Ancient Star System with Earth-like Planets Spotted by NASA's Kepler

Astronomers have spotted an ancient, sun-like star with orbiting planets in a system that dates back to the dawn of the galaxy. The system is the oldest to be discovered by far with Earth-sized planets, and proves that such planets formed throughout the history of the universe.

The researchers first spotted the system with the help of NASA's Kepler satellite. The star itself is named Kepler-444 and, in total, hosts five planets that are slightly smaller than Earth. It's estimated that the star itself is a staggering 11.2 billion years old.

"We've never seen anything like this-it is such an old star and the large number of small planets makes it very special," said Daniel Huber, one of the authors of the new paper describing the system, in a news release. "It is extraordinary that such an ancient system of terrestrial-sized planets formed when the universe was just starting out, at a fifth of 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 been formed for most of the history of the universe and we are much better placed to understand exactly when this began happening."

The planets orbit their parent star in less than 10 days, since they're less than one-tenth the Earth's distance from the sun. This closeness also means that the planets are uninhabitable; they're too hot to support liquid water, and possess high levels or radiation. Even so, though, this discovery provides 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," said Huber.

The findings are published in The Astrophysical Journal.

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