ISM

Question 1

What is the ism

Answer 1

Gas, dust, and cosmic rays between stars

Question 2

Gas makes up ____ of the ism

Answer 2

99%

Question 3

Dust makes up ____ of the ism

Answer 3

1%

Question 4

Ionized hydrogen (HII) regions

Answer 4

Hot stars heat up surrounding gas, the UV radiation ionizes hydrogen, the electrons fall back into atom as

Question 5

What color are Ionized Hydrogen regions

Answer 5

Red

Question 6

HII regions are examples of

Answer 6

Emission nebulae

Question 7

Warm ionized medium

Answer 7

Very similar to HII regions but much more extended and diffuse

Question 8

What causes warm ionized medium

Answer 8

Ionization from O and B stars

Question 9

Neutral hydrogen clouds

Answer 9

Some narrow absorption lines in visible light

Question 10

21 cm spin flip transition

Answer 10

Transition in a hydrogen atom, energy of transition corresponds to a proton with a wavelength of 21 cm

Question 11

Cold neutral medium

Answer 11

Mostly limited to a flat region in the disk of the galaxy

Question 12

Hot ionized medium or coronal gas

Answer 12

Typically gas that has been expelled and or heated by supernova

Question 13

Molecular clouds

Answer 13

Densest region of the ISM, birthplace of stars, uv radiation is shielded by gas and dust

Question 14

Complex molecules are found in

Answer 14

ISM gas

Question 15

What is dark nebulae

Answer 15

Dust blocks light from coming through it

Question 16

What is reddening

Answer 16

When interstellar dust absorbs and scatters shorter wavelength light more then longer wavelength light

Question 17

What is extinction

Answer 17

When dust absorbs a fraction of the light passing through it

Question 18

What is reflection nebula

Answer 18

Light from nearby stars scatters off dust and comes to us

Question 19

What is interstellar grains

Answer 19

Made up of core silicates or graphites and mantel off ices, very important in helping stars and planets form

Question 20

What are cosmic rays

Answer 20

Super energetic particles traveling nearly the speed of light

Question 21

What percent of cosmic rays are protons

Answer 21

90

Question 22

What percent of cosmic rays are helium or heavier nuclei

Answer 22

9

Question 23

What percent of cosmic rays are electrons and positrons

Answer 23

1

Question 24

Cosmic rays paths are affected by

Answer 24

Magnetic fields

Question 25

Where do extragalactic cosmic rays come from

Answer 25

Active galactic nuclei, including quasars or gamma ray bursts

Question 26

What role does cosmic rays play in the ISM

Answer 26

They are able to penetrate dense molecular r clouds where light cannot and serve as a source of heat and ionization, they make it harder for stars to form

Question 27

What is the gas cycle in the ISM

Answer 27

Supernova remnants, atomic ISM, molecular clouds, star forming regions, stars

Question 28

What is the Local Bubble

Answer 28

Source of X-rays in all directions from earth, very diffuse hot gas, sun is a part of

Question 29

What is the Local Fluff

Answer 29

Slightly denser then Local Bubble

Question 30

Which region is created when gas is irradiated by O and B stars

Answer 30

WIM

Question 31

Which line do we use to track neutral hydrogen

Answer 31

21 cm

Question 32

Dust makes light from stars ___ and ____

Answer 32

Dimmer and redder

Question 33

Why do HII regions glow red

Answer 33

Bc of the Ha(3->2) transition

Question 34

Which molecule is used to observe molecular clouds

Answer 34

CO

Question 35

Which phase of the ISM occupies the greatest volume

Answer 35

Coronal gas

Question 36

Which part of the electromagnetic spectrum is dust very bright

Answer 36

Far infrared