Astrophysics (index)about

emission line

(point of high intensity in a spectrum)

An emission line is a spectral line due to emission of electromagnetic radiation from a (thin) cloud of gas with enough atomic excitation that the relaxation of atoms to lower levels is a primary source of its radiation, as per Kirchhoff's laws. Such lines are used to identify clouds and analyze their properties: in addition indicating a component of their makeup, redshifted lines help estimate distance or radial velocity.

By contrast, absorption lines are produced when the continuous spectrum produced by a hot body passes through a (relatively) cooler gas, which shows a preference to absorption of the wavelengths matching the differences in energy from one atomic excitement level to another.


Referenced by:
absorption line
Atacama Pathfinder Experiment (APEX)
broad emission line region
Be star
ionized carbon fine structure line ([CII])
carbon monoxide (CO)
Carbon Monoxide Mapping Array (COMA)
Compton reflection
diffuse emission
electron orbital
emission line galaxy (ELG)
star formation feedback
foreground subtraction
helium (He)
HII region (HII)
Kirchhoff's laws
Lyman-alpha emitter (LAE)
molecular cloud turbulence
Molecular Deep Field
Palomar Four-filter Survey (PC)
P Cygni profile
redshift (z)
Seyfert galaxy
star formation rate (SFR)
submillimeter galaxy (SMG)
supernova (SN)
spectral feature
spectral line
Tully-Fisher relation (TFR)
21cm experiment
21cm line
transit spectroscopy
T-Tauri star (TTS)
water lines
white dwarf
Wilson-Bappu effect
Wolf-Rayet star
Zeeman-Doppler imaging (ZDI)