Astronomers Have Detected Water On Habitable ‘Super-Earth’

Astronomers have discovered a planet just outside our solar system which may have water and temperatures similar to Earth. About 110 light years away, this exoplanet (i.e. outside our solar system) is estimated to be eight times larger than Earth.

The potential ‘Super Earth’ planet, named K218b, lies in the constellation of Leo in the northern sky and is considered the ‘holy grail’ for astronomers searching for a planet similar to ours, with water in its atmosphere which means life could be found there.

Speaking about the discovery, first author Dr. Angelos Tsiaras, of University College London’s Centre for Space Exochemistry Data (CSED), said:

‘Finding water in a potentially habitable world other than Earth is incredibly exciting.

K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition.

However, it brings us closer to answering the fundamental question – is the Earth unique?

The water vapour found in K2-18b comes from the evaporation of water or ice on the planet, and though vapour has been found on other far away planets, this is the first to be the ideal distance from the solar system’s star to allow life to develop.’

Some news today about K2-18b, a small planet 110 light-years from Earth. Hubble has spotted water vapor & possibly clouds in its atmosphere. https://t.co/3alGmHq9wS

— Alexandra Witze (@alexwitze) September 11, 2019

Reported in Astronomical Journal, the teams research found that the water source could exist in liquid form which is crucial for sustaining life.

The combined data captured by the Hubble Space Telescope from 2016 and 2017 and their own algorithms used to analyse starlight filtered through the atmosphere. The results showed the molecular signature of water vapour and indicated the presence of hydrogen and helium, which produce energy. Undetectable at this stage, other vital molecules such as nitrogen and methane may also be present and further studies are needed to estimate cloud coverage and the percentage of atmospheric water.

First discovered in 205, K2-18b is one of hundreds of Super-Earths discovered by NASA’s Kepler spacecraft and more are expected to be found in coming years. Although K2-18b is the most promising thus far, its environment may be more hostile than that of Earth as it orbits an active red dwarf.

Artist’s concept of K2-18b, as well as another planet in this system, K2-18c, with the parent star, a red dwarf, in the background. Image via Alex Boersma

Co-author Dr Ingo Waldmann, also of UCL CSED, said:

‘With so many new super-Earths expected to be found over the next couple of decades, it’s likely this is the first discovery of many potentially habitable planets.

This is not only because super-Earths like K2-18b are the most common planets in our Galaxy, but also because red dwarfs – stars smaller than our Sun – are the most common stars.

The next generation of space telescopes, including the NASA/ESA/CSA James Webb Space Telescope and ESA’s ARIEL mission, will be able to characterise atmospheres in more detail as they will carry more advanced instruments.

ARIEL is expected to launch in 2028, and will observe 1,000 planets in detail to get a truly representative picture of what they are like.’

Co-author Prof Giovanna Tinetti, also of UCL CSED and principal investigator for ARIEL, said:

‘Our discovery makes K2-18b one of the most interesting targets for future study.

Over 4,000 exoplanets have been detected but we don’t know much about their composition and nature.

By observing a large sample of planets, we hope to reveal secrets about their chemistry, formation and evolution.

The team looked for the signal of water absorption in starlight poking through the edges of the atmosphere when the planet passed in front of its star.’

Another artist’s concept of super-Earth K2-18b. Image via ESA – Hubble, M. Kornmesser

Björn Benneke, an exoplanet researcher at the University of Montreal and author of the study, told The Verge:

‘For the first time, a planet in this temperature regime — a regime that is very, very similar to the Earth — we are demonstrating that there is actually liquid water.’

Benneke explained that climate modelling from the team’s observations found water vapour forming clouds, condensing and raining down on the planet. This liquid water is essential to the possibility of finding life on the planet.

Exoplanet expert and MIT professor Sara Seager says we shouldn’t ‘expect a mirror image of Earth just yet,’ adding: ‘These planets are not going to look a thing like Earth. It’s definitely not rocky as we know a rocky planet to be.’

Dr Tsiaras concluded:

‘This study contributes to our understanding of habitable worlds beyond our solar system and marks a new era in exoplanet research, crucial to ultimately place the Earth, our only home, into the greater picture of the cosmos.’

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