Faster Than a Speeding Bullet….
It is hard to convey the excitement that the discovery of the quasars generated in the early 1960’s. Maarten Schmidt’s picture even appeared on the cover of TIME magazine. But there was much skepticism regarding their true nature as well. Not only were the energy requirements enormous if the quasars were really distant objects, but something else was observed in the 1970’s that made the whole puzzle even more unbelievable. It seemed like some material in the jet was moving at 6 times the speed of light, which violated all our ideas about the nature of time and space. Look at the following radio “map” of 3C273 taken by researchers at the Owens Valley Radio Observatory and the National Radio Astronomy Observatory.
Look at the little blob of material that is moving outward. It appears to change its position by .002 arc-seconds in 3 years.
Project 6: How fast is the jet material moving?
(6.1) How far has the blob in the figure appeared to have moved in three years? [ L = q (arc-sec) x distance / 206,265 = .002 x 800 Mpc / 206,265 = 7.75 pc or about 25 light years ]
(6.2) What must its velocity be in order to do this? [ 25 light years / 3 years means that the object moves 8 light years per year, or it is traveling at 8 times the velocity of light! (light must travel a distance of 1 light year per year).]
How can this be? Several models have been proposed, but the most likely idea has the blob moving not across out line of sight, but rather almost along it. But this seems even more preposterous, because it would have to move even further to get to the position we observe! However, the state of affairs is easily seen with the aid of the following diagram:
Imagine that the blob emits the photon that we see at the top of the radio map at point O. It starts traveling the enormous journey towards Earth, and the photon reaches point B after 100 years. Thus, B is 100 lightyears from O. Meanwhile, the blob, moving at almost the speed of light in the direction of A, gets to A after 101 years. At A, the blob emits a photon (as it has been doing all along, of course) toward the Earth. At this point, by looking at the triangle OBA, the blob appears to be 8 lightyears from B. But the light from the blob at A is only one year behind the original photon emitted at O. So from the point of view of the Earth, the blob appears to emit light originally from the direction toward B, and once that light finally gets to us, after billions of years, the light from A will be one year behind.
Our model is saved! But how the jet get formed to begin with?