Finding a planet with all the boxes ticked to support human life is not as easy as it would seem in a universe full of choice.
And the unlikely star of TV’s Game of Thrones has had a big say in which planets humans could colonise.
Hafþór Júlíus Björnsson stars in the series as Gregor Clegane or The Mountain – a wall of muscle and flesh playing a champion of the House of Lannister.
Bjornsson, aged 30 from Iceland, holds the title of the world’s strongest man.
It’s his physique and weightlifting prowess that excited scientists at Zagreb University, Croatia.
1,000 year record smashed
After he smashed a 1,000 year old record by walking five paces with a 650 kilo longboat mast on his back, a team from university realised besides a hospitable atmosphere, the gravitational pull on any planet which humans intended to colonise needs to fall within certain parameters.
If the gravitational pull is too much, blood pulls in the legs, which leads to fainting and pins the legs to the ground leaving astronauts unable to move.
The study looked at how gravity affects the skeleton and organs.
The scientists discovered although many bones could withstand up to 90G – that’s 90 times the gravity on Earth – the heart would collapse at 5G.
The evidence for this came from jet fighter pilots who regularly sustain spells of more than 5G in combat. If they suffered 5G for too long, they would fall asleep.
Controlled falling over
Walking is another problem – and this is where Bjornsson helped with his record-breaking mast lift.
In humans, the scientists say, walking is like a controlled falling over which is recovered at the last moment to help us remain upright.
Bjornsson set the mark by calculating he could walk on a planet with a gravitational pull of 4.6G at most.
This, they say, means marking all planets with gravity of more than 4.6G off limits – which seriously narrows the choice of likely hospitable worlds.
The best choice, the team concludes, is a massive rocky planet called BD+20594b, which orbits a star 496 light years away in the constellation Taurus. The planet has gravity measuring 3G.