Star Stars · In Canis Major
Aludra
Aludra, η Canis Majoris, is a blue-white supergiant in Canis Major: the 90th brightest star in the night sky.
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- Constellation
- Canis Major
- Designation
- η Canis Majoris
- Apparent magnitude
- 2.45 · 90th brightest star in the night sky
- Spectral class
- B5Ia
- Distance
- 1,989 light-years
- Highest at midnight
- early January
- Position (J2000)
- RA 07h 24m · Dec −29° 18′
A blue-white supergiant, around 20,000 K, like Rigel and Spica. About 42× brighter than the faintest star the eye can see. Gives off about 33,000 times the Sun's visible light. The light you are seeing left around 37.
When to see it
On the night of Sat 9 Jan 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT | 21:09 | 00:08 · 9° | 03:07 |
| New York EST | 19:59 | 00:03 · 20° | 04:06 |
| Singapore GMT+8 | 19:17 | 01:13 · 59° | 07:09 |
| Sydney GMT+11 | 17:37 | 01:04 · 85° | 08:32 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 11° up in the south.
- Can I see it from 35° south?
- Yes, and well placed: at its highest it passes almost overhead, 84° up, above most of the air’s haze.
- When is the best time of year to see it?
- Around early January, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by early April it is highest in the early evening, and in early October not until the hours before dawn.
- How far away is it, and how bright?
- It is 1,989 light-years away, and shines at magnitude 2.45 in our sky. From that far, the Sun would be a star of magnitude 13.7: too faint for anything less than a telescope.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 2.45 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Wezen: Aludra is 4.5° south-east of it, three fingers at arm’s length.
Look for
From 50° north it climbs to 11°; from 35° north it climbs to 26°; from the equator it climbs to 61°; from 35° south it climbs to 84°.
Science
Aludra’s surface is about 20,000 K, some 14,200 K hotter than the Sun’s 5,772 K, so its light is strongest at about 140 nm, in the ultraviolet, past the violet end of what the eye can see, where the Sun’s is strongest at 500 nm. Moved to 33 light-years, the distance astronomers compare stars at, it would shine at magnitude −6.5, brighter than Sirius, the brightest star in our sky.
Did you know
Against Wezen, the brighter star the hop starts from: Wezen looks 1.8 times as bright as Aludra in our sky; Wezen is 1,607 light-years away and Aludra 1,989 light-years, so side by side they would give off about as much light.
Science
Aludra is the 154th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Wezen, about 410 light-years from it; on our sky the two are 4.5° apart.
Look for
The Sun passes 51° north of Aludra around early July, when it is highest at noon, in daylight: the weeks either side are its worst time of year. From 50° north it is above the horizon for about 6 hours a day, from 35° north about 9 and from 35° south about 15. It is 6° from the plane of the Milky Way, inside the band a dark sky shows.