By Danyal Hussain For Mailonline and Sam Blanchard For Mailonline
Published: 18:00 BST, 11 September 2019 | Updated: 20:24 BST, 11 September 2019
Scientists have for the first time found a planet outside of our solar system that's home to water, in a major breakthrough in the search for habitable worlds.
Water vapour has been discovered on a 'super-Earth' 110 light years away that is estimated to be twice the size of Earth and eight times its mass.
K2-18b also has an atmosphere and the correct temperature range for living things to exist, according to scientists at University College London.
It's closer to its star than the Earth is to the Sun, meaning it has shorter years, and completing its orbit in 33 days while ours takes 365.
A computer-generated image has been released by UCL researchers to suggest what the potentially-habitable planet looks like
The habitable zone is the range of orbits around a star in which a planet can support liquid water.
This habitable zone is also known as the ‘Goldilocks’ zone, taken from the children’s fairy tale.
The temperature from the star needs to be 'just right' so that liquid water can exist on the surface.
The boundaries of the habitable zone are critical.
If a planet is too close to its star, it will experience a runaway greenhouse gas effect, like Venus.
But if it's too far, any water will freeze, as is seen on Mars.
Since the concept was first presented in 1953, many stars have been shown to have a Goldilocks area, and some of them have one or several planets in this zone, like 'Kepler-186f', discovered in 2014.
The exoplanet was first spotted in 2015 by NASA's Kepler spacecraft but analysis of data has revealed new details not seen before.
Current equipment is only able to determine basic factors such as how far away it is, its mass and the surface temperature.
But sophisticated tools developed at UCL have been able to translate data from the Hubble Space Telescope to make sense of the unique molecule signatures of water vapour.
K2-18b is too far away for astronomers to see, but they can look at how starlight is filtered through the planet's atmosphere as it passes around its own sun, called K2-18.
'It's the only planet outside our solar system that we know has the correct temperature, an atmosphere and water,' said Dr Angelos Tsiaras the author of the study.'
The presence of water vapour in the planet's atmosphere suggests it could be a rocky world or an icy one with a lot of water inside it.