Question 1

Our Sun currently falls on the main sequence of the Hertzsprung-Russell diagram. When it ends its life as a visible star, our Sun will become a

Accepted Answer

Our Sun is not massive enough to become a red giant, supergiant or black hole. When it exhausts all its fuel, it will slowly cool and become a small, dim, and very dense object known as a black dwarf.

Question 2

Astronomers can distinguish galaxy types based on

Accepted Answer

Astronomers classify galaxies primarily by their shape (such as spiral, elliptical, or irregular) and the nature of the energy they emit, which includes analyzing their light spectra to understand their composition and activity.

Question 3

In the life cycle of stars, nebulae serve the purpose of being the material that

Accepted Answer

Nebulae are the clouds of gas and dust that form stars through the process of gravitational collapse. They provide the material for the birth of stars, and when a star eventually dies, the material is returned back to the interstellar medium, contributing to the formation of new nebulae and the continuous cycle of star birth and death. Therefore, nebulae make up both the birth and death of a star.

Question 4

Is it possible for a planet to safely orbit a black hole?

Accepted Answer

Beyond the event horizon, planets can orbit a black hole just as they do other celestial bodies. However, within the event horizon, the gravitational force is so strong that not even light can escape, making it impossible for planets to orbit safely. And, the option D is incorrect because having a mass greater than a supergiant star is not a possibility for a planet.

Question 5

Places within the Universe where the interstellar medium (i.e., "clouds" of gas, dust, and ice) have become denser than elsewhere are known as

Accepted Answer

Places within the Universe where the interstellar medium has become denser are known as nebulae. Nebulae are clouds of gas, dust, and ice that are the birthplace of stars in the universe.

Question 6

A very high-mass star with a mass greater than about 25Ms enters its death throes. It undergoes a supernova explosion, leaving the remnant neutron star that still contains as much mass as three Suns and can become a

Accepted Answer

When a high-mass star undergoes a supernova explosion, it can leave behind a remnant neutron star that is extremely dense and contains as much mass as three Suns. If the remnant has a mass greater than about three solar masses, it can collapse further to become a black hole. Therefore, the best choice is C - black hole. A neutron star cannot become a main sequence star or a red dwarf, and a supergiant is a type of star that is characterized by its large size, not its mass.

Question 7

In which spectral class is a yellow star like our Sun?

Accepted Answer

Our Sun is classified as a G-type star, also known as a yellow dwarf.

Question 8

A supermassive black hole is

Accepted Answer

A supermassive black hole is formed during galaxy formation and contains the mass of millions of stars within the volume of a single star or less. This is due to the collapse of a massive cloud of gas and dust in the center of a galaxy, leading to the formation of a black hole with a mass ranging from millions to billions of times that of the Sun.

Question 9

A ____________ dwarf is in the same size range as a white dwarf but is much cooler in temperature.

Accepted Answer

Red dwarfs are smaller and less massive than other types of main sequence stars, including white dwarfs. They are also much cooler in temperature, which causes them to emit less light and appear red in color.

Question 10

What is the difference between a quasar and a pulsar?

Accepted Answer

Quasars are the most distant objects detectable within the Universe and emit enormous amounts of radiation. Pulsars, on the other hand, are rotating neutron stars that emit pulses of energy with clockwork accuracy.

Question 11

The energy of a nova is provided when

Accepted Answer

Novae occur in binary star systems where one of the stars has become a white dwarf. As material from the other star accretes onto the white dwarf, it can undergo a thermonuclear explosion, which releases a large amount of energy and produces a nova. Therefore, the energy of a nova is provided by the transfer of mass from one star to another in a dying binary star system where one of the stars has become a white dwarf.

Question 12

An astronomer classifies nebulae that have distinct geometry by dividing the nebulae into

Accepted Answer

Nebulae are classified into three main types based on their predominate radiation characteristics: emission nebulae, absorption nebulae, and reflection nebulae.

Question 13

The star that has longest life span because of its size and rate of fuel consumption is known as a ____________ star.

Accepted Answer

Low-mass stars have the longest life spans because they consume their nuclear fuel at a slower rate compared to high-mass stars.

Question 14

What important forces balance each other within a star as it reaches its equilibrium condition?

Accepted Answer

The inward pull of gravity is balanced by the outward pressure generated by the heat and radiation produced by nuclear fusion in the core of the star. This equilibrium condition is maintained throughout the star's lifetime, allowing it to remain stable and prevent collapse or explosion.

Question 15

A white dwarf is a very ____________ star that glows white because of its ____________ surface temperature.

Accepted Answer

White dwarfs are small, dense stars with high surface temperatures, which is why they glow white.

Question 16

What will be the fate of Earth when the Sun's hydrogen fuel is exhausted?

Accepted Answer

When the Sun exhausts its hydrogen fuel, it will expand into a red giant, potentially engulfing the Earth in its outer layers.

Question 17

A high-mass star will end its life cycle as a

Accepted Answer

A high-mass star is one that is at least 8 times the mass of the sun. Such stars will eventually run out of fuel and collapse in a catastrophic supernova explosion that can create either a neutron star or a black hole. The collapse and explosion are a result of the immense gravitational pressure created by the star's huge mass. Therefore, the correct answer is A) neutron star or black hole.

Question 18

The ____________ can extend 3 million kilometers (1.9 million miles) from the black hole's center.

Accepted Answer

The event horizon is the boundary surrounding a black hole from which nothing can escape, not even light. It is the point of no return for anything that gets too close to the black hole, and it can extend up to 3 million kilometers (1.9 million miles) from the black hole's center.

Question 19

What are the key structural features of the Milky Way?

Accepted Answer

The Milky Way is a barred spiral galaxy with a central axis, spiral arms, galactic disk, galactic bulge, and galactic halo.

Question 20

The property of a star that is most important in determining if it will end its life cycle as a white dwarf, a neutron star, or a black hole is its

Accepted Answer

The mass of a star is the most important factor in determining its fate. Stars with masses less than about 8 times the mass of our sun will end their lives as white dwarfs, while more massive stars will either become neutron stars or black holes depending on their mass.

Quiz 23: The Sun, Stars, and Deep Space