Question 1

When a star collapses to become a black hole, its mass

Accepted Answer

When a star collapses to become a black hole, its mass remains unchanged. The process involves the gravitational collapse of the star's core, but this does not add or remove mass; it simply concentrates the existing mass into a much smaller volume.

Question 2

Which one of these elements is normally the remnant of a supernova?

Accepted Answer

Silver is normally the remnant of a supernova, as it is created in the explosive process of a supernova. Hydrogen and helium are the two most abundant elements in the universe and are not remnants of supernovae.

Question 3

A black hole is

Accepted Answer

Each statement accurately describes aspects of black holes: A) their nature as regions of space collapsed in on themselves, B) their formation from the collapse of supergiant stars, and C) the likelihood of their presence at the centers of spiral galaxies.

Question 4

A black hole has

Accepted Answer

A black hole typically has about the same mass as the original star from which it formed. While the mass can technically become larger as it absorbs more matter, it still starts out with roughly the same mass as the original star. Option B is incorrect as a black hole cannot have infinite mass according to current scientific understanding. Option C is incorrect as a black hole generally has the same mass as the star it originated from. Option D is also incorrect as mass fluctuations are not an observed characteristic of black holes.

Question 5

Why can't any star, no matter how massive, fuse elements heavier than iron?

Accepted Answer

Fusion of elements heavier than iron is not energetically favorable because iron has the most tightly bound nucleus, meaning it has the least mass per nucleon. Fusion beyond iron requires an input of energy rather than releasing energy.

Question 6

Most of the atoms in the universe are thought to be

Accepted Answer

The answer of Most of the atoms in the universe...

Question 7

If the Sun collapsed to become a black hole, the Earth's gravitational attraction to it would be

Accepted Answer

The gravitational attraction between two objects depends on their masses and the distance between them. If the Sun were to collapse into a black hole, its mass would not change, so the strength of its gravitational attraction to the Earth would remain the same. The only difference would be that the Earth would no longer receive light and heat from the Sun, which would have significant effects on its atmosphere, climate, and ecosystems.

Question 8

What determines if a star becomes a white dwarf, a neutron star, or a black hole?

Accepted Answer

The principal factor that determines if a star becomes a white dwarf, a neutron star, or a black hole is its mass. If the mass of the star is less than 1.4 times the mass of the sun, it will become a white dwarf. If the mass is between 1.4 and 3 times the mass of the sun, it will become a neutron star. If the mass is greater than 3 times the mass of the sun, it will become a black hole. Density, temperature, and luminosity are also factors that affect the evolution of a star, but mass is the primary factor that determines its fate.

Question 9

A white dwarf is a former

Accepted Answer

A white dwarf is a remnant of a low-mass star, typically less than 8 times the mass of the sun. High-mass stars end their lives in supernovae and can leave behind neutron stars or black holes, not white dwarfs. White giants are not a recognized type of star.

Question 10

A black hole is

Accepted Answer

A black hole is the remains of a giant collapsed star, in which the gravitational field is so strong that nothing, not even light, can escape from it. Option A is not accurate as a black hole is not an empty region, it has the collapsed star's mass at its center. Option B is not accurate as a black hole doesn't necessarily have the mass of many galaxies, its mass can vary.

Question 11

Metals are relatively more abundant in

Accepted Answer

The answer of Metals are relatively more abundant in
...

Question 12

The event horizon of a black hole is

Accepted Answer

The event horizon is the surface beyond which the gravitational pull of the black hole is so strong that nothing, not even light, can escape. Therefore, option A is the correct choice. Option B is partially correct as it describes the phenomenon of the photon sphere, where light can orbit the black hole, but this is not the same as the event horizon. Option C is incorrect as a black hole does not have a physical surface. Option D is incorrect as black holes do not "come into being" at a specific point in time.

Question 13

A pulsar is likely a

Accepted Answer

A pulsar is a type of spinning neutron star that emits beams of electromagnetic radiation. It is formed when a star explodes in a supernova and its core collapses, leaving behind a highly dense and rapidly rotating neutron star. The beams of radiation emitted by the pulsar can be detected from Earth as a regular series of pulses, hence the name "pulsar".

Question 14

The elements found on Earth have much to do with

Accepted Answer

Supernovae are responsible for creating and distributing many of the elements on Earth, as they are the result of massive star explosions that can generate heavy elements through nuclear fusion reactions.

Question 15

After our Sun burns its supply of hydrogen, it will become a

Accepted Answer

After our Sun burns its supply of hydrogen, it will start fusing helium and expand into a red giant. Eventually, it will shed its outer layers and collapse into a white dwarf. A black dwarf could form only if a white dwarf cools down to the point that it emits no light. However, this process takes trillions of years, much longer than the current age of the universe. Black holes form from the collapse of massive stars, not low-mass stars like the Sun. A blue giant is a rare and short-lived stage of a massive star's life, not a possible fate for the Sun.

Question 16

It is theorized that a pulsar only emits X-rays and visible light during its early history. What do you suppose is the basis of this theory?

Accepted Answer

As the pulsar's energy dissipates, it emits radiation at lower frequencies. X-rays and visible light have higher frequencies compared to other types of electromagnetic radiation, such as radio waves or infrared radiation. Therefore, if a pulsar only emits X-rays and visible light during its early history, it suggests that its energy output decreases over time, leading to lower frequency emissions.

Question 17

Supernovae are one of the most extreme events in the known universe. They are caused by

Accepted Answer

Supernovae are typically caused by the collapse of a massive star (supergiant) at the end of its life cycle, leading to a catastrophic explosion.

Question 18

Most of the energy during the collapse of the iron core of a supergiant star is released in the form of neutrinos-nearly massless subatomic particles that rarely interact with matter. So how is it they can blow away a star's outer shells?

Accepted Answer

The vast number of neutrinos produced during a supernova can impart enough energy to the star's outer layers to blow them away, despite their typically weak interaction with matter.

Question 19

Why are elements heavier than iron less abundant than those that are lighter?

Accepted Answer

The answer of Why are elements heavier than iron less...

Question 20

The gold in Uncle Harry's teeth fillings originated in

Accepted Answer

The gold in Uncle Harry's teeth fillings originated from stars that blew up eons ago. This is because gold is not formed in the Big Bang nor is it a product of fusion processes that date back about 5.5 billion years. Although gold can be found deep in the Earth, it is more likely to have been brought to the surface through volcanic activity rather than originating from the deep interior. Finally, while Fort Knox is a repository for gold, it is unlikely that Uncle Harry's fillings came from there.

Quiz 29: The Universe

When a star collapses to become a black hole, its mass

Which one of these elements is normally the remnant of a supernova?

A black hole is

A black hole has

Why can't any star, no matter how massive, fuse elements heavier than iron?

Most of the atoms in the universe are thought to be

If the Sun collapsed to become a black hole, the Earth's gravitational attraction to it would be

What determines if a star becomes a white dwarf, a neutron star, or a black hole?

A white dwarf is a former

A black hole is

Metals are relatively more abundant in

The event horizon of a black hole is

A pulsar is likely a

The elements found on Earth have much to do with

After our Sun burns its supply of hydrogen, it will become a

It is theorized that a pulsar only emits X-rays and visible light during its early history. What do you suppose is the basis of this theory?

Supernovae are one of the most extreme events in the known universe. They are caused by

Most of the energy during the collapse of the iron core of a supergiant star is released in the form of neutrinos-nearly massless subatomic particles that rarely interact with matter. So how is it they can blow away a star's outer shells?

Why are elements heavier than iron less abundant than those that are lighter?

The gold in Uncle Harry's teeth fillings originated in