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View from India: ‘Epic’ new distant planet discovered by Indian scientists

India has made it to planet-spotting club. An elitist club, comprising coveted countries that have found planets that revolve around stars has a new member.

A team of scientists from Physical Research Laboratory (PRL) Ahmedabad have, for the first time, found a distant planet revolving around a Sun-like star, which is about 600 light years away from the Earth.

Although the newly discovered planet is six times bigger than Earth, it is found to be smaller than Saturn and bigger than Neptune. This discovery has catapulted India into a different space league.

Professor Abhijit Chakraborty of PRL has been credited with this discovery, which he conducted with a team of scientists.

PRL’s parent organisation is Indian Space Research Organisation (ISRO), the primary space agency of the Indian government. An official announcement made on the ISRO web site last week indicates that the discovery was made by measuring the mass of the planet. This has been conducted at PRL’s Gurushikhar Observatory in Mount Abu, located in the north-western state of Rajasthan.

Scientists used the PARAS spectrograph, an acronym for the PRL Advance Radial-velocity Abu-sky Search spectrograph, which is integrated with a 1.2m telescope. Incidentally, the spectrograph, which can measure the mass of a planet going around a star, is the first of its kind in the country.

The name of the host star is Epic 211945201 or K2-236 and the planet has also been named the same, except that it will be identified as Epic 211945201b or K2-236b.

The Epic planet has been spotted revolving round the star approximately once every 19.5 days. It has a high surface temperature of around 600°C - understandable, given its proximity to the host star. Precise measurements indicate that it is seven times nearer than Earth-Sun distance, so the chances of it being inhabited are quite unlikely. What makes this discovery significant is that it gives an insight into the formation mechanism of such super-Neptune or sub-Saturn kind of planets that are too close to the host star.

Research throws light on the fact that initially, the source was found to be a planetary candidate from Nasa K2 (Kepler2) photometry because it was transiting; that is, the planet body comes in between the star and the observer on Earth as it goes around the star and therefore it blocks a tiny amount of star-light. The diameter or size of the planet can be derived by measuring the amount of light blocked by the planet body. However, the research team found that the K2 photometric data combined with false positive probability calculations was really not sufficient to confirm the planetary nature of the system. The spectrograph helped arrive at an independent measurement of the mass of the body required for the discovery.

The gravitational pull caused by a planet on its host star makes it wobble around their common center of mass. This has resulted in a spectra shift which has been measured in terms of Radial Velocity.

The PRL scientists observed the target over a time-baseline of 420 days in about 1.5 years using the PARAS spectrograph for probing the nature of the system. By measuring the amplitude of the wobbling of the host star, the mass of the planet was found to be 27±14MEarth.

Based on the mass and radius, model-dependent calculations suggest that the heavy elements like ice, silicates and iron content is 60-70 per cent of the total mass. This detection adds to a sparse catalog of confirmed exoplanets with masses between 10-70 MEarth and radii between 4-8 REarth, whose masses and radii are measured to a precision of 50 per cent or better. Only 23 such systems (including the present) are known to this date with such precise measurement of mass and radii.

The discovery of a distant planet comes hot on the heels of the Union Cabinet’s allocation of Rs 10,911 crore towards the holistic promotion of space programmes.

Watch this ‘Epic space’ for more.

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