Blazers in astrophysics

Blazers has a very large apparant velocity, which is usually much larger than speed of light, eg, 34c.

This problem is very nicely explained on this page: Apparent Superluminal Velocity of Galaxies .


Fig. 1 This is taken form the link metioned above. We measure the distance at 1 Jan then at 1 Feb. The apparent velocity would be the travelled distance divided by 1 month. However, the first measurement only measured the light from a place that is \(1+d/c\) further than the second spot due the the fact that light travels at a finite speed. So the distance we measured is larger than the actual distance at 1 Jan and 1 Feb. Thus leading to a apparent larger velocity and this velocity can exceed the limit of light speed.