Rigil Kentaurus
HIP 71681; Alpha2 Cen
Sep: 8.1", Companion: mag 1.3
Physical Properties
Position & Identifiers
Visibility
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Multiple Star System
Eyepiece View
Sep: 8.1″ · PA: 5° · N up, E left
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 3.1″
Size Comparison
Stellar Lifecycle
Spectral Classification
Hertzsprung-Russell Diagram
Blackbody Spectrum
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
Stellar Notes
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About Rigil Kentaurus
Description
Alpha Centauri B (Rigil Kentaurus B) is the fainter component of the Alpha Centauri binary, an orange main-sequence star of spectral type K1V at magnitude 1.33. At 4.37 light-years, it is part of the nearest star system to Earth. It is slightly smaller, cooler, and less luminous than the Sun, with about 50% of solar luminosity.
Observing Tips
Alpha Centauri B is easily resolved from the brighter A component in a small telescope — the pair currently has a separation of several arcseconds. Look for the slightly orange companion next to the golden primary. The orbital period is about 80 years, and the separation varies between 2 and 22 arcseconds. Not visible north of about 29°N.
History
Alpha Centauri B has the same naming history as its primary. In 2012, a planet candidate (Alpha Centauri Bb) was announced orbiting this star, generating worldwide excitement as the nearest exoplanet, but subsequent analysis showed the detection was likely a statistical artifact. The search for planets in this system continues.
Fun Facts
Alpha Centauri B experiences significantly different seasons and day lengths than Earth due to the gravitational influence of its binary companion. From a hypothetical planet orbiting B, Alpha Centauri A would appear as an extremely bright star (about magnitude -21), roughly 200 times brighter than our full Moon.