Stellar Classification of White Dwarfs

[piareround]

OK recently I found a really old table stars based on partally on Yerkes Classification system with a small section on white dwarf stars. It has the stars organized into groups labeled DO, DA, DB, DF, DG, DK, and DM. However, I remember that the current classification system for white dwarf stars as primarily DO, DA, DB, DQ, DZ, DC, DX.

First, Has anyone heard of the first classification system? If so why where the letters changed? What happened?

Second, I really have trouble visualizing DQ, DZ, and DC on the HR diagram compared to the other white dwarfs. Does anyone have pictures of DQ, DZ, or DC stars on the HR Diagram?

 

[lippyka]

The first classification system you are referring to is known as the Yerkes Classification System, which was developed in the early twentieth century and is no longer used today. The letters DO, DA, DB, DF, DG, DK, and DM were used to denote different types of stars based on their surface temperature. The current classification system for white dwarf stars (DO, DA, DB, DQ, DZ, DC, DX) was developed later and uses different letters to denote different types of stars based on a combination of surface temperature and spectral type. As for your second question, you can find diagrams of DQ, DZ, and DC stars on the HR Diagram online. For example, this website has a diagram that shows the locations of these stars: https://www.astronomynotes.com/starprop/s11.htm.