Astronomers have detected the oldest
known Earth-size planets, in a star system that's 11.2 billion years
old. They say the discovery suggests that life could have existed
throughout most of the universe's 13.8 billion-year history.
The five Earth-size
planets were detected through an analysis of data from NASA's Kepler
space telescope, which looks for telltale variations in starlight as
planets cross a star's disk. In this case, the star lies 117 light-years
from Earth and is 25 percent smaller than our sun. It's known as
Kepler-444. The researchers used a technique called asteroseismology, which measures tiny oscillations in a star's brightness, to determine Kepler-444's extreme age.
The planets range in size between
Mercury and Venus, but they all circle Kepler-444 within the orbit of
Mercury in our own solar system. That would make them too hot to be
habitable by life as we know it. Nevertheless, the fact that such
planets could form so early in the universe's history suggests that
life-friendly worlds could exist for billions of years.
"There are far-reaching implications for this discovery," Tiago Campante of the University of Birmingham, the lead author of a paper published Tuesday by The Astrophysical Journal, said in a news release.
"By the time the Earth
formed, the planets in this system were already older than our planet is
today. This discovery may now help to pinpoint the beginning of what we
might call the 'era of planet formation,'" Campante said.
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