Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

The Sun is a G2V star and Rigel is a B8Iab. How do astronomers get the classifications this precise?

Nick Smith, Minot, North Dakota
Stellar-classifications
Stellar classifications give a general idea of the star's temperature, age, and composition. However, astronomers have obtained sophisticated spectra of stars, which provide more detailed information about the individual objects. Astronomy: Roen Kelly
... the causes of most of the stellar spectrum variations became apparent: They were variations in surface temperatures and luminosities (so, also gravities and pressures/densities) of stars. The spectral classes became surrogates for these physical quantities.

Trust classifications to give a general idea for what kind of star you are dealing with, but if you want accurate physical knowledge about the star, you'd have to look into data acquired via more sophisticated spectral studies.

Already a subscriber? Register now!

Registration is FREE and takes only a few seconds to complete. If you are already registered on Astronomy.com, please log in below.
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
BoxProductcovernov

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook

Loading...