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.
“It is extraordinary that such an ancient system of terrestrial-sized planets formed when the universe was just starting out, at a fifth its current age. Kepler-444 is two and a half times older than our solar system, which is only a youthful 4.5 billion years old.
“This tells us that planets this size have formed for most of the history of the universe and we are much better placed to understand exactly when this began happening.”
The five planets orbit the star circle at around a tenth of the distance that Earth orbits the sun – making them too hot to be habitable.
But the discovery means other more suitable planets exist in the Milky Way which could have homed life long before Earth was even born.
Dr Daniel Huber from the University’s School of Physics said: “In the case of Kepler-444 the planets orbit their parent star in less than 10 days, at less than one-tenth the Earth’s distance from the Sun.
“Their closeness to their host star means they are uninhabitable because of the lack of liquid water and high levels of radiation. Nevertheless, discoveries like Kepler-444 provide important clues on whether a planet that is more truly comparable to Earth may exist.
“We’re another step closer towards finding the astronomers’ holy grail – an Earth-sized planet with a one year orbit around a star similar to our Sun.”