Ancient star system reveals Earth-sized planets forming near start of universe
A sun-like star with orbiting planets, dating back to the dawn of the Galaxy, has been discovered by an international team of astronomers. At 11.2 billion years old, it is the oldest star with Earth-sized planets ever found and proves that such planets have formed throughout the history of the Universe.
The discovery, announced on 28 January in the Astrophysical Journal, used observations made by NASA's Kepler satellite. The scientific collaboration was led by the University of Birmingham and contributed to by the University of Sydney. The star, named Kepler-444, hosts five planets smaller than Earth, with sizes varying between those of Mercury and Venus. "We've never seen anything like this; it is such an old star and the large number of small planets make it very special," said Dr Daniel Huber from the University's School of Physics and an author on the paper.
"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."