(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.
Referenced by pages:
asymptotic giant branch (AGB)
carbon star (C)
carbonaceous chondrite (C chondrite)
ionized carbon fine structure line ([CII])
carbon monoxide (CO)
carbon dioxide (CO2)
diffuse interstellar bands (DIBs)
horizontal branch (HB)
hydrogen cyanide (HCN)
Lambda Boötis star (λ Boo)
Millimeter-wave Intensity Mapping Experiment (mmIME)
neutrons from carbon-13
polycyclic aromatic hydrocarbon (PAH)
red clump (RC)
silicate weathering feedback
state of ionization
S-type star (S)
Tomographic Ionized-carbon Mapping Experiment (TIME)
triple alpha process
Type Ia supernova
white dwarf (WD)