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Scientists say Ross 128 b is a “temperate” planet.

A team of scientists just announced a blockbuster discovery: a potentially habitable exoplanet about the Earth’s size, orbiting a dim dwarf star just 11 light years away.

The newly named exoplanet is named Ross 128 b, after the red dwarf star it orbits, Ross 128. So far, it is the second closest exoplanet to be found, but it looks like it could be more hospitable to life than the closest one, Proxima b, which is only 4.2 light years away but orbits a much more volatile star. Scientists estimate that Ross 128 b is 1.35 times the size of Earth, with a similarly mild surface temperature.

The team of scientists, led by Xavier Bonfils at the University of Grenoble, spent more than a decade monitoring the skies using the High Accuracy Radial velocity Planet Searcher (HARPS), located at La Silla Observatory in the Chilean desert. According to their findings, published today in the journal Astronomy & Astrophysics, they made more than 150 observations of Ross 128.

This artist’s impression shows the temperate planet Ross 128 b, with its red dwarf parent star in the background. This planet, which lies only 11 light-years from Earth, was found by a team using ESO’s unique planet-hunting HARPS instrument. The new world is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. (Credit: ESO/M. Kornmesser)

This artist’s impression shows the temperate planet Ross 128 b, with its red dwarf parent star in the background. This planet, which lies only 11 light-years from Earth, was found by a team using ESO’s unique planet-hunting HARPS instrument. The new world is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. (Credit: ESO/M. Kornmesser)

The new study concludes that Ross 128 b takes 9.9 days to orbit around its star, making it 20 times closer to its star than Earth is to the Sun. But because Ross 128 is so much dimmer than the Sun, the exoplanet receives just a bit more solar radiation than Earth does, which means it may have a similar temperature on its surface.

Though the scientists aren’t calling Ross 128 b habitable quite yet, they think it might have a comfortable surface temperature, with an estimated range of between -76 degrees to 69 degrees Fahrenheit. That’s a broad range, to be sure, but one that the scientists think justifies calling it a “temperate” planet.

Last summer, the discovery of an Earth-like exoplanet orbiting the sun’s nearest neighbor, the highly active red dwarf star Proxima Centauri, rocked the scientific world. But though Proxima-b is closer to Earth than Ross 128 b is, scientists think the new find could be even more exciting. This is partly because Ross 128, though also a red dwarf, is less active than Proxima Centauri, which could make the new exoplanet both easier to study and more hospitable to life.

“Just because Proxima Centauri blasts its planet with strong flares and high-energy radiation, yes, I think Ross 128 is much more comfortable for the development of life,” co-discoverer Nicola Astudilla-Defru, from the Geneva Observatory, told BBC News. “But we still need to know what the atmosphere of Ross 128 b is like. Depending on its composition and the reflectivity of its clouds, the exoplanet may be life-friendly with liquid water as the Earth, or sterile like Venus.”

The new study also lends its weight to the growing body of evidence that dwarf stars like Ross 128, Proxima Centauri and TRAPPIST-1 are better places to look for potentially habitable Earth-like planets, as opposed to larger, brighter stars like the Sun.

As scientists discover more and more of these exoplanets (the official NASA count stands at 3,550) the next step will be to learn more about their atmospheres and composition. The way to do that, most scientists agree, is to get more observations of Ross 128 b and other exoplanets from other high-power instruments, like the Extremely Large Telescope (ELT) at the European Southern Observatory and NASA’s James Webb Space Telescope.

We may get an even closer look at Ross 128 b in the not-so-distant future (at least in cosmic terms). The exoplanet’s parent star, Ross 128, is on the move toward Earth, and scientists expect it to overtake Proxima Centauri as our closest neighbor star—in just 79,000 years.

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