Q&A: Black Holes

Q:
I had a couple of questions regarding XTE J1550-564. In your press release you spoke of the fact that the X-ray jets are, or appear to be, emitting in different strengths. You also said that you estimate this to be from the eastern jet colliding with an interstellar gas cloud. Is it possible that relativity could produce this effect? Does this eastern jet point away from our galaxy's core? Could the rotation of XTE J1550-564 around the galaxy affect its jets in any way? Thank you for taking the time to read this and answer my questions.

A:
Relativity theory and the Doppler effect - the spreading out of waves from a source moving away from the observer - imply that the receding source should be weaker. Since the receding source is observed to be brighter, the scientists have to search for another explanation. The effect of running into an interstellar cloud is the favorite one at the moment. The speed of the motion of the source around the center of the galaxy is only a fraction of the speed of light, so this could not have a significant effect.