
- Compton scattering: photon collision with a charged particle that emits a different photon
- continuum emission: continuous spectrum such as black body radiation or bremsstrahlung
- cooling function: function relating a gas's cooling rate to its temperature
- cosmic background radiation (CBR): electromagnetic radiation coming from every direction
- cosmic infrared background (CIB,CIBR): widespread infrared radiation not associated with known sources
- cosmic microwave background (CMB,CMBR,CBR,MBR): microwave radiation coming from every direction
- cosmic optical background (COB): widespread optical radiation not associated with known sources
- cosmic X-ray background (CXB,CXRB,CXBR): X-ray radiation coming from outside the Milky Way
- cross dispersion spectrograph: echelle spectrograph with additional disperser crosswise to the first
- curvature radiation: synchrotron-like radiation when particles follow curved field lines
- cyclotron radiation: radiation emitted when charged particles are accelerated
- detective quantum efficiency (DQE): measure of instrument's ability to create images
- differential spectroscopy: analysis of the comparison of two spectrographs
- diffuse emission: electromagnetic radiation not confined to a point source
- dispersion measure (DM): to what degree an EMR signal's lower frequencies are delayed
- distance modulus (μ): apparent magnitude minus absolute magnitude
- Doppler broadening: broadening of spectral lines due to velocities of the photon sources
- Earth-sized VLBI: ground-based VLBI with near-maximal baseline
- earthshine: reflected and emitted electromagnetic radiation from Earth
- Eddington approximation: approximation of a star's internal EMR's divergence from isotropic
- effective temperature (Teff,Teff): temperature of an equivalent black body in terms of total radiation
- electromagnetic radiation (EMR): radiation such as light, radio, X-rays
- electromagnetic spectrum: spectrum of EMR
- electron volt (eV): very small unit of energy
- electronic very-long-baseline interferometry (e-VLBI): real-time VLBI using electronic links
- emission: addition of photons to a beam of EMR
- emission coefficient (j): measure of how much light a substance emits
- equation of radiative transfer (RTE): equation describing energy transfer by EMR
- equilibrium temperature (Teq,Teq): temperature a planet would have if it were an externally-heated black body
- European VLBI Network (EVN): consortium of radio telescopes to coordinate VLBI efforts
- extended source: term for astronomical object producing EMR that can be focused
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- extragalactic background light (EBL): electromagnetic radiation from star formation and AGNs
- extreme ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10-124 nm
- extremely low frequency (ELF): electromagnetic radiation, frequency 3 Hz to 30 Hz
- far infrared (FIR,far-IR): infrared radiation with wavelengths in the 30-450 μm range
- fast radio burst (FRB,FRT): astronomical high energy radio pulses of a few milliseconds
- fluorescence: mechanism by which molecules emit a longer wavelength than they absorb
- flux: flow rate per unit area
- flux density: measure of the strength of a radio signal
- foreground subtraction: removing unwanted sources of EMR in intensity mapping
- frequency: number of cycles per unit of time, such as waves per second
- frequency modulation (FM): changing the frequency of a signal's carrier
- G band: band of visible light around 5100 angstroms
- galaxy SED: SED of a galaxy, sometimes synthesized from photometric surveys
- gamma rays (GR): electromagnetic radiation, wavelength 10 picometers and less
- gamma-ray burst (GRB): short flashes of gamma rays apparently from outside our galaxy
- Geiger-avalanche photodiode (G-APD,SPAD): type of solid state photon sensor
- gravitational lensing: focusing electromagnetic radiation by gravitational force
- gravitational microlensing: gravitational lensing by "small" objects such as individual stars and planets
- gravitational redshift: redshift due to GR effects of gravity
- gray body: ideal object that reflects the same fraction of light at any wavelength
- greenhouse effect: mechanism that boosts temperature through selective blocking of EMR
- Gunn-Peterson trough: spectral feature in EMR from redshift 6+
- GZK limit: limit on energy of cosmic rays
- Hawking radiation: EMR theorized to be emitted by black holes, powered by their mass
- high frequency (HF): electromagnetic radiation, frequency 3-30 MHz
- I band: photometric filter for near infrared light
- imaging Fourier transform spectroscopy (IFTS): Michelson-interferometer-based imaging spectroscopy
- imaging spectrometer: device to capture spectrum point-by-point of an image
- infrared (IR): electromagnetic radiation, wavelength 0.74-300 micrometers
- infrared cirrus: cirrus-cloud-like infrared emissions from dust, etc.
- infrared excess (IRX): more infrared than that of a star's typical spectrum
- integral field spectrograph: spectrograph that captures images
- integral field unit (IFU): instrument to allow a spectrograph to capture data over a 2D field
- intensity: power reaching a surface from a specific source
- intensity mapping: measure of cosmic matter density
- interferometer: device detecting properties of electromagnetic waves by detecting interference between waves
- ionizing radiation: radiation with photon energy sufficient to ionize
- irradiance: EMR power reaching a surface
- jansky (Jy): unit of measurement of spectral flux density
- JHK photometric system (JHK): system to classify stars according to near-infrared colors
- K band: atmospheric window centered around 2.2 microns, or 136 THz
- K correction: correction to magnitude for redshift
- Kirchhoff's law of thermal radiation: for an object in thermodynamic equilibrium, emissivity equals absorptance
- Kirchhoff's laws: laws regarding the source of spectral lines
- light curve: changing intensity of light from a transient
- line shape function: function describing the shape of a spectral line
- low-surface-brightness galaxy (LSB galaxy): galaxies less bright than those historically identified
- luminosity (L): measure of brightness
- Lyman-Werner photon: ultraviolet photon with proper energy to excite molecular hydrogen
- magnetic dipole radiation: EMR naturally generated by a spinning magnetic dipole
- magnitude: a logarithmic measure of brightness
- maser: electromagnetic radiation amplified by stimulated emission
- microwave: electromagnetic radiation, frequency 300 MHz to 300 GHz
- mid infrared (MIR,mid-IR): infrared radiation with wavelengths in the 7.5-25 μm range
- monochromatic luminosity: luminosity at a specific wavelength
- multi-object spectrograph: device to record the spectrum of multiple targets simultaneously
- multipole expansion: series expansion of a function over the surface of a sphere
- near infrared (NIR,near-IR): electromagnetic radiation in the range of 800-2500 nm
- non-thermal emission: EMR not due to a body's heat
- observational astronomy: term covering observation
- OIR: a spectral "band name" for both visible light and infrared
- opacity (κ): a measure of opaqueness of a material
- optical depth (τ): a measure of opaqueness of a path of light
- optics: science and technology regarding visible light
- oscillator strength: fraction expressing QM's contribution to the probability of absorption
- passband: range of electromagnetic wavelengths that a filter allows
- phase curve: brightness of an object according to its phase angle
- photochemistry: study of the chemical effects of light
- photodiode: class of solid state device to detect EMR
- photoevaporation: dispersal of a gas from UV radiation
- photometer: instrument measuring brightness
- photometric redshift (photo-z): method of estimating redshift without spectroscopy
- photometric system: specification of a set of filters/passbands
- photomultiplier tube (PMT): electronic device to detect light
- photon counting: sensing EMR down to the photon level
- photon energy: the energy carried by a single photon
- photon noise: variation in light measurement due to its quantum nature
- Planck function: yields black body curve
- polarimetry: measurement of polarization of EMR
- polarization: property of waves that oscillate in a particular direction
- polarization modes: electric and magnetic aspects of the polarization of electromagnetic radiation
- Poynting vector (S): measures directional energy flux density
- quantum efficiency (QE): measure of instrument's ability to sense EMR
- quenched galaxy: galaxy currently producing minimal stars
- R band: band of visible light around 6500 angstroms
- radar: probe based on reflecting radio waves
- radiance: measure of EMR to/from a solid angle through and area
- radiant flux: measure of brightness
- radiation hydrodynamics (RHD): hydrodynamics plus the effects of EMR
- radiation pressure: the pressure exerted by electromagnetic radiation
- radiation zone: region of a star transmitting energy through radiative diffusion
- radiative flux: power passing through a unit area
- radiative transfer (RT): energy transfer in the form of electromagnetic radiation
- radiative transfer code (RT code): computer model of a gas's radiative transfer
- radiative transfer model (RTM): models of radiative transfer, often computerized
- radio: electromagnetic radiation, frequency 3kHz to 300GHz
- radiometer: device for measuring radiant flux
- Rayleigh scattering: wave scattering by particles smaller than the wavelength
- Rayleigh-Jeans law: yields approximation of black body curve useful at low frequencies
- reddening: red appearance of astronomical objects because blue light is attenuated by dust
- redshift (z): change to longer wavelengths due to Doppler effects
- redshift space: concept of space using redshift as the radial dimension
- relativistic beaming: directional relativistic effect on light from relativistic speeds
- relativistic speed: a substantial fraction of the speed of light
- rest wavelength: normal wavelength observed when not moving in relation to the source
- scattering: changing the direction of a particle's movement
- Schuster-Schwarzschild model: simplified model of a star's production of absorption lines
- self-absorption: EMR absorption by the same substance that emitted it
- sensitivity function (S): function of wavelength giving the sensitivity of an instrument
- solar constant: flux from the Sun at 1 AU
- source function (S): measure indicating the effect of a material on EMR passing through
- specific intensity: intensity per unit wavelength or frequency
- spectral energy distribution (SED): function or plot of brightness at each wavelength in the spectrum
- spectral flux density (S): flux or power of radiation per unit area per unit wavelength
- spectral index (α): power by which an object's flux depends on frequency
- spectral line energy distribution (SLED): function or plot of brightness of lines in a spectrum
- spectral resolution: measure of a spectrograph's ability to resolve features of the spectrum
- spectral signature: spectral characteristics indicating the emitting material and conditions
- spectrograph: device to record the spectrum of incoming light
- spectrography: charting the strengths of different electromagnetic wavelengths
- spectrometer: device to measure light by wavelength across its spectrum
- spectrometry: measuring the strengths of different electromagnetic wavelengths
- spectropolarimetry: measurement of light's polarization by wavelength
- spectroscope: device to study the spectrum of incoming light
- spectroscopy: measurement of light with various electromagnetic wavelengths
- speed of light (c): fundamental constant measured as the speed at which light travels
- starburst galaxy: galaxy forming stars at a very high rate
- Stokes parameters: means of describing a polarization state
- Strömgren photometric system: four-color photometric system devised in 1950s
- submillimeter galaxy (SMG): galaxy that produces significant submillimeter radiation
- subradio: electromagnetic radiation, frequency below 3 kHz
- super low frequency (SLF): electromagnetic radiation, frequency 30 Hz to 300 Hz
- superconducting tunnel junction (STJ): type of Josephson junction usable in EMR sensors
- supernova light curve (SN light curve): changing intensity of light following a supernova
- superradiance: Exotic quantum-mechanics light-amplification phenomenon
- surface brightness (SB): brightness per unit area of a surface
- surface of last scattering: sphere around us from which CMB photons are just reaching us
- synchrotron radiation: radiation emitted when high-speed charged particles are accelerated
- synchrotron self-Compton (SSC): charged particle cloud scattering its own synchrotron-produced photons
- thermal bremsstrahlung: type of EMR produced by thin, hot plasma
- thermal dust emission: glow of dust heated by stars or AGNs
- thermal emission: EMR due to a body's heat
- Thomson optical depth (τT,τ): a measure of effects of Thomson scattering
- Thomson scattering: elastic scattering of photons by a charged particle
- tired light: theory that light becomes red for reasons other than Doppler shift
- transit spectroscopy: spectroscopy through an exoplanet's transit
- transmission spectroscopy: spectrum of radiation passing through a substance
- tremendously low frequency (TLF): electromagnetic radiation, frequency below 3 Hz
- two-stream approximation: approximation of a star's internal EMR's divergence from isotropic
- U: photometric filter for ultraviolet light
- UBV photometric system: commonly-cited photometric system for describing stars' colors
- ultra low frequency (ULF): electromagnetic radiation, frequency 300 Hz to 3 kHz
- ultra-high-energy gamma rays (UHEGR): energetic gamma rays with more than 100 TeV photon energy
- ultraviolet (UV): electromagnetic radiation, wavelength 10-400 nm
- UVOIR: a spectral "band name" covering UV, visible light, and IR
- V: photometric filter for visible light
- Vega system: magnitude calibration such that Vega has zero magnitude
- very low frequency (VLF): electromagnetic radiation, frequency 3-30 kHz
- very-high-energy gamma rays (VHEGR): energetic gamma rays with 100 GeV to 100 TeV photon energy
- very-long-baseline interferometry (VLBI): interferometry based upon storing timing data at each telescope
- visible light: electromagnetic radiation, wavelength 390-750 nm
- wavelength: an alternative description of an electromagnetic wave's frequency or photon energy
- wavenumber (ν): reciprocal of wavelength
- weak lensing (WL): slight lensing detected in random patterns of distant objects
- Wien approximation: yields approximation of black body curve useful at short wavelengths
- Wien's displacement law: temperature times wavelength with maximum intensity equals a constant
- X-ray: electromagnetic radiation, wavelength 0.01 to 10 nanometers
- XEUV: electromagnetic radiation in the range of 0.15-124 nm
- Zeeman effect: magnetic field influence on spectral lines
- Zeeman-Doppler imaging (ZDI): technique for imaging stellar magnetic fields
- EMRI:
- EMU:
- EMUS:
- ENA:
- ENACS:
- Enceladus: Saturn moon considered possible carrier of life
- Enceladus Life Finder (ELF): mission to search for life on Saturn moon Enceladus
- Encke-type comet:
- endothermic reaction: reaction that absorbs heat
- energetic neutral atom (ENA): high-speed neutral atom
- energy:
- electron volt (eV): very small unit of energy
- erg: CGS unit of energy
- foe: unit of energy on the order of a supernova's output
- insolation: solar energy received per unit area in given time
- joule (J): SI unit of energy
- kinetic energy (KE): an object's energy due to its motion
- potential energy (PE): an object's energy that can be released
- radiative forcing (RF): difference between a planet's incoming and outgoing radiation
- relativistic energy: energy of an object including relativistic effects
- watt (W): SI unit of power
- energy density: energy per unit volume
- energy spectral density:
- ENG:
- engineering:
- England:
- Enhanced MERLIN:
- MERLIN: VLBI array spread across England
- enrichment mode:
- entropic gravity:
- entropy (S): relative measure of the amount of usable energy available
- envelope:
- Enzo: hydrodynamic simulation system
- eon:
- EOR:
- EoR-Spec:
- EoS:
- EPA:
- Giotto: 1980s space mission carrying out a Comet Halley flyby
- EPAC:
- Ulysses: space mission to observe the Sun from off the ecliptic
- EPAM:
- EPAS:
- EPD:
- Galileo: circa 1990s space mission to Jupiter
- Solar Orbiter (SolO): Sun-observing satellite in development
- EPDP:
- SMART-1: Swedish lunary orbiter operational 2004-2008
- ephemeris: information on the position of a celestial body in the sky over time
- ephemeris time:
- time standard: method of designating points in time and quantifying time periods
- EPIC:
- EPICS:
- epicycle: small circular motion around a large circular motion
- epicyclic frequency: frequency of oscillation in an accretion disk
- epicycle: small circular motion around a large circular motion
- spiral galaxy: flat galaxy with spiraling arms
- episodic star formation:
- EPOCh:
- epoch: when an object was at a particular set of celestial coordinates
- EPOXI: mission using Deep Impact for further exploration
- epoch B1950.0: midnight 1/1/1950 GMT as used as a time reference
- epoch folding:
- epoch J2000.0: noon 1/1/2000 GMT as used as a time reference
- epoch of galaxy assembly:
- epoch of galaxy formation: before z=1, when many galaxies formed
- epoch of reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- EPOXI: mission using Deep Impact for further exploration
- EPS merger trees:
- Epsilon Eridani: third nearest visible star system in sky
- Epsilon Ind A ab:
- Epsilon Indi (ε Indi,ε Ind): nearby star system including two brown dwarf companions
- Epsilon Indi (ε Indi,ε Ind): nearby star system including two brown dwarf companions
- EPTA:
- EPTA+:
- equant:
- epicycle: small circular motion around a large circular motion
- equation:
- equation of radiative transfer (RTE): equation describing energy transfer by EMR
- equation of state (EoS): equation relating temperature, pressure, and volume
- Equation of State: Supernovae Trace Cosmic Expansion:
- ESSENCE: survey using supernova data to study dark energy
- Equator:
- circle of latitude: circle around the Earth of points equidistant from a pole or the equator
- equatorial:
- equatorial coordinate system: latitude/longitude-like system for the celestial sphere
- equatorial coordinates:
- equatorial Kelvin wave:
- Kelvin waves: pressure and gravity waves formed by Coriolis force and a barrier
- equatorial mount: telescope mount with axis parallel to Earth's
- equatorial Rossby wave:
- Kelvin waves: pressure and gravity waves formed by Coriolis force and a barrier
- equatorial wave:
- Kelvin waves: pressure and gravity waves formed by Coriolis force and a barrier
- equilibrium condensation model: chemical model explaining solar system planet abundances
- equilibrium temperature (Teq,Teq): temperature a planet would have if it were an externally-heated black body
- equilibrium-limited weathering:
- weathering: changes in surface due to contact with atmosphere
- equinox: times when tilt of Earth is neither toward or away from the Sun
- equipment:
- drogue chute: parachute to slow something moving at high speed
- filter: optical device to filter out part of the EMR spectrum
- ion engine: type of electrical spacecraft engine
- mirror support cell: units in a telescope that support the mirror
- MMRTG: power source for space probes
- plate: product of astronomical photography
- Space Launch System (SLS): launch rocket in development, e.g., for future astronomical projects
- equivalent elastic thickness:
- elastic thickness (Te): measure of the thickness of a sagging layer of a planet surface
- equivalent width:
- era of reionization:
- erg: CGS unit of energy
- ergosphere: type of region of space around rotating black hole
- black hole (BH): region of such high mass that light cannot escape
- Eridanus Supervoid:
- void: empty spaces between large scale structures
- Eridanus Void:
- Eris:
- ERNE:
- ERO:
- Eros:
- EROS: search for MACHOs
- NEAR Shoemaker (NEAR): space mission aiming to return a sample of an asteroid
- EROS-1:
- EROS-2:
- erosion:
- ablation: erosion of the surface of an object
- weathering: changes in surface due to contact with atmosphere
- erosion barrier:
- eRosita:
- eROSITA: Russian/German space X-ray telescope launched in 2019
- Spektr-RG (SRG, SXG): Russian-German X-ray observatory launched in 2019
- error bar: feature of a graph to indicate accuracy
- ERS:
- eruptive variable star:
- Es-Birm:
- ESA:
- escape fraction: fraction of ionizing photons escaping a body
- escape parameter:
- escape velocity (Ve): minimal velocity that allows something to overcome a body's gravity
- Escorial:
- ESD:
- ESEX:
- ARGOS: 1999 technology-research satellite
- ESI:
- ESO:
- ESO (B) Atlas:
- ESO 137-001: barred spiral galaxy in the Abell 3627 cluster
- ESO 3.6m Telescope: reflector telescope at La Silla
- ESO 97-G13:
- ESO B plates:
- ESO Nearby Abell Cluster Survey (ENACS): 1990s spectroscopy and photometry survey of galaxy clusters
- ESO Quick Blue Survey:
- ESO Schmidt Telescope:
- ESO VLT:
- ESO/SERC Southern Sky Atlas:
- ESO/SERC Survey:
- ESO/Uppsala Survey of the ESO (B) Atlas: 1970s southern all-sky survey
- ESO594-G004:
- Esp:
- ESPaDOnS:
- ESPRESSO:
- ESSENCE: survey using supernova data to study dark energy
- ESTEC:
- ESTRACK:
- etalon: two parallel reflective surfaces separating light according to wavelength
- ETC:
- etendue (AΩ): measure of how wide and deep a telescope observes
- ETG:
- galaxy: gravitationally-bound group of stars
- ethane:
- hydrocarbon (HC): any compound of just carbon and hydrogen
- ethene:
- ethylene (C2H4): compound of two carbon and four hydrogen atoms
- ether:
- relativity: physics models accommodating the constancy of the speed of light
- ethylene (C2H4): compound of two carbon and four hydrogen atoms
- ethyne:
- acetylene (C2H2): compound of two carbon and two hydrogen atoms
- ETNO:
- Euclid: planned observatory-satellite to measure dark energy
- EUI:
- Euler's formula: formula relating exponentials to trigonometric functions
- Fourier series: type of series able to approximate a periodic function
- Euler's identity:
- Eulerian code:
- Europa: well-known Jupiter moon
- Europa Clipper: planned Europa space probe
- Europa Lander: plan for a mid 2020s Europa probe landing on the surface
- Europa Multiple Flyby Mission:
- Europe:
- European:
- European Extremely Large Telescope (E-ELT,ELT): 39-meter telescope under construction
- European Gravitational Observatory (EGO): gravitational wave observatory in Italy
- European Large Area ISO Survey:
- European Pulsar Timing Array (EPTA): European collaboration of radio telescopes
- European Southern Observatory (ESO): organization operating telescopes in the southern hemisphere
- European Southern Observatory Very Large Telescope (ESO VLT,VLT): four 8.2-meter optical telescopes in Chile that can act together
- European Space Agency (ESA): NASA-like international space organization in Europe
- European Space Research and Technology Centre:
- European Space Tracking:
- European VLBI Network (EVN): consortium of radio telescopes to coordinate VLBI efforts
- European X-ray Observatory Satellite:
- EXOSAT: 1980s European space X-ray telescope
- europium:
- EUV:
- CHIPSat: small satellite to investigate ISM plasma
- extreme ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10-124 nm
- IMAGE: satellite mission to study magnetosphere
- ionizing radiation: radiation with photon energy sufficient to ionize
- EUVE:
- EUVIP:
- ARGOS: 1999 technology-research satellite
- eV:
- electron volt (eV): very small unit of energy
- gamma rays (GR): electromagnetic radiation, wavelength 10 picometers and less
- photon: quantum of light, i.e., light as a particle
- photon energy: the energy carried by a single photon
- X-ray: electromagnetic radiation, wavelength 0.01 to 10 nanometers
- evaluation:
- evaporating gas globule (EGG): very small dense cloud of hydrogen and dust
- evaporation: particles escaping, e.g., liquid molecules escaping as gas
- EVCC:
- EVE:
- event:
- 1947 sunspot: largest sunspot ever recorded
- 775 AD event: apparent solar eruption, based upon tree-ring evidence
- Big Bang: theoretical event when the universe expanded from a point
- Carrington event: solar storm September 1-3 1859
- epoch of reionization (EOR): time when the universe's neutral hydrogen atoms ionized
- Great Debate: historical debate regarding the nature of galaxies
- GW170817: 2017 gravitational wave detection from a neutron star merger
- late heavy bombardment (LHB): time after solar system planet-formation when many impacts occurred
- recombination: time when the universe's ionized hydrogen atoms neutralized
- SN 1987A (1987A): supernova in February 1987 rare for being visible by the naked eye
- SN 2014J: type Ia supernova in Messier 82, the Cigar Galaxy
- event horizon (EH): surface-shape around a black hole through which light cannot escape
- Event Horizon Telescope (EHT): growing VLBI network
- 3C 279: striking variable quasar
- BlackHoleCam (BHC): European project to study black holes
- event type:
- EVN:
- Evolution and Assembly of Galaxies and their Environments:
- EAGLE: simulation of galaxy formation and evolution
- Evolutionary Map of the Universe:
- evolutionary track: H-R diagram track of the life of a star
- exaFLOP:
- ExAO:
- exascale computing: exaFLOP computing capability, i.e., quintillion FLOPs
- excess kurtosis:
- kurtosis: measure of the probability of a distribution's tails
- excitation:
- excitation temperature:
- excited state:
- EXES:
- SOFIA: aircraft-based infrared observatory
- EXI:
- exit pupil: size of the image as presented to the eye
- EXO:
- EXOSAT: 1980s European space X-ray telescope
- Exo-C:
- Exo-S: a study on the concept of a starshade mission
- exo-Earth:
- Exo-S: a study on the concept of a starshade mission
- Exo-starshade:
- Exo-S: a study on the concept of a starshade mission
- exobase:
- exosphere: outer portion of atmosphere so thin that it is not gas-like
- exobiology:
- Exobiology on Mars:
- ExoMars: program to search for signs of life on Mars
- ExoCTK: collection of software for exoplanet observation and analysis
- exoearth: Earth-like exoplanet
- GJ 1132 b: Earth-like extrasolar planet discovered in 2015
- Kepler-186f: Earth-like exoplanet in a star's habitable zone
- TOI 700 d: Earth-sized exoplanet in a habitable zone
- ExoFOP: site to facilitate exoplanet follow-up observation
- ExoFOP-Kepler:
- ExoFOP: site to facilitate exoplanet follow-up observation
- ExoFOP-TESS:
- ExoFOP: site to facilitate exoplanet follow-up observation
- ExoMars: program to search for signs of life on Mars
- ExoMars Rover:
- ExoMars TGO:
- ExoMars Trace Gas Orbiter:
- exomoon:
- exoplanet:
- Exoplanet Characterization Toolkit:
- ExoCTK: collection of software for exoplanet observation and analysis
- exoplanet demographics:
- exoplanet eclipse light curve: graph of light as an exoplanet transits in front of its star
- Exoplanet Follow-up Observing Program:
- ExoFOP: site to facilitate exoplanet follow-up observation
- exoplanet occurrence rate:
- Exoplanet Starshade:
- Exo-S: a study on the concept of a starshade mission
- starshade: spacecraft to block light from a specific body
- exoplanets:
- EXOSAT: 1980s European space X-ray telescope
- exosatellite: natural satellite not in the solar system
- exosphere: outer portion of atmosphere so thin that it is not gas-like
- ionosphere: layers of Earth atmosphere with significant ions
- exothermic reaction:
- exotic star: term for theoretical stars not made of atoms/ions
- Expérience pour la Recherche d'Objets Sombres:
- expansion fan: the "sound" of a supersonic flow flowing around a convex corner
- expansion of the universe:
- experiment:
- gravity sounding: measuring a planet's gravitation field by study of nearby probe flights
- Explorer 42:
- Uhuru: 1970 satellite X-ray telescope
- Explorer 80:
- Explorers Program:
- exponential growth:
- runaway process: a process with positive feedback so progress speeds progress
- exponential profile:
- exposure time:
- exposure time calculator (ETC): app to calculate time to carry out an observation
- Extended Baryon Oscillation Spectroscopic Survey:
- Extended BOSS:
- Extended Chandra Deep Field-South Survey (ECDFS): 1100 square arcminute X-ray survey
- Extended Groth Strip (EGS): region of sky searched for distant galaxies
- Extended Roentgen Survey with an Imaging Telescope Array:
- eROSITA: Russian/German space X-ray telescope launched in 2019
- extended source: term for astronomical object producing EMR that can be focused
- extinct pulsar:
- pulsar (PSR): type of astronomical body with EMR in regular cycles of seconds or less
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- extinction coefficient:
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- extinction curve:
- extinction: the absence of any radiation from an astronomical object because all is absorbed or scattered
- extinction event:
- extra-solar planet: planet not in the solar system
- extragalactic astronomy: astronomy of other galaxies, galaxy clusters, AGNs, quasars, etc.
- extragalactic background light (EBL): electromagnetic radiation from star formation and AGNs
- extragalactic cosmic rays:
- cosmic rays (CR): very-high-energy particles from beyond the solar system
- extragalactic distance scale:
- extragalactic nebula:
- galaxy: gravitationally-bound group of stars
- extrasolar giant planet:
- extrasolar moon:
- Extrasolar Planet Observation and Characterization:
- EPOXI: mission using Deep Impact for further exploration
- Extrasolar Planet Observation and Deep Impact Extended Investigation:
- EPOXI: mission using Deep Impact for further exploration
- extrasolar satellite:
- extremal black hole:
- extreme adaptive optics (ExAO): high-performance version of AO system
- extreme emission line galaxy:
- extreme energy cosmic rays:
- cosmic rays (CR): very-high-energy particles from beyond the solar system
- extreme helium star:
- extreme horizontal branch:
- horizontal branch (HB): a second "giant" stage in the evolution of some main sequence stars
- extreme horizontal branch star:
- horizontal branch (HB): a second "giant" stage in the evolution of some main sequence stars
- extreme Kuiper Belt object:
- Kuiper Belt (K Belt,KB): further part of solar system beyond Neptune
- extreme luminous supergiant:
- extreme mass ratio inspiral (EMRI): inspiraling pair of objects with mass ratio beyond 10,000
- extreme trans-Neptune object:
- extreme trans-Neptunian object:
- extreme ultraviolet (EUV,XUV): electromagnetic radiation in the range of 10-124 nm
- Extreme Ultraviolet Explorer (EUVE): 1990s ultraviolet space telescope
- extreme-energy cosmic rays:
- Extremely Large Telescope:
- extremely low frequency (ELF): electromagnetic radiation, frequency 3 Hz to 30 Hz
- extremely luminous far infrared galaxy:
- extremely luminous infrared galaxy:
- extremely metal poor:
- extremely red object (ERO): class of galaxies showing more infrared than visible light
- extrinsic S-star:
- S-type star (S): type of star with lines indicating zirconium
- extrinsic variable:
- eye piece:
- exit pupil: size of the image as presented to the eye
- eye relief:
- exit pupil: size of the image as presented to the eye
Index