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, "OBe AFine 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.
This page updated on June 27, 2015