General Studies IIIScience and Tech

PARAS: PRL Advanced Radial-Velocity Abu-Sky Search Spectrograph

In this article, we delve into the PRL Advanced Radial-Velocity Abu-Sky Search spectrograph (PARAS), a state-of-the-art instrument developed by the Physical Research Laboratory (PRL) in India.The field of astronomy has always been driven by the quest to explore the mysteries of the universe. Scientists and researchers continually strive to develop advanced tools and technologies to study celestial objects and unravel their secrets. We will explore the key features, working principles, and significant contributions of PARAS to the field of astronomy.

Understanding PARAS:

The PRL Advanced Radial-Velocity Abu-Sky Search spectrograph, commonly referred to as PARAS, is a cutting-edge astronomical instrument designed to measure the radial velocities of celestial objects with exceptional precision. Developed at PRL’s Gurushikhar Observatory, PARAS has been operational since 2012 and has significantly contributed to various astronomical studies.

Key Features and Capabilities:

a. High Precision: PARAS is renowned for its high-precision measurements, capable of detecting radial velocity variations as small as a few meters per second. This sensitivity is crucial for studying exoplanets, where tiny wobbles induced by an orbiting planet on a star can be detected.

b. Fiber-Optic Feeding: PARAS utilizes advanced fiber-optic feeding, allowing it to collect stellar light from the telescope and deliver it to the spectrograph. This technique minimizes light losses and maintains the instrument’s overall efficiency.

c. Stability and Calibration: PARAS incorporates an ultra-stable environment and a comprehensive calibration system to ensure accurate measurements. The instrument is thermally controlled and operates under a stable vacuum, minimizing external influences on its performance.

d. Large Spectral Range: PARAS covers a wide spectral range, enabling it to analyze different wavelengths of light emitted by stars. This capability is crucial for characterizing stellar atmospheres and identifying chemical compositions.

Applications and Scientific Contributions:

a. Exoplanet Studies: PARAS has made significant contributions to the discovery and characterization of exoplanets. By detecting minute variations in a star’s radial velocity caused by the gravitational pull of an orbiting exoplanet, PARAS has helped identify and confirm the existence of several exoplanets.

b. Stellar Astrophysics: The high-precision measurements provided by PARAS have allowed astronomers to study stellar oscillations, investigate stellar magnetic fields, and understand the internal structures and evolutionary processes of stars.

c. Galactic Archaeology: PARAS has played a crucial role in the field of Galactic Archaeology, which involves studying the history and formation of our Milky Way galaxy. By measuring the chemical compositions and velocities of stars, PARAS helps astronomers trace the origins and evolution of different stellar populations.

Collaborative Efforts and Future Developments:

PARAS is not limited to the research conducted at PRL. The instrument has been a part of several international collaborations, contributing to global efforts in exoplanet research and stellar astrophysics. The future developments of PARAS include improvements in data reduction techniques, increasing its spectral resolution, and participation in upcoming astronomical surveys.

Scientists Discover an extreme Massive Giant and Most Dense Exoplanet

A new Jupiter size exoplanet with highest density of ~14 g/cm3 known till this date, and mass 13 times that of Jupiter has been discovered by an international team of scientists led by Prof. Abhijit Chakraborty at the Exoplanet Research Group of the Physical Research Laboratory (PRL), Ahmedabad. The team includes scientists from India, Germany, Switzerland and the USA. The discovery of this massive exoplanet was made using the indigenously made PRL Advanced Radial-velocity Abu-sky Search spectrograph (PARAS) at the 1.2 m telescope of PRL at its Gurushikhar Observatory in Mt. Abu by measuring the mass of the planet precisely.

The newly discovered exoplanet is found around the star called TOI4603 or HD 245134. NASA’s The Transiting Exoplanet Survey Satellite (TESS) initially declared TOI4603 as a possible candidate to host a secondary body of unknown nature. Using PARAS, scientists discovered it as a planet by measuring the mass of the secondary body and hence the planet is called TOI 4603b or HD 245134b. It is located 731 light years away. It orbits a sub-giant F-type star TOI4603 every 7.24 days. What sets this discovery apart is that the planet falls into the transition mass range of massive giant planets and low-mass brown dwarfs with masses ranging from 11 to 16 times the mass of Jupiter. Only fewer than five exoplanets are currently known in this mass range so far.

Massive giant exoplanets are those having mass greater than four times that of Jupiter. The newly discovered exoplanet TOI 4603b is one of the most massive and densest giant planets that orbits very close to its host star at a distance less than 1/10th the distance between our Sun and Earth. The exoplanet with a surface temperature of 1670 K is likely undergoing high-eccentricity tidal migration with an eccentricity value of approximately 0.3 The detection of such systems provides valuable insights into the formation, migration, and evolution mechanisms of massive exoplanets.


This discovery marks the third exoplanet discovery by India, and by the PRL scientists using PARAS spectrograph and the PRL 1.2m telescope, following the discoveries in 2018 (K2-236b) and 2021 (TOI-1789b).

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PARAS, the PRL Advanced Radial-Velocity Abu-Sky Search spectrograph, stands as a testament to the relentless pursuit of knowledge in the field of astronomy. With its exceptional precision and innovative features, PARAS has opened new avenues for understanding exoplanets, stellar astrophysics, and Galactic Archaeology. As technology continues to advance, PARAS and similar instruments will undoubtedly play a crucial role in unraveling the mysteries of the cosmos and expanding our understanding of the universe.

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