astronomy chapter 12-14

What is the approximate age of the star cluster in the accompanying figure?

10 billion years

The fusion of helium into carbon will take a temperature of at least

100 million degrees Kelvin

Globular clusters have approximately how many stars?

100,000 - 1,000,000

If you observe a variable star with a period of 50 days as a yellow, supergiant star, then you most likely have seen a(n) ____.

Cepheid variable star

What positive effect have supernovae had on the development of life on Earth?

Chemical elements necessary for life can only be formed in supernovae.

A normal white dwarf is approximately the same size as ____.

Earth

Pulsar planets are _____.

Earth-like, and may harbor life

Cepheid variable stars are classified as either ____.

Type I or Type II

Neutron stars radiate most of their energy in the ____ wavelength band(s).

X-ray and gamma-ray

The main energy source that drives a supernova explosion is ____.

a burst of neutrinos generated in the core collapse

What physical feature of our planet is most dependent on supernova events?

a nickel-iron core

A stellar core with a mass greater than 3 solar masses will collapse until it reaches _____.

a radius of zero

The Crab Nebula is the remnant of ____.

a supernova recorded by Chinese astronomers

An X-ray burster occurs in a pulsar when ____.

accreted helium suddenly fuses in a nova-like explosion

Matter falling onto a compact object, such as a neutron star or black hole, forms a(n):

accretion disk

Observing star clusters will give astronomers needed data for stellar evolution because all the stars in the cluster have the same ____.

ages

What part of the Sun's aging process will disrupt the biosphere and evaporate the oceans of Earth?

an increase in luminosity as the core becomes helium-enriched

A massive star can fuse more and more massive nuclei, but this process is limited by the fact that, at some point, an element that is produced ____.

cannot produce energy through fusion

Gamma ray bursts are ____.

capable of causing mass extinction events

Cepheid and RR Lyrae variable stars change their brightness by ____.

changing its period between pulses

Binary systems with pairs of stars orbiting each other are ____.

common, and important for some types of stellar evolution

If the Sun was replaced by a black hole of equal mass, Earth would _____.

continue in its normal orbit

Astronomers can determine the interiors of main sequence stars by _____.

creating stellar models

Because of the period-luminosity relation for Cepheids and RR Lyrae variable stars, astronomers are able to

determine the relationship between the period of pulses and luminosity

Degenerate matter has two peculiar properties that can affect a star. One is that the degenerate gas resists compression, and the other is that the degenerate gas ____.

does not depend on temperature

The supernova event for a massive star that has lost a large amount of mass to a close binary companion ____.

does not show hydrogen emission lines in the spectrum of the remnant

As a white dwarf ages, its position on a standard H-R diagram will move ____.

downward and to the right

Supernovae are the main source of ____ in the interstellar medium.

dust

A white dwarf stops collapsing and forms a stable structure due to forces arising from ____.

electron degeneracy

Which statement best describes a neutron star's formation as a supernova explodes and the core begins to collapse inward?

electrons and protons combine into neutrons and neutrinos

Pulsars were discovered because they _____.

emit short, regular bursts of radiation

Stars support their weight by generating ____.

energy in their centers

A white dwarf is always the remnant of a star that ____.

failed to ignite carbon

A "nova" is the event that creates a planetary nebula.

false

A neutron star must have a mass greater than 2.4 solar masses.

false

A white dwarf generates energy through fusion.

false

All stars ignite helium fusion as part of the aging process.

false

All supernova remnants contain pulsars.

false

All type I supernovae are caused by white dwarfs.

false

Almost all stars are in binary systems.

false

Although neutrino emission is used to detect supernovae, they do not play a role in the supernova explosion itself.

false

As a star like the Sun exhausts hydrogen in its core, the outer layers of the star become hotter and more luminous.

false

Giant and supergiant stars are rare because they do not form as often as main sequence stars.

false

Jets are composed of matter and antimatter produced in the poles of a compact object.

false

Pulsars can be created by neutron stars or black holes.

false

Stellar models can easily be accomplished by using a simple hand calculator.

false

Supernovae are triggered because iron releases the most fusion energy of any element

false

Supernovae have little effect on the development of planets such as Earth.

false

The amount of mass lost in a star's solar wind is generally greatest during its main sequence lifetime

false

The energy emitted from the surface of a main sequence star is less than the energy generated in the core.

false

The helium flash stage will always completely destroy a star and any planets nearby it

false

The oldest pulsars are billions of years old.

false

White dwarfs are rare objects.

false

X-ray bursters are caused by black holes.

false

Fusion processes in stellar cores involving heavy elements ____.

generate less total energy because less atoms are available

An astronomer examining a compact object could conclude that it was a black hole if it _____.

has a mass greater than 3 solar masses

The first confirmed black hole, Cygnus X-1, was regarded as proof that black holes exist because it

has a mass of ten solar masses

As a one-solar-mass star evolves off the main sequence, it will probably undergo a _____.

helium bang

A star with the mass of our Sun will go through several stages of energy generation through fusion. Which sequence accurately describes these stages in the correct order?

hydrogen core → hydrogen shell → helium core → helium shell

A nova is caused by the ignition of ____.

hydrogen fusion in material on the surface of a white dwarf

Where are the Cepheid and RR Lyrae variable stars located on the H-R Diagram?

in the instability strip

Most of the energy emitted by a pulsar _____.

is carried away as a 'pulsar wind' of high-speed atomic particles

A white dwarf that exceeds the Chandresekhar limit ____.

is completely destroyed by carbon deflagration

Gas falling into a black hole:

is heated to millions of degrees through the loss of gravitational energy

What is the upper limit of a brown dwarf's size?

less than 0.08 solar masses

A planetary nebula is visible due to ____.

line emission from ionized hydrogen gas ejected by a dying star

Jets from compact objects are explained by the effect of _____.

magnetic fields

To determine the structure of the interior of a star, astronomers must balance density, luminosity, and ____.

mass and temperature

Supernova remnants _____.

may not contain a pulsar, if the supernova explosion kicked the pulsar away at high speed

The production of exotic ____ particle pairs in the core of a high-mass star has a significant effect on the fusion of heavy elements.

neutrino-antineutrino

Neutron stars are supported by _____.

neutron degeneracy pressure

A compact object with a mass of 1.1 solar masses could ____.

not be a black hole or neutron star

Gamma ray bursts were first recorded while trying to detect _____.

nuclear tests

Brown dwarfs are ____.

protostars that could not ignite the fusion of hydrogen at their core

In a binary system containing two neutron stars, the objects will ____.

radiate orbital energy away as gravitational radiation and move closer together

The supernova generated by the explosion of a high mass star fades slowly because of energy generated by ____.

radioactive decay of nickel formed in the expanding shell of the supernova

Most pulsars _____.

slow down their rotation as they age

What evidence did astronomers use to prove jets travel in opposite directions?

spectral lines from fast-moving red- and blue-shifted ionized gas

The evolution of a medium-mass star like the Sun, when off of the main sequence, is ____.

strongly affected by mass loss due to increased solar winds

A hypernova is a violent event caused by _____.

the collapse of a rapidly rotating massive star

The event horizon of a black hole is the point where _____.

the escape velocity equals the speed of light

What part of the Sun's aging process will destroy Earth itself?

the expansion of the outer layers of the Sun as a red giant

The main observable difference separating Type I and Type II supernovae is ____.

the presence or absence of hydrogen emission lines

During the Sun's main-sequence lifetime, ____.

the solar wind will remove a tiny fraction of the Sun's total mass

Red dwarf stars (stars between 0.08 and 0.5 solar masses) evolve very differently than other stars as they age because ____.

their interiors are well mixed, through strong convection

Astronauts approaching a black hole would observe that _____.

they become stretched thin - their heads and feet are pulled apart by gravitational tides

Stars with a mass of about 0.5 to 8 solar masses evolve differently than other mass ranges because ____.

they will never reach the temperature required to establish a helium-fusion shell

A compact object with a mass of 4 solar masses must be a black hole.

true

A hypernova is one of several types of events that create a gamma ray burst.

true

A pulsar emits bursts of radio photons.

true

All the elements heavier than helium on the periodic table, including the ones in your body, were created in the cores of massive stars.

true

Astronomers determine the internal structure of a star by using stellar models, since they cannot "see" into the interior of a star.

true

Gamma ray bursts never last longer than a minute.

true

It is possible for a medium-mass star to collapse and form a white dwarf, but no planetary nebula.

true

Many pulsars are not associated with supernova remnants.

true

Observing star clusters will give astronomers needed data for stellar evolution because all the stars are the same age.

true

Stars in binary systems can transfer mass from one star to another at a Lagrange point.

true

Stars larger than about 1.4 solar masses must lose mass in order to become white dwarfs

true

Supernovae can trigger star formation.

true

The age of a star cluster can be approximated by finding its turnoff point in the distribution of data points that represent stars on the H-R Diagram

true

The collapse of the iron core of an isolated massive star produces a type II supernova.

true

The event horizon is located at the Schwarzschild radius

true

The first steps of evolution off the main sequence are the same for both medium-mass and high-mass stars.

true

The process and result of a star's evolution off of the main sequence are determined primarily by the star's mass.

true

There is a mass-luminosity relationship because stars support their weight by generating energy, and more massive stars have more weight to support.

true

When the Sun moves off the main sequence, it will initially become a red supergiant.

true

Most neutron stars are the remnants of _____ explosions.

type II supernovae