K2-18b

What is K2-18b? Describe it. 

Scientists from University College London (UCL) announced that they had detected for the first time, water vapor in the atmosphere of an exoplanet eight times the mass of Earth and 110 light years away.

The so-called super-Earth, known as K2-18b, is twice the size of Earth and is located in the Leo constellation in the Milky Way. It is one of hundreds of planets with a mass between that of Neptune and the Earth.

It is said to be in a Goldilocks zone. What is it?

K2-18b is in a "Goldilocks," or habitable zone with the right proximity to its sun(star) to make water in liquid form, and thus life, possible.

Which telescope discovered it and when?

K2-18b was discovered by NASA's Kepler Space Telescope in 2015. 

How did the research team come to believe life could exist in the K2-18b?

The team looked through the planets discovered by the Hubble Space Telescope between 2016 and 2017. The researchers determined some of the chemicals in their atmosphere by studying the changes to the starlight as the planets orbited their suns. The light filtered through the planets' atmospheres was subtly altered by the composition of the atmosphere.

Only K2-18b revealed the molecular signature of water, which is a vital ingredient for life on Earth.

Is there a dispute?

Some astronomers, however, dispute the claim that the planet is potentially habitable. 

• One analysis indicates that planets that are 1.5 times the mass of the Earth are unlikely to have a rocky surface. 
• There is also concern that K2-18b's size and gravity would make it difficult for the world to support life.

How will we ever know about the habitability?

The viability of K2-18b and other “potentially habitable" planets can only be ascertained by future space missions and instruments like the 

1. James Webb Space Telescope, which is due to be launched in 2021 and will be able to characterize an exoplanet’s atmosphere in greater detail and 
2. the ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) space mission, expected to be launched by the European Space Agency in 2028, will observe 1,000 exoplanets in detail. ARIEL will be the first mission to measure the chemical composition and thermal structures of exoplanets.

What is an exoplanet?

• Planets beyond our Solar System are called exoplanets
• The first exoplanet was discovered in 1992, orbiting a pulsar (a neutron star that emits electromagnetic radiation)
• More than 4,000 have been detected to date using several techniques
• Many of these worlds are large planets believed to resemble Jupiter or Neptune