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-P7- > p7.4 pt 2 > Flashcards

p7.4 pt 2 Flashcards

1
Q
  1. What happens in the formation of a protostar?
A

-cloud of dust and gas (hydrogen and helium)= contract by gravity= dense= protostars

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2
Q
  1. What happens when the cloud of gas forming protostars collapses?
A

-its temperature increases (and pressure) as its volume decreases

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3
Q
  1. What provided a possible explanation of the Sun’s energy source?
A

-nuclear processes discovered in the early 20th Century provided a possible explanation of the Sun’s energy source

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4
Q
  1. What is nuclear fusion?
A

-when, if brought close enough together, hydrogen nuclei can fuse into helium nuclei releasing energy

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5
Q
  1. What happens when light nuclei fuse to make heavier nuclei with masses up to that of the iron
    nucleus?
A

-energy is liberated

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6
Q
  1. What does everything stand for in Einstein’s equation E = mc2?
A
  • E is the energy produced
  • m is the mass lost
  • c is the speed of light in a vacuum
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7
Q
  1. What is used to calculate the energy released during nuclear fusion and fission?
A

-Einstein’s equation E = mc2

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8
Q
  1. What happens to the more massive stars?
A

-the more massive the star, the hotter its core and the heavier the nuclei it can create by fusion

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9
Q
  1. What is the significance of the core of a star?
A

-it is where the temperature and density are highest and where most nuclear fusion takes place

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10
Q
  1. How is energy transferred from core to surface in a star?
A
  • by photons of radiation

- by convection

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11
Q
  1. What is the significance of the photosphere?
A

-energy is radiated into space from the star’s surface (photosphere)

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12
Q
  1. What is the stars surface called?
A

-photosphere

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13
Q
  1. What is the Hertzsprung-Russell diagram?
A

-a plot of temperature (highest to lowest) and luminosity (lowest to highest)

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14
Q
  1. Where are supergiants located on the Hertzsprung-Russell diagram?
A

-top right

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15
Q
  1. Where are giants located on the Hertzsprung-Russell diagram?
A

-top right

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16
Q
  1. Where are main sequence stars located on the Hertzsprung-Russell diagram?
A

-diagonal from top left to bottom right

17
Q
  1. Where are white dwarfs located on the Hertzsprung-Russell diagram?
A

-bottom left

18
Q
  1. Why are supernovas not on the Hertzsprung-Russell diagram?
A

-they happen to quickly, and are not a stable part of the stars life cycle

19
Q
  1. Where does hydrogen fusion to helium take place in in main sequence stars?
A

-in the core

20
Q
  1. When does a star leave the main sequence? What happens next?
A

-when its core hydrogen runs out; it swells to become a red giant or supergiant and its photosphere cools

21
Q
  1. What happens in a red giant or supergiant star?
A

-helium nuclei fuse to make carbon, followed by further reactions that produce heavier nuclei such as nitrogen and oxygen

22
Q
  1. What is an example of a low mass star?
A

-the sun

23
Q
  1. What happens to a low mass star at the end of its life?
A

-becomes a red giant, which lacks the mass to compress the core further at the end of helium fusion; it then shrinks to form a white dwarf

24
Q
  1. What happens in a white dwarf star?
A

-there is no nuclear fusion; the star gradually cools and fades

25
Q
  1. What is the mess of a high mass star?
A

-several times the mass of the Sun

26
Q
  1. What happens to a high mass star at the end of its life?
A

-in a high-mass star nuclear fusion can produce heavier nuclei up to and including iron; when the core is mostly iron, it explodes as a supernova creating nuclei with masses greater than iron and leaving a dense neutron star or a black hole

27
Q
  1. What have astronomers found convincing evidence of?
A

-planets around hundreds of nearby stars

28
Q
  1. What may scientists think if even a small proportion of stars have planets?
A

-that it is likely that life exists elsewhere in the Universe

29
Q
  1. What evidence of extraterrestrial life has been found?
A

-no evidence of extraterrestrial life (at present or in the past) has so far been detected.

-P7- (6 decks)

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