Caption: Image stellar spectra for the visible band (fiducial range 0.4--0.7 μm).

Features:

1. The 13 top stellar spectra show regular spectral types from the OBAFGKM stellar classification: temperature decreases top to bottom.

   The bottom 3 stellar spectra are special types.

2. The spectral types are labeled on the left side of the image.

3. The right side of the image gives the star catalog name for stars drawn from the Henry Draper Catalogue (1918--1949), Smithsonian Astrophysical Observatory Star Catalog (1966), Bonner Durchmusterung (BD), and Bright Star Catalogue (Yale Bright Star Catalogue, YBS (1930--1991).

   Note usually only bright stars have star proper names: i.e., the named stars. Also note that stars often have multiple names: e.g., star proper names, Bayer designations, and multiple star catalog names.

4. The hydrogen Balmer lines (i.e., the visible band atomic hydrogen lines) are strongest in absorption for A0--A5 A stars which have photospheric temperatures of order 9000 K (FK-424).

5. In the image, the blue-green Hβ (486.132 nm) and violet-blue Hγ (434.046 nm) absorption lines are quite apparent on and about the A1 spectrum (FK-423).

6. The red Hα (656.280 nm) is somewhat darkened out for the A1 spectrum, but can still be made out (FK-423).

7. The sodium (Na) I double D lines (588.995, 589.592 nm) in the yellow are quite noticeable for the M0 and M5 M stars (FK-423). The Na I double D lines are the strongest lines of neutral sodium. They give low-pressure sodium-vapor lamps their nearly monochromatic yellow light.

8. As we know from Wien's law, the maximum of a blackbody spectrum should shift to the red as temperature decreases.

   This is apparently shown in this image since bright zone forms a broad diagonal from upper right to lower left. But since colors in images can be easily manipulated, it is hard to know if we are really seeing this effect.