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Stellar Spectral Classes – Explained – Updated

12 Jan 2012, 21:28 UTC
Stellar Spectral Classes – Explained – Updated
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As I explained in a previous post about star types there are many varieties of stars; they range from red dwarfs to blue supergiants. As I’m sure you can see these are broad groups with, in some cases, very different types of stars being lumped together under the same banner. Thankfully astrophysicists have another stellar classification system that is considerably more definitive, this is the spectral class system.
The system first splits all the stars visible in the universe into broad categories based on their colour: -

O – Blue
B – Blue-white stars
A – White
F – Yellowish white (cream)
G – Yellow
K – Orange
M- Red

If you have difficulty in remembering these classes why not use the mnemonic
Oh Be A Fine Girl\Guy Kiss Me
An image showing Spectral classes of main sequence stars Credit: Kieff

With the discovery of brown dwarfs, three new groups have been added to this system:

L – Very dim red dwarfs & hot brown dwarfs
T – Cool brown dwarfs
Y – As of yet hypothetical cold brown dwarfs, with surface temperatures close to room temperature

These groups are also quite broad but are subdivided by adding a number ...

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