Researchers have found planets orbiting sun-like stars throughout the galaxy which are almost as old as the universe.
Scientists from the University of Birmingham have found a star – Kepler-444 – with orbiting planets that are almost as old as the Milky Way and more than twice the age of the solar system.
The solar system is less than five billion years old, with life on Earth arising around a billion years later.
The Milky Way is 13.2 billion years old, just a few hundred million years younger than the universe, and planets began to form around 11 billion years ago.
If one of these planets in the massive galaxy is capable of supporting life, then aliens may have arisen long before life on Earth began, according to research.
Tiago Campante, research leader from the University of Birmingham, said: "We now know that Earth-sized planets have formed throughout most of the Universe's 13.8-billion-year history, which could provide scope for the existence of ancient life in the galaxy.