NASA's Spitzer Space Telescope marks a new discovery for the most Earth-sized planets found in the habitable zone of a single star, called Trappist-1 and celebrates its new discovery with a retro- style poster. Three of these planets are firmly located in the habitable zone, the area around the parent star where a rocky planet is most likely to have liquid water.

The discovery sets a new record for greatest number of habitable-zone planets found around a single star outside our solar system. All of these seven planets could have liquid water–key to life as we know it–under the right atmospheric conditions, but the chances are highest with the three in the habitable zone.

''This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life,'' said Thomas Zurbuchen, associate administrator of the agency’s Science Mission Directorate in Washington. 

This illustration shows the possible surface of Trappist-1f, one of the newly discovered planets in the Trappist-1 system. Scientists using the Spitzer Space Telescope and ground-based telescopes have discovered that there are seven Earth-size planets in the system. Image © NASA/JPL-Caltech

''Answering the question ‘are we alone’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.''

At about 40 light-years (235 trillion miles) from Earth, the system of planets is relatively close to us, in the constellation Aquarius. Because they are located outside of our solar system, these planets are scientifically known as exoplanets.

The Trappist-1 star, an ultra-cool dwarf, has seven Earth-size planets orbiting it. This artist's concept appeared on the cover of the journal Nature on Feb. 23, 2017. Image © NASA/JPL-Caltech

This exoplanet system is called Trappist-1, named for The Transiting Planets and Planetesimals Small Telescope (Trapppist) in Chile. In May 2016, researchers using Trappist announced they had discovered three planets in the system. Assisted by several ground-based telescopes, including the European Southern Observatory's Very Large Telescope, Spitzer confirmed the existence of two of these planets and discovered five additional ones, increasing the number of known planets in the system to seven.

The new results were published Wednesday in the journal Nature, and announced at a news briefing at NASA Headquarters in Washington.

Using Spitzer data, the team precisely measured the sizes of the seven planets and developed first estimates of the masses of six of them, allowing their density to be estimated.

This poster imagines what a trip to Trappist-1e might be like. Image © NASA/JPL-Caltech

Based on their densities, all of the Trappist-1 planets are likely to be rocky. Further observations will not only help determine whether they are rich in water, but also possibly reveal whether any could have liquid water on their surfaces. The mass of the seventh and farthest exoplanet has not yet been estimated–scientists believe it could be an icy, "snowball-like" world, but further observations are needed.

"The seven wonders of Trappist-1 are the first Earth-size planets that have been found orbiting this kind of star," said Michael Gillon, lead author of the paper and the principal investigator of the Trappist exoplanet survey at the University of Liege, Belgium. "It is also the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds."

This 360-degree panorama depicts the surface of a newly detected planet, Trappist 1-d, part of a seven planet system some 40 light years away. Explore this artist’s rendering of an alien world by moving the view using your mouse or your mobile device. Video by NASA

Spitzer, Hubble, and Kepler will help astronomers plan for follow-up studies using NASA's upcoming James Webb Space Telescope, launching in 2018. With much greater sensitivity, Webb will be able to detect the chemical fingerprints of water, methane, oxygen, ozone, and other components of a planet's atmosphere. Webb also will analyze planets' temperatures and surface pressures–key factors in assessing their habitability.

NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate. Science operations are conducted at the Spitzer Science Center, at Caltech, Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at Caltech/IPAC. Caltech manages JPL for NASA.

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