Distance to Alpha Centauri A
| Value | 4.13e16 m |
| Status | Measured: ± 34,000,000,000,000 m (0.00082 relative) |
| Source | Kervella et al. (2016) parallax 747.17 ± 0.61 mas (Hipparcos-based re-reduction) |
| Categories | Astronomicalstellar |
| Planck length | 2.5552899e+51 lP |
| femtometer | 4.1300000e+31 fm |
| picometer | 4.1300000e+28 pm |
| bohr radius | 7.8045689e+26 a0 |
| angstrom | 4.1300000e+26 Å |
| nanometer | 4.1300000e+25 nm |
| micrometer | 4.1300000e+22 μm |
| thou | 1.6259843e+21 thou |
| point | 1.1707087e+20 pt |
| millimeter | 4.1300000e+19 mm |
| pica | 9.7559055e+18 pc |
| centimeter | 4.1300000e+18 cm |
| inch | 1.6259843e+18 in |
| decimeter | 4.1300000e+17 dm |
| hand | 4.0649606e+17 hh |
| link | 2.0530104e+17 li |
| foot | 1.3549869e+17 ft |
| US survey foot | 1.3549842e+17 ftUS |
| yard | 4.5166229e+16 yd |
| meter | 4.1300000e+16 m |
| fathom | 2.2583115e+16 ftm |
| rod | 8.2120417e+15 rd |
| chain | 2.0530104e+15 ch |
| cable length | 223,002,160,000,000 cb |
| furlong | 205,301,040,000,000 fur |
| kilometer | 41,300,000,000,000 km |
| mile | 25,662,630,000,000 mi |
| nautical mile | 22,300,216,000,000 nmi |
| league | 8,554,210,100,000 lea |
| megameter | 41,300,000,000 Mm |
| Earth radius | 6,482,498,800 REarth |
| light-second | 137,761,970 ls |
| lunar distance | 107,440,450 LD |
| solar radius | 59,364,669 Rsun |
| light-minute | 2,296,032.9 lmin |
| astronomical unit | 276,073.45 AU |
| light-year | 4.3654134 ly |
| parsec | 1.3384418 pc |
| kiloparsec | 0.0013384418 kpc |
| megaparsec | 0.0000013384418 Mpc |
| gigaparsec | 1.3384418e-09 Gpc |
Learning zone
Alpha Centauri is the closest star system: A and B, a tight pair orbiting each other in 79.9 years, with faint Proxima circling both about 0.2 light-years nearer to us. The A component is the prize — a G2 star, the Sun's own spectral class, close enough in every property to be called a twin. Its parallax of 747 milliarcseconds was among the first ever measured: Thomas Henderson observed it from the Cape of Good Hope in 1832–33, but hesitated to publish and was scooped by Bessel's 61 Cygni in 1838 — caution costing him one of astronomy's great firsts.
The measurement is ironically harder today: Alpha Centauri is too bright for Gaia's detectors, so the best distance still rests on Hipparcos-era astrometry refined by the binary orbit. At 4.4 light-years, a radio message and its reply span a decade — the benchmark every conversation about interstellar anything eventually quotes.