Why were quasars named 'quasi-stellar radio sources'?

Why were quasars named 'quasi-stellar radio sources'?

• A. They looked like stars but emitted radio energy
• B. They were visible only in infrared
• C. They were located in the Andromeda galaxy
• D. They rotate around rapidly

Answer: (A)

Quasars got their name because they appeared point-like, like stars, when viewed in optical telescopes, yet they were strong emitters of radio waves. The phrase “quasi-stellar radio source” captures both traits: quasi-stellar means star-like in appearance, and radio source means they stood out in radio surveys. Later observations showed their spectra have large redshifts, revealing they are extremely distant and incredibly luminous—far more powerful than any normal star. So the name reflects the unusual combination of a star-like image with strong radio emission. The other ideas don’t fit because quasars aren’t defined by infrared visibility, by being located in Andromeda, or by rapid rotation.

Quasars got their name because they appeared point-like, like stars, when viewed in optical telescopes, yet they were strong emitters of radio waves. The phrase “quasi-stellar radio source” captures both traits: quasi-stellar means star-like in appearance, and radio source means they stood out in radio surveys. Later observations showed their spectra have large redshifts, revealing they are extremely distant and incredibly luminous—far more powerful than any normal star. So the name reflects the unusual combination of a star-like image with strong radio emission. The other ideas don’t fit because quasars aren’t defined by infrared visibility, by being located in Andromeda, or by rapid rotation.