Proxima Centauri: The Star Scientists Are Racing to Reach and Why Its Exoplanet Changes Everything

Alpha Centauri gets the fame. It is the brightest point in the southern sky and the one that appears in science fiction as humanity's first destination. But the actual closest star to our solar system is not Alpha Centauri A or B. It is a dim red dwarf called Proxima Centauri, gravitationally bound to the Alpha Centauri system and sitting 4.24 light-years from Earth. At the speed of the fastest spacecraft ever launched, NASA's Parker Solar Probe, which hit roughly 692,000 kilometres per hour during its closest solar pass, it would still take about 6,300 years to reach Proxima. That number is not a reason for despair. It is the reason the star has become the fixed target of the most ambitious propulsion project in the history of spaceflight.

In 2016, the European Southern Observatory announced that Proxima Centauri hosts a planet. Proxima b orbits its star every 11.2 Earth days, sits within the habitable zone where liquid water could theoretically exist on a rocky surface, and has a mass at least 1.07 times that of Earth. The announcement landed like a small earthquake in the astronomy community. The nearest star to the Sun had a potentially habitable world. Then, in 2022, a team using the ESPRESSO spectrograph at the Very Large Telescope in Chile confirmed a second candidate: Proxima d, with a mass roughly a quarter of Earth's, orbiting far closer to the star than Proxima b. A third candidate, Proxima c, remains contested. Scientists are cautious about calling any of these worlds truly Earth-like. The habitable zone of a red dwarf is not the same as the habitable zone of a Sun-like star, and what sits inside that zone faces conditions that would be catastrophic on Earth.

Proxima Centauri is a flare star. In May 2019, astronomers using nine separate telescopes simultaneously, including the Atacama Large Millimeter Array and the Hubble Space Telescope, recorded a superflare from Proxima that was 14,000 times brighter than the largest flares our own Sun produces. These events are not rare. Proxima flares regularly and violently. For Proxima b, which orbits so close to its star that a year lasts just 11.2 days, the radiation environment during a major flare would strip away an unshielded atmosphere in geological time. Whether Proxima b has retained an atmosphere at all is one of the central open questions in exoplanet science. Some models suggest a thick atmosphere or a strong magnetic field could offer protection. Others suggest the planet is a scoured rock. No telescope currently operating can resolve the question. The James Webb Space Telescope may eventually provide atmospheric data, but Proxima b does not transit its star from Earth's line of sight in a way that makes spectroscopy straightforward.

In 2016, the same year Proxima b was announced, physicist Stephen Hawking and investor Yuri Milner unveiled Breakthrough Starshot: a proposal to send a fleet of gram-scale laser-sail probes to the Alpha Centauri system at 20 percent the speed of light, reaching Proxima Centauri in roughly 20 years of travel time. The engineering challenges are extraordinary. The laser array required would need to deliver around 100 gigawatts of focused power. The probes would need to survive interstellar dust at relativistic speeds. Communication across 4.24 light-years at any useful bandwidth remains an unsolved problem. Starshot is not a funded mission with a launch date. It is a research programme identifying which of these problems are solvable in principle. But it is the first serious, peer-reviewed framework for reaching another star within a human lifetime, and Proxima Centauri is the destination precisely because it is the closest. The science of that star matters to the engineering of the probe, and the engineering of the probe matters to whether the science ever gets answered.

The convergence is unusual. A star close enough to be a plausible target. A planet in its habitable zone confirmed by multiple independent observations. A propulsion concept that, however distant from realisation, is grounded in known physics. And a generation of telescopes, ESPRESSO, JWST, and the forthcoming Extremely Large Telescope, that will push the atmospheric question as far as ground and space-based observation allows. Scientists are not excited about Proxima Centauri because it is romantic or because the name sounds like a destination. They are excited because it is the one star where the question of life elsewhere in the universe might produce a concrete, checkable answer within the next few decades, rather than remaining permanently hypothetical.

The flare data and the exoplanet data are pulling in opposite directions, and that tension is exactly what makes Proxima Centauri scientifically alive. A star that looked hospitable from a distance and turned out to be violent up close, hosting a world that may or may not have survived that violence, that is not a dead end. That is the most interesting question the nearest star could possibly be asking.