An Etymological Dictionary of Astronomy and Astrophysics
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→ CH (methylidine).

→ CH (methylidine); → molecule.

The simplest molecule formed by the → cyano radical. The CN molecule is of considerable astrophysical importance, since many of its transition lines/bands are observed in various astronomical objects: interstellar medium, comets, various stars such as late-type F and G-dwarfs, and late-type giants. CN was the second interstellar molecule, after → CH (methylidine), to be identified; toward the bright star → Zeta Ophiuchi at ultraviolet wavelengths (A. McKellar, 1940 ASP Conf. Ser. 52, 187). CN was also one of the earliest molecules to be detected in other galaxies (Henkel et al. 1988, A&A 201L, 23).

→ cyano-; → molecule.

A molecule in the → interstellar medium comprising at least six atoms (e.g. Herbst & van Dishoeck, 2009, ARA&A).

→ complex; → molecule.

A → complex molecule containing C, H, O, and N atoms and involved in life developing processes. See also → organic molecule.

→ complex; → organic; → molecule.

A molecule that is composed of only one type of → chemical element, e.g. the → molecular hydrogen and → ozone.

→ homo-; → nuclear; → molecule.

Any molecule that occurs naturally in clouds of gas and dust in the interstellar medium. So far more than 140 species have been discovered, many of which nonexistent on Earth.

→ interstellar; → molecule.

A molecule that consists of the ions of the chemical elements that make up the molecule.

→ ionic; → molecule.

The smallest unit of a chemical compound. A molecule consist of two or more atoms held together by covalent bonds.

From Fr. moléclue, from Mod.L.molecula, diminutive of L. moles "mass, massive structure, barrier;" → -ula

A molecule that is normally found in or produced by living systems. Organic molecules typically consist of carbon atoms in rings or long chains, where other atoms (e.g. hydrogen, oxygen, and nitrogen) are attached, except for → carbon monoxide (CO) and → carbon dioxide (CO₂), etc.

→ organic; → molecule.

The molecule initially produced when a comet nucleus sublimates, soon changed to different daughter molecules because of solar radiation.

→ parent; → molecule.

A molecule in which the centers of positive and negative charge distribution do not converge and therefore has a mostly positive charge on one side and a mostly negative charge on the other. Different atoms around a central atom will always be polar molecules. Some polar molecules are H₂O, HF, COS, and CH₃Cl. Polar molecules are characterized by a → dipole moment.

→ polar; → molecule.

The chemical combination of one → oxygen (O) atom bonded to two → hydrogen (H) atoms. The bonding between the oxygen atom and each hydrogen atom is known as → covalent bonds. The two hydrogen atoms are bonded to the oxygen atom at a 105° angle. This geometry of the water molecule causes it to have positively and negatively changed ends, known as → polarity. Water is referred to a polar or dipolar molecule. The large nucleus of the oxygen atom attracts the shared electrons causing this side of the water molecule to be negatively charged while the hydrogen side is positively charged. This polarity allows water to bond easily with adjacent water molecules.

→ water; → molecule.