Chapter 11: Supernova, Neutron Stars, Black Holes

____ are neutron stars that have magnetic fields 100 times stronger than the average neutron star

Magnetars

____ is a form of electromagnetic radiation produced by rapidly moving electrons spiraling though magnetic fields

Synchrotron Radiation

____ occurs when light travels out of a gradational field, loses energy, and its wavelength grows longer

A gravitational redshift

A ____ has a radius of about 10 km and is supported by the pressure associated with degenerate neutrons

Neutron Star

A Black hole can be thought of as

A massive body of infinitely small size

A pulsar requires a neutron star

• Rotates rapidly

• Has a strong magnetic field

• Rotates on an axis that is different from the axis of the magnetic field

A star on the main sequence has 7 solar masses. The star will evolve into a ____ and its core will be supported by ___

White dwarf, electron degeneracy pressure

A supernova is almost always associated with

a white dwarf in a close binary system

A Type Ia supernova is believed to occur when

A white dwarf’s mass exceeds the Chandrasekhar limit

A type II supernova

Occurs when the iron core of a massive star collapses and is characterized by a spectrum that shows hydrogen lines

Although neutron stars are very hot, they are faint and not easy to see at visual wavelengths because

they have only a small surface area from which to emit and the peak of their thermal emission is at much shorter wavelengths than visual

An isolated black hole in empty intergalactic space would be difficult to detect because

• no matter would be falling into it to create an X-ray-emitting accretion disk.

• no companion stars would be affected by its gravitational field.

• there would be no stars behind it whose light would be affected by gravitational lensing.

• it could not emit light from inside its event horizon

An isolated black hole in space would be difficult to detect because

very little matter would be falling into it

As material flows intoelectrom a black hole as viewed from well outside the event horizon

the material will experience time dilation and the material will become hotter

At extremely high densities and temperatures, electrons can be forced to fuse with protons. This reaction produces

neutrons and neutrinos

Complete the reaction e + p —> ____; the reaction applies to ____

n + v, neutron stars

Cygnus X-1 was finally determined to be a black hole when the mass of the unseen companions was confirmed to be

more than 3 solar masses

For a point mass equal to that of the Sun, how far does the Schwarschild radius extend from its center?

a few kilometers away

Fraud in science is rare because it is difficult to commit. Why is it difficult to commit fraud in science?

Science requires that experimental and theoretical findings be reproducible and scientific results are reviewed by other scientists before they are published.

Gamma-ray bursts seem to be associated with violent events involving

neutron starts OR black holes

Giant and supergiant stars are rare because

the giant or supergiant stage is very short

How fast are newly formed pulsars hypothesized to spin?

at lest 10 times per second

Hypernovas are

supernovas that occur when stars more massive than 25 solar masses explode and one hypothesis to explain the production of gamma-ray bursters.

number 40?

In A.D. 1054, Chinese astronomers observed the appearance of a new star, the location of which is now occupied by

A supernova remnant

Millisecond pulsars that are very old are

believed to be the result of mass transfer from a companion that increased the spin of the pulsar.

Neutron stars are expected to spin rapidly because

they conserved angular momentum when they collapsed

Observations from the Compton Gamma Ray Observatory showed that gamma-ray bursts were located throughout the sky. This told us that

• the bursts were not produced among stars in the disk of our Galaxy.

• the bursts were not produced in our Sun.

• the bursts are not associated with planets in our Solar System.

• the bursts were not produced among stars in the nuclear bulge of our Galaxy.

Order the following form most to least dense:

black hole, neutron star, white dwarf

Pulsars cannot be spinning white dwarfs because

a white dwarf spinning that fast would fly apart.

Pulsars do not emit pulses of visible light because

Incorrect: A few pulsars do emit visible light pulses.

Rank the degenerate pressures from least supportive to most supportive

electron, neutron

Note: Black holes have no degeneracy pressure.

Similar to our Sun, pulsars’ rotations are believed to slow down because

they are losing angular momentum into space via outward streaming particles

Synchrotron radiation is produced

in supernova

Synchrotron radiation is produced by

high-velocity electrons moving through a magnetic field.

The ____ of a black hole is the radius of the region from which the escape velocity is equal to or greater than the speed of light

Schwarzschild radius

The calculated Schwarzschild radius of a 2 solar-mass black hole is approximately

6 km

The Crab Nebula is

a supernova remnant

The Crab pulsar emits light in which wavelengths bands?

• X-rays

• Visual

• Gamma

The density of a ____ is greater than the density of a ____

pulsar, white dwarf

The density of a neutron star is

about the same as an atomic nucleus

The escape speed at the event horizon around a black hole is

equal to the speed of light

The escape speed of an object depends on

• the mass of that object

• the distance from the center of the object and the escaping object

The event horizon

has a radius equal to the Schwarzschild radius.

The explosion of a type II supernova can leave behind

a shell of hot, expanding gas with a neutron star at the center

The first pulsar was discovered by ____ in November of 1967

Jocelyn Bell

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

the detection of neutrinos from the supernova of 1987.

The mass of a neutron star is

serval times that of the Sun

The material that accretes onto a neutron star of black hole is expected to emit X-rays because

the material will become hot enough that it will radiate most strongly at X-ray wavelengths.

The object left behind after the supernova explosion seen in the year 1054 has been observed at the center of the Crab Nebula. The object is a

neutron star

The peculiar system SS 433

• I. is emitting beams of energy and matter

• II. is producing a spectrum with both a red and a blue shift.

• III. probably contains an accretion disk.

The Schwarzschild’s radius of a 1 solar-mass black hole is approximately

3km

The search for black holes involves searching for

X-ray binaries with a compact companion larger than 3 solar masses

The singularity of a black hole

is located within the event horizon

The size of a neutron star is

smaller than any of these.

• about the same as that of the Sun.

• about the same as that of the Solar System.

• about the same as Earth.

The slowing of clocks in strongly curved spacetime is known as

time dilation

The stability of a neutron star is expected only if a neutron star is a

fluid

Unseen objects in our Galaxy have been found by the bending effect they have on more distant stars' light passing near them. These small objects that don't emit light are calculated to have masses of about 10×the mass of the Sun. Which is the best choice for these objects?

black holes

What happens when a core’s density exceeds that which electron degeneracy pressure can support?

The core collapses to a neutron star or a black hole.

What happens when a core’s mass exceeds solar masses and its density exceeds that which neutron degeneracy pressure can support?

The core collapses into a black hole

What happens when a core’s mass is less than 3 solar masses but greater than 1.44 solar masses

Electron degeneracy pressure can no longer support the core and the electrons combine with the protons to generate neutrons and neutrinos, the neutrons of which supply neutron degeneracy pressure to support the neutron star.

What is the shape of the event horizon

sphere

Which are compact objects?

• White dwarfs

• blacks holes

• neutron stars

Which items can be a pulsar

neutron star

Which of the following nuclear fuels does a twenty-solar -mass star NOT fuse during its time as a stable star?

iron

Which of the following objects is considered to possibly contain a black hole?

Cygnus X-1

Why do higher-mass stars live shorter lives on the main sequence than lower-mass stars?

Higher-mass stars burn through their fusion fuel faster

____ were observed coming from supernova 1987A, confirming models and theories of core collapse formation of neutron stars

Neutrinos

A pulsar wind is nearly entirely electromagnetic radiation

False

A scientific hypothesis can be proven true if the correct experiments are performed.

False

A type II supernova produces a planetary nebula

False

Because more massive stars have more gravitational energy, they can fuse heavier nuclear fuels

True

Giant and supergiant stars are rare because that stage of stellar evolution is short

True

If the accretion disk around a black hole emits X-rays outside the event horizon, the X-rays can escape

True

Many pulsars have periods that are gradually getting longer as the spinning neutron stars lose energy

True

Neutron stars have densities roughly the same as that of the atomic nucleus

True

Neutron stars were first discovered in the 1930s

False

Pulsars could not be ordinary stars that are pulsating because the pulses are too short

True

Supernovas of type Ia and type Ib both involve binary star systems

True

Synchrotron radiation occurs when high-speed electrons move though a magnetic field

True

The event horizon marks the boundary within which the density is roughly the same as that of the atomic nucleus

False

The spectra of Type II supernovas contain no hydrogen lines

False

The Sun will eventually become a supernova

False

Theory predicts that neutron star masses should not exceed about 3 solar masses

True

To tell the difference between a neutron star and a black hole in an X-ray binary, we must find the temperature of the object

False

Type II supernovas are believed to occur when the cores of massive stars collapse

True

We expect neutron stars to spin rapidly because they conserved angular momentum as they formed

True

When a star of mass comparable to the Sun dies it becomes a black hole

False

When an aging massive star generates an iron core, the iron cannot fuse and thus the star cannon support its weight outside the core. The star is no longer in hydrostatic equilibrium and collapses, forming a supernova.

True