week 3: molecular gas + dust extinction

Question 1

strength of spectral lines of molecular molecules is due to

Answer 1

how asymmetric the molecule is

Question 2

molecular hydrogen spectral line is weak becasue

Answer 2

the H-H molecule is perfectly symmetric

Question 3

molecules can emit radiation by

Answer 3

changing either their rotational or vibrational states

Question 4

H_2

Answer 4

molecular hydrogen, 2 hydrogens share 2 electrons

Question 5

for every 10,000 H_2 molecules theres

Answer 5

1 carbon monoxide CO molecule, which is easier to detect and used for H_2 mapping in the galaxy

Question 6

molecular hydrogen is vital in

Answer 6

star formation!

Question 7

molecular hydrogen is mainly found in what part of the galaxy

Answer 7

the spiral disk

Question 8

interstellar extinction is due to

Answer 8

dust grains absorbing blue light because they are comparable to the wavelength so dust either absorbs or scatters this light

Question 9

interstellar extinction

Answer 9

the dimming (more than expected) of distant objects by dust

Question 10

interstellar reddening

Answer 10

the reddening of dust due to absorption/scatter of blue light by dust grains of comparable size as wavelength of the blue light

Question 11

moving to what wavelengths will allow for the extinction/reddening to not be an issue?

Answer 11

to infrared

Question 12

main process of destroying H_2 in galaxies

Answer 12

photodissociation

Question 13

photodissociation

Answer 13

H_2 + hv -> H+H+KE
absorption of a resonance line photon

Question 14

types of energy of molecular gas

Answer 14

translation, rotation, vibration

Question 15

degrees of freedom for molecular hydrogen

Answer 15

H_2:
translation: 3 dof
rotation: 2
vibration: 2 (stretching:symmetric&asymmetric)

Question 16

main process of forming H_2

Answer 16

dust grain catalysis