Astrophysics (Index)About


(element, C, atomic number 6)

Carbon (C) is the element with atomic number 6, symbol C. Its usual isotope has mass number 12, but mass number 13 is stable and 14 has a 5730 year half-life. It is the fourth most common element in the universe: Milky-Way baryonic matter is on the order of 0.5% carbon by mass. Carbon results from the CNO cycle and the triple alpha process.

The carbon forbidden lines [CII] (e.g., 1900 GHz, 158 μm) of singly-ionized carbon (CII, i.e., C+) and [CI] (e.g., 492 GHz) of neutral carbon (CI) are observed in cooling clouds, being the result of fine structure atomic excitation from collisions: the resulting photons have a high probability of escaping the clouds, effectively turning thermal kinetic energy into outgoing electromagnetic radiation. Thus they are used, along with carbon monoxide spectral lines, to locate molecular clouds. The former maps to a microwave atmospheric window at high redshifts, thus has been proposed for mapping the high-redshift universe.

The carbon to oxygen ratio of stars is of interest in identifying systems similar to ours, i.e., planets with Earth-like composition.

Further reading:

Referenced by pages:
asymptotic giant branch (AGB)
alpha process
carbonate-silicate cycle
carbonate system
carbon burning
carbon planet
carbon star (C)
carbonaceous chondrite (C chondrite)
methylidyne (CH)
methane (CH4)
ionized carbon fine structure line ([CII])
CNO cycle
carbon monoxide (CO)
carbon dioxide (CO2)
cosmic dust
dalton (Da)
diffuse interstellar bands (DIBs)
ethylene (C2H4)
fine structure
horizontal branch (HB)
acetylene (C2H2)
hydrogen cyanide (HCN)
helium burning
hydrocarbon (HC)
ice giant
Lambda Boötis star (λ Boo)
mass number
metallicity (Z)
Millimeter-wave Intensity Mapping Experiment (mmIME)
neutron scattering
neutrons from carbon-13
nitrogen (N)
polycyclic aromatic hydrocarbon (PAH)
PAH emissions
post-main-sequence star
radioactive dating
red clump (RC)
silicate weathering feedback
spectral class
state of ionization
S-type star (S)
Tomographic Ionized-carbon Mapping Experiment (TIME)
triple alpha process
Type Ia supernova
white dwarf (WD)
Wolf-Rayet star