xlv. SARAS Radio Telescope

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xlv. SARAS Radio Telescope

SARAS 3 (Shaped Antenna measurement of the background Radio Spectrum 3) telescope is an indigenously developed radio telescope of India. Recently, the SARAS radio telescope has provided astronomers with clues to the nature of the Universe’s first stars and galaxies.

There are a variety of ground- and space-based telescopes looking into the sky for a deeper understanding of the Universe. Humans have attempted to capture the faint signals arising from the depths of the cosmos to know about how the early stars and galaxies formed and what they looked like.

Scientists have determined the properties of radio-luminous galaxies formed just 200 million years post the Big Bang, a period known as the Cosmic Dawn.

This provides an insight into the properties of the earliest radio-loud galaxies that are usually powered by supermassive black holes.

What are radio telescopes?	The purpose of a radio telescope is to detect radio-frequency radiation from extraterrestrial sources, such as stars, galaxies, and quasars, between the wavelengths of around 10 meters (30 megahertz [MHz]) and 1 mm (300 gigahertz [GHz]), using a radio receiver and an antenna system. Since radio wavelengths are much longer than those of visible light, radio telescopes must be very large to attain the resolution of optical telescopes. The first radio telescope was built in 1937 by Grote Reber of Wheaton, U.S. It was a steerable paraboloid, a device with a parabolically shaped reflector, dubbed the “dish,” that focuses the incoming radio waves onto a small pickup antenna, or “feed.” Radio telescopes vary widely, but they all have two primary components: a large radio antenna a radiometer or radio receiver. The sensitivity of a radio telescope is the ability to measure weak sources of radio emission. It depends on the area and efficiency of the antenna, the sensitivity of the radio receiver used to amplify and detect the signals, and the duration of the observation. Radio astronomy has the advantage that sunlight, clouds, and rain do not affect observations
What are Radio waves?	Radio waves have the longest wavelengths in the electromagnetic spectrum. They range from the length of a football to larger than our planet. Heinrich Hertz proved the existence of radio waves in the late 1880s. Astronomical objects that have a changing magnetic field can produce radio waves. The radio astronomy instrument called WAVES on the WIND spacecraft recorded a day of bursts of radio waves from the Sun’s corona and planets in our solar system.
SARAS 3 Radio telescope	Shaped Antenna measurement of the background Radio Spectrum 3 (SARAS) telescope was indigenously designed and built at Raman Research Institute. It was deployed over Dandiganahalli Lake and Sharavati backwaters, located in Northern Karnataka, in early 2020. SARAS plans to design, build, and deploy a precise radio telescope in India to detect incredibly faint radio wave signals from the depths of time, from our “Cosmic Dawn,” when the first stars and galaxies formed in the early Universe. In a first-of-its-kind work, using data from SARAS 3, researchers from the Raman Research Institute (RRI), Bengaluru, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia, along with collaborators at the University of Cambridge and the University of Tel-Aviv, estimated the energy output, luminosity, and masses of the first generation of galaxies that are bright in radio wavelengths.
Findings of SARAS 3 Radio telescope	Scientists study the properties of very early galaxies by observing radiation from hydrogen atoms in and around the galaxies, emitted at a frequency of approximately 1420 MHz. The radiation is stretched by the expansion of the universe, as it travels to us across space and time, and arrives at Earth in lower frequency radio bands 50-200 MHz, also used by FM and TV transmissions. The cosmic signal is extremely faint, buried in orders of magnitude brighter radiation from our Galaxy and man-made terrestrial interference. Therefore, detecting the signal, even using the most powerful existing radio telescopes, has remained a challenge for astronomers. SARAS 3 has improved our understanding of the astrophysics of Cosmic Dawn, telling us that less than 3 percent of the gaseous matter within early galaxies was converted into stars. Also, the earliest galaxies that were bright in radio emission were strong in X-rays, which heated the cosmic gas in and around the early galaxies

Image Courtesy: Britannica