Hadar (Beta Centauri)
Hadar (Beta Centauri) is a star in the constellation Centaurus, magnitude 0.6.
The inner Pointer to the Southern Cross — three hot blue stars, two of them heavy enough to explode.
Hadar looks like one star, but it is three. Two blue giants, each 10 to 12 times the Sun’s mass, swing around each other every 357 days on a long, stretched orbit. A third, smaller star circles farther out. All three are hot stars of the same B1 spectral type, shining blue-white.
The two giants are heavy enough to end their lives as supernovae; the third will swell into a red giant and fade into a white dwarf. The brightest star also pulses gently — a variable star of the Beta Cephei kind — though the changes are far too small to notice by eye.
Its name comes from Arabic. Its other name, Agena, probably comes from the Latin for ‘knees’: it marks the left knee of the centaur.
Hadar (Beta Centauri) is 390 light-years away: the light we see from it set off around 1635, 25 years after Galileo first turned a telescope to the sky.
Did you know?
- Two brothers and an emu. The Boorong people of Victoria saw Hadar and Alpha Centauri as two brothers who speared Tchingal, the Emu — the dark Coalsack Nebula beside the Southern Cross.
- One star becomes three. Joan Voûte spotted the faint third star in 1935. In 1967 a shifting spectrum hinted that the main star was itself double, which was confirmed in 1999.
- Waar. The Mursi people of Ethiopia call Hadar Waar. It forms a pattern with Alpha Centauri and two stars of the Southern Cross.
A brilliant blue-white star, the inner of the two Pointers to the Southern Cross. A line from Alpha Centauri through Hadar leads to the Cross. Compare its cool blue-white with the warmer, yellowish light of Alpha Centauri beside it.
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 30°N and never sets south of 30°S.
At its highest it stands below the horizon from 50°N, below the horizon from 35°N, 30° up from the equator, 65° up from 35°S.
Facts
- Type
- Star
- Constellation
- Centaurus
- Designations
- Beta Centauri, Agena, β Cen, HR 5267, HD 122451, HIP 68702
- Magnitude
- 0.6
- Position
- RA 14h 3.8m, Dec −60° 22′ (J2000)
- Spectral type
- B1III
- Distance
- 390 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Hadar (Beta Centauri) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.