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ASTR 1P01 > Test 1 > Flashcards

Test 1 Flashcards

0
Q

The blue colour of a nebula arises because…

A

The blue light is scattered most efficiently by dust in the nebula.

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1
Q

A dark nebula emits energy mostly in the form of…

A

Infrared radiation.

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2
Q

A nebula which produces light by fluorescence is called _____ nebula.

A

Emission

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3
Q

A bluish nebula is called _____ nebula.

A

Reflection

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4
Q

The spin rate of a pulsar…

A

Decreases over time.

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5
Q

About one quarter of material in a nebula is…

A

Helium.

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6
Q

The wavelength of a source of light approaching the event horizon of a black hole is…

A

Redshifted.

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7
Q

Which one of these stars spends more time in protostar stage? One solar mass star or ten solar mass stars.

A

One solar mass star.

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8
Q

True or false? The stronger the force of gravity on a clock, the faster it runs.

A

False.

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9
Q

During the protostar stage, a star derives its energy from…

A

Gravitational contraction.

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10
Q

A protostar with mass 0.3 solar mass will become…

A

A red dwarf.

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11
Q

Stars like the Sun do not form iron cores during their evolution because…

A

Their cores never get hot enough to form iron by nucleosynthesis.

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12
Q

Which of the following sequences describes the evolution of the Sun from young to old?

A

Protostar, main-sequence, red giant, yellow giant, red giant, white dwarf.

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13
Q

The non-fusing dead core of a star is supported against its collapse by…

A

Degenerate electrons.

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14
Q

The main-sequence of the Sun is estimated to be…

A

10 billion years long.

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15
Q

Once the hydrogen in the Sun’s core is fused into helium, further fusion of hydrogen into helium will go on in…

A

A shell surrounding the helium core.

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16
Q

When a medium-mass main-sequence star exhausts its core hydrogen fuel supply…

A

The core shrinks while the rest of the star expands.

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17
Q

The helium burning into carbon in the core of a medium mass star proceeds via…

A

Triple alpha-process.

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18
Q

Planetary nebula is…

A

A glowing shell of material ejected by a dying medium-mass star.

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19
Q

True or false? If the mass of an object composed of degenerate material increases, the radius decreases.

A

True.

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20
Q

True or false? White dwarfs with masses in excess of two solar masses have been observed.

A

False.

21
Q

Which one of these white dwarfs has a larger radius? One solar mass white dwarf or half a solar mass white dwarf.

A

Half a solar mass white dwarf.

22
Q

A white dwarf is composed of…

A

Carbon nuclei, some oxygen nuclei and degenerate electrons.

23
Q

The gravitational collapse of a high-density white dwarf prevented by…

A

The pressure created by degenerate electrons.

24
Q

The density of a while dwarf is about…

A

10 grams per centimeter cubed (ie, equal to typical metallic density).

25
Q

True or false? There are hydrogen spectral lines in the spectrum of Type Ia supernova.

A

False.

26
Q

Chandrasekhar’s limit is…

A

The maximum mass of a body composed of degenerate matter.

27
Q

Type Ia supernova occurs…

A

In a white dwarf-star binary system when the mass transfer pushes the mass of the white dwarf above the maximum value it can have.

28
Q

The maximum mass that a white dwarf can have is…

A

1.4 solar masses.

29
Q

Which of the following nuclei has the lowest binding energy per nucleon?

A

The nucleus of helium.

30
Q

Which is the heaviest element that can be obtained through nuclear fusion of the lighter ones with a release of energy?

A

Iron.

31
Q

True or false? There are hydrogen spectral lines in the spectru Type II supernova.

A

True.

32
Q

Which of these fusion reactions in a high-mass star lasts the shortest period of time?

A

The fusion of silicon into iron.

33
Q

Why does the core of a high mass star collapse?

A

Because the iron core’s mass becomes so big that degenerate electrons cannot sustain the pressure and the electrons combine with protons in the nuclei to produce neutrons and neutrinos.

34
Q

Type II supernova occurs when…

A

A large mass stars explodes.

35
Q

Type II supernovae are important because…

A

The elements heaver than iron are synthesized.

36
Q

True or false? Most of supernova 1987A energy output (luminosity) was in the form of neutrinos.

A

True.

37
Q

Crab nebula is a…

A

Supernova remnant.

38
Q

A pulsar is…

A

A fast spinning neutron star.

39
Q

What causes the radio pulses of a pulsar?

A

As the star spins, beams of radiation from it sweep through space. If one of these beams points towards the Earth, we observe a pulse.

40
Q

True or false? According to General Theory of Relativity, mass/energy curves spacetime.

A

True.

41
Q

In order to detect a black hole one looks for…

A

A binary system where a companion star is not visible but has a mass greater than 3 solar masses and is an intense X-ray source.

42
Q

Which of these stars spends the longest times as a main sequence star?

A

0.5 solar mass star.

43
Q

The current luminosity of the Sun is…

A

Larger than when it was formed 4.6 billion years ago.

44
Q

Which of these fusion reactions in a high-mass star creates the most energy per nuclear reaction?

A

The fusion of hydrogen into helium.

45
Q

True or false? The pressure of degenerate electrons increases with temperature.

A

False.

46
Q

Sirius B is…

A

A white dwarf.

47
Q

A star of 5 solar mass fuses hydrogen into helium via…

A

CNO cycle.

48
Q

A star of 0.5 solar mass fuses hydrogen into helium via…

A

Proton-proton chain.

49
Q

True or false? White dwarfs will stop emitting light in a distant future.

A

True.

ASTR 1P01 (2 decks)

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