Definition

Noun: A quasi-stellar radio source is a type of extremely luminous astronomical object. It appears star-like ("quasi-stellar") through optical telescopes but emits powerful radio waves and other forms of electromagnetic energy. Many of these objects exhibit large redshifts, which indicates they are very distant and receding from Earth at high velocities.

Usage and Examples

• The term quasi-stellar radio source is used to describe the specific class of active galactic nuclei that were first identified by their strong radio emissions.
  • The discovery of the first quasi-stellar radio source revolutionized our understanding of the distant universe.
  • Astronomers detected a new quasi-stellar radio source with an exceptionally large redshift.

Advanced Usage and Context

• The term is often abbreviated to quasar, which is now the more common term in both professional and popular science contexts. The full term quasi-stellar radio source is frequently used when discussing the historical discovery and classification of these objects or when emphasizing their radio-loud properties.
  • The paper traced the etymology of the word "quasar" back to its origin as a quasi-stellar radio source.
  • Not all quasi-stellar objects are strong radio emitters; the term quasi-stellar radio source specifically denotes the radio-loud subset.

Variants and Related Words

• Quasar (n): The standard short form for "quasi-stellar radio source."
• QSO (Quasi-Stellar Object) (n): A broader term that includes all quasi-stellar objects, both radio-loud and radio-quiet.
• Blazar (n): A related type of active galactic nucleus, a subclass of quasars with unique observational properties.
• Active Galactic Nucleus (AGN) (n): The general category of energetic galactic cores, which includes quasars.

Synonyms

• Radio-loud quasar: A more descriptive synonym emphasizing the defining radio emission.
• Quasi-stellar object (QSO): A closely related, more general term.

Notes on Meaning

• The term specifically refers to the objects as they were first discovered and defined by their radio emissions. Modern astronomy recognizes that many similar, extremely luminous objects are "radio-quiet." The more inclusive term for all such objects is "quasi-stellar object" (QSO) or simply "quasar," though the original term quasi-stellar radio source remains precise for the radio-loud class. The "large red shifts" are a key feature used to determine their immense distances and high energies.

Noun

1. a starlike object that may send out radio waves and other forms of energy; many have large red shifts