Question 1

About how long will a 0.5-  star spend on the main sequence?

Accepted Answer

The answer of About how long will a 0.5- ...

Question 2

Synchrotron radiation is produced

Accepted Answer

Synchrotron radiation is produced when charged particles, such as electrons, are accelerated in magnetic fields, which can occur in various astronomical settings, including the shock waves from supernovae. This process generates a broad spectrum of electromagnetic radiation, from radio waves to X-rays, as the particles spiral at nearly the speed of light. Supernovae, with their powerful explosions and resulting shock waves, can create the conditions necessary for synchrotron radiation to occur.

Question 3

The Algol paradox is explained by considering

Accepted Answer

The Algol paradox refers to the fact that the less massive star in a binary system undergoes more rapid evolution and ends up becoming a giant star before its more massive companion. However, the less massive star is expected to transfer mass to the more massive star, which should result in the opposite scenario. This paradox is explained by the fact that the mass transfer between the two stars is not a smooth process, but rather occurs in bursts and can be highly asymmetrical. This can result in the actual mass transfer being much lower than predicted by theoretical models, allowing the less massive star to evolve more quickly. Therefore, mass transfer between the two stars in a binary system is the best choice to explain the Algol paradox.

Question 4

A planetary nebula has a radius of 0.5 pc and is expanding at 20 km/s. What is the approximate age of this planetary nebula? (1 pc is equal to 3 × 10¹³ km and 1 year is equal to 3.15 × 10⁷ seconds.)

Accepted Answer

The answer of A planetary nebula has a radius of...

Question 5

Synchrotron radiation is produced by

Accepted Answer

Synchrotron radiation is produced when high-velocity electrons are accelerated by a magnetic field. As the electrons spiral around the magnetic field lines, they emit synchrotron radiation in the form of electromagnetic waves. This process is commonly observed in astrophysical objects such as pulsars, black holes, and active galactic nuclei.

Question 6

The diagram below shows a light curve from a supernova. How many days after maximum light did it take for the supernova to decrease in brightness by a factor of 100?
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Accepted Answer

The answer of The diagram below shows a light curve...

Question 7

A planetary nebula

Accepted Answer

A planetary nebula is a type of emission nebula that forms when a low-mass star, such as the Sun, reaches the end of its life and expels its outer layers. The expelled gas is ionized by the central star's ultraviolet radiation, producing an emission spectrum.

Question 8

A white dwarf is composed of

Accepted Answer

A white dwarf is composed of carbon and oxygen nuclei and degenerate electrons. This is because as a small to medium-sized star runs out of fuel and uses up all of its hydrogen and helium, it eventually undergoes gravitational collapse that results in a core collapse supernova. The outer layers are expelled, and the core collapses until it becomes a white dwarf. The electrons in the white dwarf are so tightly packed that they become degenerate, and the carbon and oxygen nuclei are packed closely together as well, resulting in a very dense object.

Question 9

As a white dwarf cools its radius will not change because

Accepted Answer

The pressure in a white dwarf comes from the electrons being packed so tightly together that they become degenerate, meaning their energy is determined solely by their momentum, not their temperature. As the white dwarf cools, the electrons lose momentum and become less degenerate, but their density remains the same, so the pressure can still support the star's weight without the need for nuclear reactions or accretion. Because the pressure does not depend on temperature, the radius of the white dwarf remains stable.

Question 10

When material expanding away from a star in a binary system leaves a star's Roche lobe,

Accepted Answer

The Roche lobe is the region surrounding a star in a binary system where material is gravitationally bound to that star. Anything outside of the Roche lobe is no longer bound to the star and can be accreted by the companion or drift off into space. Therefore, when material expanding away from a star in a binary system leaves the star's Roche lobe, it is no longer gravitationally bound to that star. Choice D is incorrect because thermonuclear fusion requires high pressure and temperature, which are not necessarily present just because material is no longer gravitationally bound. Choice A is incorrect because material leaving the Roche lobe will continue to move away from the star due to its own momentum. Choice B is incorrect because some of the material may escape the companion's Roche lobe and continue moving away from the binary system.

Question 11

The lowest-mass stars cannot become giants because

Accepted Answer

Low-mass stars have convective interiors that continue to mix hydrogen into their cores, preventing the development of an inert helium core. This means that they don't undergo the necessary nuclear reactions to become giants.

Question 12

The theory that the collapse of a massive star's iron core produces neutrinos was supported by

Accepted Answer

Neutrino detection from the supernova of 1987 provided direct evidence supporting the theory that the collapse of a massive star's iron core produces neutrinos.

Question 13

If the theory that novae occur in close binary systems is correct, then recurrent novae should

Accepted Answer

Recurrent novae are called so because they have repeated outbursts after some interval, unlike classical novae that occur only once. This supports the theory that novae occur in close binary systems, where the white dwarf accretes matter from the companion star until a critical mass is reached and a thermonuclear explosion occurs on the white dwarf's surface.

Question 14

The Chandrasekhar limit tells us that

Accepted Answer

The Chandrasekhar limit states that white dwarfs above 1.4 solar masses are not stable and will collapse under gravitational pressure. This is because the electrons in the star become degenerate and cannot support the weight of the star anymore, causing it to collapse and eventually become a supernova.

Question 15

For a star of Sun-like mass, what is the last stage of the nuclear fusion?

Accepted Answer

The last stage of fusion for a Sun-like star is helium to carbon and oxygen. This is because once all the hydrogen has been fused into helium, the core shrinks and heats up enough for helium fusion to occur, creating carbon and oxygen. The fusion process cannot continue beyond this point because the core temperature and pressure are not high enough for heavier elements to fuse.

Question 16

A supernova is almost always associated with

Accepted Answer

The answer of A supernova is almost always associated with
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Question 17

A planetary nebula is

Accepted Answer

A planetary nebula is the result of a medium-mass star shedding its outer layers as it approaches the end of its life cycle. The central star of the nebula then becomes a white dwarf. B, C, D and E are not accurate descriptions of a planetary nebula.

Question 18

A type II supernova

Accepted Answer

A type II supernova is characterized by its spectrum showing hydrogen lines, indicating that the progenitor star had not lost its hydrogen envelope, and it occurs when the iron core of a massive star collapses under gravity, leading to a catastrophic explosion.

Question 19

Stars with masses between 0.4-  and 4-

Accepted Answer

Stars with masses between 0.4 and 4 solar masses are considered low to intermediate mass stars. These stars undergo thermonuclear fusion of hydrogen and helium in their cores, but they do not have enough mass to ignite carbon. Instead, they will eventually exhaust their nuclear fuel and become white dwarfs.

Question 20

A Type Ia supernova is believed to occur when

Accepted Answer

A Type Ia supernova occurs when a white dwarf star in a binary system exceeds the Chandrasekhar limit (about 1.4 solar masses), causing it to collapse and triggering a runaway fusion reaction that destroys the entire star.

Quiz 10: The Deaths of Stars

About how long will a 0.5- star spend on the main sequence?