The first photos of planets outside our Solar System have been taken by two teams of astronomers who published them on Thursday in the online edition of the journal Science.

An infrared photo of a planet orbiting a star 25 light-years away was among them. The astronomers believe the planet is the coolest and also the lowest-mass object outside our Solar System.

The astronomers took pictures of four planets outside our Solar System. Three of those planets are orbiting the same star, while the fourth is orbiting a different one. The four planets are gaseous and aren’t Earth-resembling at all, but their existence does raise the possibility of other more hospitable planets.

“It’s the tip of the iceberg,” said Christian Marois of the Herzberg Institute of Astrophysics in Victoria, British Columbia.

“Now that we know they are there, there is going to be an explosion.”

Bruce Macintosh of the Lawrence Livermore National Lab, the lead astronomer of one of the teams, said that it’s just a matter of time before they discover a more Earth-like planet. He described the photos of the four gaseous planets as “a step on that road to understand if there are other planets like Earth and potentially life out there."

The two teams used different ways to obtain photos of planets outside our Solar System. The team led by Mr. Macintosh used two ground-based telescopes, while the other team, led by Paul Kalas of the University of California, Berkeley, used photos from the Hubble Space Telescope.

It’s not the first time astronomers discover exoplantes (planets that do not circle the Sun). So far, astronomers found more than 300 exoplanets using indirect measures such as measuring changes in gravity and speed or light around stars. The photos are a first.

"For years we've been hearing the elephants (exoplanets), finding the tracks, seeing the trees knocked down by them, but we've never been able to snap a picture. Now we have a picture,” said NASA's space sciences chief, Ed Weiler. He added that the photos of the four exoplanets fulfill one of the objectives set by NASA for the Hubble telescope before it launched in 1990.

Want to know more about the four exoplanets?

The lowest-mass of them is less than three times Jupiter’s mass. The star around which the one of the four planets is orbiting is from Piscis Australis constellation (25 light-years from Earth), a.k.a. as the Southern Fish. The planet is called Fomalhaut b and the star is called Fomalhaut.

The star around which the other three planets are orbiting is called HR 8799 and is 130 light-years away in the constellation Pegasus.