Fresh hope that Trappist-1 planets contain water
THREE potentially habitable Earth-sized planets in another solar system are likely to contain substantial amounts of water, astromers say.
Three potentially habitable Earth-sized planets in another solar system are likely to contain substantial amounts of water, astronomers have discovered.
The presence of water is one of the key things astronomers look for on exoplanets to indicate the possibility of life. So the discovery made via data collected from the Hubble Space Telescope increases the chances of life evolving on planets orbiting Trappist-1, a dwarf star about 39 light years from the sun.
In February NASA announced seven Earth-sized worlds had been found orbiting the star, which a year prior was thought to have just three planets in its orbit. Each of the worlds orbits in the star’s “habitable zone”, the narrow corridor where temperatures are mild enough to permit bodies of surface water such as lakes and oceans.
Red dwarfs stars — which Trappist-1 is — are the most common type of star in our galaxy. Up to 50 per cent of the Milky Way is made up of red dwarfs. The fact that there is seven potentially habitable worlds around Trappist-1 has enormous implications for the odds of there being alien life.
The new research published in the journal Astronomical suggests that the outer planets in the system still harbour large quantities of water, despite powerful radiation from the star leading to enormous levels of water loss.
“In terms of habitability, this is a positive step forward to say that hopes are still high,” said study co-author from MIT, Julien de Wit.
“A few of these outer planets could have been able to hold onto some water, if they accumulated enough during their formation. But we need to gather more information and actually see a hint of water, which we haven’t found yet.”
The question is how much water loss has taken place over the many years. Ultraviolet radiation from a star can cause planets to dry out through a process called disassociation which causes water molecules to break up.
The astronomers studied levels of UV radiation emitted by Trappist-1 which suggest its inner planets could have lost 20 times more water in the lpast eight billion years than all the Earth’s oceans combined.
But the system’s outer planets — including the three in the habitable zone — may have lost less than three Earth-oceans worth of water. This means the planets could have retained “substantial” amounts of water on their surfaces, said the scientists.
Researchers believe the planets originally formed further away from their current orbits in a cooler zone which allowed them to collect a lot of water ice crystals, creating massive stores of liquid.
“It depends a lot on their initial water content,” said lead author of the paper, Vincent Bourrier.
“If they formed as ocean planets, even the inner ones would likely still harbour a lot of water. We are still a long way to determining the habitability of these planets, but our results suggest that the outer ones might be the best targets to focus our future observations.”
- With AAP
