Evolution of the Universe from Dark Ages on

CREDI:T National Astronomical Observatory of Japan

When the Dark Ages of the universe began, after the last flash of light from the Big Bang faded, the cosmos was a formless sea of complete darkness. In a range between 300 hundred million years and 1 billion years after the Big Bang and Dark Ages began, the universe transitioned into what scientists call the cosmic dawn, the moment the universe dramatically transitioned (known as the Epoch of Re-ionization) from unending darkness to a star-clustered sky of bright galaxies.  The Dark Ages lasted less than 2% of the universe’s current age, but in that time to Cosmic Dawn the universe went from a primordial soup of neutral gas to the star-filled cosmos we see today.  To understand what happened during this transition astronomers search for distant star forming galaxies over the larger vastness of the universe.

To narrow this massive search for extremely distant old galaxies in the early universe astronomers look for the Lyman alpha (radiation) emitting galaxies (LAEs) which are extremely distant, giving astronomers a peak at the ancient history of the universe.  Arizona State University astronomers Sangeeta Malhotra and James Rhoads, working with international teams in Chile and China, have been using the Dark Energy Camera (DECam), and discovered 23 small star-forming LAEs galaxies.  To detect these galaxies, DECam, enhances quantum efficiency in the red part of the visible spectra and in the near infrared and is installed on the National Optical Astronomy Observatory (NOAO)’s 4-meter Blanco Telescope. The Blanco telescope is inside the Cerro Tololo Inter-American Observatory (CTIO), in northern Chile, at an altitude of 7,200 feet.

Finding these galaxies at a time when the universe was only 800 million years old, helps astronomers to further close in on when the Cosmic Dark Ages ended, and the first stars and galaxies formed.  This discovery published in the Astrophysical Journal has helped the team calculate that LAEs galaxies multiplied by 4 times from 800 million years to 1 billion years.  That is the type of big jump astronomers are looking for to understand the initial formation of the universe.  The National Optical Astronomy Observatory (NOAO) team have concluded:  “The results imply that the process of ionizing the universe began early and was still incomplete at 800 million years, with the intergalactic gas about half neutral and half ionized at that epoch.”