May 30, 2001
You were born on a tiny world orbiting an ordinary star in an unremarkable galaxy — and yet, the fact that you exist at all is the most...
Stellar Spectral Types: OBAFGKM
Birthday · May 30, 2001
A little universe, just for you
Your date.
Ready to give.
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APOD published May 30, 2001. Credit: KPNO. A publication-date match, not a photo taken on your date. Independent of NASA.
Astronomers divide stars into different spectral types. First started in the 1800s, the spectral type was originally meant to classify the strength of hydrogen absorption lines. A few types that best describe the temperature of the star remain in use today. The seven main spectral types OBAFGKM are shown above with the spectrum of a single "O" star at the top followed by two spectra each from the progressively cooler designations, respectively. Historically, these letters have been remembered with the mnemonic "Oh Be A Fine Girl/Guy Kiss Me." Frequent classroom contests, however, have come up with other more/less politically correct mnemonics such as "Oven Baked Apples From Grandpa's/Grandma's Kitchen. Mmmm." Our Sun has spectral type "G".
Image credit: KPNO