If there are other species like us in the universe, they've probably been around for a lot longer than we have.

According to new research presented at the 220th meeting of the American Astronomical Society and published online in Nature, habitable Earth-like planets orbiting other stars may have formed billions of years before ours did.

Earlier, researchers had found that giant, gaseous exoplanets preferably form around stars with a relatively high abundance of heavier elements like iron.

Since heavier elements are forged in earlier generations of stars and then dispersed through supernova explosions, Jupiter-like giants must be pretty new to the scene.

However, a study of the parent stars of a few hundred smaller exoplanets found by Nasa's Kepler space telescope reveals that they have a wide variety of heavy-element abundance.

Apparently, small planets can easily form around stars that were born much earlier in the history of the universe. Who knows how many civilisations have already risen and fallen in the cosmic past.

Science Now