Scientists have discovered five small planets ancient enough dating back to the days when the Milky Way Galaxy was just young at 2 billion years old.
Using data from NASA’s Kepler mission, the found the tightly packed system, named Kepler-444, is also home to five planets that range in size, the smallest comparable to the size of Mercury and the largest to Venus.
All five planets orbit their sun-like star in less than ten days, which makes their orbits much closer than Mercury’s sweltering 88-day orbit around the sun.
“While this star formed a long time ago, in fact before most of the stars in the Milky Way, we have no indication that any of these planets have now or ever had life on them,” said Steve Howell at NASA’s Ames Research Center in California.
“At their current orbital distances, life as we know it could not exist on these ancient worlds.” Kepler-444 formed 11.2 billion years ago, when the universe was less than 20% its current age, making them the oldest known terrestrial-size planets, two and a half times older than the Earth.
Their age was measured with the very small change in brightness of the host star caused by pressure waves within the star, called asteroseismology and allows the researchers to measure the diameter, mass and age of a star.
The Kepler-444 system is approximately 117 light-years away toward the constellation Lyra. A paper reporting this discovery has been published in The Astrophysical Journal.