When is the best time to observe Rigil Kentaurus?

Rigil Kentaurus is best observed from March through May, with peak visibility during April when it transits around midnight in the Northern Hemisphere.

Where is Rigil Kentaurus located in the sky?

Rigil Kentaurus lies in the constellation Centaurus at right ascension 14h 40m and declination -60° 50′.

What telescope do I need to split Rigil Kentaurus?

Splitting Rigil Kentaurus requires an aperture of roughly 80 mm or larger — the components are separated by about 8.1″ at magnitudes near 1.3. Larger apertures and steady seeing help resolve the pair cleanly.

Rigil Kentaurus — Double Star in Centaurus

HIP 71681; Alpha2 Centauri

Observable Double Star Showpiece (80/100)

Sep: 8.1", Companion: mag 1.3

Magnitude 1.3^m DoubleStar Centaurus (Cen) Visible

Star Map + List + Plan

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.

Observe

1Physical Properties

Magnitude 1.33

Spectral Type K1V

Star Color Orange (B-V 0.88)

Temperature 5794 K

Radius 1.3 R☉

Distance 4 ly

2Position & Identifiers

RA 14h 39m 36.1s

Dec -60° 50' 08.0"

Constellation Centaurus (Cen)

HR 5460

HIP 71681

HD 128621

Bayer Alpha2

SIMBAD Wikipedia

3How easy to split?

Primary 1.3 mag Companion 1.3 mag Separation 8.1″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
150 mm Newton 150mm Newt.	Easy	Easy	Easy
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Mar – May (peak: Apr)

5Multiple Star System Triple

Components 3 (triple)

Component IDs AB

Separation 8.1″

Companion Mag 1.3

Companion Sp K1V

Position Angle 5°

Star Colors A: Orange B: Orange

Discoverer RHD 1

Notes

See HR 5459.

Separation over time

Measured 1752 → 2023 (271 y)

Separation drift 20.5" → 8.1" (-12.40")

Rate -0.0458" / y

PA drift 218° → 5° (+147°, +0.542°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.