Q&A: Cosmology

Q:
I would like to know if all these new galaxies spotted with Chandra are going to affect the previous calculations of the total mass contained in the universe, and also if this is going to help to estimate a more accurate date for the Big Bang.

A:
A recent discovery (see http://chandra.harvard.edu/press/00_releases/press_011300bg.html) points to two new types of source: veiled galactic nuclei in which an X-ray emitting, but optically obscured black hole is at the center of a known galaxy, and a mysterious type of source that has yet to be identified with a known galaxy. The first type of source should not change our estimate of dark matter significantly, since the central black holes contain less than 1 percent of the total mass of the galaxy. It is impossible to say what the effect of the second type will be on our understanding of dark matter or the age of the universe, since we are not yet sure exactly what these mysterious objects are, or why they give off so many X rays. I would say that there is a good chance they could affect both.