SARAS 3 Telescope and Cosmic Dawn Research

SARAS 3 (Shaped Antenna measurement of the background Radio Spectrum 3) is a radio telescope designed and built at the Raman Research Institute, India. It is significant for its role in studying the Cosmic Dawn—the period when the universe’s first stars and galaxies formed. By measuring the 21-centimeter line from hydrogen atoms, SARAS 3 provides insights into the properties of the earliest radio-loud galaxies.

SARAS 3 detects faint signals emitted by hydrogen atoms in the early universe, stretched to lower frequencies by the expansion of space as they travel to Earth. Despite challenges from brighter galactic radiation and terrestrial interference, its exceptional sensitivity allows for the study of the early universe’s properties.

SARAS 3 has improved understanding of the astrophysics of the Cosmic Dawn, indicating that less than 3% of gaseous matter within early galaxies was converted into stars. It suggests these early galaxies were also strong in X-ray emissions, heating the cosmic gas around them.

In 2022, SARAS 3 data was used to reject claims of detecting an anomalous 21-cm signal from the Cosmic Dawn by the EDGES radio telescope. This helped restore confidence in the standard model of cosmology, which had been questioned by the EDGES claim.

After undergoing upgrades for improved sensitivity, the SARAS team is evaluating secluded sites in India for the telescope’s next deployment. These sites, despite logistical challenges, offer promising conditions for detecting the elusive 21-cm signal from the early universe.

While SARAS 3 primarily focuses on the 21-cm line from hydrogen, its research contributes broadly to understanding the cosmic microwave background (CMB) by providing constraints on the early universe’s properties. This includes limits on galaxy masses and their energy outputs across different wavelengths.