Caelum
What is Caelum?
Constellations· Southern summer · a gap between Eridanus and Columba. Lacaille's tribute to the sculptor's chisel. The eighth-smallest constellation, with just two fourth-magnitude stars, it ranks among the least conspicuous in the sky.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Caelum is in your sky right now: https://nowsky.org/solar/sky?sel=con:Caelum — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Alpha Caeli | 4.4 |
The 1 brightest of the 3 stars used in the figure (2 lines). Lower magnitude means brighter.
Constellation basics
| Season | Dec–Jan evenings; skims the horizon from Korea |
|---|---|
| Brightest star | α Caeli, mag 4.4 |
| How to find | southwest of Lepus, west of Columba |
| Area rank | 81st of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Caelum?
- Dec–Jan evenings; skims the horizon from Korea.
- How do I find Caelum?
- southwest of Lepus, west of Columba.
- What is the brightest star in Caelum?
- Alpha Caeli, magnitude 4.4.
- Where is Caelum in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
The quasar without a host — HE 0450-2958 in Caelum
In 2005 the quasar HE 0450-2958, five billion light-years away in the direction of Caelum, drew attention. A quasar is the glowing black hole at a galaxy's centre and so must have a galaxy, yet no matter how Hubble and the VLT looked, no galaxy could be seen around this one. The reading that it was a black hole drifting without a galaxy earned it the name of the naked quasar.
Later observations found a galaxy in a burst of star formation next to the quasar, and the explanations became that the quasar had been flung out after colliding with it, or that its own galaxy was too small and faint to show beside the glare. In 2009 it was reported that the quasar's jet was triggering star formation in the neighbouring galaxy. Beyond this small constellation of two 4th-magnitude stars, the accepted idea that black holes and galaxies grow together was put to the test.
The constellation in depth
Caelum was placed by Lacaille in the 1750s in an empty patch of the southern sky, originally as the Sculptor's Chisel — a name chosen to pair with the neighbouring constellation Sculptor. With little area and no bright stars, even old atlases could only mark it with a drawing of two crossed engraving tools. It ranks 81st of the 88 constellations by area.
Alpha Caeli, the brightest star at magnitude 4.4, is a white main-sequence star about 66 light-years away with a faint red-dwarf companion. Gamma Caeli is a double star that small telescopes can split. The region holds almost no bright clusters or nebulae, so deep-sky observers rarely visit this quiet corner. Its main appeal is simply completing the map of the sky.
At declinations of −27° to −49° only its top edge grazes the southern horizon from Korea around midnight in December and January. From the southern hemisphere, drop south from Orion past Lepus and Columba on a summer evening. In the Sky view, set Sydney on a January evening. Without the constellation lines it looks like empty sky, so leave them on.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.