Kepler-138c and Kepler-138d: Scientists detect two water worlds 218 light years away

Source: The post is based on the article “Scientists detect two water worlds 218 light years away” published in Down To Earth on 18th December 2022

What is the News?

A team of researchers has announced that two previously discovered exoplanets Kepler-138c and Kepler-138d are Water Worlds which means they are primarily made of water.

Background

In 2014, astronomers discovered three exoplanets orbiting Kepler-138, a star 218 light years from Earth. 

They observed two of these exoplanets Kepler-138c and Kepler-138d with Hubble and the retired Spitzer space telescopes.

What were the key findings of the researchers?

The unique factor of the two exoplanets was that watery liquid makes up a large part of their composition.

Notably, water on these exoplanets wasn’t detected directly. Researchers compared the sizes and masses of the planets to conclude that a significant fraction of their volume — up to half of it — should be made of materials that are lighter than rock but heavier than hydrogen or helium — and water is the most common material that fits that criteria.

The closest comparisons to these water worlds are Europa and Enceladus — icy moons orbiting Jupiter and Saturn, respectively — but because Kepler-138 c and Kepler-138 d are so much closer to their star, their water would not be frozen.