What did the universe look like as the very first stars and galaxies blazed into existence? An experiment designed to look back at that critical cosmic transition just got a huge funding boost.
The Hydrogen Epoch of Reionization Array (HERA), also known as the "Cosmic Dawn" telescope, will use radio waves to study the hydrogen atoms that filled the universe around the time that the first stars began to form.
The Nation Radio Astronomy Observatory (NRAO) announced last week that the National Science Foundation approved $9.5 million in funding to expand HERA. The additional funding will increase the number of radio antennas by more than 10 times what is currently planned, from 19 to 240, by 2018, according to NRAO. [The Universe: Big Bang to Now in 10 Easy Steps]
About a half a million years after the universe exploded into existence with the Big Bang, the cosmos was filled with a thick fog of neutral hydrogen atoms (meaning the atoms had no electric charge). When the first stars were born (an event sometimes called the "cosmic dawn"), much of the light they emitted was blocked by the hydrogen fog, so this period is often referred to as the cosmic "dark ages."
Over time, the radiation from those stars and galaxies effectively began to clear away the fog: by freeing electrons from those neutral hydrogen atoms (a processes called ionization), the newly formed stars eventually made the universe transparent. This process lasted nearly a billion years and is known as cosmic reionization.
"The ultraviolet light and X-ray emissions from these primitive objects altered the fundamental nature of the universe surrounding them, and HERA is designed to detect these changes," Rich Bradley, a HERA team member and an NRAO senior scientist, said in a statement from the observatory.
Rather than looking for light from those early stars and galaxies, HERA will study the neutral hydrogen that lies between those early cosmic candles, according to a statement from the NRAO. The telescope's radio antennae's will focus on a specific wavelength that corresponds to light "emitted by the slowly vanishing sea of neutral hydrogen that filled the space between the galaxies," the statement said.
"We are at a rare juncture in which the most basic measurement of a fundamental cosmological phenomenon — cosmic reionization — has yet to be made. HERA will enable that measurement, showing us never-before-seen details of the early history of our universe,” Chris Carilli, an astronomer with the NRAO in Socorro, New Mexico, and a member of the HERA team, said in the statement.
Observations with HERA may also fill in some information about how the first galaxies came to form galaxy clusters in the later universe, Carilli said.
The HERA array is located in South Africa, and consists of 14-meter-wide (46 feet) antennas. NRAO is a key partner and founding member of HERA. The experiment's international scientific collaboration consists of members from multiple institutes.