# Astronomy college course/Star (Wikipedia)/questions

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## AstroWikipStar_Study

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### AstroWikipStar_Study-v1s1

1. Why is a star made of plasma?

___ a) it is so hot that electrons are stripped away from the protons
___ b) plasma is always present when there are strong magnetic fields
___ c) the interstellar gas was mostly plasma
___ d) plasma is generic word for "important"
___ e) the intense gravity liquifies the substance, just as red blood cells liquify plasma in the body

2. What is the difference between a constellation and an asterism?

___ a) asterisms are smaller than constellations
___ b) none of these is correct
___ c) constellations represent regions of the sky, like state boundaries on a map of the USA
___ d) asterisms are larger than constellations
___ e) constellations consist of never more than ten stars.

3. Stellar parallax is

___ a) Two of these is correct
___ b) Triangulation to deduce the distance to nearby stars
___ c) Using changes in the angular position of a star to deduce the star’s distance
___ d) Using spectral lines to deduce the distance to nearby stars
___ e) None of these is correct.

4. Giant molecular clouds with sufficient conditions to form a star cluster would have formed them long ago. Any stellar births in the past couple of billions years probably resulted from _____ between clouds.

___ a) photon exchange
___ b) collisions
___ c) None of these is correct.
___ d) ion exchange
___ e) Two of these are correct

5. A starburst galaxy.

___ a) Two of these are correct
___ b) All of these are correct
___ c) usually is a result of collisions between galaxies
___ d) is a region of active stellar birth
___ e) has only dead or dying stars

6. Which of the following expresses Jean's criterion for the collapse of a giant molecular cloud of mass, M, radius, R, and temperature T, and pressure P? (Here ? is some constant)

___ a) P>?MR
___ b) R>?MT
___ c) M>?RT
___ d) T>?RM
___ e) P>?MT

7. Which of the following changes in the properties of a giant molecular cloud might cause it to collapse?

___ a) Decrease mass at fixed temperature and size
___ b) Two of these are correct
___ c) Increase mass at fixed temperature and size
___ d) Increase temperature at fixed mass and size
___ e) Increase size at fixed pressure and mass

8. What happens if you increase the size of a giant molecular cloud while keeping temperature and mass fixed?

___ a) It is more likely to collapse because this will increase the temperature
___ b) It is less likely to collapse because temperature can never be kept fixed
___ c) It is more likely to collapse because larger things have more gravity
___ d) It is equally likely to collapse because size is not part of the Jean's criterion.
___ e) It is less likely to collapse spreading it out weakens the force of gravity

9. What is a Bok globule in the formation of stellar systems?

___ a) A black hole that enters a cloud and triggers the collapse
___ b) A small planet that formed before any stars have formed
___ c) A supernovae precurser that attracts more gas atoms
___ d) A small portion of a giant cloud that collapses
___ e) A cluster of giant molecular clouds that coalesce to form a solar system

10. Pre–main sequence stars are often surrounded by a protoplanetary disk and powered mainly by

___ a) the release of gravitational energy
___ b) chemical reactions
___ c) the fission of Carbon from Helium
___ d) collisions between protoplanets
___ e) the fusion of Helium to Carbon

11. Stars that begin with more than 50 solar masses will typically lose _______ while on the main sequence.

___ a) 10% of their magnetic field
___ b) 10% their mass
___ c) 1% their mass
___ d) 50% their mass
___ e) all of their magnetic field

12. The Hayashi and Henyey tracks refer to how T Tauri of different masses will move

___ a) through a cluster as they are born
___ b) through an HR diagram as they are born
___ c) Two of these are true
___ d) through a cluster as they die
___ e) through an HR diagram as they die

13. How do low-mass stars change as they are born?
Birth of stars HR path tracks
___ a) Decreasing luminosity with no change in temperature
___ b) Increasing luminosity with no change in temperature
___ c) Increasing temperature with no change in luminosity
___ d) Decreasing temperature and increasing luminosity
___ e) Decreasing temperature with no change in luminosity

14. When a star with more than 10 solar masses ceases fuse hydrogen to helium, it

___ a) it fuses helium to carbon to iron (and other elements), then continues to release more energy by fusing the iron to heavier elements such as uranium.
___ b) it fuses helium to carbon and other elements up to iron and then ceases to produce more energy
___ c) ceases to convert nuclear energy.
___ d) it fuses helium to carbon and then ceases to produce more energy
___ e) it fuses elements up to uranium, and continues to produce energy by the fission of uranium.

15. Many supernovae begin as a shock wave in the core that was caused by

___ a) electrons being driven into protons to form neutrons
___ b) iron fusing into heavier elements such as uranium
___ c) the conversion of carbon into diamonds,
___ d) all of these processes contribute to the shock wave
___ e) carbon and other elements fusing into iron

16. A dying star with more than 1.4 solar masses becomes a ______, and those with more than 5 solar masses becomes a _____

___ a) blue giant....red giant
___ b) white dwarf....black hole
___ c) neutron star....black hole
___ d) white dwarf....neutron star
___ e) white dwarf...red dwarf

17. According to Wikipedia, a star with over 20 solar masses converts its Hyrogen to Helium in about 8 billion years, but the conversion of Oxygen to heavier elements take about _____

___ a) 1 thousand years
___ b) 10 billion years
___ c) 1 year
___ d) 1 million years
___ e) 1 billion years

#### Key to AstroWikipStar_Study-v1s1

1. Why is a star made of plasma?

+ a) it is so hot that electrons are stripped away from the protons
- b) plasma is always present when there are strong magnetic fields
- c) the interstellar gas was mostly plasma
- d) plasma is generic word for "important"
- e) the intense gravity liquifies the substance, just as red blood cells liquify plasma in the body

2. What is the difference between a constellation and an asterism?

- a) asterisms are smaller than constellations
- b) none of these is correct
+ c) constellations represent regions of the sky, like state boundaries on a map of the USA
- d) asterisms are larger than constellations
- e) constellations consist of never more than ten stars.

3. Stellar parallax is

+ a) Two of these is correct
- b) Triangulation to deduce the distance to nearby stars
- c) Using changes in the angular position of a star to deduce the star’s distance
- d) Using spectral lines to deduce the distance to nearby stars
- e) None of these is correct.

4. Giant molecular clouds with sufficient conditions to form a star cluster would have formed them long ago. Any stellar births in the past couple of billions years probably resulted from _____ between clouds.

- a) photon exchange
+ b) collisions
- c) None of these is correct.
- d) ion exchange
- e) Two of these are correct

5. A starburst galaxy.

+ a) Two of these are correct
- b) All of these are correct
- c) usually is a result of collisions between galaxies
- d) is a region of active stellar birth
- e) has only dead or dying stars

6. Which of the following expresses Jean's criterion for the collapse of a giant molecular cloud of mass, M, radius, R, and temperature T, and pressure P? (Here ? is some constant)

- a) P>?MR
- b) R>?MT
+ c) M>?RT
- d) T>?RM
- e) P>?MT

7. Which of the following changes in the properties of a giant molecular cloud might cause it to collapse?

- a) Decrease mass at fixed temperature and size
- b) Two of these are correct
+ c) Increase mass at fixed temperature and size
- d) Increase temperature at fixed mass and size
- e) Increase size at fixed pressure and mass

8. What happens if you increase the size of a giant molecular cloud while keeping temperature and mass fixed?

- a) It is more likely to collapse because this will increase the temperature
- b) It is less likely to collapse because temperature can never be kept fixed
- c) It is more likely to collapse because larger things have more gravity
- d) It is equally likely to collapse because size is not part of the Jean's criterion.
+ e) It is less likely to collapse spreading it out weakens the force of gravity

9. What is a Bok globule in the formation of stellar systems?

- a) A black hole that enters a cloud and triggers the collapse
- b) A small planet that formed before any stars have formed
- c) A supernovae precurser that attracts more gas atoms
+ d) A small portion of a giant cloud that collapses
- e) A cluster of giant molecular clouds that coalesce to form a solar system

10. Pre–main sequence stars are often surrounded by a protoplanetary disk and powered mainly by

+ a) the release of gravitational energy
- b) chemical reactions
- c) the fission of Carbon from Helium
- d) collisions between protoplanets
- e) the fusion of Helium to Carbon

11. Stars that begin with more than 50 solar masses will typically lose _______ while on the main sequence.

- a) 10% of their magnetic field
- b) 10% their mass
- c) 1% their mass
+ d) 50% their mass
- e) all of their magnetic field

12. The Hayashi and Henyey tracks refer to how T Tauri of different masses will move

- a) through a cluster as they are born
+ b) through an HR diagram as they are born
- c) Two of these are true
- d) through a cluster as they die
- e) through an HR diagram as they die

13. How do low-mass stars change as they are born?
Birth of stars HR path tracks
+ a) Decreasing luminosity with no change in temperature
- b) Increasing luminosity with no change in temperature
- c) Increasing temperature with no change in luminosity
- d) Decreasing temperature and increasing luminosity
- e) Decreasing temperature with no change in luminosity

14. When a star with more than 10 solar masses ceases fuse hydrogen to helium, it

- a) it fuses helium to carbon to iron (and other elements), then continues to release more energy by fusing the iron to heavier elements such as uranium.
+ b) it fuses helium to carbon and other elements up to iron and then ceases to produce more energy
- c) ceases to convert nuclear energy.
- d) it fuses helium to carbon and then ceases to produce more energy
- e) it fuses elements up to uranium, and continues to produce energy by the fission of uranium.

15. Many supernovae begin as a shock wave in the core that was caused by

+ a) electrons being driven into protons to form neutrons
- b) iron fusing into heavier elements such as uranium
- c) the conversion of carbon into diamonds,
- d) all of these processes contribute to the shock wave
- e) carbon and other elements fusing into iron

16. A dying star with more than 1.4 solar masses becomes a ______, and those with more than 5 solar masses becomes a _____

- a) blue giant....red giant
- b) white dwarf....black hole
+ c) neutron star....black hole
- d) white dwarf....neutron star
- e) white dwarf...red dwarf

17. According to Wikipedia, a star with over 20 solar masses converts its Hyrogen to Helium in about 8 billion years, but the conversion of Oxygen to heavier elements take about _____

- a) 1 thousand years
- b) 10 billion years
+ c) 1 year
- d) 1 million years
- e) 1 billion years