May 12, 2016 6:11 AM EDT

THEIR SIZE

All three planets are about the diameter of Venus or Earth, which means they probably have rocky surfaces where life can emerge and thrive.

THEY’RE WARM

The planets orbit very close to their star, which should make them too hot, except the star is what’s known as an “ultracool dwarf,” meaning that close is good. That could make for shirt-sleeve temps.

THEY’RE WET (MAYBE)

Water is common in space. If it exists on these three worlds with their balmy temperatures, it would likely be liquid.

THEY HAVE AIR (MAYBE)

It takes gravity to hold on to atmosphere. Mars, with half the size and gravity of Earth, lost its air. The three new planets are big enough to keep their air–if they have it.

–Jeffrey Kluger

This appears in the May 23, 2016 issue of TIME.

Write to Jeffrey Kluger at jeffrey.kluger@time.com.

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