Hadar
What is Hadar?
Stars· Distance ~390 ly · size 9× Sun. One of the two Pointer stars that lead to the Southern Cross, alongside Alpha Centauri. The eleventh-brightest star in the sky, it is a group of three hot blue stars 390 light-years away. It cannot be seen from Europe or most of the United States.
📍 Visible from where you are right now — computed in your browser
Distance and spectral type
Hadar is about 392 light-years away, a blue-white bright giant (spectral type B1III), in the constellation Centaurus. Its apparent magnitude is 0.6, visible to the naked eye.
Stellar figures
| Distance | ~390 ly |
|---|---|
| Magnitude | 0.61 — eleventh brightest |
| Type | B1 blue giant, triple |
| Constellation | Centaurus |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Behind the name
Arabic "ground". With Alpha Centauri it forms the Pointers to the Southern Cross.
Telling the real Southern Cross from the False Cross with Hadar
The southern sky has a 'False Cross' that is easily mistaken for the Southern Cross. It is a cross shape made by four stars in Carina and Vela. It is larger than the real cross, and its stars are a little fainter. The key to telling them apart is Hadar and Alpha Centauri. Beside the true Southern Cross, these two bright stars stand side by side and point toward it. No such pointer stars stand beside the False Cross.
Once the Southern Cross is found, it also shows the way south. Extend the long bar of the cross downward about four and a half times, and you reach the area of the south celestial pole. Draw another line straight out from the midpoint between the two Pointers, and where the two lines meet marks the pole more precisely. Sailors in the southern hemisphere found their way like this long before modern instruments. In the Sky view, set the location to Sydney to see Hadar, Alpha Centauri and the Southern Cross lined up.
The star in depth
Hadar, also called Agena, is the second-brightest star in Centaurus. At magnitude 0.61 it is the eleventh-brightest star in the night sky. In the sky it sits right next to Alpha Centauri, but their real distances are very different. Alpha Centauri is 4.4 light-years away, while Hadar is about 390. A star about ninety times farther away just happens to appear in the same direction.
Hadar looks bright from so far away because it is a very powerful star. Its surface is about 25,000 K, more than four times as hot as the Sun's, which is why it glows blue. It has more than ten times the Sun's mass and gives off tens of thousands of times as much light. It is a completely different kind of star from Sun-like Alpha Centauri.
Hadar is actually three stars. Two heavy stars circle each other every 357 days, and a third star orbits far outside them. The brightest one swells and shrinks slightly every few hours, so its light flickers a little. Stars this heavy burn their fuel fast and live only tens of millions of years. Scientists expect them to end their lives as supernovae.
Hadar lies too far south to be seen from Europe or most of the United States; it rises only south of about latitude 30° N. In the southern hemisphere it stands high in the south on evenings from April to June. Following the line from Alpha Centauri through Hadar leads to the Southern Cross, so the two stars are called the Pointers. In the Sky view, switch the location to Sydney or Cape Town to see bluish Hadar beside Alpha Centauri.
Frequently asked
- How far is Hadar from Earth?
- The distance of Hadar is ~390 ly.
- How bright is Hadar (apparent magnitude)?
- The magnitude of Hadar is 0.61 — eleventh brightest.
- What kind of object is Hadar?
- Hadar is a B1 blue giant, triple.
- Which constellation is Hadar in?
- Hadar lies in the constellation Centaurus.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.