PHYS 1080 Exam 3 Practice

left over from the death of a massive star.

A neutron star is

the ejection of mass from a low-mass star

A planetary nebula forms from

has a magnetic axis that is not aligned with the rotation axis.

A pulsar occurs when a neutron star

The blue star is hotter than the gold star

Albireo, a star in the constellation of Cygnus, is a binary system whose two components can be seen easily with even a small telescope. Viewers describe the brighter star as "golden" and the fainter one as "sapphire blue." What does this tell you about the relative temperatures of the two stars?

the gravity charges dramatically over a short distance.

An astronaut who falls into a black hole would be stretched because

Star A is brighter than star B

An eclipsing binary system has a primary eclipse (star A is eclipsed by star B) that is deeper than the secondary eclipse (star B is eclipsed by star A). What does this tell you about stars A and B?

The most massive stars remaining on the main sequence indicate the cluster's age.

An experienced astronomer can take one look at the H-R diagram of a star cluster and immediately estimate its age. Select the statement that explains how this is possible.

up and to the right

As a star leaves the main sequence, its position on the H-R diagram moves

radiation; convection; radiation

As energy moves out from the Sun's core toward its surface, it first travels by _______, then by _______, and then by _______.

too far away

Astronomers cannot use parallax to find the distance to most stars. This is because the stars are

two points in the orbit of Mars, separated by half a Martian year.

Astronomers use two points in Earth's orbit to get the best possible parallax measurement. Even better measurements would be possible with observations from

O5, B0, A0, F0, G0, K0, M0

Choose the list of spectral types that is ordered by decreasing strength of any given property or properties from the table.

degenerate-matter object gets smaller as it gets more massive.

Degenerate matter is different from ordinary matter because

explosions of high-mass stars

Elements heavier than iron originated in the

Radiative zone

Energy is absorbed, emitted and deflected by matter in unpredictable directions.

1. main-sequence star 2. white dwarf 3. neutron star 4. black hole

Following a supernova explosion, if a star's leftover core is between 1.4 and 3 times the mass of the Sun, neutron degeneracy pressure will balance its self-gravity, and it will be a neutron star—a ball of hot neutrons glowing with the release of thermal radiation, slowly fading as it cools. Above 3 solar masses, the star's self-gravity is stronger than neutron degeneracy pressure, and the star collapses instead into a singularity (a single point) called a black hole. Recall that conservation of angular momentum causes collapsing objects to rotate faster. With that in mind, sort the following objects in order of the rotational speed you would expect them to have when they first form, from slowest to fastest.

Add mass to the sun

Heavier elements require higher temperatures to fuse. After stars run out of hydrogen in their cores, they leave the main sequence, collapse, and eventually get hot enough to fuse the helium in their cores into carbon. As discussed in the previous chapter, the Sun will never get hot enough to fuse carbon. Which of these hypothetical situations would allow the temperature of the Sun's core to rise enough for carbon fusion to be possible?

High-mass stars produce energy at a faster rate, High-mass stars use carbon in a process that fuses hydrogen to helium

How does the energy production in a high-mass, main-sequence star differ from energy production in the Sun?

Dark lines, also called absorption lines, within the spectra are "fingerprints" for the different atoms and molecules within a star's atmosphere.

How does the spectrum of a distant star reveal the star's chemical composition?

Sunspots are at higher latitudes at the beginning of a cycle, and lower latitudes at the end of the cycle.

Identify the statement that best describes how the latitude of sunspots varies over a sunspot cycle, which is defined to begin at solar minimum.

exactly c

If a spaceship approaches you at 0.5𝑐, and a light on the spaceship is turned on pointing in your direction, how fast will the light be traveling when it reaches you?

It is cooler than the Sun

If a star is found directly to the right of the Sun on the H-R diagram, what can you conclude about its temperature?

It would remain about the same.

If it were possible to watch a high-mass star move along the topmost of these post-main-sequence lines, what would you observe to be happening to the star in terms of its luminosity?

It would become much larger.

If it were possible to watch a high-mass star move to the right along one of the post-main-sequence lines, what would happen to the star's size?

less than 10 seconds

Imagine you are on a spaceship that isn't moving. A second spaceship rockets past yours at 0.5c (c is the speed of light). You start a stopwatch and stop it 10 seconds later. For an astronaut in the other spaceship, the number of seconds that have ticked by during the 10 seconds on your watch is

CNO cycle

In a high-mass star, hydrogen fusion occurs via the

The marble will travel in a straight line on the flat sheet and in a line curving toward the central mass on the curved sheet.

In his general theory of relativity, Einstein explains the apparent force of gravity as a distortion of the shape of spacetime itself, which changes the paths of objects moving through it. It may be impossible for a human being to imagine a four-dimensional spacetime, but we can think about what it would look like by simplifying it down to a two-dimensional rubber sheet. The image on the left shows a flat rubber sheet, undisturbed by gravity. If a heavy mass, such as a green bowling ball, is placed on the flat sheet, the sheet bows and becomes curved, as shown in the image on the right. How will the motion of the red marble placed at the edge of the flat sheet and given an initial velocity in the direction of the arrow compare with its motion on the curved sheet with a large mass in its center?

- a precise amount of energy - a bluer photon than to jump up one energy level - more energy than to jump up one energy level

In order for an electron to jump up two energy levels in an atom at once, it requires

very high temperatures and pressures

In the proton-proton chain, four hydrogen nuclei are converted to a helium nucleus. This does not happen spontaneously on Earth because the process requires

Convective zone

Moving matter physically transports energy outward

1. 1 Msun black hole 2. 1.5 Msun neutron star 3. 1 Msun white dwarf 4. 1 Msun star

Order the following objects from smallest to largest, according to their radii.

the star swells until the surface gravity is too weak to hold material.

Post-main-sequence stars lose up to 50 percent of their mass because

light; matter

Radiation transports energy by moving __________, while convection transports energy by moving __________.

White dwarf, neutron star, black hole

Rank the objects from least to greatest mass, according to the stars that produce each.

- The temperature is right for hydrogen to make lots of transitions - Hydrogen is abundant in the star because it is absorbing at these wavelengths

Select all that apply. If a star has very strong hydrogen absorption lines, that means

Star B

Star A is blue and star B is red. They have equal luminosities, but star A is five times as far away as star B. Which star appears brighter in the night sky?

Star B

Star A is blue and star B is red. They have equal luminosities, but star A is six times as far away as star B. Which one is larger?

Star A

Star A is blue and star B is red. They have equal luminosities, but star A is six times as far away as star B. Which star is hotter?

More massive stars emit more energy and run out of hydrogen fuel in their cores faster.

Stars are defined to be on the main sequence if they are burning hydrogen in their cores (hydrogen is combining into helium through nuclear fusion). Eventually, a star will run out of hydrogen fuel in its core, nuclear fusion will stop, and the star will enter a new stage of its lifetime.

gravitational collapse

Stars begin burning helium to carbon when the temperature rises in the core. This temperature increase is caused by

1. A clump forms in a giant molecular cloud. 2. Hydrogen fusion begins. 3. The star moves onto the red giant branch. 4. The star moves onto the horizontal branch. 5. The star moves onto the asymptotic giant branch. 6. The white dwarf cools.

Steps of the evolution of a low-mass star in order.

1. Two low-mass main sequence stars orbit each other. 2. Star 1 (the more massive star) begins to evolve on the main sequence. 3. Star 1 fills its Roche lobe and begins transferring mass to Star 2. 4. Star 2 gains mass, becoming hotter and more luminous. 5. A white dwarf orbits a more massive main sequence star. 6. Star 2 fills its Roche lobe and begins transferring mass to the white dwarf. 7. The white dwarf becomes either a nova or a supernova.

Steps which lead some low-mass stars in binary systems to become novae or supernovae.

they are cooler than their surroundings

Sunspots appear dark because

the magnetic field of the Sun

Sunspots change in number and location during the solar cycle. This phenomenon is connected to

The G5 may have transferred all its mass to the Sun, causing the Sun to explore as a Type I supernova, The sun would have already become a white dwarf, and as the G5 swelled into a red giant, material from it would be transferred to an accretion disk around the Sun, making the Sun explode as a nova.

Suppose Jupiter were not a planet, but instead were a G5 main-sequence star with a mass of 0.8 MSun. How could this affect the Sun as the G5 star came to the end of its life?

3, 5, 2

Suppose an atom has three energy levels, specified in arbitrary units as 10, 7, and 5. In these units, which of the following energies might an emitted photon have?

red giant

Suppose you are studying a star with a luminosity of 8.0000 LSun and a surface temperature of 3100 K. According to the H-R diagram, this star is a

at three times the distance, the intensity is 1/9 as great.

The "square" in the inverse square law for intensity of light means that

Earth moves in its orbit during this time

The Sun rotates once every 25 days relative to the stars. The Sun rotates once every 27 days relative to Earth. Why are these two numbers different?

the self-correcting nature of science.

The fact that the speed of light is a universal constant forces us to rethink classical physics completely. This is an example of

heavier atoms fuse closer to the center, where the temperature and pressure are higher.

The interior of an evolved high-mass star has layers like an onion because

fusion temperature

The layers in a high-mass star occur in order of

neutrinos and seismic vibrations

The physical model of the Sun's interior has been confirmed by observations of

The corona has a much lower density

The solar corona has a temperature of more than a million kelvins; the photosphere has a temperature of only about 6000 K. Why isn't the corona significantly brighter than the photosphere?

creates a teardrop-shaped bubble around the Solar System

The solar wind

pressure; loss

The structure of the Sun is determined by both the balance between the forces due to _______ and gravity and the balance between energy generation and energy _______.

Core, radiative zone, convective zone, photosphere, chromosphere, corona

The sun's order starting from the center

the chromosphere and the corona

The temperature and density of the Sun change abruptly at the interface between

H, He, C, Ne, O, S

Think about how you would expect the temperatures in the star to vary between each of the layers shown, and use this to sort the following elements in order of increasing temperature at which they burn in a nuclear fusion reaction.

velocities; period; distance

To find the masses of both stars in a binary system, you must find the ______ of each star, the _______ of the orbit, and the average ________ between the stars.

the mass of hydrogen nuclei

Ultimately, the Sun's energy comes from

at the top left of the main sequence

Very young star clusters have main-sequence turnoffs

true

We can find the age of the stars in a cluster from the H-R diagram.

the innermost core

What is the immovable object in a supernova explosion?

Solar flares happen where there are sunspots/

What is the relationship between sunspots and solar flares?

mass

What is the single most important property of a star that will determine its evolution?

When the neutron star grows to 3 solar masses, it will collapse.

What may happen to a neutron star near this 3 solar mass limit that is in a close binary and is accreting (i.e., stealing) mass from its companion?

The "furnace" at the core turns off.

What triggers a supernova explosion?

conversion of mass to energy

When hydrogen is fused into helium, energy is released from

Radius, luminosity, mass, temperature

Which of the following can be determined from the location of a main-sequence star on the H-R diagram? Select all that apply.

The star will become redder in color, the star will change spectral type, the star will become larger in diameter

Which of the following describe how a more evolved high-mass star will differ from when it was on the main sequence?

a star 1/20 as massive as the Sun

Which of the following stars will have the longest lifetime?

The higher a star's mass, the greater the percent of heavier elements from which it formed, and heavier elements burn hotter and faster.

Which of the following statements about massive stars having the shortest lifetimes is not true?

It will collapse.

While on the main sequence, a star is stable because there is a balance between its self-gravity trying to make the star collapse in on itself and the outward pressure of the gas heated by nuclear fusion trying to make it expand. When the core of a star runs out of fuel and nuclear fusion stops, what will happen to the star?

Pulsars sometimes have material around them that looks like the ejecta from supernovae.

Why do astronomers think that neutron stars were formed in supernova explosions?

It exploded in a supernova, it will become a neutron star, and it is emitting neutrinos.

a high-mass star explodes in a spiral galaxy. Which of the following statements are true regarding the state of the star?

Core

nuclear fusion reactions create energy