Finding a ‘second Earth’ may be a matter of ‘when’ than ‘if’, say scientists who have recently found a solar system of seven planets with the potential to host life. It is a discovery that has taken the astronomy world by storm: seven Earth-like planets in a not-too-distant galaxy that look like they could support life.

The National Aeronautics and Space Administration’s (NASA) announcement in this regard on February 22 was a big taking point in the conversation about life out there and future planetary homes for humans.

Principal Investigator of the Trappist Exoplanet Survey at the University of Liege (Belgium) Michael Gillon said that the American space agency’s Spitzer Space Telescope found the first known system of seven Earth-sized planets around a single star. This planetary system, Trappist-1, is named for the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile. The planters were detected by observing changes in the colour spectrum of the star in that system. The Trappist-1 solar system resembles the moons of Jupiter and the sizes of the planets and their relative orbits are equivalent.

According to Gillon, the newly discovered solar system is 39 lights years (or around 235 trillion miles) away from the Earth or 2.5 million times away than the distance between the Earth and the sun. It means a probe, like Voyager 1, would take 700,000 years to reach the Trappist-1 system. The system of the planets is relatively close to us in the constellation Aquarius. Because they are located outside of our solar system, these planets are known as exoplanets.

NASA scientists have opined that at least three of the planets represent the “holy grail for planet-hunting astronomers” as they sit within the “temperate zone” and are the right temperature to allow alien life to flourish. These three planets are located in the habitable zone, the area around the parent star where a rocky planet is most likely to have liquid water. Based on their densities, scientists have come to the conclusion that all of the Trappist-1 planets are likely to be rocky. In contrast to our sun, the Trappist-1 star – classified as an ultra-cool dwarf – is so cool that liquid water could survive on planets orbiting very close to it. Scientists also found that the seven planets have orbits ranging from one to 20 days. If Trappist-1 were our sun, all these planets would fit inside the orbit of Mercury. Interestingly, the planets may be tidally locked to their star and it means the same side is always facing the star. Therefore, the two sides would each be in either perpetual daylight or darkness.

However, scientists are yet to confirm whether the new planets are rich in water and if any could have liquid water on their surfaces. The mass of the seventh and farthest exoplanet has not yet been estimated and scientists believe it could be an icy, snowball-like world.

Gillon stressed: “The seven wonders of Trappist-1 are the first Earth-size planets that have been found orbiting this kind of star. It is also the best target yet for studying the atmospheres of potentially habitable Earth-size world.”

Altogether, astronomers have confirmed close to 3,600 planets outside our solar system since the 1990s and they think there could be 100 billion or more in total. But barely four dozen are in the potential habitable zone of their stars and of those, only 18 are approximately the size of Earth.

Koushik Das, based in the Indian capital of New Delhi, is a senior news editor with more than 15 years of experience. He also runs a blog - Boundless Ocean of Politics. E-Mail: [email protected]