WE ARE NOT ALONE!!!

4. They're Especially Bullish About These Planets

Adventures in the "Goldilocks zone."

Scientists now think every one in five or six planets might be habitable, based on two general criteria: They're rocky, and they reside in a region of the star's orbit called the "Goldilocks zone," where it's not too cold and not too hot, but just right to allow for liquid water to form on the surface. And where there's water, there can be life. Extraterrestrial researchers and enthusiasts are most excited about these seven:

Proxima B: The closest exoplanet ever discovered is also a potentially habitable world in its own right, if the intense stellar winds don't make it barren. It's not totally inconceivable we might be able to actually send a probe and study it directly this century — even travel to it ourselves one day.

TRAPPIST-1 System: The red dwarf at the center of this possesses a whopping seven planets in its orbit — three of which reside in the Goldilocks zone, but all of which seem to possess some degree of potential habitability — and they're so close to one another that life on one planet could quickly spread to another.

LHS 1140b: This wouldn't be a planet we could colonize. It's almost seven times the mass of the Earth and 40 percent larger, making it a "super-Earth." But its mass means that it would retain a thicker atmosphere capable of keeping it warmer and more comfortable for life than most other places.

Ross 128 b: One of the best chances we have so far at finding life on another planet. It orbits an inactive red-dwarf star, meaning it's likely not being bludgeoned by solar radiation. And we've detected strange signals emanating from the nearby host star — signals that perhaps have intelligent origins?

Mars: Mars has water, as we've known since 2015. Although the planet looks like a barren wasteland these days, there's little reason to write off any chance we might find aliens residing in some cavern or crevice.

The Ocean Worlds (Europa, Enceladus, Titan): Many of Jupiter's and Saturn's moons show signs of possessing a liquid ocean underneath the surface.

GJ 1214b: Nicknamed "waterworld" by scientists; signs of potential clouds give us some hope the planet has an atmosphere.

—N.P.