Our nearest stellar neighbors, a genuine triple star system.
Alpha Centauri isn't one star but three. Alpha Centauri A (proper name Rigil Kentaurus) and Alpha Centauri B (proper name Toliman) are a true binary pair, locked in a tight, eccentric 79.9-year orbit around their common center of mass, swinging between 11.4 and 36.0 AU apart. A is a G2V star just slightly hotter and more massive than the Sun; B is a cooler, more orange K1V star. Together they're just 4.37 light-years away, the closest Sun-like stars to our own. Much farther out, the faint red dwarf Proxima Centauri orbits that same binary pair roughly every 550,000 years at a distance of about 8,700 AU, over 350 times the AB pair's own separation. At 4.25 light-years away, Proxima itself holds the record as the single closest star to the Sun. A and B's shared center of mass, the true point both stars revolve around and the one Proxima's own distance is actually measured from, is marked here too, sitting closer to A since it's the more massive of the pair.
How do we actually know all of this?
The A/B pair has been tracked by naked-eye and telescopic observers since the 17th century, and its binary nature was suspected as early as 1689. Proxima is a much more recent discovery: Scottish-South African astronomer Robert Innes found it in 1915 while searching photographic plates from the Union Observatory for anything with the AB pair's own proper motion. But whether Proxima was actually gravitationally bound to A and B, rather than just a chance alignment, remained genuinely unsettled for a century. It wasn't until 2017 that precise astrometry (led by Pierre Kervella) confirmed Proxima's orbit is real and bound, revising its distance from the pair down from the older, often-quoted "~13,000 AU" estimate to the tighter, dynamically consistent ~8,700 AU used here.
A separate infrared survey, based on observations between 2007 and 2012 (Wiegert et al. 2014), found a faint emission excess around the AB pair that may be evidence of an extremely sparse debris disc, or could just as easily be dense interplanetary dust; the authors themselves only call it suggestive, not confirmed. At a system age of roughly 5-6 billion years, older than the Sun, this can't be a genuine planet-forming disc; if real, it would be a much fainter, second-generation dust cloud, stirred up by ongoing collisions among any leftover planetesimals, totaling perhaps a millionth of the Moon's mass. Modeling suggests A's share would be confined well inside its own frost line, while a sliver of B's would just poke past its own.
Proxima b was announced in 2016 by a team led by Guillem Anglada-Escude, the result of the "Pale Red Dot" campaign, a public, live-blogged radial-velocity search built specifically to hunt for it. It remains the closest known exoplanet to the Solar System. A second planet, Proxima c, was proposed in 2019 from the same kind of radial-velocity data, but its existence is still disputed; a 2025 re-analysis found the original signal probably isn't real, though a different, smaller planet in a similar orbit hasn't been ruled out. Because of that unresolved status, Proxima c is deliberately left out of this rendering rather than presented as confirmed. A third, much smaller planet, Proxima d, was confirmed in 2022 and independently verified with the NIRPS spectrograph in 2025, making it one of the lightest planets ever measured by the radial-velocity method.
None of Proxima's planets have ever been observed to transit their star, so unlike TRAPPIST-1's planets, only their minimum masses are directly measured; their physical sizes shown here are modeled estimates, not measurements. It's also worth knowing that this system has already produced one cautionary tale about overclaiming: a 2012 announcement of a planet orbiting Alpha Centauri B ("Alpha Centauri Bb") was retracted in 2015 after follow-up analysis showed the signal was an artifact of how the original data was processed, not a real planet. Separately, ground-based imaging in 2021 and a JWST MIRI observation in 2024 turned up a tentative point source near Alpha Centauri A that could be a Saturn-mass planet in its habitable zone, but it hasn't been recovered in follow-up observations and isn't confirmed, so it's also left out here.
Where do this app's numbers come from? Stellar masses, radii, and the AB orbit come from Kervella et al. (2016, 2017); Proxima's bound orbit and distance from Kervella et al. (2017); the tentative circumstellar debris disc from Wiegert et al. (2014); Proxima b's parameters from Anglada-Escude et al. (2016); Proxima d's parameters from Faria et al. (2022) and its 2025 NIRPS confirmation, as aggregated on the NASA Exoplanet Archive.