tip of the red giant branch method (TRGB)
raveš-e nok-e šâxe-ye qulhâ-ye sorx
Fr.: méthode du haut de la branche des géantes
A technique for deriving extragalactic distances which uses the → luminosity of the brightest → red giant branch stars in old → stellar populations as a → standard candle. For old (> 2-3 Gyr), → metal-poor ([Fe/H] < -0.7) stellar populations, this luminosity is relatively well determined, and the → absolute magnitude of these stars in the I band is roughly constant (MI = -4.1 ± 0.1).
Exhausted of strength and energy.
Past participle of tire "to weary; become weary," M.E. tyren, O.E. teorian, of unknown origin.
Xasté "tired; hurt, wounded;" Mid.Pers. xastan, xad- "to injure, wound;" Av. vīxaδ- "to crush;" Proto-Iranian *xad- "to wound, hurt."
Fr.: fatigue de la lumière
The hypothesis that photons from distant objects lose energy during their intergalactic journey to us, thereby increasing in wavelength and becoming redshifted. This would provide an alternative to the → Big Bang model in accounting for the → redshifts of distant galaxies. However, there is no evidence for any such tired-light effect. First discussed by F. Zwicky (1929, Proceedings of the National Academy of Sciences, 15, 773).
triggered star formation
diseš-e mâše-yi-ye setâré
Fr.: formation d'étoiles déclanchée
ultraluminous infrared galaxy (ULIRG)
kahkešân-e forusorx-e ultar-tâbân
Fr.: galaxie ultralumineuse en infrarouge
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.
Unidentified Infrared Band (UIB)
bând-e forusorx-e nâ-idânidé
Fr.: bande infrarouge non identifiée
A no longer in general use name for → Aromatic Infrared Band.
Fr.: étoile non rougie
Fr.: ensemble bien ordonné
Wide-field Infrared Survey Explorer (WISE)
puyešgar barâye bardid-e bozorg-meydân dar forusorx
Fr.: Explorateur pour l'étude grand champ dans l'infrarouge
A → NASA infrared astronomical → space telescope launched in December 2009 to carry out an → all-sky survey from 3 to 22 → microns. With its 40-cm → telescope telescope and → infrared cameras, WISE aimed at a wide variety of studies ranging from the evolution of → protoplanetary disks to the history of → star formation in normal galaxies. In early October 2010, after completing its prime science mission, the spacecraft ran out of → coolant that keeps its instrumentation cold. However, two of its four infrared cameras remained operational. Hence, NASA extended the NEOWISE portion of the WISE mission by four months, with the primary purpose of hunting for more → asteroids and → comets, and to finish one complete scan of the main → asteroid belt. In August 2013, the WISE telescope's mission was extended for more three years to search for asteroids that could collide with Earth.