The two possible water worlds, Kepler-138c and d, are not located in the habitable zone (Picture: NASA, ESA, Leah Hustak )
A crew of exoplanet hunters have once again discovered alien planets and these ones have water on them.
Two planets 218 light years from Earth are waterworlds, according to new research published on Thursday, in the journal Nature Astronomy.
A team led by of researchers at the University of Montreal found evidence that two exoplanets orbiting a red dwarf star are ‘water worlds’ where water makes up a large fraction of the entire planet.
These worlds, located in a planetary system 218 light-years away in the constellation Lyra, are unlike any planets found in our solar system.
The team, led by Caroline Piaulet of the Institute for Research on Exoplanets (iREx) at the University of Montreal, published a detailed study of this planetary system, known as Kepler-138, in the journal Nature Astronomy today.
Piaulet and colleagues observed exoplanets Kepler-138c and Kepler-138d with Nasa’s Hubble and the retired Spitzer space telescopes and discovered that the planets could be composed largely of water.
A crew of exoplanet hunters have once again discovered alien planets and these have water on them (Picture: Université de Montréal / SWNS)
These two planets and a smaller planetary companion closer to the star, Kepler-138b, had been discovered previously by Nasa’s Kepler Space Telescope. The new study found evidence for a fourth planet, too.
Water wasn’t directly detected at Kepler-138c and d, but by comparing the sizes and masses of the planets to models, astronomers conclude that a significant fraction of their volume – up to half of it – should be made of materials that are lighter than rock but heavier than hydrogen or helium (which constitute the bulk of gas giant planets like Jupiter). The most common of these candidate materials is water.
‘We previously thought that planets that were a bit larger than Earth were big balls of metal and rock, like scaled-up versions of Earth, and that’s why we called them super-Earths,’ explained Björn Benneke, study co-author and professor of astrophysics at the University of Montreal.
‘However, we have now shown that these two planets, Kepler-138c and d, are quite different in nature and that a big fraction of their entire volume is likely composed of water,’
The two possible water worlds, Kepler-138c and d, are not located in the habitable zone, the area around a star where temperatures would allow liquid water on the surface of a rocky planet.
But in the Hubble and Spitzer data, researchers additionally found evidence for a new planet in the system, Kepler-138e, in the habitable zone.
This newly found planet is small and farther from its star than the three others, taking 38 days to complete an orbit. The nature of this additional planet, however, remains an open question because it does not seem to transit its host star.
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Sadly, the planets are not located in the habitable zone.
