6.3.13

OBAFGKM

When looking at stellar classification, O B A F G K M, we need to obtain an example of a star for each category.

O
Class O stars are very hot and extremely luminous, being bluish in color. An example of this star category is Alpha Camelopardalis
Spectral Type: O9.5
Apparent Magnitude: 4.3 v
Distance: 6,000 ly
Mass: 43.2 solar mass
Radius: 36.8
Temperature: 27,700k
Age: 2 million years
Rotational Velocity: 80 km/s

B
Class B stars are very luminous and blue eg Rigel
Spectral Type: B8
Apparent Magnitude: 0.1 v
Distance: 772.9 ly
Mass: 18 solar mass
Radius: 74 r
Temperature: 12,130 k
Age: 8 million years
Rotational Velocity: 40 km/s

A
Class A stars are among the more common naked eye stars, and are white or bluish-white eg Sirius
Spectral Type: A1
Apparent Magnitude: -1.5 v
Distance: 8.6 ly
Mass: 2.0 solar mass
Radius: 1.7 r
Temperature: 9,940 k
Age: 250 million years
Rotational Velocity: 16 km/s

F
Class F stars are mostly white eg Polaris
Spectral Type: F7
Apparent Magnitude: 1.9 v
Distance: 433.8 ly
Mass: 4.5 solar mass
Radius: 46 r
Temperature: 6,015 k
Age: 70 million years
Rotational Velocity: 14 km/s

G
Class G stars are probably the best known, if only for the reason that the Sun is of this class eg Our Sun
Spectral Type: G2
Apparent Magnitude: -26.7 v
Distance: 8.3 minutes at light speed
Mass: 1 solar mass
Radius: 1 r
Temperature: 5,778 k
Age: 4.5 billion years
Rotational Velocity: 20 km/s

K
Class K are orangish stars that are slightly cooler than the Sun eg Arcturus
Spectral Type: K1.5
Apparent Magnitude: -2.3 v
Distance: 36.7 ly
Mass: 1.1 solar mass
Radius: 25.7 r
Temperature: 4,290 k
Age: 5 trillion years
Rotational Velocity: 2.4 km/s

M
Class M is by far the most common class. An example is Betelgeuse
Spectral Type: M2
Apparent Magnitude: 0.42 v
Distance: 643 ly
Mass: 18 solar mass
Radius: 1180 r
Temperature: 3,500 k
Age: 10 million years
Rotational Velocity: 5 km/s

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