The Closest Star

The above graphic showing Proxima Centauri, the closest star to Earth except the Sun

Located just 4.24 light-years away, Proxima Centauri is our closest stellar neighbor. While it is part of the Alpha Centauri triple-star system, it is vastly different from its brighter companions. As a red dwarf (M-type star), it is invisible to the naked eye, possessing only about 12% of the Sun's mass and being only slightly larger than Jupiter.

1. A Relentless "Flare Star"

The most salient—and violent—feature of Proxima Centauri is its extreme magnetic activity. It is classified as a flare star, meaning it undergoes sudden, dramatic increases in brightness. In 2017 and again in observations leading into 2026, astronomers recorded "superflares" that increased the star's brightness by over 1,000 times in mere seconds.

Unlike our Sun, which is only partially convective, Proxima is likely fully convective. This means its plasma circulates from the core to the surface like a boiling pot, constantly twisting magnetic fields that eventually "snap," releasing bursts of high-energy X-rays and ultraviolet radiation into the surrounding system.

2. The Proxima Planetary System

Despite its volatile nature, Proxima Centauri hosts a fascinating family of planets:

• Proxima b: Discovered in 2016, this is an Earth-sized, rocky world sitting right in the "habitable zone." It orbits every 11.2 days.

• Proxima d: Confirmed in 2022, this is one of the lightest exoplanets ever found (about 25% of Earth's mass), orbiting even closer to the star.

• Proxima c: A controversial "Super-Earth" or "Mini-Neptune" candidate that orbits much further out in the cold, dark reaches of the system.

3. The Habitability Paradox

Because Proxima is so cool and dim, its habitable zone is incredibly close—about 20 times closer than Earth is to the Sun. While this allows for liquid water temperatures on Proxima b, it also means the planet is likely tidally locked (one side always faces the star) and is constantly "sandblasted" by stellar flares. Current 2026 research suggests that unless Proxima b has an incredibly strong magnetic field, its atmosphere may have been stripped away eons ago.

4. Our First Interstellar Destination

Due to its proximity, Proxima Centauri is the primary target for the first-ever interstellar missions. Projects like Breakthrough Starshot aim to use ultra-powerful lasers to propel "light sails"—tiny, chip-sized probes—to 20% the speed of light. This would allow us to reach Proxima in just over 20 years, finally giving us a close-up look at our nearest cosmic cousins.