What do the spectral types mean?
The sequence goes O,B,A,F,G,K,M,L,T and relates to temperature, hottest (O) to coldest (M). M stars are only red-hot, G stars are like the Sun, and O stars are blue-hot.
Masses, brightness and number usually vary with spectral type too. M stars are the least massive, dimmest, and yet most common, while O stars are the most massive and brightest... but they are so rare there aren't any O (or B) stars within 10 parsecs, and only 4 A-type stars.
The L and T classes are for objects that are smaller than stars and larger than planets. They're very cool, very red, extremely dim, and (unexpectedly) rare. WD are white dwarfs, which are the blue-hot remains of dead stars.
How many of these can I see?
All of the A, F, and G-type stars should be visible without a telescope from somewhere on the Earth. A few of the closest K stars can be seen without a telescope, but you'll need one to see any of the M stars, or (despite being blue-hot) any white dwarfs
Is this everything within 10 parsecs?This is everything known as of January 2011 with parallax errors less than 10 mas (10%). On the other hand, there are 50 systems (counting the Sun) within 5 parsecs, so there should be roughly 400 systems within 10 parsecs (Volume: 2x2x2=8). This is only 64% of what's probably out there.
Why do you count systems, not stars?
Current star formation theory expects that star systems form as systems, not as stars. One collapsing cloud = one mention here. On a more practical note, all the members of the multiple systems fall well within the plotted dots.
Why isn't Pluto (etc...) on there?
I've only plotted objects on Dr. Henry's list. Either they haven't been published, they haven't been confirmed yet, or they've been reassigned. Pluto is a dwarf planet, not a planet (but that's a discussion for another place) so the Sun is only listed as one star + eight planets.
How was this made?
A list of all objects within 10 parsecs from Dr. Todd Henry; a custom IDL program, and GIMP to assemble the frames.
May I use this image elsewhere?
Yes, but please credit A. Riedel, T. Henry, and RECONS.
Can I get the list?
Dr. Henry is preparing the list for publication. In the mean time, a list of the nearest 100 systems (plus a few) are available here.
I'm having trouble seeing it.
It's rotating clockwise, and viewed from 30 degrees above the equatorial plane.
Where's Barnard's Star?
It's a cooler M dwarf "above" and a little ahead of the blue galactic center line, and very near the Sun.