SARAS 3 radio telescope

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Background-

• In 2018 a team of researchers from Arizona State University (ASU) and MIT in the US detected a signal from stars emerging in the early universe using data from the EDGES radio telescope. 
• ASU/MIT team had claimed the discovery of a radio wave signalling the birth of the First Stars, which was also hailed by Harvard astrophysicist Avi Loeb as worthy of two Nobel prizes. 
• However, the world awaited confirmation from independent researchers.
• Utilizing the indigenously invented and built SARAS 3 radio telescope, researchers from Raman Research Institute, an autonomous institute of the Department of Science & Technology, Govt. of India has refuted this claim.

SARAS-3 radio telescope & its discovery-

• SARAS is a niche high-risk high-gain experimental effort of RRI initiated and led by Prof. Ravi Subrahmanyan, along with Prof. N. Udaya Shankar.
• SARAS is a correlation spectrometer designed for precision measurements of the cosmic radio background and faint features in the sky spectrum at long wavelengths and operates in the octave band 87.5–175 MHz.
• It was built to deploy in India a precision radio telescope to detect extremely faint radio wave signals from the depths of time, from our “Cosmic Dawn” when the first stars and galaxies formed in the early Universe.

• SARAS-3 is the first telescope worldwide to reach the required sensitivity and cross-verify the claim of the signal detection.

• The signal from Cosmic Dawn is expected to arrive on Earth stretched in wavelength to meters and lowered in frequency by the expansion of the Universe to lie in the radio frequency band 50-200 MHz.
• Detecting a faint signal from such an early period of the Universe is extremely difficult. 
• The celestial signal is exceptionally faint – buried in sky radio waves that come to us from the gas in our own Galaxy, the Milky Way, which are a million times brighter.
• Besides, this cosmic signal is in a radio wavelength band used by numerous terrestrial communications equipment and TV and FM radio stations, which makes detecting the extra-terrestrial signal extremely difficult.
• However, RRI scientists and engineers have risen to the challenge and designed and calibrated the SARAS radio telescope to discern signals from Cosmic Dawn. 
• The telescope was first deployed in rural Timbaktu Collective in Anantapur district. 
• The subsequent deployment took place in the wilderness of trans-Himalayan Ladakh, logistics supported by the Indian Astronomical Observatory, operated by the Indian Institute of Astrophysics. 
• Recently, RRI astronomers came up with the idea of floating the radio telescope on a raft on water, which had never been conceived of in the world. 
• This helped provide a homogenous medium of high dielectric constant below the antenna improving sensitivity and reducing confusing radio waves emitted by the very ground beneath radio telescopes.
• In 2020, the radio telescope was deployed in lakes in Northern Karnataka, on Dandiganahalli Lake and Sharavati backwaters.
• After a rigorous statistical analysis led by Dr. Saurabh Singh, a research scientist at RRI, SARAS 3 did not find any evidence of the signal claimed by the EDGES experiment. 
• The presence of the signal is decisively rejected after a careful assessment of the measurement uncertainties.
• Therefore, the finding implies that the detection reported by EDGES was likely contamination of their measurement and not a signal from the depths of space and time.

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