Physics_Astronomy

Front 1

Interstellar gas is composed mainly of 1)
A) only hydrogen.
B) ammonia, methane, and water vapor.
C) 10% hydrogen, 90% helium by numbers of atoms.
D) some hydrogen, but mainly carbon dioxide.
E) 90% hydrogen, 9% helium by weight.

Back 1

90% hydrogen, 9% helium by weight

Front 2

What happens to light passing through even thin clouds of dust? 2)
A) Its motion causes the light of stars beyond to twinkle.
B) Its motion causes all light to be red shifted as it passes through these clouds.
C) It dims and reddens the light of all more distant stars.
D) The light that passes though them is blue shifted due to the cloud's approach.
E) Even a little can completely block all light, such as the Horsehead Nebula.

Back 2

It dims and reddens the ligth of all more distant stars

Front 3

Which statement about dark dust clouds is true? 3)
A) They can be penetrated only with longer wavelengths such as radio and infrared.
B) They comprise the majority of the mass of the Galaxy.
C) They can be penetrated only with shorter waves, such as UV and X-ray.
D) Hydrogen and helium are the chief absorbing and scattering agents.
E) They block the vast majority of radio waves from our Galaxy.

Back 3

They can be prenetrated only with longer wavelengths such as radio and infrared

Front 4

Some regions along the plane of the Milky Way appear dark because 4)
A) many black holes absorb all light from those directions.
B) there are no stars in these areas.
C) stars in that region are hidden by dark dust particles.
D) many brown dwarfs in those areas absorb light, which they turn into heat.
E) stars in that region are hidden by interstellar gas.

Back 4

stars in that region are hidden by dark dust particles

Front 5

Emission nebulae like M42 occur only near stars that emit large amounts of 5)
A) X-rays and gamma rays.
B) visible light.
C) infrared heat.
D) ultraviolet radiation.
E) microwaves.

Back 5

ultraviliot radiation

Front 6

What is the primary visible color of an emission nebula? 6)
A) blue due to ionized helium atoms
B) blue from the scattering of light off the tiny molecules
C) black, because of dust
D) red because of reddening by dust
E) red due to ionized hydrogen atoms

Back 6

red due to ionized hydrogen atoms

Front 7

Due to absorption of shorter wavelengths by interstellar dust clouds, distant stars appear 7)
A) brighter.
B) bluer.
C) redder.
D) larger.
E) to have a higher radial velocity.

Back 7

redder

Front 8

The spectra of interstellar gas clouds show that they have the same basic composition as 8)
A) interstellar dust.
B) Earth's atmosphere.
C) the Martian polar caps.
D) stars.
E) none of the above.

Back 8

stars

Front 9

Which statement is true about the interstellar medium? 9)
A) Dust is spread uniformly through the galaxy.
B) Dust blocks the longest electromagnetic wavelengths.
C) Gas obscures the light from distant stars.
D) We know more about the gas than the dust.
E) Gas contains a lot of carbon atoms.

Back 9

we know more about the gas than the dust

Front 10

The density of interstellar dust is very low, yet it still blocks starlight because 10)
A) the dust particles are irregular in shape.
B) it is so cold it absorbs higher energy photons.
C) there is 100 times more opaque gas than dust present in the ISM.
D) the dust particles are about the same size as the light waves they absorb.
E) ice particles reflect all light back toward their stars, not toward us.

Back 10

the dust particles are about the same size as the light wasves they absorb

Front 11

What two things are needed to create an emission nebulae? 11)
A) hot stars and interstellar gas, particularly hydrogen
B) hydrogen fusion and helium ionization
C) interstellar gas and dust
D) cool stars and much interstellar dust
E) hydrogen gas and carbon dust

Back 11

hot stars and interstellar gas, particulary hydrogen

Front 12

A large gas cloud in the interstellar medium that contains several type O and B stars would appear
to us as
12)
A) a dark patch against a bright background.
B) a dark nebula.
C) a reflection nebula.
D) an emission nebula.
E) bright blue.

Back 12

an emission nebula

Front 13

Neutral hydrogen atoms are best studied from their energy given off as 13)
A) Neutral hydrogen gives off no detectable radiation, since it is cold, not hot.
B) 0.2 nm as X-rays.
C) 121.3 nm as Lyman alpha emission in the UV.
D) 21-cm waves in the radio region.
E) red hydrogen alpha emission, at 656.3 nm.

Back 13

21-cm waves in the radio region

Front 14

Complex molecules in the interstellar medium are found 14)
A) only around the supergiant stars like Betelgeuse that make their heavy atoms.
B) uniformly throughout the disk of the Galaxy.
C) primarily in the dense dust clouds.
D) on the surfaces of the coolest class K and M stars only.
E) scattered evenly throughout the universe, a product of the Big Bang itself.

Back 14

primarily in he dense dust clouds

Front 15

Why are dark dust clouds largely misnamed? 15)
A) The cloud is an illusion, for the dust is evenly distributed around the Galaxy.
B) It is ice, not dust, which make them look dark.
C) Dust clouds do radiate energy, but not as much light as the stars do.
D) They contain much more gas than dust.
E) All of the above are correct.

Back 15

they contain much more gas than dust

Front 16

The average temperature of the typical dark regions in space are 16)
A) 3,000 K.
B) 0 K.
C) 2.73 K.
D) 100 K.
E) 6,000 K.

Back 16

100 k

Front 17

When an electron in hydrogen changes its spin from the same to the opposite direction as the
proton, it
17)
A) neither emits nor absorbs a photon.
B) absorbs a radio wave photon.
C) emits an X-ray photon.
D) absorbs a visible light photon.
E) emits a radio wave photon.

Back 17

emits a radio wave photon

Front 18

Interstellar dust clouds are best observed at what wavelength? 18)
A) visible only
B) Visible and UV
C) UV and infrared
D) Radio and X-ray
E) Radio

Back 18

radio

Front 19

Which of these is not a consequence of dust in the interstellar medium? 19)
A) red light from the emission nebulae
B) reddening of stars' light that passes through the dust
C) the dark nebulae that block 90% of the Milky Way from us visually
D) blue reflection nebulae around the Pleiades
E) all of these are consequences.

Back 19

red light from the emission nebulae

Front 20

It is important to study interstellar dust because 20)
A) there is almost as much mass between the stars as therre is in them.
B) this is where stars are formed.
C) old stars expel their matter here when they die.
D) all of the above.
E) its not important at all.

Back 20

all the above

Front 21

Reflection nebula have their blue colour because 21)
A) they are very high temperature.
B) the interstellar dust absorbs the red light.
C) the interstellar dust deflects the blue light.
D) helium is the main absorber and emits light in this colour.
E) they are very low temperature.

Back 21

the interstellar dust deflects the blue ligth

Front 22

What is true of emission nebula? 22)
A) they are often part of much larger interstellar clouds.
B) their temperature can exceed that of our sun.
C) they are bigger than earth.
D) they produce an emission spectrum.
E) All of the above.

Back 22

all the above

Front 23

During the T-Tauri phase of a protostar, it 1)
A) lies on the main sequence.
B) may develop very strong winds.
C) expands dramatically.
D) begins a period of reduced activity.
E) changes its spin direction.

Back 23

may develop very strong winds

Front 24

What is the critical core temperature required for fusion? 2)
A) 5,800 K
B) 10 million K
C) 3,000 K
D) 100 million K
E) 1 million K

Back 24

10 million k

Front 25

Which statement about the stages of starbirth is false? 3)
A) nuclear reactions begin in the core by stage 4.
B) The T-Tauri wind is prevalent in stage 5.
C) By stage 3, the star has formed a photosphere.
D) At stage 1, only the cloud exists.
E) By stage 7, the star has reached the main sequence.

Back 25

nuclear reactions begin in the core by stage 4

Front 26

On an H-R diagram, a protostar would be 4)
A) above and near the upper left of the main sequence.
B) above and to the right of the main sequence.
C) on the main sequence at the extreme lower right.
D) below and to the left of the main sequence.
E) below and near the right side of the main sequence.

Back 26

above and to the right of the main sequence

Front 27

The single most important determinant of the temperature, density, radius, luminosity,
and pace of evolution of a protostar is its
5)
A) magnetic field.
B) molecular composition.
C) mass.
D) spin.
E) chemical composition.

Back 27

mass