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Planet Earth is about four and a half billion years old. On the timescale of the universe, that makes it quite young. The oldest known planets that are similar to Earth are about 11 billion years old. That means they formed when the universe was just 20 percent of its current age.

The planets are part of a star system known as Kepler-444, which is about 120 light-years away, in the constellation Lyra. The planets were discovered by the Kepler space telescope.

The planets orbit the system’s main star. It’s about three-quarters the size and mass of the Sun.

The system includes two other stars. Both of them are small, faint cosmic embers known as red dwarfs. Their presence in the system is important, though, because they probably limited the region where planets could form.

Kepler-444 contains five known planets. Like Earth, all of them are dense and rocky. But they’re smaller than Earth. And they’re all packed quite close to the star — far closer in than Mercury, the closest planet to the Sun.

Such worlds are extremely hot. So it’s unlikely that conditions were ever comfortable enough for life to form on any of them. So these planets aren’t just ancient — they’re probably barren as well.

Lyra is dropping lower in the evening sky. It’s in the west-northwest at nightfall. Kepler-444 is above brilliant Vega, Lyra’s brightest star. It’s faint, though, so you need a telescope to pick out this old star system with a big family.

Script by Damond Benningfield

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