Astronomy Flashcards Quiz

Questions and Answers

What powers a star?

fusion

In which of the following ways are earthquakes and oscillations on the Sun similar?

They propagate through the entirety of the objects.

A fusion reaction between nuclei A and B releases energy if the resulting nucleus:

is less massive than the total mass of A and B.

What is required to overcome the electrical repulsion of atomic nuclei?

high velocities. Signup and view all the answers

The Sun produces energy through:

the proton-proton chain. Signup and view all the answers

What has provided the best data about the interior of the Sun?

helioseismology. Signup and view all the answers

What is the fate of positrons produced through fusion in the Sun's core?

They are annihilated. Signup and view all the answers

Why does fusion take place at very high temperatures?

High temperatures mean high collisional velocities, which can allow protons to overcome their mutual electrical repulsion. Signup and view all the answers

The most direct measurement of the fusion reactions within the Sun comes from:

neutrinos. Signup and view all the answers

Solar neutrinos: (Select all that apply)

Change their identities en route to Earth. Signup and view all the answers

What is the net result of the proton-proton chain in the Sun?

four protons to one helium-4 nucleus, two neutrinos, two positrons, and gamma rays. Signup and view all the answers

When energy is carried by photons, astronomers call it:

radiative energy transport. Signup and view all the answers

Which of the following energy transport mechanisms does NOT occur to a significant degree in the Sun? (Select all that apply)

Conduction Signup and view all the answers

Convection in the Sun can be observed through:

granulation. Signup and view all the answers

Approximately what fraction of the Solar System's mass is inside the Sun?

99.9%. Signup and view all the answers

Sunspots are areas of:

intense magnetic fields. Signup and view all the answers

What forces maintain hydrostatic equilibrium in an object?

pressure and gravity. Signup and view all the answers

Which of the following is necessary for the solar dynamo to operate? (Select all that apply)

Differential rotation Signup and view all the answers

Which of the following events have caused extensive power outages on Earth?

coronal mass ejections. Signup and view all the answers

Which of the following is NOT related to the solar magnetic cycle? (Select all that apply)

The solar neutrino problem Signup and view all the answers

A sunspot has a temperature 80% as large as the rest of the Sun's surface. How much LESS light does it produce per unit area than the rest of the Sun?

40% as much. Signup and view all the answers

Where does fusion occur in the Sun?

the core. Signup and view all the answers

How are oscillations of the Sun's surface measured?

redshifts and blueshifts of absorption lines. Signup and view all the answers

Arrange the following layers of the Sun in order from most to least dense:

Core = Most dense Radiative zone = Moderately dense Convective zone = Less dense Photosphere = Least dense Signup and view all the answers

Which of the following properties decreases from the Sun's core to its outermost layer?

density. Signup and view all the answers

How have astronomers learned about the life cycles of stars?

by measuring the properties of many stars at a single instant. Signup and view all the answers

Two stars orbit each other on circular orbits. The star with the larger orbital radius has a:

smaller mass. Signup and view all the answers

Which of the following must be measured in order to determine a star's proper motion?

angular position at multiple times. Signup and view all the answers

Stars A and B have equal brightness, but star B is eight times as far from Earth as star A. How much more luminous is star A than star B?

1/64. Signup and view all the answers

What properties of Cepheid variable stars are most often measured to determine their distance?

period and brightness. Signup and view all the answers

What was Henrietta Leavitt's most important contribution to astronomy?

the period-luminosity relation of Cepheid variables. Signup and view all the answers

Star A's spectrum is most intense at 500 nm, while star B's spectrum is most intense at 750 nm. If star A has a temperature of 5,800 K, what is the temperature of star B?

3,850 K. Signup and view all the answers

Which of the following combinations of measurements CANNOT be used to determine a star's radius? (Select all that apply)

Brightness and peak wavelength Signup and view all the answers

Star A has an apparent magnitude of 7, while star B has an apparent magnitude of 12. If star A is four times more luminous than star B, how do the distances of the two stars compare?

Star A is 5 times closer than star B. Signup and view all the answers

Star A is twice as luminous as star B but has half the temperature of star B. How large is the radius of star A compared to star B?

25/2 as large. Signup and view all the answers

Star A is four times as luminous as star B. Star B's spectrum peaks at 300 nm, while star A's spectrum peaks at 150 nm. How large is the radius of star A compared to star B?

1/2 as large. Signup and view all the answers

Which of the following correctly orders the spectral types of stars from coolest to hottest? (Select all that apply)

M Signup and view all the answers

Which of the following is necessary to construct a modern model of a star? (Select all that apply)

Equations of hydrostatic equilibrium Signup and view all the answers

What quantities must be measured in order to calculate the luminosity of a star?

brightness and distance. Signup and view all the answers

What determines the location of a star on the main sequence?

mass. Signup and view all the answers

Massive stars:

burn their fuel rapidly, so they have shorter lifetimes than low-mass stars. Signup and view all the answers

Which of the following stellar spectral types shows the most molecular absorption lines?

M. Signup and view all the answers

A stellar model:

predicts the nature of energy transport within the star. Signup and view all the answers

On the main sequence, a star's spectral type is ultimately determined by its:

mass. Signup and view all the answers

If star A has an apparent magnitude of 8 while star B has an apparent magnitude of 13, then star A is ________ than star B.

100 times brighter. Signup and view all the answers

Which of the following quantities is NOT necessary to observe in order to construct an HR diagram of a system of stars?

mass of each star. Signup and view all the answers

Which of the following inputs are necessary for astronomers to compute the stellar evolutionary track of a star?

mass and composition. Signup and view all the answers

A star has a parallax of 0.05 arcseconds. How far away from Earth is the star?

20 parsecs. Signup and view all the answers

What property of a star can best be used to determine its temperature?

color. Signup and view all the answers

What property of a star's spectral lines allows astronomers to measure stellar masses?

width. Signup and view all the answers

Which of the following is a key constituent of the interstellar medium? (Select all that apply)

Gas Signup and view all the answers

Which of the following lists the phases of the interstellar medium in order, from densest to least dense:

Molecular clouds = Most dense H I clouds = Moderately dense H II regions = Less dense Warm interstellar medium = Even less dense Coronal gas = Least dense Signup and view all the answers

Giant molecular clouds are typically:

hierarchical, with structure on a wide range of length scales. Signup and view all the answers

Which of the following adjectives best describes the interstellar medium?

turbulent. Signup and view all the answers

Which of the following helps support molecular clouds against gravitational collapse? (Select all that apply)

Turbulence Signup and view all the answers

A T Tauri star is a:

protostar that produces X-ray flares. Signup and view all the answers

A massive protostar is more luminous than a low-mass protostar because it:

had more potential gravitational energy before it collapsed. Signup and view all the answers

A protostar becomes a star when:

nuclear fusion begins. Signup and view all the answers

A brown dwarf is a:

failed star. Signup and view all the answers

A star with which of the following masses is most likely to form in a molecular cloud?

0.5 MSun. Signup and view all the answers

What is the net result of the CNO cycle?

Four hydrogen nuclei are transformed into one helium nucleus, two neutrinos, and energy. Signup and view all the answers

An isolated star's eventual fate is ultimately determined by its:

mass. Signup and view all the answers

As a star moves along the red giant branch, how does it move on the HR diagram?

upward and to the right. Signup and view all the answers

What causes a planetary nebula?

shocks from colliding winds around dying stars. Signup and view all the answers

What supports a white dwarf star against gravity?

electron degeneracy pressure. Signup and view all the answers

Which of the following describes the evolutionary stages of a star with three times the mass of the Sun? (Select all that apply)

Asymptotic giant branch Signup and view all the answers

How does a horizontal branch star produce energy?

fusion of helium in the core and hydrogen in a shell. Signup and view all the answers

Why does a red giant grow in radius?

The opacity in the outer layer increases. Signup and view all the answers

The Sun will end its life as a:

white dwarf. Signup and view all the answers

What is the source of most of the carbon and oxygen in the interstellar medium?

winds from asymptotic giant branch stars. Signup and view all the answers

A white dwarf has a temperature 10 times that of the Sun, but it has a radius 1,000 times smaller than the Sun. What is its luminosity?

0.01 solar luminosities. Signup and view all the answers

Why does a red giant fuse hydrogen more rapidly than a main sequence star of the same mass?

The star's interior heats up. Signup and view all the answers

What happens when a massive star's core becomes iron?

The star can no longer support itself against gravity. Signup and view all the answers

What carries the bulk of the energy from the gravitational collapse of a massive star's core during a supernova?

neutrinos. Signup and view all the answers

Why does stellar fusion end with an iron core?

Iron does not produce energy when it undergoes fusion. Signup and view all the answers

Which of the following is closest in radius to a neutron star?

a small city. Signup and view all the answers

What kind of remnant will a 100 MSun star leave?

black hole. Signup and view all the answers

An astronomer observes two Type Ia supernovas in different galaxies. The first is in a galaxy 100 Mpc away. If the second supernova is 106 times fainter than the first but has an identical light curve, how far away is the second supernova's host galaxy?

105 Mpc. Signup and view all the answers

Why are pulsars periodic?

Their radiation sweeps across Earth periodically. Signup and view all the answers

The period between pulses from a particular pulsar increases slowly with time. This implies that the:

pulsar's radiation carries angular momentum. Signup and view all the answers

Two stars orbit each other as a close binary system. When the system forms, star A has 10 solar masses and star B has 3 solar masses. Which of the following is most likely to happen in the future?

Star A will transfer mass to star B. Signup and view all the answers

Which of the following did Einstein determine to be a constant of nature?

the speed of a photon. Signup and view all the answers

Einstein showed that Newton's physics is:

accurate only at low velocities. Signup and view all the answers

The general theory of relativity includes an explanation of:

gravity and space-time. Signup and view all the answers

What are black holes?

regions from whose gravity nothing can escape. Signup and view all the answers

The first experimental verification of the general theory of relativity was:

gravitational lensing. Signup and view all the answers

According to the general theory of relativity, gravity: (Select all that apply)

Is a warping of space-time Signup and view all the answers

According to the general theory of relativity, a satellite orbits Earth because:

Earth has deformed space-time in such a way that the satellite falls freely through it. Signup and view all the answers

Which of the following effects must be accounted for to make accurate measurements with global positioning system satellites? (Select all that apply)

Special relativity Signup and view all the answers

A galaxy is positioned precisely behind another, very massive galaxy on the sky. We would observe the more distant galaxy as a:

ring, displaced from the galaxy's true location. Signup and view all the answers

What kind of stars are most likely to form black holes?

stars with masses greater than 30 MSun. Signup and view all the answers

Why is the Schwarzschild radius significant?

It is the distance within which nothing can escape a black hole. Signup and view all the answers

What do astronomers believe exists in the center of nearly every galaxy?

a black hole. Signup and view all the answers

The first evidence for supermassive black holes at the centers of galaxies came from:

their light output. Signup and view all the answers

An accretion disk around a black hole is threaded by magnetic fields. What is a likely result of this configuration?

a jet of material moving near the speed of light. Signup and view all the answers

What is the observational evidence that black hole jets are launched very close to the event horizon?

the relativistic speeds of the jet. Signup and view all the answers

What stops the collapse of the most massive stars at the end of their lives?

nothing. Signup and view all the answers

A set of stars all initially have the same mass of 20 MSun, but their other properties differ. Which is LEAST likely to form a black hole at the end of its life?

the star that transfers most of its mass to a binary companion. Signup and view all the answers

Study Notes

Stellar Fusion and Energy Production

Fusion reactions in stars, like the Sun, are powered by nuclear fusion, particularly via the proton-proton chain.
Energy from fusion is released when the resultant nucleus is less massive than the initial nuclei.
High temperatures are essential for fusion as they enable protons to overcome their mutual electrical repulsion through high velocities.
Fusion occurs in the Sun's core, producing helium-4 nuclei, neutrinos, positrons, and gamma rays.

Neutrinos and Helioseismology

Helioseismology provides insights into the Sun's interior, revealing data about its structure.
Neutrinos, emitted during fusion, are crucial for studying the fusion process, allowing for direct measurement of reactions.
Solar neutrinos have had detection issues until 2002, serving as valuable probes of the proton-proton chain and changing identities en route to Earth.

Energy Transfer Mechanisms in the Sun

Energy transport in the Sun principally occurs through radiative transport and convection; conduction is negligible.
Granulation on the Sun’s surface is observable evidence of convective processes.

Solar Structure and Dynamics

Approximately 99.9% of the Solar System's mass resides in the Sun, located within various layers including the core, radiative zone, and convective zone.
Hydrostatic equilibrium in stars is maintained by the balance of pressure and gravity, with rapid and differential rotation essential for solar dynamo operation.

Solar Phenomena

Sunspots are associated with intense magnetic fields and have lower temperatures compared to the Sun's surface, resulting in less light output.
Coronal mass ejections can lead to extensive power outages on Earth, affecting communication systems.

Stellar Lifecycles and Classification

The life cycle of stars is determined by their mass; massive stars have shorter lifetimes due to fast fuel consumption.
The Hertzsprung-Russell (HR) diagram is used to characterize star properties, which include brightness and color.
Stellar spectral types are classified from coolest to hottest as MKGFABO.

Star Measurement Techniques

To determine a star’s proper motion, angular position must be measured over time.
Luminosity calculations require brightness and distance, while temperature is most effectively assessed via color.

Black Holes and Stellar Remnants

The fate of stars crucially depends on their initial mass, with those exceeding about 30 solar masses likely forming black holes.
A black hole’s Schwarzschild radius marks the event horizon, beyond which nothing can escape.
Supernovae and pulsar observations provide crucial data on stellar evolution and black hole formation.

Theoretical Foundations in Astronomy

Einstein's theories revolutionized understanding of gravity, describing it as warped space-time and establishing the speed of light as a universal constant.
General relativity accounts for light travel times and the relative effects of gravity, both significant for precise astronomical measurements, such as those used in GPS.

Interstellar Medium and Protostars

The interstellar medium consists of gas and dust with varying densities spanning molecular clouds to coronal gas.
A protostar becomes a star when nuclear fusion starts, with all stars forming from molecular clouds.

Additional Stellar Insights

The ongoing study of Cepheid variable stars has revealed insights into distance measurement in astronomy.
The evolution of stars like T Tauri and red giants involves phases that shape their eventual transformation into remnants like white dwarfs or supernovae.

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Description

Test your knowledge of astronomy with these flashcards. This quiz covers topics such as stellar fusion, seismic activities related to the Sun, and details about nuclear reactions. Perfect for students needing a quick review or anyone interested in the wonders of the universe.