Constellation Andromeda Declination +43° 02′ 07.80″ Type BLLAC | Right ascension 02 22 39.612 Redshift 0.444 | |
 | ||
Distance 4.5 billion light-years
(Light travel time)
5.4 billion light-years
(present) | ||
3C 66A is a blazar located in the constellation Andromeda.
The "distance" of a far away galaxy depends on what distance measurement you use. With a redshift of 0.444, light from this active galaxy is estimated to have taken around 4.5 billion years to reach us. But as a result of the expansion of the Universe, the present (co-moving) distance to this galaxy is about 5.4 billion light-years (1647 Mpc). Even at this great distance this blazar has an apparent magnitude of about 15.5. Although 0.444 is used as the common redshift value, 0.3347 is a new strict lower limit "inferred through observing the far-UV absorption by the low-z IGM."
3C 66A underwent an optical outburst in 2007 August, as monitored by the Tuorla blazar monitoring program. The event was monitored by the Whole Earth Blazar Telescope project.