In a major scientific discovery, a team from the Physical Research Laboratory (PRL) in Ahmedabad has found for the first time a distant planet roughly six times the size of Earth and revolving around a Sun-like star. The planet, which has a mass that is 27 times that of Earth, goes around the star in about 19.5 days, the Indian Space Research Organisation (ISRO) claimed on its website. Both the planet and the star, which have been located about 600 light years away from Earth, have been named EPIC. The name of the planet is EPIC 211945201b or K2-236b, while that of the host star is EPIC 211945201 or K2-236. With this discovery, India has joined the elite club of a handful of countries which have discovered planets around stars, ISRO said. The scientific team which made the discovery was led by Professor Abhijit Chakraborty of PRL, Ahmedabad.
The discovery of these celestial objects was made by measuring the mass of the planet using the indigenously-designed PRL Advance Radial-velocity Abu-sky Search (PARAS) spectrograph, which was integrated with a 1.2 metre telescope at PRL’s Gurushikhar Observatory in Mount Abu, according to the space agency.
"This is the first of its kind spectrograph in the country, which can measure the mass of a planet going around a star. Very few such spectrographs exist around the world (mostly in the USA and in Europe) that can do such precise measurements," the official statement said.
The gravitational pull caused by a planet on its host star makes it wobble around their common center of mass, which can be measured using high resolution spectrographs such as the PARAS. The PRL scientists observed the celestial objects over a time-baseline of 420 days (about 1.5 years) using the PARAS spectrograph to understand the nature of the star system. By measuring the amplitude of the wobbling of the host star, the mass of the planet was found to be about 27 times the mass of Earth.
The surface temperature of the planet is around 600 degrees Celsius as it is very close to the host star (seven times nearer than Earth is to the Sun). Although this distance might mean that the planet is uninhabitable, the discovery is still significant for understanding the formation of such super-Neptune or sub-Saturn kind of planets that are too close to the host star.
Based on the planet's physical properties, calculations suggested that heavy elements like ice, silicates and iron comprise 60 to 70 percent of its total mass. This detection is important as it adds to a sparse catalog of confirmed exoplanets with masses between 10-70 times that of Earth and radii between 4-8 times that of Earth. Only 23 such systems (including the present) are currently known to humans with precise measurement of mass and radii, the statement added.