Question 1

What is the difference between a helium flash and a helium shell flash?

Accepted Answer

A helium flash occurs once when the core of a low-mass star ignites helium fusion suddenly. A helium shell flash can occur multiple times as the helium shell around the core reignites periodically.

Question 2

Which important component does a planetary nebula contribute to the interstellar medium?

Accepted Answer

Planetary nebulae contribute nuclei of moderately heavy elements to the interstellar medium, which are essential for forming planets and other celestial bodies.

Question 3

A planetary nebula is a(n):

Accepted Answer

A planetary nebula is formed by the expanding gas shell surrounding a hot, burned-out stellar core. The name "planetary nebula" is actually a misnomer; it has nothing to do with planets, but was named so because early astronomers thought their spherical shape resembled that of a planet.

Question 4

The light from the expanding shell of gas in a planetary nebula consists of:

Accepted Answer

Planetary nebulae are formed when low- to intermediate-mass stars eject their outer layers, which are then ionized by the radiation from the central star. The resulting expanding shell of gas emits bright emission lines of hydrogen, carbon, nitrogen, and other elements. This is known as the nebular spectrum and is a characteristic feature of planetary nebulae.

Question 5

The diameter of a typical planetary nebula,after 10,000 years of expansion,is:

Accepted Answer

After 10,000 years of expansion, the diameter of a typical planetary nebula can reach a few light-years. Therefore, the correct option is D. A is too large, B is too small, and C is too specific and does not provide a numeric value.

Question 6

A planetary nebula is:

Accepted Answer

A planetary nebula is a shell of ejected gases formed by a dying star. As the star burns through its remaining fuel, it sheds its outer layers, forming a glowing shell of gas that can be seen from Earth. These shells are often very colorful and can take on complex shapes, making them a favorite subject of astronomers.

Question 7

In astronomical terms,planetary nebulae are:

Accepted Answer

Planetary nebulae are very short-lived in astronomical terms, with lifetimes of about 50,000 years. They form when a star sheds its outer layers at the end of its life, leaving behind a white dwarf.

Question 8

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 10⁴ m/s,while its radius is measured to be 1 ly,or about 10¹⁶ m.Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 × 10⁷ sec.)

Accepted Answer

The time can be calculated using the formula time = distance/speed. Here, the distance is 10¹⁶ m and the speed is 10⁴ m/s. So, time = 10¹⁶ m / 10⁴ m/s = 10¹² s. Converting seconds to years: 10¹² s / (3.15 × 10⁷ s/year) ≈ 30,000 years.

Question 9

In the asymptotic giant branch (AGB)phase of their lives,stars like the Sun lose mass to space through an outflowing "stellar wind." Over a period of 1000 years,how much mass would such a star eject?

Accepted Answer

During the AGB phase, stars like the Sun can lose mass at a rate of about 10^-7 solar masses per year. Over a period of 1000 years, this would result in a mass loss of about 10^-4 solar masses, which is approximately 1/100 of the Sun's mass. Therefore, choice C is the most accurate answer.

Question 10

What is the last nuclear fusion stage in the life of a low-mass star like the Sun?

Accepted Answer

The last nuclear fusion stage in the life of a low-mass star like the Sun involves the fusion of helium nuclei to form carbon and oxygen. After this stage, the star lacks the necessary gravitational pressure to fuse heavier elements and eventually becomes a white dwarf.

Question 11

A planetary nebula is a:

Accepted Answer

A planetary nebula is formed from the outer layers of a red giant star that have been expelled as the star's core collapses to become a white dwarf. The expanding gas shell glows due to ionization by the hot core of the star, creating a colorful, spherical shape resembling a planet (hence the name "planetary nebula") when viewed through a telescope.

Question 12

What happens to the surface of a low-mass star after the helium core and shell fusion stages are completed?

Accepted Answer

After the helium core and shell fusion stages are completed, the outer layers of the low-mass star are expelled and form a planetary nebula. The remaining core becomes a white dwarf.

Question 13

The event that follows the asymptotic giant branch (AGB)phase in the life of a low-mass star is:

Accepted Answer

During the AGB phase, the star sheds its outer layers forming a planetary nebula leaving behind a hot white dwarf star. There is no core collapse or supernova explosion in low-mass stars. Helium flash and the onset of hydrogen fusion in the core occur in different stages of the star's life, but they do not directly follow the AGB phase.

Question 14

What will be the mass of the Sun at the end of its asymptotic giant branch (AGB)phase,due to mass loss to space by its stellar wind?

Accepted Answer

The Sun is expected to lose a significant portion of its mass due to stellar winds by the end of its asymptotic giant branch (AGB) phase, leaving behind a core that is about 0.5 solar mass.

Question 15

In the process of helium shell fusion in a low-mass star near the end of its life,the star moves upward and to the right on the asymptotic giant branch of the Hertzsprung-Russell diagram.In this process,the star is:

Accepted Answer

During helium shell fusion, the outer layers of the star expand and cool, causing it to move upward and to the right on the Hertzsprung-Russell diagram. This results in the star becoming larger and more luminous, which is represented by expanding, cooling, and becoming more luminous. Therefore, option D is the correct choice.

Question 16

A planetary nebula is created:

Accepted Answer

Planetary nebulae are formed over a few thousand years or more, in a slow expansion away from a low-mass star, driven by a series of thermal pulses from helium fusion. This process occurs towards the end of the star's life, when it has exhausted its nuclear fuel and starts to contract and heat up. As the temperature rises, helium fusion begins in a shell around the star's core, causing the outer envelope to expand and cool. This expansion is what creates the planetary nebula.

Question 17

What physical process provides the energy for the ejection of a planetary nebula from a low-mass star?

Accepted Answer

Helium shell flashes in the helium fusion shell provide the energy for ejection of a planetary nebula. As the hydrogen fuel in the outer layers of a low-mass star is exhausted, it contracts and heats up causing helium fusion in the shell surrounding the core. This leads to pulses of energy that cause the star to expand and contract, resulting in the ejection of the outer layers as a planetary nebula.

Question 18

How much mass are planetary nebulae estimated to return to the interstellar medium each year over the Galaxy as a whole?

Accepted Answer

The answer of How much mass are planetary nebulae estimated...

Question 19

A planetary nebula is a:

Accepted Answer

A planetary nebula is formed when a red giant star runs out of fuel and the core collapses. This collapse causes the outer layers of the star to be ejected into space, creating a shell of gases that can be seen as a planetary nebula.

Question 20

The fraction of the mass of a low-mass star that is ejected in its evolutionary phases,up to and including the planetary nebula phase,is:

Accepted Answer

Low-mass stars typically eject a significant fraction of their mass in their evolutionary phases, up to and including the planetary nebula phase. This can be up to 80% of the star's original mass, leaving behind a white dwarf.

Quiz 12: The Deaths and Remnants of Stars

What is the difference between a helium flash and a helium shell flash?

Which important component does a planetary nebula contribute to the interstellar medium?

A planetary nebula is a(n) :

The light from the expanding shell of gas in a planetary nebula consists of:

The diameter of a typical planetary nebula,after 10,000 years of expansion,is:

A planetary nebula is:

In astronomical terms,planetary nebulae are:

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 10⁴ m/s,while its radius is measured to be 1 ly,or about 10¹⁶ m.Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 × 10⁷ sec.)

In the asymptotic giant branch (AGB) phase of their lives,stars like the Sun lose mass to space through an outflowing "stellar wind." Over a period of 1000 years,how much mass would such a star eject?

What is the last nuclear fusion stage in the life of a low-mass star like the Sun?

A planetary nebula is a:

What happens to the surface of a low-mass star after the helium core and shell fusion stages are completed?

The event that follows the asymptotic giant branch (AGB) phase in the life of a low-mass star is:

What will be the mass of the Sun at the end of its asymptotic giant branch (AGB) phase,due to mass loss to space by its stellar wind?

In the process of helium shell fusion in a low-mass star near the end of its life,the star moves upward and to the right on the asymptotic giant branch of the Hertzsprung-Russell diagram.In this process,the star is:

A planetary nebula is created:

What physical process provides the energy for the ejection of a planetary nebula from a low-mass star?

How much mass are planetary nebulae estimated to return to the interstellar medium each year over the Galaxy as a whole?

A planetary nebula is a:

The fraction of the mass of a low-mass star that is ejected in its evolutionary phases,up to and including the planetary nebula phase,is: