Blue-white supergiant · Canis Major

Aludra

Also known as: η Canis Majoris (η CMa), HIP 35904

mag 2.52,000 light-years

About

Aludra (η Canis Majoris) is a blue-white supergiant of magnitude 2.5 in Canis Major, about 2,000 light-years away.

Aludra is in the constellation Canis Major.
Best evenings: around late February it is highest at about 9 pm (10 pm in summer time); a month earlier, two hours later.
Where on Earth: it is seen well, at least 10° up, from south of 51° N.

When it rises and sets tonight, how high it climbs and how much the Moon gets in the way are worked out in your browser for your place.

EyesEasy, even from town. It looks blue-white.
Binoculars (10×50)A sharp point; binoculars bring out its colour and the fainter stars around it.
Telescope (6–8 inch)Still a point of light at any magnification — stars are too far away to show a disc. Low in the sky, bright stars twinkle and flash colours.

Stars look the same in any instrument: brighter and sharper, but never bigger.

Proper name	Aludra
Designation	η Canis Majoris (η CMa)
Hipparcos number	HIP 35904
Type	Blue-white supergiant
Spectral type	B5Ia
Colour	WhiteB−V colour index −0.08
Magnitude	2.5The smaller the number, the brighter.
Distance	2,000 light-yearsThe light you see left it around AD 0. Distances this large are uncertain by 10% or more.
Proper motion	0.008″ per year across the sky
Constellation	Canis Major
Right ascension (J2000)	07h 24m 05.7s
Declination (J2000)	−29° 18′ 11″

Star data: HYG Database by David Nash, CC BY-SA 4.0. All data sources →