Astronomers have discovered water in the atmosphere of an exoplanet in the habitable zone of his star with the Hubble Space Telescope. If confirmed, this is the first time we detect water on an exoplanet – a vital ingredient as we know it. The water was recognized as vapor in the atmosphere, but the temperature of the planet means that it can absorb liquid water on its surface when it is rocky.
The planet is called K2-18b and is about 110 light-years away. The planet is much different than the earth. It is a super-earth and twice the size of the earth and about eight times as massive. K2-18b orbits a red dwarf star and was first discovered in 2015 by the Kepler Space Telescope.
Astronomers at the Center for Space Exochemistry at University College London in the United Kingdom made the discovery in data from the wide-field camera 3 of the Hubble Space Telescope. Their findings are contained in an article published in Nature Astronomy titled "Water vapor in the atmosphere of the eight-earth mass planet K2-1
In a press release, first author Dr. Angelos Tsiaras (UBC Center for Space X-ray Data, CSED): "Looking for water in a potentially habitable other world than Earth is incredibly exciting. K2-18b is not "Earth 2.0" because it is much heavier and has a different atmospheric composition. However, this brings us closer to answering the basic question: is the earth unique?
The team behind the discovery developed algorithms and ran through the archived Hubble data from 2016 and 2017. They analyzed the starlight of the red dwarf star as it flew through the atmosphere of the exoplanet. They discovered the molecular signature of water as well as hydrogen and helium.
These results still need to be confirmed, but if and when, the implications are intriguing. Scientists believe that super-earths like these are the most common type of planet in the Milky Way. And red dwarf stars like the K2-18b orbits are the most common types of stars. They are also the coolest and most durable and the smallest. This suggests that there may still be many similar exoplanets.
Kepler discovered hundreds of super-Earths, planets with masses between Earth and Neptune, and NASA's TESS is expected to find hundreds more. According to the co-author of this new work, Ingo Waldmann, this is a good sign to find potentially habitable exoplanets.
In a press release, Dr. Waldmann: "With so many new super-earths expected to be found over the next few decades, this is likely to be the first discovery of many potentially habitable planets. This is not only because super-earths such as K2-18b are the most common planets in our Milky Way, but also because red dwarfs – stars smaller than our sun – are the most common stars. "
The planet has a very short length of year. One round takes only 33 days. The researchers believe that K2-18b is either a rocky or an icy planet. If it is icy, it may contain a large amount of water. However, these are only preliminary results.
According to the authors, the atmosphere may also contain nitrogen and methane, two life-threatening chemicals. Unfortunately they could not recognize her. This will have to wait for further studies that will allow them to estimate the cloud cover and the percentage of water in the atmosphere.
K2-12b is really close to its star, but because red dwarfs are not as energetic as Our Sun, the exoplanet gets about as much energy as the earth from our sun. The astronomers' calculations show that its temperature is similar to Earth's: somewhere in the range of about -72 to 47 degrees Celsius.
These are exciting results, but the prospects for life on this exoplanet are not great. Although the planet itself is in the habitable zone of the star, the star it circles around may not be very hospitable. Red dwarfs can emit many torches, and all of this energy can severely limit the potential for life.
"This study contributes to our understanding of the habitable worlds outside of our solar system and marks a new era in exoplanet research that is critical to the ultimate inclusion of the Earth, our only home, in the overall picture of the cosmos," said Dr. Tsiaras.
This discovery needs further observations to confirm it. We also need better telescopes to study the atmosphere and atmospheres of other exoplanets. Two telescopes on the horizon will take on this task. The James Webb Space Telescope will have the ability to study the atmosphere of exoplanets. This is the next step in understanding all of the exoplanets found by Kepler and is found by TESS.
The ARIEL (Atmospheric Remote) of the ESA-Isolated Infrared Exoplanet Large-survey) will launch in 2028 and investigate in detail the atmosphere of about 1000 exoplanets. ARIEL, together with the JWST, will give us a much better understanding of K2-12b and similar exoplanets.
Professor Giovanna Tinetti (UCL CSED), co-author and principal investigator at ARIEL, said: "Our discovery makes K2-18b one of the most interesting targets for future study. Over 4,000 exoplanets have been discovered, but we do not know much about their composition and nature. By observing a large number of planets, we hope to reveal secrets about their chemistry, education and development. "
" Understanding how habitability develops in a hydrogen-rich atmosphere will be a very intense topic next 10 years, "Waldmann said.