Two planets in fascinating star system could be habitable

24 Jan 2018

Image: Vladimir Arndt/Shutterstock

In our search for planets that could be habitable for humans, we have found not one, but two prime candidates in the TRAPPIST-1 star system.

Just under a year ago, NASA announced the massive discovery of a star system dubbed TRAPPIST-1, which contains seven Earth-like planets, six of which could sustain liquid water.

The massive haul of planets was considered a major astronomical achievement – never had so many Earth-like planets been discovered around one star.

Now, new research into these planets has found that two of them are likely candidates to be habitable for any potential human visitors in the very distant future.

In a paper published to Astronomy & Astrophysics, researchers Amy Barr, Vera Dobos and Laszlo Kiss analysed all of the seven planets, referred to as planets b through h, in order of their distance from the star.

Based on Dobos’ analysis, planets d and e are the most likely to be habitable due to their moderate surface temperatures and modest amounts of tidal heating, as well as the fact that their heat fluxes are low enough to avoid entering a runaway greenhouse state.

Meanwhile, on planet d, a vast global ocean likely covers its surface based on estimates of the masses of each planet. These can help determine whether or not the planets have a significant amount of water.

Similar to moons of Jupiter and Saturn

Based on calculations of the balance between tidal heating and heat transport by convection in the mantles of each planet, planets b and c are likely to have partially molten rock mantles, in addition to the fact that planet c could have a solid rock surface that experiences volcanic eruptions similar to those that occur on Saturn’s moon, Io.

“Because the TRAPPIST-1 star is very old and dim, the surfaces of the planets have relatively cool temperatures by planetary standards, ranging from 127C, which is cooler than Venus, to -106C, which is colder than Earth’s poles,” Barr said.

“The planets also orbit very close to the star, with orbital periods of a few days. Because their orbits are eccentric – not quite circular – these planets could experience tidal heating just like the moons of Jupiter and Saturn.”

Colm Gorey was a senior journalist with Silicon Republic