SUPER EARTH

 k2-18b

K2-18b:- It is also known as EPIC 201912552 b. It is an exoplanet , located 124 light-years (38 Parsec) away from Earth. This planet was initially discovered with the help of Kepler space telescope. This planet is about eight times the mass of Earth, and is thus classified as a super Earth. It has approximately 33-day orbit within the star's habitable zone. 

In BRIEF:-

PLANET NAME   :- SUPER EARTH

GRAVITY               :-11.57 m/s²

RADIUS                  :-14,271 km

ORBITAL PERIOD :-Approximately 33 days

DISCOVERED         :- 2015

ORBITS                    :- K2-18

DETECTION Method :- TRANSIT

DISCOVERY:-

K2-18b was identified as part of the Kepler space telescope program, one of over 1,200 exoplanets discovered during the "Second Light" K2 mission. The discovery of K2-18b was made in 2015, orbiting a red dwarf star (now known as K2-18) with a stellar spectral type of M2.8 . The planet was detected through variations in the star's light curve caused by the transit of the planet in front of the star as seen from Earth. The planet was designated "K2-18b" as it was the eighteenth planet discovered during the K2 mission. The predicted relatively low contrast between the planet and its host star would make it easier to observe K2-18b's atmosphere in the future. In 2017, data from the Spitzer Space Telescope confirmed that K2-18b orbits in the habitable zone around K2-18 with approx 33-day period. Later studies on K2-18b using the High Accuracy Radial Velocity Planet Searcher (HARPS) and the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs (CARMENES) instruments also identified a likely second exoplanet, K2-18c. 

FACTUAL DETAILS :-

One of the research teams, led by Angelos Tsiaras of University College London's Centre for Space Exochemistry Data (CSED), determined that water vapor makes up between 0.01% and 50% of K2-18 b's atmosphere. With such a big range, it's tough to characterize the exoplanet; it could be completely flooded, for instance, or a world with lakes and oceans but lots of exposed land, study team members said.

The other research group, led by Björn Benneke of the Institute for Research on Exoplanets at the Université de Montréal, posited another scenario. These scientists suggested that K2-18 b consists of a planetary core surrounded by a huge, hydrogen-dominated atmosphere that contains mere smidges of water vapor. Such a world wouldn't have a surface, at least not the kind we're used to here on Earth. 

K2-18 b's gravitational pull is better understood, because we know the planet's mass and diameter. If most of the exoplanet is solid rock and ice, a visitor to the world's surface would feel 37% heavier than he or she feels on Earth

This was the first super-Earth exoplanet within a star's habitable zone whose atmosphere was detected, and the first discovery of water in a habitable-zone exoplanet. Water had previously been detected in the atmospheres of non-habitable-zone exoplanets such as HD 209458 b, XO-1b, WASP-12b, WASP-17b, and WASP-19b.

Astronomers emphasised that the discovery of water in the atmosphere of K2-18b does not mean that the planet can support life or is even habitable, as it probably lacks any solid surface or an atmosphere that can support life. Nevertheless, finding water in a habitable zone exoplanet helps understand how planets are formed. A study led by astronomers from the University of Cambridge considered the interior structure of the planet and found a range of possible solutions, from a rocky core with a thick hydrogen envelope to a planet primarily made up of water with a thinner atmosphere.

A subset of these solutions could allow for liquid water on the surface of the planet, albeit at temperatures and pressures higher than STP. K2-18b is now expected to be observed with the James Webb Space Telescope, due to launch in 2021, and the ARIEL space telescope, due to launch in 2028. Both will carry instruments designed to determine the composition of exoplanet atmospheres.