Apus
What is Apus?
Constellations· Southern winter · between the Southern Triangle and the pole. The bird of paradise, whose Latin name means 'without feet'. A few faint stars close to the south celestial pole.
📍 Visible from where you are right now — computed in your browser
Stars of the figure
| Star | Magnitude |
|---|---|
| Alpha Apodis | 3.8 |
The 1 brightest of the 2 stars used in the figure (1 lines). Lower magnitude means brighter.
Constellation basics
| Season | circumpolar in the south, best Jun–Jul; never visible from London or New York |
|---|---|
| Brightest star | α Apodis, mag 3.8 |
| How to find | south of Triangulum Australe, north of Octans |
| Area rank | 67th of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
NGC 6101, a cluster that may hide hundreds of black holes
Apus holds the globular cluster NGC 6101, about 50,000 light-years away. A globular cluster is a ball of hundreds of thousands of old stars packed tightly together. Usually the stars crowd more and more toward the centre, but NGC 6101's centre is surprisingly loose, which puzzled scientists.
In 2016 a team at the University of Surrey in Britain recreated the cluster's history on a computer. They concluded that its present shape can be explained only if hundreds of black holes, left behind by dead stars, still remain inside it. Until then black holes were thought to be mostly thrown out of such clusters. These black holes have not yet been detected directly.
Black holes in a cluster can pair up and merge, giving off gravitational waves, ripples in space and time made by heavy moving objects. Some scientists therefore suggest that part of the black-hole collisions detected since 2015 happened in clusters like this one.
The constellation in depth
Apus is one of twelve southern constellations that came from Dutch navigators' observations in the 1590s, and it appeared in Bayer's atlas of 1603. The bird of paradise is a brightly feathered bird of New Guinea and nearby islands. Its Latin name, Apus, means 'without feet', and there is a story behind that.
In the 16th century no European had seen a living bird of paradise. In 1522 survivors of Magellan's expedition brought skins of the bird from the Moluccas to Spain, and the skins had no feet, because they had been cut off when the skins were prepared. Europeans came to believe the bird had no feet and spent its whole life flying, and that mistake lives on in the constellation's name.
The brightest star, Alpha Apodis, is an orange giant of magnitude 3.8 about 450 light-years away. Delta Apodis is a wide pair of red giants side by side, good for comparing colours in binoculars. The constellation also holds NGC 6101 and IC 4499, globular clusters made of old stars packed into a ball.
At declinations of −67° to −83° it cannot be seen from Europe or most of the United States, while from the southern hemisphere it never sets. On June and July evenings look below Triangulum Australe, short of the pole, for a few faint stars. In the Sky view, set Cape Town on a July evening and it appears low in the southern sky.
Frequently asked
- When can I see Apus?
- Apus is best seen in circumpolar in the south, best Jun–Jul; never visible from London or New York.
- How do I find Apus?
- To find Apus, look for south of Triangulum Australe, north of Octans.
- What is the brightest star in Apus?
- The brightest star in Apus is Alpha Apodis, at magnitude 3.8.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.