QUICK FACTS

CAPE CANAVERAL, Fla. — Scientists have spotted seven Earth-size planets around a nearby star, some or all of which could harbour water and possibly life. That's the biggest cluster of planets like this yet to be found. Here's a quick look:

AGE OF AQUARIUS This star system is less than 40 light-years

from Earth, or 235 trillion miles away, in the constellation Aquarius. At the hub is a small, faint star known as Trappist-1. Seven planets circle Trappist-1, with orbits ranging from 1 1/2 to 20 days. If Trappist-1 were our sun, all these planets would fit inside the orbit of Mercury. That’s how close they are to their star and why their orbits are so short. The planets have no real names. They’re only known by letters, b through h. The letter A refers to the star itself.

GOLDILOCKS ZONE

Three of the planets are smack dab in the so-called habitable zone, also known as the Goldilocks zone, where conditions are just right for water and life to flourish — not too much and not too little stellar energy. The four other planets are tantalizingly close to the Goldilocks zone — so close that they, too, could harbour water and potentially life. But just because a planet is in this sweet spot, doesn’t mean life exists or ever did. If aliens were observing our solar system from the Trappist-1 network, they might be saying, “Hey, there are three habitable planets there, Venus, Earth and Mars,” said Sara Seager, a Massachusetts Institute of Technology astrophysicist who did not take part in the study.