We know very little about exoplanets. Despite thousands out there confirmed by astronomers, little is known about whether they have atmospheres, water or anything else that may make them habitable.
We only sometimes know how big they are and even how far they orbit from their host star.
So the claim that a planet has been found around a star that has volcanoes that light-up its night sky is a big one. Until now, researchers have found no evidence of global tectonic activity on planets outside our Solar System.
The ground-breaking work, published this week in The Astrophysical Journal Letters, concerns an exoplanet called LHS 3844b, which orbits a red dwarf star—the most common type of star in the Milky Way—about 49 light-years distant in the constellation of Indus.
What we know about this volcanic planet
Here’s everything you need to know about LHS 3844b:
- It’s a “super-Earth,” but only just—it’s radius is 1.3 times bigger than our planet and its got 2.25 times the mass.
- A year on LHS 3844b lasts just 11 hours—that’s how quickly it takes for it to orbit its star.
- Day and night on LHS 3844b last forever. That’s because LHS 3844b is tidally-locked to its star, showing one side to it—just as the Moon does to Earth.
- It’s a bare, rocky planet of basalt that makes it dim—about the same as Mercury and the dark mares on the Moon.
- It likely doesn’t have an atmosphere so is not habitable—and in any case, it’s 1,410ºF/770ºC on its day-side and -418°F/-250°C on its night-side.
- Its host star is a red dwarf-type star that’s about a fifth the size of our Sun.
- Its discovery was announced in September 2018 using data from the Transiting Exoplanet Survey Satellite (TESS).
What’s so bizarre about LHS 3844b
Its surface may be covered mostly in dark lava rock, according to observations in 2019 by NASA’s Spitzer Space Telescope. It also discovered that very little heat travels from the planet’s star-facing dayside to its space-facing nightside. That indicates a lack of wind and weather—and therefore no atmosphere.
Now scientists at the University of Bern and the National Center of Competence in Research NCCR PlanetS in Switzerland have found that the material inside LHS 3844b flows from one hemisphere to the other. It could be responsible for numerous volcanic eruptions on one side of the planet.
How tectonic activity works on LHS 3844b
“Observing signs of tectonic activity is very difficult, because they are usually hidden beneath an atmosphere,” said Tobias Meier at the Center for Space and Habitability (CSH) at the University of Bern. “We thought that its severe temperature contrast might affect material flow in the planet’s interior.”
To test that theory, the team ran computer simulations with different strengths of material and internal heating sources—such as heat from the planet’s core and the decay of radioactive elements.
“Based on what we are used to from Earth, you would expect the material on the hot dayside to be lighter and therefore flow upwards, and vice versa”, said co-author Dan Bower at the University of Bern and the NCCR PlanetS. However, some simulations showed the opposite flow direction. “This initially counter-intuitive result is due to the change in viscosity with temperature—cold material is stiffer and therefore doesn’t want to bend, break or subduct into the interior,” said Bower. “Warm material is less viscous—so even solid rock becomes more mobile when heated—and can readily flow towards the planet’s interior.”
It seems clear that LHS 3844b works in a very different way to Earth, where plate tectonics brings material from the planet’s interior to the surface and the atmosphere, and then transports it back beneath the Earth’s crust—and in doing so helps makes Earth habitable.
Volcanoes light-up the night on LHS 3844b
The strange material flow inside LHS 3844b has bizarre consequences. “On whichever side of the planet the material flows upwards, one would expect a large amount of volcanism on that particular side,” said Bower. “Similar deep upwelling flows on Earth drive volcanic activity at Hawaii and Iceland”
The conclusion is that LHS 3844b likely has one hemisphere peppered with volcanoes and one with almost none.
What comes next for LHS 3844b
These conclusions are drawn from computer simulations, so more detailed observations are needed of LHS 3844b—such as a higher-resolution map of surface temperature that could reveal outgassing from volcanoes.
How long it would it take to get to LHS 3844b
Not good news here/ Although 49 light-years puts it firmly in our cosmic backyard, LHS 3844b is way too far away to reach.
If you were traveling at light-speed then it would take 49 years. Come down a notch to humanity’s fastest-moving space probe, New Horizons—which travels at around 33,000 mph/53,100—and it would take 987,026 years to reach LHS 3844b. Via – Forbes