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Key Facts
Constellation
: Canis Major
Location (RA)
: 07h 24m 05.71
Location (Dec)
: -29d 18` 11.2
Distance
: 1,988.8 light years
Colour
: blue
Type
: very luminous supergiant star
Apparent Magnitude
: 2.45
Summary
Aludra, also known as Eta Canis Majoris (Bayer) is a very luminous supergiant star located in the constellation of Canis Major, The Big Dog.Aludra is a major star and forms part of the constellation.
Based on the spectral type (B5Ia), Aludra colour is blue, which means that the star is one of the hottest stars in the Universe, hotter than our star.
Aludra temperature is in the range of 10,000 to 30,000 Kelvin.Based on the spectral type (B5Ia) as we don't have the exact temperature', we can deduce that the surface temperature of Aludra is in the order of 10,000 and 25,000K based on the notes from Harvard University. To put this in context, the temperature of our Sun is about 5,778 Kelvin as said by Google.
Aludra is the 87th brightest star in the night sky and the 5th brightest star in Canis Major based on the Hipparcos 2007 apparent magnitude.Based on a parallax of 1.64, Aludra distance from Earth can be calculated at being 1,988.80 light years away or 980.39 parsecs.
Aludra is a naked-eye star, so you don't need a telescope or binoculars when you look up on a clear night. The lower the magnitude, the easier it will be to see it.
Aludra is a variable star, its brightness varies in magnitude between 2.3820 to 2.4780. The smaller number is the brightest the star gets.
Star Map
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Location
The location of the Aludra in the night sky is determined by the right ascension (R.A.) and declination (Dec.). These are equivalent to the Longitude and Latitude on Earth.The Right Ascension (Longitude) is expressed in time (hh:mm:ss) and is how far the star is along Earth's celestial equator. If the R.A. is positive, then it's eastwards and vice versa.
The Declination (Latitude) is how far north or south the object is compared to the celestial equator and is expressed in degrees. If the value is positive, it is north of the celestial equator. ForAludra, the location is 07h 24m 05.71 and -29° 18` 11.2 .
Based on the location of Canis Major, Aludra can be located in the southern hemisphere of the celestial sky. The celestial hemisphere is equivalent to the hemispheres on Earth.Aludra is south of the Ecliptic. The Ecliptic is the path that the Earth takes as it orbits the Sun. As the Earth is titled, we therefore have Celestial and Ecliptic hemispheres and they can be different for a star.
Physical Properties
Spectral Type
Aludra spectral type of B5Iawhich means its colour and type is blue supergiant star.There is no relationship between colour and size. For example, a red star can be large or small. Small stars are more energy efficient than larger stars and live longer.
Magnitude (Apparent / Absolute / Visible)
A number represents a star’s magnitude, whether apparent/visual or absolute. The smaller the number, the brighter the star is. The Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.
Aludra apparent magnitude is 2.45, which is a measure of the star's brightness as seen from Earth. Apparent Magnitude is also known as Visual Magnitude.
If you use the 1997 parallax value, Aludra' absolute magnitude is -7.51.If you use the 2007 parallax value, Aludra' absolute magnitude is -6.48.Absolute Magnitude is the star's apparent magnitude from 10 parsecs or 32.6 light years. The magnitude assumes nothing is between the object and the viewer, such as dust clouds. To compare different stars' actual brightness, you would best use Absolute rather than Apparent Magnitude.
Aludra is visible from Earth without needing binoculars or a telescope. The lower the Apparent Magnitude of a star or other object is, the easier it is to see in the night sky. An object with a magnitude greater than 6.5 cannot be seen without a telescope or other device.
Radial Velocity and Proper Motion
In simplistic terms, all non-rogue stars, like planets, orbit around a central object, although that is actually not true. Where is the centre of the Solar System. For simplicity it's the central star, such as the Sun. In the case of a star, it's the galactic centre. The constellations we see today will be different than they were 50,000 years ago or 50,000 years from now.
Proper motion details the movements of these stars and is measured in milliarcseconds. Aludra is moving 5.81± 0.35milliarcseconds/year towards the north and -4.14± 0.4milliarcseconds/year east if we saw them in the horizon.
The radial velocity, the speed at which the Aludra ismoving away fromthe Sun, is 41.10000 km/swith an error of about 2.50 km/s. When the value is negative, the star and the Sun are getting closer to one another; likewise, a positive number means that two stars are moving away. It's nothing to fear as the stars are so far apart they won't collide in our lifetime, if ever.
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