Volcano-covered world spotted 90 light years from Earth

A new exoplanet discovered orbiting a small red dwarf star some 90 light-years from Earth might be covered in explosive volcanoes.

The exoplanet – named LP 791-18 d – was discovered by NASA’s Spitzer Space Telescope and the Transiting Exoplanet Survey Satellite (TESS). It brings the number of known exoplanets orbiting the star LP 791-18 in the Crater constellation to three – two others are known as b and c.

Size-wise, d is slightly larger than the Earth, b would be about 20% bigger, c is a super-Earth, at about 2.5 times the size and seven times the mass of our planet.

It’s a size differential that matters because c and d have very close orbits.

When they come near, c’s superior gravitational force tugs at d’s orbit. This, the researchers say, causes a spike in d’s internal friction, heating its interior and leading to widespread volcanic activity across its surface.

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This could be enough for the planet to sustain an atmosphere, although liquid water on its surface is unlikely.

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That’s because d is tidally locked, meaning the planet rotates in time with its orbit around the red dwarf – the same principle applies to Earth’s Moon (which is why we always see the same side).  

As such, liquid water is highly unlikely to be found on the star-facing side of d. 

“But the amount of volcanic activity we suspect occurs all over the planet could sustain an atmosphere, which may allow water to condense on the night side,” says University of Montreal exoplanet investigator Professor Björn Benneke, who worked on the project. 

Volcanic, but potentially a life-friendly world 

LP 791-18 d looks promising as a potential candidate for atmospheric studies by the James Webb Space Telescope.

Its volcanic activity could also suggest the presence of plate tectonics like those on Earth.  

And as d sits just within its star’s habitable zone, there’s a slender possibility it could have conditions conducive to some forms of life.  

“A big question in astrobiology, the field that broadly studies the origins of life on Earth and beyond, is if tectonic or volcanic activity is necessary for life,” says Dr Jessie Christiansen, an Australian astrophysicist based at the NASA Exoplanet Science Institute at the Caltech, USA.  

“In addition to potentially providing an atmosphere, these processes could churn up materials that would otherwise sink down and get trapped in the crust, including those we think are important for life, like carbon.”