NASA has announced that its Spitzer Space Telescope has found seven Earth-like planets in the orbit of a small star located some 40 light-years away.
“The discovery gives us a hint that finding the next Earth is not a question of if, but of when," said NASA Science Directorate head Thomas Zurbuchen during a Wednesday press conference.
All of the planets share similarities with Earth, three of which are in the habitable zone -- the orbital region surrounding a star in which planets have conditions capable of sustaining liquid water.
The recently discovered planets all orbit a red dwarf star called TRAPPIST-1 much smaller and cooler than the Sun.
"This is the most exciting result I have seen in the 14 years of Spitzer operations," said Sean Carey, manager of NASA's Spitzer Science Center.
In comparison to the distance between our Sun and its planets, the planets around TRAPPIST-1 are located very close together.
"If a person was standing on one of the planet's surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the Moon in Earth's sky," said NASA.
The discovery was also announced in the journal Nature in a report whose lead author, Michaël Gillon, is an astrophysicist at the University of Liège in Belgium.
“The star is so small and cold that the seven planets are temperate, which means that they could have some liquid water and maybe life, by extension, on the surface,” said Gillon.
His team has now started to analyze the chemical make-up of the planets’ atmospheres.
"There is at least one combination of molecules, if present with relative abundance, that would tell us there is life, with 99 percent confidence," he said referring to a mixture of oxygen or ozone, and carbon dioxide, which is usually emitted from biological sources.
"But except for detecting a message from beyond our solar system from intelligence out there, we will never be 100 percent sure," he added.