Earth-Sized Planet Detected Just 11 Light Years Away

Orbiting the star Ross 128, our new planetary neighbor is thought to be temperate, with days up to a balmy 68 degrees Fahrenheit

Ross 128 b
Artists impression of Ross 128 b ESO/M. Kornmesser

Astronomers have announced the discovery of an Earth-sized exoplanet orbiting Ross 128—a red dwarf star just 11 light years away. It's the closest planet orbiting a “quiet star” found so far, reports Sarah Kaplan at The Washington Post, making it a prime candidate for potential life.

According to a press release from the European Space Agency, the new planet, called Ross 128 b, was discovered by the High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile. The data shows that 128 b orbits its parent star every 9.9 days and is 20 times closer to its star than the Earth is to the sun.

Despite that closeness, Ross 128 b is thought to be a temperate planet, only receiving 1.38 times the amount of radiation that Earth does. This is thanks to the low energy of its parent star Ross 128, which has surface temperatures around half of our own sun. But, according to the release, there is still some uncertainty whether the planet lies directly within the star's “Goldilocks” habitable zone, where conditions make it possible for liquid water to exist on its surface.

Ross 128 b isn’t the closest planet that we’ve found so far, reports Marina Koren at The Atlantic. That honor goes to Proxima Centauri b, just 4.33 light-years away, whose discovery was announced in August 2016. While researchers originally suspected Proxima b had the right stuff to support life, further analysis suggested that atmosphere, which is essential in protecting delicate organisms, likely wouldn’t survive around the planet.

The reason behind this is its parent star, Proxima Centauri. It's a very active red dwarf, which means it shoots flares of radiation into space that could strip any atmosphere from Proxima b, allowing excessive solar radiation to reach the surface. 

As Kaplan reports, Ross 128, on the other hand, is a very chill red dwarf that doesn’t often flare, making it possible that 128 b may have developed an atmosphere. But it will be a while before astronomers can confirm any of this speculation. The planet is far too distant and dim to be seen on its own.

Instead, HARPS detects planets by measuring the “wobble” in the light emitted by a star caused by the gravitational tug of any planets orbiting it. The researchers were able to measure that tug 150 times, giving them a pretty good idea of the size and distance of Ross 128 b, but we haven’t actually viewed it. Sometime in the next decade, however, Koren reports, a new generation of ground-based telescopes like the Extremely Large Telescope, currently being built in Chile, will allow us to look at these planets and scan them for an atmosphere and signs of life.

Speculation is already rising about life on Ross 128 b. As Koren reports, in May the Arecibo radio telescope in Puerto Rico detected a strange 10-minute radio signal emanating from Ross 128. In July, Arecibo and the SETI Institute concluded that the signal likely came from geostationary satellites orbiting Earth, though that does not explain all of the signal's elements.

After the discovery of the planet orbiting Ross 128, researchers are reassessing the radio transmission. “We are considering additional follow-up in light of the new discovery at radio and optical wavelengths,” Andrew Siemion, director of the Berkeley SETI Research Center which is looking for signs of extraterrestrial intelligence. “Nearby exoplanets are particularly exciting from a SETI perspective as they permit us to search for and potentially detect much weaker signals than from more distant targets.”

Eventually, Ross 128 will come even closer. According to the European Space Agency, 79,000 years from now, the system will become our nearest stellar neighbor. Hopefully humanity will survive that long and advance enough in the meantime to check out this neighborhood addition in person.

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