So I understand that in OBAFGKM(LT), O would be the hottest, and L and T are the coolest (so cool they only show in infrared). I also understand that each of these categories are numbered from 0-9, 0 being the coolest, and 9 being the hottest.
In my class notes, it says that B-9 stars are hotter than O-9 stars. Is this something either the instructor or I incorrectly wrote down, or am I missing something? From what I understand, even and O-0 star should be hotter than a B-9 star.
Thank you.
In my class notes, it says that B-9 stars are hotter than O-9 stars. Is this something either the instructor or I incorrectly wrote down, or am I missing something? From what I understand, even and O-0 star should be hotter than a B-9 star.
Thank you.
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You have two things wrong here. Fist, the LOWER numbered classes are HOTTER, not the other way round - and yes, O9 is hotter than B9.
So to be quite clear about the first point,
"A5 is five tenths between A0 and F0, and A2 is two tenths of the full range from A0 to F0. Lower numbered stars in the same class are hotter." )from Wikipedia, 'spectral class')
Also, as a matter of interest, there is a slightly tentative cooler class still, namely y. and the classification keeps changing. When I first learned it, it went
OBAFGKRMNS
So to be quite clear about the first point,
"A5 is five tenths between A0 and F0, and A2 is two tenths of the full range from A0 to F0. Lower numbered stars in the same class are hotter." )from Wikipedia, 'spectral class')
Also, as a matter of interest, there is a slightly tentative cooler class still, namely y. and the classification keeps changing. When I first learned it, it went
OBAFGKRMNS
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A 0 is hottest in a spectrum class followed by 1,2,3,4,5,6,7,8, and 9, 9 being the coolest in the spectrum class
An O9 star is hotter than a B0 star, which is hotter than a B1 star, and B1 hotter than B2, etc
An O9 star is hotter than a B0 star, which is hotter than a B1 star, and B1 hotter than B2, etc
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Yes, that's a mistake. O-9 stars are hotter than B-9.