And the first observed quasars light from these stars

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and the first observed quasars. Light from these stars may have been observed in 2005 usingNASA's Spitzer Space Telescope,[63] although this observation remains to be confirmed.Quasar subtypesThe taxonomy of quasars includes various subtypes representing subsets of the quasarpopulation having distinct properties.Radio-loud quasars are quasars with powerful jets that are strong sources of radio- wavelengthemission. These make up about 10% of the overall quasar population.[64]Radio-quiet quasars are those quasars lacking powerful jets, with relatively weaker radioemission than the radio-loud population. The majority of quasars (about 90%) are radio-Spectrum from quasar HE 0940-1050 after it has travelled through intergalactic mediumThis view, taken with infrared light, is a false-color image of a quasar- starburst tandem withthe most luminous starburst ever seen in such a combination.quiet.[64]Broad absorption-line (BAL) quasars are quasars whose spectra exhibit broad absorption linesthat are blueshifted relative to the quasar's rest frame, resulting from gas flowing outwardfrom the active nucleus in the direction toward the observer. Broad absorption lines are foundin about 10% of quasars, and BAL quasars are usually radio-quiet.[64] In the rest- frameultraviolet spectra of BAL quasars, broad absorption lines can be detected from ionized carbon,magnesium, silicon, nitrogen, and other elements.
Type 2 (or Type II) quasars are quasars in which the accretion disc and broad emission lines arehighly obscured by dense gas and dust. They are higher-luminosity counterparts of Type 2Seyfert galaxies.[65]Red quasars are quasars with optical colors that are redder than normal quasars, thought to bethe result of moderate levels of dust extinction within the quasar host galaxy. Infrared surveyshave demonstrated that red quasars make up a substantial fraction of the total quasarpopulation.[66]Optically violent variable (OVV) quasars are radio-loud quasars in which the jet is directedtoward the observer. Relativistic beaming of the jet emission results in strong and rapidvariability of the quasar brightness. OVV quasars are also considered to be a type of blazar.Weak emission line quasars are quasars having unusually faint emission lines in theultraviolet/visible spectrum.[67]Role in celestial reference systemsBecause quasars are extremely distant, bright, and small in apparent size, they are usefulreference points in establishing a measurement grid on the sky.[69] The International CelestialReference System (ICRS) is based on hundreds of extra-galactic radio sources, mostly quasars,distributed around the entire sky. Because they are so distant, they are apparently stationary toour current technology, yet their positions can be measured with the utmost accuracy by very-long-baseline interferometry (VLBI). The positions of most are known to 0.001 arcsecond orbetter, which is orders of magnitude more precise than the best optical measurements.

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Term
Fall
Professor
Diskin
Tags
Test, Monster, Quasar

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