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‘Proxima b could be habitable’

According to a new analysis, Proxima b could be a habitable ‘ocean planet’ encircled by a thin, gas atmosphere much like our own.

An international team of researchers has calculated the dimensions of the rocky exoplanet, along with the properties of its surface, finding it may have features that favour the ability to support life.

The planet orbits within the habitable zone of our sun’s nearest neighbour, Proxima Centauri, and may have a mass just 1.3 times that of Earth, with a surface that’s covered by a single liquid ocean 124 miles deep.

In the new study, set to be published in The Astrophysical Journal Letters, researchers led by a team from the Marseille Astrophysics Laboratory (CNRS/Aix-Marseille Université) found a variety of potential compositions for Proxima b.

Scientists first announced the planet’s discovery this past August, and many hope it will soon become the first exoplanet to be visited by Earth robots.

Building off of earlier observations, researchers have now determined that Proxima b orbits its star at a distance of 0.05 astronomical units – just one tenth of the sun-Mercury distance.

Despite the close proximity to its sun, it’s thought that this planet is still cool enough to harbour liquid water at the surface, as Proxima Centauri is a red dwarf with a mass and radius just one-tenth that of the Sun, and a brightness a thousand times smaller.

Proxima b could have a radius anywhere between .94 and 1.4 times that of the Earth, the researchers say.

In one possible composition, the researchers say Proxima b may be an ‘ocean planet’ with water similar to the subsurface oceans seen in icy moons around Jupiter and Saturn.

By this explanation, it would have a radius of 5,543 miles and be composed of 50 percent rock, surrounded by a massive ocean that makes up the other 50 percent.

Beneath this 124-mile-deep ocean would be a layer of high-pressure ice until it reaches the mantle at 1,926 miles deep.
According to the researchers, Proxima b could also be covered by a thin gas atmosphere, as seen on Earth, making it potentially habitable.

Another possible composition would see Proxima b with a make-up similar to Mercury’s if its radius is the minimum value estimated by the researchers, at just 3,722 miles.

This would make Proxima b a ‘very dense planet,’ with a metal core that accounts for 65 percent of its mass, while the rest is a rocky, silicate mantle.

According to the researchers, these regions would meet at a boundary 932 miles deep, and could also host liquid water – but at less than .05 percent of the planet’s mass, similar to what’s seen on Earth.

The team also estimated the radius of Proxima b for scenarios proposed in earlier efforts, including one in which the planet is completely dry.

On Proxima b, the researchers say ultraviolet and X-rays from the host star could leave water prone to evaporation, and future measurements of stellar abundances of heavy elements, including magnesium, iron, and silicon, will help to close in on the planet’s true composition and radius.

Source: The Mail

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