Question

Astronomers can now report that active star formation was going on at a time when the universe was only 20% as old as it is today. When astronomers make such a statement, how can they know what was happening inside galaxies way back then?A. They look at open clusters in our galaxy and extrapolate to the past.B. They look at radio emission from quasars.C. They look at the way galaxy redshifts change with time.D. They examine the spectra of extremely high-redshift galaxies.

Answer 1

Answer: D.

They examine the spectra of extremely high-redshift galaxies.

Step-by-step explanation:

Astronomers Measure Redshift and the most accurate way to measure redshift is by using spectroscopy. When a beam of white light strikes a triangular prism it is separated into its various components (ROYGBIV). This is known as a spectrum (plural: spectra).

With an estimated distance of about 32 billion light-years (comoving distance,) or 13.4 GLY (light-travel distance,) astronomers announced it as the mostdistant astronomical galaxy known