Astronomers today announced the discovery of a potentially habitable Earth-sized planet orbiting the star closest to the Sun, Proxima Centauri.
Proxima Centauri is 4.24 light-years away. To put that in perspective, the Milky Way galaxy (of which our solar system is a part) is about 100,000 light years across. If trekking the Milky Way from one end to another was equivalent to walking from New York City to California, Proxima Centauri would be within the first 200 yards. So on a cosmic scale, our nearest star is extremely close.
Not much is yet known about this new planet (formally called Proxima Centauri b). Its mass is believed to be between 1.27 and 3 times Earth’s mass, so it probably has a solid surface. Its orbit lies in the habitable zone, which means its surface is capable of supporting liquid water. The star it orbits is a red dwarf, a smaller and different kind of star than our Sun. Beyond these basic facts, many questions about this planet are still unanswered. Does it keep one side always facing its host star? Does it have any moons? Does it have an atmosphere? Does it have liquid water? Does it have life? What kind of life might evolve on such a planet?
These questions will not be answered quickly, but fortunately we will learn more about the planet in the coming years. The European Extremely Large Telescope, currently under construction and planned to be fully functional in 2024, will provide images 16 times sharper than the Hubble Space Telescope. This telescope will be able to resolve Proxima Centauri b and help study its properties. Moreover, now that astronomers all over the world know exactly where to look, further discoveries about the planet are likely to be made sooner.
As for the future of interstellar travel: How lucky we are to have a convenient stepping stone to the rest of the universe. Current technology does not allow us to reach this planet, by manned or unmanned probe, in an average human lifetime. But technology is always evolving, and efforts to dramatically increase probe speed — already underway — will undoubtedly accelerate following this announcement. It is not unreasonable to suggest that we will one day have the capability to visit and even settle worlds beyond our solar system. When we do, Proxima Centauri b will be Destination One and August 24, 2016 is a day that will be remembered.