Two new Water worlds detected

About twin planets-

• As per the new study, the exoplanets, Kepler-138 c and Kepler-138 d are unlike any other discovered outside the Solar System. These two planets are filled with water.
• These water worlds located in a planetary system 218 light-years away in the constellation Lyra are unique since the liquid makes up a large volume of their composition. 
• Astronomers observed these exoplanets with Hubble and the retired Spitzer space telescopes to make the watery discovery.
• They are also larger-scale versions of Enceladus (Saturn’s moon) and Europa (Jupiter’s moon).
• These twin planets of the same size and mass are more massive than Earth but lighter than ice giants Uranus and Neptune.   
• But they are different from the planets in our solar system, which is chiefly composed of rocky planets like Earth and gas giants like Jupiter.
• These exoplanets, along with Kepler-138 b, orbit Kepler-138, a red dwarf star. The star is smaller and cooler than the Sun, a yellow dwarf star.
• The volume of the two alien worlds is three times that of Earth and mass twice as big
• Further, researchers observations showed that the Kepler- 138 c and d are made up of ingredients lighter than rock (rocky planets like Earth) but heavier than hydrogen or helium (gas-giant planets like Jupiter). 
• This signals the presence of water: Up to half of the mass of the twin worlds should be water, the researchers estimated.
• Until now, scientists expected that worlds slightly larger than Earth would likely have rocky features.
• Further, the density of the twin exoplanets was lower than Earth but comparable to Enceladus and Europa.
• But unlike Enceladus or Europa, these worlds are not ocean worlds. 
• The temperature in Kepler-138 c’s and Kepler-138d’s atmospheres is likely above the boiling point of water.
• Further, the researchers also discovered a fourth planet in the Kepler planetary system: Kepler-138 e.
• The new planet takes 38 days to complete an orbit. It is in the habitable zone, meaning it is located in an orbit that receives just the right amount of heat from its star to allow water to exist in a liquid form.