Stellar Classification

Question 1

Annie Jump Cannon: OBADGKM System

Answer 1

Classification of types of stars from Hot to Cold. O Stars are the hottest; M stars are the coolest

Question 2

Williamina Fleming: What did she do?

Answer 2

Stellar classification based on strength of hydrogen lines.

A Stars : Strongest H lines
B Stars : Strong H lines . . .
O Stars: Weakest H lines

Question 3

How do spectral lines relate to atomic energy levels?

Answer 3

Spectral lines form when light interacts with electrons. (Spectral lines are about energy conservation!)

Moving from higher to lower energy states.

Question 4

Electrons emits a photon, losing energy. (Drops in orbit)

Answer 4

Emission Spectrum

Question 5

Electron absorbs photon, gaining energy (moving up orbit)

Answer 5

Absorption Spectrum

Question 6

Relationship between Electrons, Photons, and Energy State

Answer 6

If electrons absorb enough energy according to its atomic levels, the atom can become ionized. The electron leaves the atom.

Question 7

Relationship between Types of Stars and Electrons

Answer 7

Hot Stars; No electrons (ionized)

Goldilocks Stars: Electrons are at around 2nd or 3rd energy state.

Cool Stars: Electrons stuck in ground state.

NOTE: All stars are ionized. In blue stars, they are too hot for electrons to orbit the nuclei.

Question 8

What did Cecilia Payne-Gaposchkin do?

Answer 8

All stars are composed of mainly Hydrogen (74%) and Helium (25%).

Hot stars drive electrons to higher energy levels.

Ionized Hydrogen gas no electrons so it can’t absorb or emit light.

Strong lines form when temperature puts electrons in the best place to absorb light.