spaceSpace and Physics

Scientists Have Found One Of The Youngest Earth-Sized Planets We Know Of


Jonathan O'Callaghan

Senior Staff Writer

What early Earth might have looked like. Simone Marchi/NASA

Roll up, roll up, it’s time for a new planet announcement. Today, we look at the wonderful world of EPIC 247589423 b, which may offer us a glimpse at what Earth looked like billions of years ago.

The planet was one of three found by noticing the dip in light as they passed in front of their host star, known as the transit method. This discovery, submitted to the journals of the American Astronomical Society, was led by Andrew Mann from the University of Texas at Austin.


This planet is found in the Hyades cluster and is thought to be about 195 light-years from Earth. The star it orbits is a late K dwarf, which is slightly dimmer than our Sun, and just 800 million years old.

Most enticingly though, it is estimated to be 0.99 times the radius of Earth. This makes it one of the few Earth-sized planets with a known young age. The two other planets (c and d) are larger, with radii of 2.91 and 1.45 Earths, a mini-Neptune and super-Earth respectively. They are predicted to orbit the star in 7.9 (the Earth-sized planet), 17.3, and 25.6 days.

“This is basically the first young Earth-size planet with a well-determined age,” Mann told IFLScience, noting the paper had yet to be peer-reviewed so the finding was not technically confirmed yet. “So it is certainly our best shot for leaning about the history of Earth as it stands.”

In their paper, the team note this discovery offers “the possibility of studying the history and evolution of Earth-sized planets.” The proximity of the planet to the star (given its short orbital period) pretty much rules out habitability, but it could tell us more about how Earth-sized worlds form and take shape.


The brightness of the star also makes this system a prime target for follow-up radial velocity measurements, which could work out the masses of the planets and tell us more about them. The relatively small size of the star also means it should be possible to measure the atmospheres of the planets.

The most important thing, though, is the age of the world. At the moment, they note there is only one Earth-sized planet that could be younger, Kepler-78, which we don’t yet know the age of. The EPIC 247589423 system offers a tantalizing glance into our past regardless.

After 800 million years, we think our planet may already have started to form life. That’s unlikely the case for EPIC 247589423 b, but who knows what secrets it might hold.


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