Large rocky planet 124 light-years away from Earth appears to be covered with WATER and “could have the right conditions to sustain extraterrestrial life”
- The planet is about twice as big as the earth with possible lakes and vast seas
- Researchers predict that they will know if it has signs of life within the decade
- Large amounts of water vapor have been discovered that surround the planet
- It has been named K2-18b by astronomers planning to study it in more detail when the James Webb Space Telescope comes online
A large rocky planet has been discovered that is twice the size of the Earth, circling around the habitable zone of its star and could have the right conditions to sustain extraterrestrial life.
The exoplanet, called K2-18b, is 124 light-years away and appears to be covered with water, according to researchers at Cambridge University.
Although they cannot say whether there is now life on the planet, scientists think by the end of the decade that new telescopes will be able to recognize the gasses of strange species.
Computer models suggest an ocean world – with liquid water under the atmosphere at pressures and temperatures similar to those in our seas.
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Artist’s impression of K2-18b with its potentially vast oceans and lakes across the ‘waterworld’ planet – it can contain signs of life
Last fall, two different teams of astronomers discovered water vapor around the exoplanet and new analysis tips for a life-sustaining ecosystem.
The Cambridge team confirmed that the atmosphere is hydrogen-rich with a significant amount of water vapor, but levels of other chemicals such as methane and ammonia were lower than expected.
The next generation of space telescopes launched this decade will be able to investigate whether this is related to biological processes.
If the lower levels of methane and ammonia are the result of biological processes, it is likely that the planet contains active life in one form or another.
Main author Dr. Nikku Madhusudhan said that water vapor has been detected in the atmosphere of a number of exoplanets studied so far.
“Even if the planet is in the habitable zone, it doesn’t necessarily mean that there are habitable conditions on the surface,” said Madhusudhan.
“To determine the outlook for habitability, it is important to gain a uniform understanding of the internal and atmospheric conditions on the planet – in particular, whether liquid water can exist under the atmosphere.”
The researchers first determined the composition and structure of both the atmosphere and the interior using existing observations.
They used detailed numerical and statistical models and took into account the radius and mass. These are 2.6 and 8.6 times larger than those of the earth respectively.
K2-18b is in a planet category known as a ‘super-earth’ – and has a temperature that is cool enough to have liquid water, between 32F and 104F – comparable to the earth.
Given its size, it has been suggested that it looks more like a small Neptune than a large earth.
This probably has the consequence that it has a significant hydrogen ‘enclosure’ that surrounds a layer of water under high pressure – with an inner core of stone and iron.
If the hydrogen envelope is too thick, the temperature and pressure on the surface of the underlying water layer would be much too large to support life.
However, the latest findings, published in The Astrophysical Journal Letters, show that this is not the case and is probably closer to the Earth’s atmosphere.
Co-author Matthew Nixon said: ‘We wanted to know the thickness of the hydrogen envelope – how deep the hydrogen goes.
“Although this is a question with multiple solutions, we have shown that you do not need much hydrogen to explain all the observations together.”
The James Webb Space Telescope will be launched in 2021 and will help astronomers discover the conditions on exoplanets and find possible signs of life
The researchers discovered that the maximum size of the hydrogen envelope allowed by the data is about six percent of the planet’s mass.
The minimum amount of hydrogen is comparable to the Earth’s atmosphere.
A number of scenarios in particular make an ocean world possible, according to the researchers.
The study will also make it possible to search for habitable conditions and signs of life on planets outside the solar system that are much larger than the Earth.
Moreover, planets such as K2-18b are more accessible for atmospheric observations with current and future facilities.
The techniques used by the Cambridge experts can be further refined using future observations from NASA’s James Webb Space Telescope.
The long-awaited observatory in space will be launched next year to speed up the search for extraterrestrial life.
The findings are published in the Astrophysical Journal Letters.
HOW SCIENTISTS STUDY THE ATMOSPHERE OF EXOPLANETS?
Distant stars and their rotating planets often have different circumstances than we see in our atmosphere.
To understand this new world, and what they are made of, scientists must be able to detect what their atmosphere consists of.
They often do this using a telescope similar to Nasa’s Hubble telescope.
These huge satellites scan the sky and hold onto exoplanets that NASA may find interesting.
Here the on-board sensors perform various forms of analysis.
One of the most important and useful is called absorption spectroscopy.
This form of analysis measures the light that comes from the atmosphere of a planet.
Each gas absorbs a slightly different wavelength of light, and when this happens, a black line appears on a full spectrum.
These lines correspond to a very specific molecule, indicating that it is present on the planet.
They are often called Fraunhofer lines after the German astronomer and physicist who first discovered them in 1814.
By combining all the different wavelengths of light, scientists can determine all the chemicals that form the atmosphere of a planet.
The key is that what is missing gives the clues to find out what is present.
It is vital that this is done by space telescopes, because then the Earth’s atmosphere would interfere.
Absorption by chemicals in our atmosphere would warp the sample, so it is important to study the light before it has had the chance to reach the earth.
This is often used to search for helium, sodium and even oxygen in alien atmospheres.
This diagram shows how light passing through a star and the atmosphere of an exoplanet produces Fraunhofer lines that indicate the presence of important compounds such as sodium or helium