Headline : Indian scientists discover planet 600 light years away

Details :

The News

A team of scientists from the Physical Research Laboratory (PRL), Ahmedabad, have discovered a sub-Saturn or super-Neptune size planet, which is about 27 times the mass of Earth and six times the radius of Earth.

Key Highlights

The discovery was made by measuring the mass of the planet using the PARAS spectrograph integrated with 1.2m telescope in Mount Abu.
The plant revolves around a Sun-like star, some 600 light years away from Earth.
The name of the host star is EPIC 211945201 or K2-236 and the planet will be known as EPIC 211945201b or K2-236b.
The planet was found to go around the star in about 19.5 days.
The surface temperature of the planet was found to be around 600 degrees Celsius, as it is very close to the host star.
It is seven times nearer to its star, in comparison with Earth-Sun distance which might make it uninhabitable

Importance of the discovery

The discovery is of importance for understanding the formation mechanism of such super-Neptune or sub-Saturn kind of planets that are too close to the host star.
With this discovery, India has joined a select league of countries which has discovered planets around stars.

About Exoplanets
Planets outside our solar system are called exoplanets.
Most exoplanets are part of star systems.
Besides there are some rogue exoplanets that are not a part of any star system.
According to NASA there are 3449 confirmed exoplanets from among 4,669 candidates in 2,577 solar systems.
The search for exoplanets is also the search for alien life and habitable spaces beyond our star system.
NASA’s Kepler and K2 missions have identified several such candidates.
In order to be considered habitable exoplanets must orbit within a distance of their stars in which liquid water can exist on the planet’s surface.
This distance is called the “Goldilocks” zone.

NASA’s K2 method to identify planetary body
Initially Nasa’s K2 (Kepler2) photometry found a planetary candidate transiting the star.
This method looks for the rare situation in which a planet comes between us on earth and its parent star, an event called a transit.
As in a partial solar eclipse, this causes a small but measurable dimming of the star’s light.
By measuring the amount of light blocked by the planet body, the diameter or size of the planet can be measured which was found to be 6 Earth radii.
However, that data was not sufficient to confirm the planetary nature of the system.

Contribution of PARAS
Paras spectrograph made a measurement of the mass of the planet body.
PARAS uses radial velocity method to determine the mass of the planet.
While the gravity of the star makes the planet revolve around it, planet’s weaker gravity can make the star to wobble.
If astronomers can detect the star’s wobbling motion, they could tell that there was a large planet orbiting the star.
A wobbling star will alternately move away from and toward the planet.
In the radial velocity method, astronomers measure the Doppler shift of the star’s spectrum as it moves alternately toward and away from the Earth.
The amount of Doppler shift determines the size of the star’s orbit, which in turn tells us about the unseen planet’s orbit.
The spectrography also helped in identifying the nature of the body by making calculations that suggested that the heavy elements like ice, silicates and iron content make 60%-70% of the total mass.

About PARAS (PRL Advanced Radial velocity Abu Sky Search Spectrograph)
PARAS is a spectrograph designed and developed by the members of the Astronomy and Astrophysics Division of PRL.
The primary aim of PARAS is to search for planets around a sample of 100s of Dwarf main-sequence stars.
It has wavelength coverage of 400nm to 680nm.

UPSC Premils, 2015
Question
The term ‘Goldilocks Zone’ is often seen news in the context of:
(a) the limits of habitable zone above the surface of the Earth
(b) regions inside the Earth where shale gas is available
(c) search for the Earth-like planets in outer space
(d) search for meteorites containing precious metals