The mysterious world is older, larger, warmer and even wetter than our own planet, making it a prime target for future alien hunting missions.
These planets are 100 light-years from Earth, too far away for them to be visited, but can be studied using future advanced space telescopes.
Probes like the European Space Agency's ARIEL mission, scheduled for launch in 2028, are designed specifically to look for signs of life on distant worlds.
WSU scientist Professor Dirk Schulze-Makuch said: "With the next space telescope, we will get more information, so it is important to choose some targets."
"We must focus on certain planets with the most complex life conditions. However, we must be careful not to get stuck looking for a second Earth, as there may be planets more suitable for life than ours."
The team developed "super-habitability criteria" to align them with the 4,500 known exoplanets (planets outside our solar system).
Livability is not defined as a definite marker of life, but rather as the conditions that allow it to grow and mature.
Criteria include being 10% larger than Earth, having a surface temperature 5C (9F) warmer than that of our own planet, and being between 5 and 8 billion years old (4.5 billion years for Earth).
What is an exoplanet?Here's what you need to know...
- An exoplanet is a planet that lies outside our solar system and is orbiting its own star as the Earth orbits the sun
- They're hard to see with binoculars because they're often obscured by the brightness of the star.
- Nasa sends the Kepler space telescope into orbit with the goal of finding Earth-sized exoplanets that might support life
- More than 4,000 exoplanets have been discovered so far, and more missions are planned to find more
- A good way to find exoplanets is to look for "wobbly" stars, since damage to the starlight may indicate that the planet is orbiting and intermittently blocking its light.
- Spaceships are so common in the universe that the more we discover that it looks like Earth, the closer we get to whether or not Earth is the only planet of life
A total of 24 potentially "super-habitable" planets have been discovered, which may have better life support conditions than Earth.
No single planet could ultimately meet all five of the criteria that scientists had proposed, but one of them met four.
The researchers stress that these results do not mean that 24 worlds are absolutely livable.
In a press release, Washington State University said, "Habitability does not mean that these planets are definitely life-friendly, but merely conditions conducive to life."
Distant rocks could be the primary target of future planet-scanning space telescopes.Scientists have discovered more than 4,500 exoplanets, but we don't know much about them.
The next generation of space probes, including the ARIEL mission and NASA's James Webb Telescope, will be able to look at the atmosphere in greater detail.
ARIEL aims to observe 1,000 planets in detail to give us a more accurate understanding of potential alien worlds.
By observing a large number of planets, scientists hope to reveal the secrets of their chemistry, formation and evolution.
The study was published in the journal Astrobiology.