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Flashcards in Spectral Classes Deck (20)
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1
Q

What is the Balmer Series?

A

A set of lines that represent the visible part of the emission/absorption spectrum of hydrogen

2
Q

For a hydrogen absorption line to occur in the visible part of a star’s spectrum, what excitation level must electrons in the hydrogen atom already be in?

A

n = 2

3
Q

How do hydrogen atoms in the n = 2 excitation level occur?

A

High temperatures, where collisions between atoms give the electrons extra energy

4
Q

What happens to the excitation level if the temperature is too high?

A

The majority of the electrons will reach the n = 3 level

So there are no Balmer transitions

5
Q

What is the density of the Balmer lines dependent on?

A

The temperature of the star

6
Q

What is the order of the spectral classes?

A

O, B, A, F, G, K, M

7
Q

What do astronomers do for the particular intensity of the Balmer lines for which two temperatures are possible?

A

Look at the absorption lines of other atoms and molecules

8
Q

What spectrum is used for the Balmer series?

A

Spectrum of Hydrogen

9
Q

What is the diagram of absolute magnitude against temperature called?

A

Hertzsprung-Russell

10
Q

What are the three categories of stars?

A

White Dwarfs, Main Sequence, Red Giants/Supergiants

11
Q

What spectral classes do White Dwarfs occupy?

A

half of O
all of B
a bit of A

12
Q

What spectral classes do Main Sequence occupy?

A

half of O → all of M

13
Q

What spectral classes do Red Giants/Red Supergiants occupy?

A

a bit of G → all of M

14
Q

What is the absolute magnitude of White Dwarfs?

A

5 → 15

15
Q

What is the absolute magnitude of the Main Sequence?

A

-10 → 15

16
Q

What is the absolute magnitude of the Red Giants/Red Supergiants?

A

-10 → -4

17
Q

What happens inside a main sequence star?

A

Hydrogen fuses to helium

18
Q

What happens inside a White Dwarf?

A

They are slowly cooling

19
Q

What is unusual about the Hertzsprung-Russell Diagram y-axis?

A

Absolute magnitude goes from positive to negative,

because a lower number is a greater brightness

20
Q

What is unusual about the Hertzsprung-Russell Diagram x-axis?

A

Temperature is decreasing, because it is in order of spectral class