Question

What are the four main classes of chemically peculiar stars? How is their classification determined?

Answer 1

Chemically peculiar stars show unusual chemical composition in their spectra.

Explanation:

Chemically peculiar (CP) stars are hot main sequence stars who's composition is different from other stars. They typically have high abundance of heavier elements. There are four categories of peculiar star.

CP1 stars have weak spectral lines for Calcium and/or Scandium. They also show unusual amounts of heavier elements.

CP2 stars show unusual amounts of Silicon, Chromium, Strontium and Europium.

CP3 stars show unusual amounts of Mercury and Manganese.

CP4 stars show unusually low amounts of Helium.