Scientists have discovered a remarkable cluster of planets resembling the core of our own solar system, but better: seven Earth-size worlds, each potentially capable of hosting liquid water and therefore life, in orbit around a nearby star.
The planets closely circle a dwarf star called Trappist-1, which at 39 light years away makes the system a prime candidate to explore for signs of life. Only marginally larger than Jupiter, the star shines with a feeble light about 2,000 times fainter than our sun.
“The star is so small and cold that the seven planets are temperate, which means that they could have some liquid water and maybe life, by extension, on the surface,” said Michaël Gillon, an astrophysicist at the University of Liège in Belgium. Details of the work are reported in Nature.
While the planets have Earth-like size, their dimension ranging from 25% smaller to 10% larger, they could not be more distinct in other features. Most surprising is how close the planet’s orbits are. Mercury, the inmost planet in the solar system, is six times further from the sun than the outermost seventh planet is from Trappist-1.
Any life that gained a foothold and the ability to look up would have a extraordinary view from a Trappist-1 world. From the fifth planet, considered the most habitable, the salmon-pink star would loom 10 times larger than the sun in our sky. The other planets would soar above as their orbits required, appearing up to twice the size of the moon as seen from Earth. “It would be a beautiful show,” said Amaury Triaud at the Institute of Astronomy at Cambridge University.
Standing on the surface of one of the planets, you would receive 200 times less light than you get from the sun, but you would still receive just as much energy to keep you warm since the star is so close. It would also afford some picturesque views, as the other planets would appear in the sky as big as the moon (or even twice as big).
The researchers hope to know whether there is life on the planets “within a decade,” Amaury added. “I think we’ve made a crucial step in finding out if there’s life out there,” he said. “If life managed to thrive and releases gases in a similar way as on Earth, we will know.”.
Astronomers are now focussing on whether the planets have atmospheres. If they do, they could uncover the first hints of life on the surfaces below. The Hubble telescope could detect methane and water in the alien air, but both can be produced without life. More complex and convincing molecular signatures might be spotted by Nasa’s James Webb Space Telescope, which is due to launch next year, and other instruments, such as the Giant Magellan Telescope, a ground-based observatory due to switch on in 2023. But there is only so much that can be done from afar. “We’ll never be 100% sure until we go there,” said Gillon.
“I think we’ve made a crucial step towards finding if there is life out there,” said Amaury Triaud, one of the study authors and an astronomer at the University of Cambridge. “I don’t think any time before we had the right planets to discover and find out if there was (life). Here, if life managed to thrive and releases gases similar to what we have on Earth, we will know.”
Based on preliminary climate modeling, the researchers believe that the three planets closest to the star may be too warm to support liquid water, while the outermost planet, TRAPPIST-1h, is probably too distant and cold to support water on the surface. But further observation is needed to know for sure.
Although 40 light-years away doesn’t sound too far, it would take us millions of years to reach this star system. But from a research perspective, it’s a close opportunity and the best target to search for life beyond our solar system.