The stunning discovery of seven Earth-like planets orbiting a small star in our galaxy opens up the most promising hunting ground so far for life beyond the Solar System.
Nasa researchers announced the discovery of the Trappist 1 system this morning.
All seven roughly match the size and mass of our own planet and are almost certainly rocky, and three are perfectly perched to harbour life-nurturing oceans of water, they reported in the journal Nature.
Most critically, their proximity to Earth and the dimness of their red dwarf star, called Trappist-1, will allow astronomers to parse each one's atmosphere in search of chemical signatures of biological activity.
"We have made a crucial step towards finding life out there," said co-author Amaury Triaud, a scientist at the University of Cambridge.
"Up to now, I don't think we have had the right planets to find out," he said in a press briefing.
"Now we have the right target."
The Trappist-1 system, a mere 39 light years distant, has the largest number of Earth-sized planets known to orbit a single star.
It also has the most within the so-called "temperate zone" - not so hot that water evaporates, nor so cold that it freezes rock-solid.
The discovery adds to growing evidence that our home galaxy, the Milky Way, may be populated with tens of billions of worlds not unlike our own -- far more than previously suspected.