An artistic illustration of the early universe. (Image credit: Shutterstock)
For the first time, scientists have used ground-based telescopes to peer into the cosmic morning – the period more than 13 billion years ago when the light of the first stars began to change the face of our universe.
The residual light from that ancient era has a wavelength of a few millimetres and is extremely weak, meaning that although space observatories have been able to detect it, the signal is suppressed by electromagnetic radiation from the Earth's atmosphere before ground-based telescopes can register the primary light.
But now, by deploying a specially designed telescope, researchers from the Cosmology Large Angular Scale Surveyor (CLASS) have detected traces left by the first stars against the light of the Big Bang. They published their findings June 11 in The Astrophysical Journal.
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“People thought this couldn’t be done from the ground,” said study co-author Tobias Marridge, CLASS project leader and professor of physics and astronomy at Johns Hopkins University, in a commentary. “Astronomy is a technology-limited field, and the microwave signals from Cosmic Dawn are notoriously difficult to detect. Observations from the ground face additional challenges compared to observations from space. Overcoming those hurdles makes this measurement a significant achievement.”
The CLASS observatory is located at an altitude of 16,860 feet (5,138 meters) in the Andes of northern Chile’s Atacama Desert. The telescope, which saw first light in 2016, is designed to observe the sky at microwave frequencies. In addition to being able to map 75 percent of the night sky, its unprecedented sensitivity allows it to pick up microwave signals from the cosmic dawn, or the first billion years of the universe.
For the first 380,000 years after the Big Bang, the universe was filled with a cloud of electrons so dense that light could not penetrate it. Eventually, however, our cosmos expanded and cooled, and the electrons were captured by protons, forming hydrogen atoms.
These hydrogen atoms not only allowed microwave light to move freely—filling space with the cosmic microwave background (CMB)—but also, where they were dense enough, collapsed under gravity and ignited, creating the first stars. The light from these stars then re-ionized patches of unclumped hydrogen gas, splitting their electrons so that some of them crossed paths with the CMB light, causing it to polarize.
The signal from this polarized portion of the cosmic microwave background is an important piece of the cosmological puzzle; without it, our understanding of the early Universe remains murky.
And while previous efforts by space telescopes, such as NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency's Planck space telescope, have partially filled in the gap,
Sourse: www.livescience.com
