An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A chemically peculiar A- or early F-type star showing an overabundance of → heavy elements and an underabundance of calcium and scandium. An Am star cannot receive a unique spectral type, as different methods (using the metallic lines, the hydrogen Balmer lines, and the calcium Ca II K-lines) yield three different spectral types. Contrarily to Ap stars, Am stars do not have significant external magnetic fields. Their rotational velocities are about 100-120 km s^-1 smaller than those of → Ap stars.

A for the spectral type, m for → metal; → star.

A type of star, usually G or K → giants, whose spectra show unusually strong absorption lines of → barium, → strontium, and other → s-process elements.

→ barium; → star.

An → evolved star which has lost most or all of its hydrogen-rich envelope, leaving just a core of helium.

→ helium; → star.

A peculiar evolved star of spectral type G or M whose spectrum displays a high abundance of lithium.

→ lithium; → star.

A cool, red star of spectral type M with a surface temperatures of less than 3600 K. The spectra of M stars are dominated by molecular bands, especially those of TiO. Naked-eye examples are Betelgeuse and Antares.

M, letter of alphabet, → star.

Stars for the observation of which telescope time has been awarded.

→ program; → star.