Menkent (Theta Centauri)

Menkent (Theta Centauri) is a star in the constellation Centaurus, magnitude 2.0.

The Centaur’s shoulder — an orange giant just passing through our part of the galaxy.

Menkent’s name is a blend: the Arabic mankib, “shoulder”, run together with a clipped form of “kentaurus”. It marks the shoulder of the Centaur, a constellation better known for its brilliant pair of Pointers, Alpha Centauri and Hadar.

This is an orange giant of about 1.3 solar masses, 11 times the Sun’s width and 56 times as luminous. Having finished with hydrogen in its core, it now fuses helium into carbon, which makes it what astronomers call a red clump star. Its surface, near 4,850 kelvin, is cooler than the Sun’s.

Menkent is also a visitor. Its relatively quick drift across the sky suggests it was born in the outer disc of the Milky Way and is only passing through the Sun’s neighbourhood.

Menkent (Theta Centauri) is 59 light-years away: the light we see from it set off in 1967, around the time Apollo 11 landed on the Moon.

Did you know?

• Pollux of the south. Menkent is often called a southern counterpart of Pollux in Gemini, the closest giant star to the Sun: both are orange, helium-burning giants.
• Third star of the Arsenal. In Chinese astronomy it is Kù Lóu sān, the Third Star of the Arsenal, an asterism of ten stars spread across the Centaur.

An orange 2nd-magnitude star in the Centaur’s shoulder, due north of Hadar and Alpha Centauri. Compare its warm tint with blue-white Hadar, the Pointer directly south of it.

What is a star?

When and where to see it

It is best placed in the evening sky around May, when it crosses the meridian at about 10 pm local time (around midnight in April). It can be seen from everywhere south of 54°N and never sets south of 54°S.

At its highest it stands 4° up from 50°N, 19° up from 35°N, 54° up from the equator, 89° up from 35°S.

Facts

Type

Star

Constellation

Centaurus

Designations

Theta Centauri, θ Cen, 5 Cen, HR 5288, HD 123139, HIP 68933

Magnitude

2.0

Position

RA 14h 6.7m, Dec −36° 22′ (J2000)

Spectral type

K0-IIIb

Colour

orange (B−V 0.99)

Distance

59 light-years

Discovered

Known since antiquity

Open AstroPilot to see when Menkent (Theta Centauri) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.