India’s SARAS radio telescope gives clues to Universe’s 1st stars & galaxies

India’s SARAS radio telescope gives clues to Universe’s 1st stars & galaxies

Subject : Science and Technology

In the news-

• Raman Research Institute (RRI) in Bengaluru said that in a first-of-its-kind work, using data from an Indian telescope, scientists have determined properties of radio luminous galaxies formed just 200 million years after the Big Bang, a period known as the Cosmic Dawn.

What was the research about-

• They used the Shaped Antenna measurement of the background RAdio Spectrum-3 (SARAS-3) telescope.
• For the study, SARAS-3,indigenously designed and built at RRI, was deployed over Dandiganahalli Lake and Sharavathi backwaters, located in Karnataka, in early 2020.
• Scientists study properties of very early galaxies by observing radiation from hydrogen atoms in and around 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.

Why detection of the signal is a challenging task-

• The cosmic signal is extremely faint, buried in orders of magnitude brighter radiation from our own Galaxy and man-made terrestrial interference.
• So detecting the signal, even using the most powerful existing radio telescopes, has remained a challenge for astronomers.

Research findings-

• The results from the SARAS-3 telescope are the first time that radio observations of the averaged 21-cm line have been able to provide insight into the properties of the earliest radio-loud galaxies that are usually powered by supermassive black holes.
• This work takes forward the results from SARAS-2, which was the first to inform the properties of the earliest stars and galaxies.
• It has shown that less than 3% of the gaseous matter within early galaxies was converted into stars and that the earliest galaxies that were bright in radio emission were also strong in X-rays, which heated the cosmic gas in and around the early galaxies.
• SARAS-3 has been able to put an upper limit to excess radiation at radio wavelengths, lowering existing limits set by the ARCADE and Long Wavelength Array (LWA) experiments in the US.
• The analysis has shown that the 21-cm hydrogen signal can inform about the population of first stars and galaxies.

Challenges ahead-

• Constraints on the calculation of the masses of the early galaxies, along with limits on their energy outputs across radio, X-ray, and ultraviolet wavelengths.

What are Radio Waves and Radio Telescopes?

• 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.
• Radio telescopes collect weak radio light waves, bring it to a focus, amplify it and make it available for analysis.
• They help study naturally occurring radio light from stars, galaxies, black holes, and other astronomical objects.
• These specially-designed telescopes observe the longest wavelengths of light, ranging from 1 millimetre to over 10 metres long.
• For comparison, visible light waves are only a few hundred nanometers long, and a nanometer is only 1/10,000th the thickness of a piece of paper! In fact, we don’t usually refer to radio light by its wavelength, but by its frequency.

Shaped Antenna measurement of the background RAdio Spectrum-3 (SARAS-3) telescope-

• SARAS is a niche high-risk high-gain experimental effort of RRI.

SARAS aims to design, build and 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.