Astronomy questions.

[gridlore]

I'm still loving the Astrogator's Handbook, but I have a question or three for those of you on my friends list with more formal astronomy training.

I'm a little confused by some of the information on the star tables. I understand basic stellar classifications, but there are notations on some of the stars I don't get. Many of the stars have extra letters after the basic type and size classification. For example, Proxima Centauri is listed as "dM5 e" I know that dM5 means that this is a dwarf M5, but what does the "e" indicate? "e" seems to be a pretty common modifier, but I also see "p" and "J" used after regular . Also, many stars are listed only by a letter. "k", "m", and "0" seem to be used in this role. what does this mean?

There's also some confusion with binary systems. Take UV Ceti. The remarks section for the companion includes the following a=5.57" P=200 years. It's obvious that P is the companion's orbital period, but what is a? Is there a good on-line source for known binaries?

Comments

[pauldrye.livejournal.com]

And just to add a bit of actual meaning to the "e" notation, an emission feature in the spectrum normally means that there's something hot -- dust or gas around the star, usually -- chipping some light into the mix.

"J" is an spectrum as well -- emission or absorption, I don't know which -- one where carbon silicate is the culprit. Stars are normally too hot for any compound substances to survive in their atmospheres, but if it's sufficiently dim and cool, carbon and SiO-related compounds are the first to form (and so muck up the spectrum by getting in the way).