question

The light we see from the Sun comes from which layer?

answer

photosphere

question

What natural barrier tries to prevent two protons from combining?

answer

electromagnetic repulsion

question

Which is the weakest of the fundamental forces?

answer

the gravitational force

question

When the chromosphere can be seen during a solar eclipse, what is its color?

answer

red

question

How many planet Earths could fit inside the Sun?

answer

A million

question

From where does most of the solar wind flow?

answer

coronal holes

question

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

answer

4 hydrogens are fused into 1 helium, 2 neutrinos + energy

question

In the proton-proton cycle, what fraction of the hydrogen's mass doesn't end up as helium?

answer

.007

question

The density of the Sun is similar to which object?

answer

Jupiter

question

What is the size of a typical granule or convection cell seen in the photosphere?

answer

1,000 km

question

Why couldn't you stand on the Sun's surface?

answer

The Sun doesn't have a solid surface.

question

By what mechanism does radiation reach the Sun's surface from its interior?

answer

Convection

question

What is the meaning of the "solar constant"?

answer

the solar energy reaching Earth per unit area per unit time

question

Which of the following is NOT a property of neutrinos?

answer

never interact with matter

question

Why are scientists bothered by the small number of neutrinos they detect coming from the Sun?

answer

They are not detecting the number of neutrinos predicted by current theories.

question

Which is the strongest of the fundamental forces?

answer

the force that binds atomic nuclei

question

What is it about the Sun's corona that astronomers don't understand?

answer

The corona is much hotter than layers of the Sun that are closer to the solar interior.

question

How would sunspots appear if you could magically remove them from the Sun?

answer

They would shine bright orange in color.

question

The numbers of sunspots and their activity peak about every:

answer

eleven years

question

The critical temperature to initiate the proton-proton cycle in the cores of stars is:

answer

10 million K

question

Loops of glowing hydrogen seen hanging out over the solar limb during totality are:

answer

prominences

question

The _______ Minimum was a period of solar inactivity between 1645 and 1715.

answer

Maunder

question

The pattern of rising hot gas cells all over the photosphere is called:

answer

Granulation

question

The ESA satellite which gave us our most accurate distances to stars is called:

answer

Hipparcos

question

If two stars differ in brightness by 5 magnitudes, the light ratio received by us is ______ to 1.

answer

100✕

question

In comparing first magnitude Deneb with second magnitude Polaris, we find that:

answer

Deneb appears 2.5✕ brighter to us than does Polaris

question

What are the two most important intrinsic properties used to classify stars?

answer

Luminosity and surface temperature.

question

If a star has a parallax of 0.05", then its distance in light years is about:

answer

66 light years

question

If a star is found by spectroscopic observations to be about 500 parsecs distant, its parallax is:

answer

.002"

question

Hipparcos observations have given us good data on stars out to about:

answer

200 parsecs

question

About how many stars has Hipparcos given us accurate distance data on?

answer

a million, those with parallaxes of .005" or larger

question

Which of the following spectral types is the hottest?

answer

G2

question

While Sirius, the Dog Star, is type AO, a star just a step hotter than M0 is a related:

answer

K9

question

The Hertzsprung-Russell Diagram plots ______ against the spectral type or temperature.

answer

luminosity or absolute magnitude

question

Two stars which differ by 5 magnitudes in apparent brightness have the same parallax; thus, one star must be intrinsically ______ times as luminous as the other.

answer

a hundred

question

Stellar masses are determined directly by observation of the orbits and periods of ______ stars.

answer

all types of bianary

question

In what range of masses are most stars found?

answer

.1 to 20 solar masses

question

Why are star clusters almost ideal "laboratories" for stellar studies?

answer

Stars in clusters have the same age, similar composition, and are at the same distance away.

question

Perhaps the greatest of the Greek astronomers, _______ compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightnesses.

answer

Hipparcos

question

Which of the following spectral types is the hottest?

answer

O9

question

Which of these pairs of spectral types is most similar in temperature?

answer

K9 and M0

question

What physical property of a star does the spectral type measure?

answer

temperature

question

The star's color index is a quick way of determining its:

answer

temperature

question

Which of the following is the most common type of star?

answer

main sequence

question

Which of the following apparent magnitudes is the brightest?

answer

-1.1

question

What is the absolute magnitude of our Sun?

answer

+4.8

question

What is the single most important characteristic in determining the course of a star's evolution?

answer

mass

question

The absolute magnitude of a star is its brightness as seen from a distance of:

answer

1o parsecs

question

Which statement about stellar motion is incorrect?

answer

proper motion is measured over intervals of exactly six months

question

If the radial velocity were -3 km/sec, and the transverse velocity were +4 km/sec, then:

answer

the space velocity would be 5 km/sec.

question

What characteristic of the stars in a binary system can be determined by knowing the period of the stars' common orbit and the distance between them?

answer

mass

question

Which type of binary can have their sizes measured directly by photometry?

answer

eclipsing

question

Upon what data do measurements of sizes of eclipsing binaries depend?

answer

their Doppler shifts and the duration of stages of the eclipse

question

The HR diagram can be a plot of _________.

answer

absolute magnitude versus color index

question

What is the typical main sequence lifetime of a B-type star?

answer

20 million years

question

What is the typical main sequence lifetime of a G-type star?

answer

10 billion years

question

What is the typical main sequence lifetime of a M-type star?

answer

a trillion years

question

A nearby star has a parallax of 0.2 arc seconds. What is its distance?

answer

5 pc

question

Procyon lies about 13 light years distant, thus its parallax is about:

answer

0.25"

question

In the H-R diagram, the bright blue-white stars that dominate the naked eye sky lie to the:

answer

upper left quadrant

question

On the H-R diagram, the Sun lies:

answer

about the middle of the main sequence

question

On the H-R diagram, white dwarfs lie Sirius B and Procyon B lie:

answer

to the lower left

question

On the H-R diagram, red supergiants like Betelguese lie:

answer

the top right

question

______ have masses like that of the Sun, and radii like that of the Earth.

answer

white dwarfs

question

What is proper motion?

answer

It is the annual apparent motion of a star across the sky.

question

In order to turn a star's proper motion into its space velocity, we must also know:

answer

its distance and radial velocity

question

Which of the following best describes the size and distance relationship of our Sun and the nearest star?

answer

Two golfballs separated by 100 kilometers.

question

Compared to the size of the Sun, in what range of sizes are most stars found?

answer

0.01 to 100 solar radii

question

How might the most common occurring stars be described, based on our stellar neighborhood?

answer

M-type main sequence stars

question

What are the characteristics of an open cluster of stars?

answer

a few hundred, mainly main sequence stars

question

What are the characteristics of globular cluster stars?

answer

old age and hundreds of thousands of stars

question

What makes the subject of star formation so difficult and complex?

answer

Stars live too long to be observed from birth to death.

question

A typical protostar may be several thousand times more luminous than the Sun. What is the source of this energy?

answer

From the release of gravitational energy as the protostar continues to shrink.

question

Which of these is not typical of a condensing protostar?

answer

fusion of helium into carbon in their cores

question

What is the critical temperature at which hydrogen can fuse into helium in the star's core?

answer

10 million K.

question

What happens when an interstellar cloud fragment shrinks?

answer

all

question

What is characteristic of a main sequence star?

answer

The rate of nuclear energy generated in the core equals the rate radiated from the surface.

question

Most stars probably formed:

answer

in clusters

question

How long does it take for a star like our Sun to form?

answer

50 million years

question

Which relationship concerning the mass of protostars is false?

answer

The more massive ones glow red, accounting for the color of H II regions.

question

What is the key factor that determines the temperature, density, radius, luminosity, and pace of evolution of a protostellar object?

answer

Mass

question

When an H II region is observed, it signals what stage in stellar formation?

answer

Depending on their masses, the stars inside may be at different stages of formation.

question

What is the size of a typical interstellar cloud that is dense enough to form stars?

answer

10 pc

question

As a star forms, the photosphere first appears:

answer

When the protostar forms

question

For gravity to contract a spinning interstellar cloud, there needs to be sufficient:

answer

Mass

question

If the initial interstellar cloud in star formation has a mass sufficient to form hundreds of stars, how does a single star form from it?

answer

The cloud fragments into smaller clouds and forms many stars at one time.

question

A cloud fragment too small to form a star becomes:

answer

A brown dwarf

question

Which event marks the birth of a star?

answer

Fusion of hydrogen atoms into helium atoms.

question

At what stage of evolution do T Tauri stars occur?

answer

When a protostar is on the verge of becoming a main sequence star.

question

How many hydrogen atoms does it take to make a typical star?

answer

10^57

question

How are T Tauri stars characterized observationally?

answer

By sudden changes in their brightness.

question

Evidence for star formation theory comes from:

answer

Studying different objects at different stages and piecing together an evolutionary picture.

question

How long does it take an M-type star to form, compared to the time for a solar-type star to form? `

answer

20 times as long.

question

When a typical open cluster forms, which type of stars are formed most often?

answer

low mass M type dwarfs

question

A star will evolve "off the main sequence" when it uses up which of the following?

answer

most of the hydrogen in the core

question

On the main sequence, massive stars do which of the following?

answer

burn their hydrogen fuel more rapidly than the Sun

question

When the Sun is on the red-giant branch, it will be found where on the H-R diagram?

answer

upper right

question

After the core of a Sun-like star starts to fuse helium on the horizontal branch, the core becomes which of the following?

answer

hotter

question

When the Sun leaves the main sequence, it will become which of the following?

answer

brighter

question

A star like the Sun will end up as what?

answer

a white dwarf

question

The order of evolutionary stages of a star like the Sun would be Main Sequence, giant, planetary nebula, and finally ______.

answer

none of these

question

The helium flash converts helium to the heavier element _____.

answer

carbon

question

How many helium atoms must be fused at 100 million K in the helium flash?

answer

three

question

Which of the following best describes the evolutionary track followed in the HR diagram for the most massive stars?

answer

horizontally right

question

What is used, observationally, to determine the age of a star cluster?

answer

the luminosity at the main-sequence turnoff

question

What is the source of pressure in the core of a red giant that resists the force of gravity?

answer

electrons which have become incompressible

question

In a white dwarf, we have packed the mass of the Sun into the volume of Earth, so the density is:

answer

a million times that of the Sun.

question

What, in addition to its HR diagram, is needed to age-date a star cluster?

answer

theoretical models of stellar evolution

question

What characteristic of a star cluster is used to determine its age?

answer

The main sequence turnoff.

question

The brightest stars of a young open cluster will be:

answer

massive blue main sequence stars

question

In globular clusters, the brightest stars will be:

answer

red supergiants

question

A high-mass star dies more violently than a low-mass star because:

answer

It generates more heat and its core eventually collapses.

question

A ______ is a relatively gentle mass-loss event which allows a star to peacefully readjust its structure into a white dwarf configuration.

answer

planetary nebula

question

Which of these will the Sun probably become in the very distant future?

answer

planetary nebula

question

The evolution of stars appears inevitable. But what likely circumstance can radically alter this evolutionary sequence?

answer

The stars can be in a short period binary system.

question

Which statement is true, in terms of stellar evolution?

answer

Sooner or later, gravity wins.

question

Can a star become a red giant more than once?

answer

Yes

question

Which statement about blue stragglers is false?

answer

They are much more massive than any other stars known.

question

If one star of a binary fills its Roche lobe and is spilling matter onto the other, then the system is a:

answer

mass-transfer binary

question

If two stellar cores share a single envelope, we have a:

answer

contact bianary

question

What results from the mass loss from K and M red giants?

answer

The wind is rich in dust particles and molecules, including diamonds.

question

In a star cluster, just as the most massive stars are evolving into giants and supergiants, what is happening for the lowest mass stars?

answer

They are just starting to approach the zero-age main sequence.

question

Luminous hot stars and luminous cool stars:

answer

have stellar winds, but each are driven by a different source.

question

What is a typical age for a globular cluster?

answer

12 billion years

question

What temperature is needed to fuse helium?

answer

100 million K

question

What are black dwarfs?

answer

cooled off white dwarfs

question

Which of the following is true regarding planetary nebulae?

answer

They are the ejected envelopes of highly evolved low-mass stars.

question

The Roche lobe of a star in a binary star system:

answer

is, in terms of the star's gravity, its "zone of influence."

question

What is a planetary nebula?

answer

The ejected envelope of a red giant surrounding a stellar core remnant.

question

Astronomers talk about "low-mass" and "high-mass" stars with regard to their evolution. In units of solar masses, what is the dividing line, that is, the lowest mass for a high-mass star?

answer

8 solar masses

question

What inevitably forces a star like the Sun to evolve away from being a main sequence star?

answer

It builds up a core of hellium

question

In the evolution of massive stars, what is the significance of the temperature 600 million K?

answer

The ejected envelope of a red giant surrounding a stellar core remnant.

question

A star spends most of its life:

answer

as a main sequence star.

question

What is the significance of 100 million K to the core of a star?

answer

Temperature need to start triple alpha process and turn helium into carbon.

question

The "helium flash" occurs at what stage in stellar evolution?

answer

red giant

question

Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible?

answer

The core contracts, raising the temperature of the region of hydrogen shell-burning.

question

A white dwarf can dramatically increase in brightness only when which of the following applies?

answer

It has another star nearby.

question

Which of the following stars will become hot enough to form elements heavier than oxygen?

answer

A Star that is eight times more massive than the Sun.

question

When does a massive star become a supernova?

answer

When it forms iron in its core.

question

An observable supernova should occur in our Galaxy how often?

answer

about once every century

question

Which one of the following does not provide evidence that supernovae have occurred in our Galaxy?

answer

The existence of binary stars in our Galaxy.

question

Most of the carbon in our bodies originated where?

answer

the core of a red-giant star

question

The silver atoms found in jewelry originated where?

answer

a supernova

question

A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?

answer

Nova

question

For a nova to occur, the system must have already been a:

answer

mass-transfer bianary

question

Which type of heavy atomic nuclei are most common, and why?

answer

Even numbered elements, for helium is "giant food" for everything beyond itself.

question

Nearly all the elements found in our environment were formed inside stars, except for:

answer

Hydrogen and Hellium

question

The production of which element in the core of a highly evolved giant leads to type II supernovae?

answer

iron

question

Why does neutron capture work?

answer

Neutrons have no repulsive barrier to overcome in combining with positively charged nuclei.

question

What is the only way that a white dwarf can suddenly explode in a type I supernova?

answer

if it is a member of a mass-transfer binary

question

What is stellar nucleosynthesis?

answer

The formation of heavier elements inside stars.

question

Of the elements in your body, the only one not formed in stellar nucleosynthesis is:

answer

hydrogen

question

How long does it take a stellar iron core to collapse?

answer

one second

question

The heaviest nuclei of all are formed:

answer

By neutron capture during a supernova explosion

question

An iron core cannot support a star because:

answer

Iron cannot fuse with other nuclei to produce energy.

question

What direct evidence do astronomers have that supports the heavy element formation in stars?

answer

all of these

question

What was most surprising about SN1987A?

answer

The parent star was a B supergiant, not a red supergiant.

question

The upper mass limit of 1.4 solar masses for white dwarfs won a Nobel prize for:

answer

Chandrasekhar

question

The Chandrasekhar mass limit is ______.

answer

1.4 solar masses

question

A 20 solar mass star has a main sequence lifetime of 10 million years, yet its iron core exists for only about how long?

answer

less than a day

question

As a star evolves, heavier elements tend to form by various processes. Which of the following is not one of these processes?

answer

Neutronization

question

The iron we commonly find in our surroundings came from this source.

answer

decay of nickel-56 and cobalt-56 in a supernova remnant

question

What is the reason a type-II supernova slows its dimming after about 2 months?

answer

Energy is released from the decay of radioactive cobalt-56 to iron-56.

question

The transformation of cobalt 56 into iron 56 is an example of:

answer

the weak force and nuclear fission

question

The making of abundant iron nuclei is typical of:

answer

type II supernova

question

What made supernova 1987a so useful to study?

answer

all of these

question

Where was supernova 1987a located?

answer

In our companion galaxy, the Large Magellanic Cloud

question

Which of these is least likely to happen?

answer

recurrent supernova of type I

question

Which of these is the likely progenitor of a type I supernova?

answer

a mass-transfer binary, with the white dwarf already at 1.3 solar masses

question

Which of these is the likely progenitor of a type II supernova?

answer

an evolved red giant which is just starting to make silicon in its core

question

Which of the following does not fit a type I supernova?

answer

Implosion-explosion of the core of a massive star.

question

A star can be a supernova:

answer

once

question

The supernova that formed M-1, the Crab Nebula, was observed in what year?

answer

1054 AD by the Chinese

question

What is the total energy radiated by a supernova equal to?

answer

1 billion suns

question

The total energy emitted by the brightest nova explosions is about:

answer

1 million suns

question

What produces a type-I supernova?

answer

Mass transfer to a white dwarf in a binary where the Chandrasekhar mass is exceeded.

question

When helium capture occurs with a carbon-12 nucleus, what results?

answer

oxygen-16

question

When two silicon-28 nuclei fuse, the initial result is:

answer

nickel-56

question

What evidence is there that supernovae really have occurred?

answer

All of these

question

When a stellar iron core collapses, large numbers of neutrinos are formed, then:

answer

They immediately pass through the core and escape to space.

question

A recurrent nova can eventually build up to a:

answer

type I supernova

question

In order of visual luminosity at the start, which is most luminous?

answer

type I supernova

question

Which of these do not depend on a mass-transfer binary to occur?

answer

a type II supernova

question

The alpha process tends to produce chiefly:

answer

even numbered elements

question

Which of the following is not an argument for Cygnus X-1's being a true black hole?

answer

The mass of the visible B star is even greater than Cygnus X-1, at around 30 solar masses.

question

What explanation does general relativity provide for gravity?

answer

Gravity is a result of curved spacetime.

question

What makes the Crab pulsar somewhat unusual among pulsars in general?

answer

It is rather bright at visible wavelengths.

question

Three terrestrial planetary-sized masses have been discovered orbiting what type of object?

answer

a millisecond pulsar

question

What compelling evidence links pulsars to neutron stars?

answer

Only a small rotating source of radiation is thought to be able to emit precisely timed pulses such as those from pulsars.

question

The key to identifying a black hole candidate in a binary system is the following:

answer

the unseen companion in the system must have a sufficiently high mass

question

Which of these is least likely to exist?

answer

a 1.8 solar mass white dwarf

question

Almost half of all known millisecond pulsars are found in what type of object?

answer

globular clusters

question

Who discovered the first object that eventually became known as a pulsar?

answer

Jocelyn Bell

question

Who received the Nobel Prize in Physics for relating pulsars to neutron star formation?

answer

Anthony Hewish.

question

The supernova of 1054 AD produced:

answer

a pulsar with a period of 33 milliseconds, visible optically.

question

Which of the following is not a property of the first discovered pulsar (nor any other pulsar)?

answer

emissions only in the visible part of the spectrum

question

In the Lighthouse model,

answer

if the beams sweeps across us, we can observe the pulse.

question

What are X-ray bursters?

answer

They are neutron stars on which accreted matter builds up, then explodes in a violent nuclear explosion.

question

What is Cygnus X-1?

answer

a leading candidate for being a black hole

question

X-ray bursters occur in binary star systems. What are the two types of stars that must be present to make up such an object?

answer

a main sequence or giant star and a neutron star

question

Which of the following are attracted by gravity?

answer

all of these

question

Which of the following can actually escape a black hole?

answer

nothing

question

What would happen if mass is continually added to a 1.4 solar mass neutron star?

answer

The star would eventually become a black hole.

question

What would happen if mass is added to a 1.4 solar mass white dwarf?

answer

The star would erupt as a type I supernova.

question

Which statement about gamma ray bursts is not correct?

answer

They are a scaled up version of the X-ray bursts, with more massive stars involved.

question

In a "hypernova", the very energetic supernova creates a:

answer

black hole

question

While perhaps affected by rotation and magnetism, we think the lower limit for black holes is:

answer

Schwartzchild's limit of 3 solar masses.

question

When we use Hubble's law to estimate the age of the universe, which of the following is true of the answer?

answer

the answer is the same for all galaxies

question

Olber's paradox is resolved by which of the following?

answer

the finite age of the universe

question

On the basis of our current best estimate of the present mass density of the universe, astronomers think which of the following?

answer

the universe is infinite in extent and will expand forever

question

Because almost all of the galaxies are redshifted, we know that:

answer

the universe is expanding

question

The redshift of galaxies in the universe is correctly interpreted as:

answer

Space itself is expanding with time; the wavelengths of photon are stretched while they travel through space.

question

From the 1970's through the 1990's, the accepted value of H was almost doubled. This meant:

answer

the Hubble Time was halved.

question

What does the Hubble law imply about the history of the universe?

answer

The universe started expanding at some time in the past; the universe has an age.

question

The cosmic microwave background is important mostly because:

answer

It confirmed a major prediction made by the Big Bang theory.

question

Who was involved in the discovery of the cosmic microwave background radiation?

answer

Bell Labs and Princeton

question

The universe has three possible futures. Which one is correct depends only on the average density of matter in the universe. Why is this?

answer

The density of matter determines the strength of gravity, which decelerates the expansion over time.

question

The presently accepted values for Hubble constant gives which range of ages for the universe?

answer

10 to 20 billion years

question

What is the meaning of a "closed" universe?

answer

The universe will someday stop expanding and start to collapse.

question

Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as:

answer

The cosmological principle.

question

In which of the following models will the universe stop expanding?

answer

Closed universe.

question

The geometry of a closed universe, in two dimensions, resembles which one of the following?

answer

The surface of a sphere.

question

What is the meaning of isotropic?

answer

The same in all directions.

question

The darkness of the night sky in a seemingly infinite universe is addressed in:

answer

Olbers' Paradox.

question

The explanation for the darkness of the night sky is that (select all that apply):

answer

-the Big Bang means the universe is not infinitely old or large. -the energy of the distant galaxies has been weakened in their red shifting.

question

If the density of the universe is less than critical, then:

answer

the universe will "survive" to expand forever.

question

For a Hubble constant of 65 km/s/Mpc, the critical density is about:

answer

8 ✕ 10-27 kg/m3

question

Recent work with supernovae at great distances suggests the universe may in fact be accelerating its expansion, a startling discovery attributed to a new:

answer

dark energy

question

In the critical universe now proposed, the ratio of matter/energy is about:

answer

35/65

question

According to their H-R diagram turn-off points, the oldest globular clusters are about:

answer

12 billion years old

question

The satellite most responsible for studying the microwave universe is:

answer

COBE

question

For a spatially flat (Euclidean) universe, o is:

answer

1.0

question

If the presently accepted value of o = 0.3 is indeed correct, then the universe will:

answer

expand forever

Honors Astronomy Sem 2 Final: Bodecker – Flashcards

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