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)
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)