Last week, astronomers from the European Southern Observatory (ESO) announced the discovery of an Earth-like exoplanet near Earth. Named Proxima Centauri b, it orbits within the habitable zone of the red dwarf star Proxima Centauri, the closest star to the Sun.
Proxima b follows the trend set by the media to describe these kind of planets are similar to Earth without knowing its habitability or atmosphere. Other exoplanets discovered before like Kepler-452b and Gliese 667 Cc have gone through the same coverage.
NASA exoplanet scientist Steve Howell said that labels such as second Earth and Earth 2.0 only wears out the interest from the general public. When an exoplanet is confirmed to be a sequel to Earth, people will not be thrilled, or what’s even worse they will not believe it.
So far, the only proven fact is that the three planets orbit within the habitable zone of their respective stars.
First, it was Kepler-452b
Nicknamed Earth 2.0 or Earth’s Cousin, the exoplanet Kepler-452b was the first potentially Earth-like planet discovered orbiting within the habitable zone of a star very similar to the Sun. NASA also calls it Coruscant, like the globe in Star Wars, due to its resemblance. Based on its small radius, Kepler-452b is likely a rocky super-Earth.
The Kepler space telescope discovered it, hence its name, and announced by NASA in 2015. The planet is about 1,400 light-years away from the Solar System and onboard the New Horizons, the fastest spacecraft ever launched, it would take approximately 26 million years to get there. It’s still unknown if it offers habitable environments.
Then came Gliese 667 Cc
Discovered by ESO’s High Accuracy Radial Velocity Planet Searcher (HARPS) in 2011, Gliese 667 Cc was also depicted as an Earth-like exoplanet. Its discovery was officially announced the following year. Gliese 667 Cc orbits within the habitable zone of the red dwarf star Gliese 667 C and is believed to be a super-Earth just like Kepler-452b.
Initially thought to be a little bit warmer than Earth, further studies suggest that it could be more much hotter. If Gliese 667 Cc is subject to tidal heating 300 times that of Earth, its chances of hosting life may be lower than initially estimated.
Fun fact about Gliese 667 Cc: it’s the most famous of the trio. In the Alien vs. Predator franchise, it was the first exoplanet to be terraformed by the Weyland Corporation in 2039.
And now it’s Proxima Centauri b
Referred to as a second Earth by ESO astronomers, Proxima Centauri b is located about 4.2 light-years from Earth, making it the closest known exoplanet to the Solar System. Sci-fi fans, however, shouldn’t get too excited because out of the three it’s not the best candidate for hosting life.
Researchers think that due to its proximity to Earth, robotic exploration of the exoplanet with the Starshot project is closer to time. But like with Gliese 667, its habitability may be compromised because Proxima b is close enough to its star that it might be tidally locked.