Scientists have revealed that they have found five small planets that orbit an 11.2-billion-year-old star, which is nearly as old as our 13.7-billion-year-old universe.
The planetary system is the oldest to be found and is significantly older than our solar system, which is estimated to be about 4.5 billion years old.
The discovery of the five exoplanets was made after astronomers looked at four years worth of data that were gathered by NASA's Kepler mission. The Kepler space telescope scouts for planets by observing the tiny brightness dips that are produced when they cross their host star's face.
The findings, which were published in The Astrophysical Journal on Jan. 27, suggest that Earth-sized planets have been a feature of the Milky Way since nearly the beginning.
The alien planets circle a star dubbed Kepler-444, which is about 24 percent smaller than the solar system's sun and lies 117 light-years away from our planet. Scientists were able to determine the size, mass and age of stars through a method known as asteroseismology.
The existence of these old planets came as a surprise to scientists. The universe is known to have started out with a very short period table since the Big Bang only produced hydrogen, helium and lithium. It took some time before the universe became richer in carbon, silicon, oxygen and other elements that are necessary for the formation of Earth-like planets.
"This is one of the oldest systems in the galaxy," said study researcher Steve Kawaler from the Iowa State University. "Kepler-444 came from the first generation of stars. This system tells us that planets were forming around stars nearly 7 billion years before our own solar system. "
The newfound alien worlds have the size of planet Venus or smaller and complete an orbit in less than 10 days, which means that they are too hot to support life. Their parent star, however, hints that other ancient planetary systems, which may be more hospitable to life, may possibly exist.
"We thus show that Earth-size planets have formed throughout most of the Universe's 13.8-billion-year history, leaving open the possibility for the existence of ancient life in the Galaxy," the researchers wrote. "The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation."