Hydrogen in Far Galaxy

A team of astronomers from European Southern Observatory (ESO) detected the presence of molecular hydrogen in the farthest system ever, an otherwise invisible galaxy that we observe when the Universe was less than 1.5 billion years old (The universe is estimated to be about 15 billion years old). The astronomers find that there is about one hydrogen molecule for 250 hydrogen atoms. This also implies that the gas in this galaxy must be rather cold, about -90 to -180 degrees Celsius. In addition, several lines from 'metals' are also seen, allowing the researchers to deduce the amount of various chemical elements.

The team arrived at this conclusion analyzing light from a quasar located 12.3 billion light-years away. A similar set of observations for two other quasars, together with the most precise laboratory measurements, allows scientists to infer that the ratio of the proton to electron masses may have changed with time (our last posting).

These exciting results will be available in a paper accepted for publication in the Astrophysical Journal Letters ("Molecular Hydrogen in a Damped Lyman-α system at zabs=4.224", by C. Ledoux, P. Petitjean, and R. Srianand).