NATS 1740 Assignment 17

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Which of these stars does not have fusion occurring in its core?

1. a red giant
2. a red main-sequence star
3. a blue main-sequence star

1. a red giant

What would you be most likely to find if you returned to the solar system in 10.0 billion years?

1. a neutron star
2. a white dwarf
3. a black hole

2. a white dwarf

Which of these elements had to be made in a supernova explosion?

1. calcium
2. uranium
3. oxygen

2. uranium

What do astronomers mean when they say that we are all "star stuff"?

1. that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores
2. that the Universe contains billions of stars
3. that the Sun formed from the interstellar medium: the "stuff" between the stars
4. that life would be impossible without energy from the Sun
5. that Earth formed at the same time as the Sun

1. that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores

Which two energy sources can help a star maintain its internal thermal pressure?

1. nuclear fusion and nuclear fission
2. nuclear fission and gravitational contraction
3. chemical reactions and gravitational contraction
4. nuclear fusion and chemical reactions
5. nuclear fusion and gravitational contraction

5. nuclear fusion and gravitational contraction

What type of star is our Sun?

1. high-mass star
2. low-mass star
3. intermediate-mass star

2. low-mass star

What is the range of star masses for high-mass stars?

1. between 500 and 1,000 solar masses
2. between 200 and 500 solar masses
3. between 8 and 100 solar masses
4. between 2 and 10 solar masses
5. between 2 and 5 solar masses

3. between 8 and 100 solar masses

What can we learn about a star from a life track on an H-R diagram?

1. how long ago it was born
2. when it will die
3. what surface temperature and luminosity it will have at each stage of its life
4. where it is located
5. all of the above

3. what surface temperature and luminosity it will have at each stage of its life

Compared to the star it evolved from, a red giant is

1. cooler and brighter.
2. hotter and dimmer.
3. the same temperature and brightness.
4. cooler and dimmer.
5. hotter and brighter.

1. cooler and brighter.

At approximately what temperature can helium fusion occur?

1. 100,000 K
2. 100 billion K
3. 100 million K
4. 1 million K
5. a few million K

3. 100 million K

What is a planetary nebula?

1. the molecular cloud from which protostars form
2. the expanding shell of gas that is left when a white dwarf explodes as a supernova
3. a disk of gas surrounding a protostar that may form into planets
4. the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
5. what is left of the planets around a star after a low-mass star has ended its life

4. the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star

What happens to the core of a star after a planetary nebula occurs?

1. It breaks apart in a violent explosion.
2. It becomes a neutron star.
3. It becomes a white dwarf.
4. It contracts from a protostar to a main-sequence star.
5. none of the above

3. It becomes a white dwarf.

Which of the following sequences correctly describes the stages of life for a low-mass star?

1. red giant, protostar, main-sequence, white dwarf
2. white dwarf, main-sequence, red giant, protostar
3. protostar, main-sequence, red giant, white dwarf
4. protostar, red giant, main-sequence, white dwarf
5. protostar, main-sequence, white dwarf, red giant

3. protostar, main-sequence, red giant, white dwarf

Compared to the star it evolved from, a white dwarf is

1. the same temperature and brightness.
2. cooler and brighter.
3. hotter and dimmer.
4. cooler and dimmer.
5. hotter and brighter.

3. hotter and dimmer.

Most interstellar dust grains are produced in

1. the Big Bang.
2. the interstellar medium.
3. the atmospheres of red giant stars.
4. supernova explosions.
5. the solar nebula.

3. the atmospheres of red giant stars.

Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission?

1. uranium
2. iron
3. oxygen
4. hydrogen
5. silicon

2. iron

What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?

1. The core contracts and becomes a black hole.
2. The star explodes violently, leaving nothing behind.
3. The core contracts and becomes a ball of neutrons.
4. Gravity is not able to overcome neutron degeneracy pressure.
5. The core contracts and becomes a white dwarf.

1. The core contracts and becomes a black hole.

What types of stars end their lives with supernovae?

1. stars that have reached an age of 10 billion years
2. all stars that are yellow in color
3. all stars that are red in color
4. stars that are at least several times the mass of the Sun
5. stars that are similar in mass to the Sun

4. stars that are at least several times the mass of the Sun

Which event marks the beginning of a supernova?

1. the expansion of a low-mass star into a red giant
2. the sudden collapse of an iron core into a compact ball of neutrons
3. the beginning of neon burning in an extremely massive star
4. the sudden outpouring of X rays from a newly formed accretion disk
5. the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun

2. the sudden collapse of an iron core into a compact ball of neutrons

After a supernova event, what is left behind?

1. always a neutron star
2. always a black hole
3. always a white dwarf
4. either a neutron star or a black hole
5. either a white dwarf or a neutron star

4. either a neutron star or a black hole

Why is Supernova 1987A particularly important to astronomers?

1. It provided the first evidence that supernovae really occur.
2. It was the first supernova detected in nearly 400 years.
3. It was the nearest supernova detected in nearly 400 years.
4. It occurred only a few dozen light-years from Earth.
5. It provided the first evidence that neutron stars really exist.

3. It was the nearest supernova detected in nearly 400 years.

Why do scientists think that our solar system must have formed sometime after nearby supernovae explosions?

1. Existence of heavy elements
2. Our Sun is a G-type star
3. Solar temperature too low
4. They don't scientists believe our Sun is among the first generation of stars

1. Existence of heavy elements

The following figures show various stages during the life of a star with the same mass as the Sun. Rank the stages based on when they occur, from first to last.

- main-sequence G star
- protostar
- white dwarf
- planetary nebula
- contracting cloud of gas and dust
- red giant

- contracting cloud of gas and dust
- protostar
- main-sequence G star
- red giant
- planetary nebula
- white dwarf

Provided following are various stages during the life of a high-mass star. Rank the stages based on when they occur, from first to last.

- protostar
- supernova
- contracting cloud of gas and dust
- main-sequence O star
- red supergiant
- neutron star

- contracting cloud of gas and dust
- protostar
- main-sequence O star
- red supergiant
- supernova
- neutron star

Provided following are various elements that can be produced during fusion in the core of a high mass main sequence star. Rank these elements based on when they are produced, from first to last.

- carbon
- iron
- helium
- oxygen

- helium
- carbon
- oxygen
- iron

Listed following are characteristics that describe either high-mass or low-mass stars. Match these characteristics to the appropriate category.

- late in life fuse carbon into heavier eements
- the Sun is an example
- have higher fusion rate during main sequence life
- final corpse is a white dwarf
- end life as a supernova
- end life as a planetary nebula
- have longer lifetimes

High-Mass Stars

- have higher fusion rate during main sequence life
- late in life fuse carbon into heavier eements
- end life as a supernova

Low- Mass Stars
- have longer lifetimes
- the Sun is an example
- final corpse is a white dwarf
- end life as a planetary nebula

How do the properties of long-lived stars compare to those of short-lived stars?
Check all that apply.

1. Long-lived stars begin their lives with more mass and a larger amount of hydrogen fuel.
2. Long-lived stars begin their lives with less mass and a smaller amount of hydrogen fuel.
3. Long-lived stars are more luminous during their main-sequence lives.
4. Long-lived stars are less luminous during their main-sequence lives.

2 and 4

A main-sequence star twice as massive as the Sun would last __________.

1. about half as long as the Sun
2. much less than half as long as the Sun
3. about twice as long as the Sun
4. much longer than twice as long as the Sun

2. much less than half as long as the Sun

If stars A and B are both main-sequence stars and star A has a greater fusion rate than star B, which of the following statements hold(s)?
Check all that apply.

1. Star A must be more luminous than star B.
2. Star A must be less luminous than star B.
3. Star A must be more massive than star B.
4. Star A must be less massive than star B

1 and 3

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