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

A galaxy that emits more than 90% of its energy in the infrared (8-1000 µm) and whose infrared luminosity exceeds 10¹² solar luminosities. → luminous infrared galaxy (LIRG). Quasars can also have such high or even higher bolometric luminosities. However LIRGs and ULIRGs emit the bulk of their energy in the infrared. Most of ULIRGs are found in merging and interacting galaxy systems. It is thought that their luminosity results from galactic collisions, which increase the rate of star formation.

→ ultraluminous; → infrared; → galaxy.

A type of galaxy that releases a tremendous amount of energy, on the average 10⁵⁸ ergs, compared with a supernova release of 10⁴⁹ ergs. Violent galaxies include quasars and exploding galaxies. About 1 percent of the galaxies are classified as violent. The nearest violent galaxy is Cen A.

→ violent; → galaxy.

A gas-rich galaxy that has weak stellar → spiral arms with → interarm gas and star formation more important than a typical → spiral galaxy, such as NGC 4414.

→ weak; → arm; → spiral; → galaxy.

A large → spiral galaxy of type Sc seen → face-on in the constellation → Canes Venatici and lying about 31 million → light-years away. Also known as M51 and NGC 5194. It is interacting with a small irregular galaxy NGC 5195.

→ whirlpool; → galaxy.

A subset of → starburst galaxies whose integrated spectra show broad emission features attributed to the presence of hundreds to thousands → Wolf-Rayet stars. The most massive stars formed in the burst evolve rapidly into a substantial population of Wolf-Rayet stars in aggregations of ionized gas.

→ Wolf-Rayet star; → galaxy.