Meet the Neighbors: Proxima Centauri and its Rocky Planet

view from Proxima Centauri b
An artist's concept of what Proxima Centauri would look like from the surface of its nearby rocky planet. ESO

Our Sun and planets inhabit a relatively quiet part of the galaxy and don't have many really close neighbors. Among the nearby stars is Proxima Centauri, which is part of ​the Alpha Centauri system of three stars. It's also known as Alpha Centauri C, while the others stars in the system are called Alpha Centauri A and B. They're much brighter than Proxima, which is a smaller star and cooler than the Sun. It is classified as a M5.5-type star and is just about the same age as the Sun. That stellar classification makes it a red dwarf star, and most of its light is radiated as infrared. Proxima is also a highly magnetic and active star. Astronomers estimate it will live for a trillion years.

Proxima Centauri's Hidden Planet

Astronomers have long wondered if any of the stars in this nearby system could have planets. So, they began searching for worlds in orbit around all three stars, using ground-based and space-based observatories.

Finding planets around other stars is difficult, even for ones as close as these. Planets are pretty small compared to stars, which makes them hard to spot. Astronomers searched for worlds around this star and eventually found evidence for a small rocky world. They've named it Proxima Centauri b. This world appears to be slightly larger than Earth, and orbits in its star's "Goldilocks Zone." That's a safe distance away from the star and is a zone where liquid water could exist on the surface of the planet.

There's not yet been any attempt to see if life exists on Proxima Centauri b. If it does, it would have to contend with strong flares from its sun. It's not impossible that life could be there, although astronomers and astrobiologists are debating about what the conditions would be like to protect any nascent living beings. The way to find out if life is abundant on that planet is to study its atmosphere as light from the star filters through. Evidence for atmospheric gases friendly to life (or produced by life) would be hidden in that light. Such studies will take more diligent searching over the next few years.

Even if there ultimately is no life on Proxima Centauri b, this world would most likely be the first stop for future explorers that venture out beyond our own system of planets. After all, it is the closest star system and would mark a "milestone" in space exploration. After visiting those stars, humans could truly call themselves "interstellar explorers."

Can We Go to Proxima Centauri?

People often ask if we could travel to this nearby star. Since it lies only 4.2 light-years away from us, it IS reachable. However, no space ship travels anywhere near the speed of light, which is required to get there in about 4.3 years. If the Voyager 2 spacecraft (which is traveling at a speed of 17.3 kilometers per second) was on a trajectory for Proxima Centauri, it would take 73,000 years to arrive. No human-bearing spacecraft has ever gone that fast, and in fact, our current space missions travel much more slowly. Even if we could send them at the speed of Voyager 2, it would consume the lives of generations of travelers to get there. It's not a quick trip unless we somehow develop light-speed travel. If we did, then it would take just over four years to get there.

Finding Proxima Centauri in the Sky

The stars Alpha and Beta Centauri are quite easily visible in southern hemisphere skies, in the constellation Centaurus. Proxima is a dim reddish star that has a magnitude of 11.5. That means a telescope is needed to spot it. The star's planet is very small and was discovered in 2016 by astronomers using telescopes at the European Southern Observatory in Chile. No other planets have been found yet, although astronomers keep looking. 

Exploring Further in Centaurus

Aside from Proxima Centauri and its sister stars, the constellation Centaurus has other astronomy treasures. There's a gorgeous globular cluster called Omega Centauri, which glitters with around 10 million stars. It's easily visible with the naked eye ​and can be seen from extreme southern parts of the northern hemisphere. The constellation also contains a massive galaxy called Centaurus A. This is an active galaxy that has a supermassive black hole at its heart. The black hole is spewing jets of material out at high speeds across the heart of the galaxy. ​

Edited and updated by Carolyn Collins Petersen.