LHS 1140b, named for the small, faint red dwarf star it orbits, has all the right features.
The planet is 1.4 times the size of Earth, and its mass is seven times greater, suggesting it is made of made of rock with an iron core.
The exoplanet is estimated to be around 5 billion years old, and may not have always been so hospitable - it's likely that the red dwarf star when younger may have been more volatile, potentially stripping water from LHS 1140b's atmosphere, if it once had one.
"Right now we're just making educated guesses about the content of this planet's atmosphere", Dittmann said.
We live in a wondrous age where scientists don't exactly find it hard to make out exoplanets against the inky blackness of the night sky - but as for discovering worlds that might also support life, it's not always easy.
Make that super-sized, because it belongs to a class of planets called super-Earths that are more massive than Earth but not quite the size of giants Neptune or Jupiter.
In follow-up work the team was able to detect LHS 1140 wobbling as the planet orbits it, using the High Accuracy Radial velocity Planet Searcher (HARPS) installed on the European Southern Observatory's 3.6m telescope at La Silla Observatory in Chile. Charbonneau said recent studies show that the Trappist planets may not be rocky like Earth, while Trappist discoverer Michael Gillon said the newest planet has such intense gravity that its atmosphere may be smooshed down so telescopes can't get a good look at it.
The new planet, known as LHS 1140b, receives enough starlight to allow for liquid water, a prerequisite for life on Earth.
"This super-Earth may be the best candidate yet for future observations to study and characterise its atmosphere, if one exists", according to ESO.
Scientists do caution that it is possible that the planet had its water stripped in the formation of its solar system, causing a runaway greenhouse effect.
"We could hardly hope for a better target to perform one of the biggest quests in science: searching for evidence of life", said Jason Dittmann of the Harvard Smithsonian Center for Astrophysics.
Charbonneau said it may take decades to confirm a world is habitable. The first planet outside our solar system was discovered in 1995. But after the discovery of LHS 1140b, astronomers were clouded out from locations where it should be visible. During that time, the habitable zone of the star would be much further out, which means that LHS 1140b was exceptionally heated. That cycle could preserve water on the planet, enhancing its potential to host life.
That's important because the amount of heat and light coming from the star isn't so hot that liquid water can't exist on the planetary surface - something which is essential for life as we know it, and the definition of whether a planet falls within a star's habitable zone (aka Goldilocks zone). Too far away and the object won't be warmed.
The habitable zone is also dependent on the type of star the planet orbits. If a star emits this radiation often enough, the atmosphere has no time to fix itself. "In the search for signs of habitability, signs of life elsewhere, the more the merrier".
"With this planet and TRAPPIST-1, our list is growing larger and larger, and when the next telescopes are built it's just going to completely change everything", he said.
The scientists aren't wasting any time following up with observations: the next transit (where the planet crosses in front of the star) will occur on October 26 and they've booked several telescopes in Chile to search for signatures of oxygen molecules in the planet's atmosphere.
"What I truly find exciting is that we have a potentially habitable, rocky planet orbiting a nearby star that is now very calm and stable and doesn't flare", Dittman said.