Proxima B: 5 Things You Need to Know About the New Earth-Like Planet

A new Earth-like planet was recently discovered. Find out everything you need to know about Proxima b.

Sabrina Stierwalt, PhD
5-minute read
Episode #205

 ESO/M. KornmesserThe world of science news was recently abuzz with an incredibly exciting new discovery—a roughly Earth-mass planet orbiting the star Proxima Centauri a mere 4.2 lightyears away. The discovery has been described as an “astronomy dream come true.”

As shocking as it sounds, we find exoplanets, or planets orbiting stars other than our Sun, all the time now. We know of nearly 3,000 such planets plus another 2,500 planet candidates. So what makes this recent discovery, dubbed Proxima b, so particularly exciting? Not only is this newfound planet very similar to the Earth in mass at 1.3 times the mass of the Earth, but it also orbits its host star in that star’s habitable zone.

As we’ve previously discussed, the habitable zone describes the range of distances from a star with the right temperature for liquid water to exist. You can think of the habitable zone as a band or torus around the host star. Planets too close to the star will have temperatures that are too high, causing any liquid water to boil while planets too far from the star will be too cold leading to frozen worlds. Planets within the habitable zone—also called the “Goldilocks zone”—have temperatures that are “just right” and thus at least have the potential to host liquid water.

One of the main drivers of the search for planets outside of our solar system is the search for life similar to what we see on Earth. Finding planets similar to our Earth is the first, very important step.

There have been a few previous discoveries of Earth-sized planets in their host star’s habitable zone, including the planet dubbed Earth’s bigger, older cousin Kepler 452b. However, Kepler 452b is over 1400 lightyears from Earth. That means that even traveling at 5% of the speed of light—which, by the way, is far faster than the fastest spacecraft—the trip there would take over 28,000 years to complete. And that’s just one way!

So another reason that the discovery of Proxima b is so special is that it is not only much closer than previously known Earth-mass planets, but it actually resides in the closest star system beyond our own. The host star Proxima Centauri resides in the triple star system Alpha Centauri at a distance of 4.2 lightyears away.

Thus the odds of us being able to visit or send probes to Proxima b are greatly improved over our chances of exploring any other planet outside of our solar system. Loyal listeners may also remember that the program Breakthrough Starshot recently announced plans to send nanocraft propelled by ground-based lasers at 20% the speed of light toward the Alpha Centauri system.

So should we start packing our bags now? Will future generations have the possibility of visiting and eventually settling Proxima b? Here are five reasons why Proxima b might not be ready for visitors just yet.


Please note that archive episodes of this podcast may include references to Ask Science. Rights of Albert Einstein are used with permission of The Hebrew University of Jerusalem. Represented exclusively by Greenlight.

About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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