•many strong radio sources (3C catalog) - no obvious
optical counterparts
•3C48 (1960), 3C273 (1962) identified with faint
star-like optical sources – but
spectra inexplicable
•1963 - Schmidt & Greenstein (Caltech) ® highly redshifted hydrogen Balmer
lines
•3C 273 at 620 Mpc , 3C 48 at 1300 Mpc (from Hubble
Law)
•(recessional velocity of 3C 48 ~ 1/3 velocity of
light)
• L > 1012 L¤ !!
• light varies
within 1 month ® size < 0.1
lyr
•¯
•QUAsi-Stellar radio
sources – QUASARS
•now Quasi-Stellar
Objects QSOs