Rotating Question Curious About Astronomy? Ask an Astronomer

What do stellar classifications mean?

I am 14 years old and love astronomy. I need to get some specific information for a project on the big dipper. I'm mapping the big dipper's bowl and I want to know everything possible, but I can get most of that through simple research. My computer gave me some spectral type information on the stars in the area but I don't know what it means. If you could explain what A51v means I would be very grateful. Thank you.

Sure. Spectral type gives you a good idea about the color nad temperature of a star, as well as where it is in its life cycle. The "A" means that the star's surface is about 10,000 degrees Kelvin and the color is white. The "A5" is a subclass of "A," pinning down the temperature to a more exact value, but I wouldn't worry about that. The "1v" should really be the roman numeral "IV" which tells you that the star is a subgiant.

From hot (50,000 K) to cold (2,500 K), blue to red, the spectral types are:

O B A F G K M.

You can remember this with the mneumonic, "O Be A Fine Girl/uy, Kiss Me."

The roman numerals represent:
V: Main Sequence stars, like the sun, which are burning
hydrogen in their cores.
IV: Subgiant stars which have just recently run out of core
hydrogen and are burning hydrogen in a shell around
the core.
III: Red giant stars which have exhausted their supplies of
hydrogen and which are larger and brighter than IV
stars. RGs also burn hydrogen in a shell.
II: Asymptotic Giants and Horizontal Branch stars which are
burning elements other than hydrogen in shells (AGs) and
cores (HBs).
I: Supergiant stars are huge, very massive stars at the end of
their lifetimes.

The sun is a G2V-class star.

March 1999, Dave Kornreich (more by Dave Kornreich) (Like this Answer)

Still Curious?

Get More 'Curious?' with Our New PODCAST:

Related questions:

More questions about Stars: Previous | Next

How to ask a question:

If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.

Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist

This page has been accessed 18830 times since September 22, 2002.
Last modified: December 3, 2002 3:43:18 PM

Legal questions? See our copyright, disclaimer and privacy policy.
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.

Warning: Your browser is misbehaving! This page might look ugly. (Details)