PY 123 Exam 2
Remember Kepler's third law, which relates the period of revolution to the average distance to a planet. How do we modify that law to use with binary stars?
Add the total mass of the two stars.
Star clusters are important to the study the stellar evolution because stars in a given cluster have the same
Age
Which molecule has not been detected in molecular clouds?
All of these have been detected: molecular hydrogen ethyl alcohol carbon monoxide nitrous oxide
The ---- effect changes the observed wavelength of an emitted photon if the source is moving toward or away from the observer.
Doppler
When mapping the interior of the Sun, astronomers must measure _____ as the photosphere moves up and down.
Doppler shifts
All telescopes must be operated on site by an astronomer or a technician.
False
Almost all the light we receive from the Sun escapes from underneath its photosphere.
False
As a star like the Sun exhausts hydrogen in its core, the outer layers of the star become hotter and more luminous.
False
Blackbody radiation only occurs in stars.
False
Calculations of the Sun's future evolution indicate that it will blow away almost half of its mass in several relatively short episodes about 4 to 5 billion years from now before it is finally extinguished.
False
Cosmic rays are made of photons.
False
Giant and supergiant stars are rare because they do not form as often as main-sequence stars.
False
Gravity waves have never been detected.
False
Main sequence O stars have convective cores because they fuse hydrogen in the proton-proton chain.
False
No radio waves penetrate the Earth's atmosphere.
False
Nuclear fusion within the Sun proceeds step-by-step in a series of reactions called the neutron-neutron chain.
False
Open clusters are older than globular clusters.
False
Recently discovered brown dwarfs have spectra similar to cool O-type stars.
False
Spicules can trigger communications blackouts and auroras on Earth.
False
Stars are born in reflection nebulae.
False
Stellar models can easily be accomplished by using a simple hand calculator.
False
The ISM is easily visible to human eyes.
False
The amount of energy needed to pull an electron completely away from the nucleus is called the Coulomb energy.
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 intercloud medium is believed to make up 90 percent of the mass of the interstellar medium.
False
The most accurate way to determine the surface temperature of a star is to study the pattern of emission lines from various atoms.
False
The proton-proton chain for fusing hydrogen into helium is a much more complicated process than the CNO Cycle for fusing hydrogen into helium.
False
The spectral classification of stars started with the amount of hydrogen present in their spectra, but a better method now uses the amount of oxygen in the star's spectra.
False
The temperature at the core of a star must be at least 1 million degrees Kelvin before fusion can begin.
False
The terms "temperature" and "heat" are synonymous.
False
When a large gas cloud starts to collapse in a free-fall due to gravity, it will start to cool down as it contracts because of the atoms fall inward.
False
When the Sun generates its own energy, it uses weak forces to bind together atomic nuclei.
False
X-rays come from certain regions of the interstellar medium because gas molecules in those regions are at a very high density.
False
A continuous spectrum is created by a hot ionized gas.
False
An atom that has gained one or more electrons is called an isotope.
False
Helioseismology maps of rotation in the Sun's interior show that its internal gases rotate with equal periods.
False
If absorption lines of sodium are not present in a star's spectrum, the star must not contain any sodium.
False
Nuclear fusion in the Sun is tremendously powerful.
False
Radio telescopes are often located near populated areas.
False
Reflecting telescopes suffer from chromatic aberration because the light must pass through the glass.
False
Refracting telescopes use a mirror to gather and focus light.
False
Resolving power is measured in nanometers.
False
Small differences in temperature between two stars produce small differences in the amount of energy they radiate.
False
Sunspot numbers follow a seven-year cycle.
False
The Kelvin temperature scale is based on the freezing point of water.
False
The layer above the chromosphere is the photosphere.
False
The lowest permitted energy level of an atom is called the neutral state.
False
The visible surface of the Sun is composed of solid matter.
False
Our Sun's spectral temperature type is classified as a(n) ____ on the spectral sequence.
G star
The Sun is what spectral type?
G2
What unit is used to measure wavelengths?
Nanometer
In which spectral sequence are the hottest stars categorized?
O stars
Elements such as carbon, silicon and oxygen have been produced in stars and expelled as stars age in the interstellar medium. This is most likely due to these elements having cooled and condensed from aging stars to form dust grains, and carried out by a powerful winds.
True
For stars that are too distant to have measurable parallaxes, their distances can be estimated from the star's spectral type, luminosity class, and apparent magnitude with a procedure called spectroscopic parallax.
True
Granulation is caused by convection currents just below the photosphere.
True
Granules on the Sun's photosphere can be several thousand kilometers across.
True
H II Regions are also called emission nebulae.
True
A star's apparent magnitude is a measure of how bright it appears to us if it is at its actual distance.
True
All stars produce an absorption spectra.
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
An average star spends about 90% of its life on the main sequence.
True
Astronomers determine the internal structure of a star by using stellar models, since they cannot "see" into the interior of a star.
True
At infrared wavelengths, the ISM glows with blackbody radiation emitted by the interstellar dust.
True
Atoms are mostly empty space
True
Because blue light has a shorter wavelength than red light, it will be more readily scattered.
True
Convection is important in stars because it transports energy outward in the star.
True
If two stars are emitting the same amount of light, the star that is farther will appear dimmer.
True
Low-mass stars like the Sun transport energy near their surface using convection.
True
Nebula is just another name for the interstellar medium (ISM)
True
Observing star clusters will give astronomers needed data for stellar evolution because all the stars are the same age.
True
One of the factors that a large molecular cloud must overcome in order for gravitational contraction to begin is rotation of the gas cloud.
True
One of the factors that a large molecular cloud must overcome in order for gravitational contraction to begin is the thermal energy of the gas.
True
One of the major star forming regions in space is the Orion Nebula.
True
One trigger that could start the gravitational contraction of a molecular cloud to form stars is a passing shock wave.
True
Refracting and reflecting telescopes form an image that is small, inverted, and difficult to observe directly; therefore, an eyepiece is normally used to magnify the image and make it convenient to view.
True
Stars are born from the interstellar medium, and aging or dying stars return gas and dust back into the interstellar medium.
True
Sunspots are parts of active solar regions dominated by magnetic fields that encompass all layers of the Sun's atmosphere.
True
The ISM magnetic field is typically about 0.0001 times as strong as Earth's magnetic field at its surface.
True
The Sun is a ball of hot gas held together by its own gravity.
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 composition of the interstellar dust suggests that it is formed primarily in the atmospheres of cool stars.
True
The coronal gas in the interstellar medium has very high temperatures similar to the Sun's corona.
True
The luminosity class is assigned to a star by studying the absorption lines in the spectrum of the star.
True
The solar wind can blow past Earth with speeds as high as 1000 km/s.
True
The upper chromosphere is hot enough to emit X-rays.
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
he Hertzsprung-Russell Diagram is a plot for stars using absolute magnitude versus temperature.
True
A certain type of atom can only absorb certain wavelengths.
True
A hot object that is glowing orange will become redder as it cools.
True
An absorption spectrum is created when blackbody radiation passes through a cool gas.
True
If you move an electron from the ground state to a higher energy level, the atom becomes an excited atom.
True
In blackbody radiation, short-wavelength and long-wavelength photons are rare.
True
Red light of the visible light spectrum has longer wavelengths than blue.
True
Short-focal-length lenses and mirrors must be strongly curved.
True
Space-based telescopes carrying long-wavelength infrared detectors must carry coolant such as liquid helium to chill their optics to near absolute zero temperature.
True
Stars of low luminosity will always have large positive absolute magnitude.
True
Sunspots tend to occur in groups, or pairs, with the magnetic field around the pair resembling that around a bar magnet.
True
The agitation of atoms in a hot body creates a continuous spectrum of radiation.
True
The corona is so dim that it is not visible in Earth's daytime sky.
True
The larger the diameter of a telescope, the more light it will collect
True
The number of protons in the nucleus determines which element it is.
True
Emission lines are produced by ____.
electrons that transfer from a high energy level to a low energy level
Absorption lines are produced by ____.
electrons that transfer from a low energy level to a high energy level
A spectrum that displays no energy except at very specific wavelengths where intense radiation is observed is a(n) ____ spectrum.
emission
A(n) ---- spectrum is produced by a hot, excited gas.
emission
The photons coming from an excited gas create a(n) ____ spectrum.
emission
Which type of nebula is produced when a star, hotter than 25,000 K, excites the gas near it to produce an emission spectrum producing a distinctive pink color?
emission nebulae
Physicists and astronomers usually refer to the permitted orbits of an atom as the atom's ----- levels.
energy
Stars support their weight by generating ____.
energy in their centers
As a main-sequence star evolves off the main sequence, the helium core is contracting while the outer envelope is ----
expanding
A lens called the ----- is typically used to magnify the image and make it convenient to view distant objects.
eyepiece
To an observer on Earth, dust in the interstellar medium will cause a star to appear ------ and_______________than it really is.
fainter; cooler
A(n) ---- is an image of the Sun made using only light within a particular band of wavelengths.
filtergram
A blackbody with absolute temperature T has a wavelength of peak intensity λmax. If the temperature is tripled, the wavelength of peak intensity will become ________.
λmax/3
The corona can reach temperatures of up to ____.
2,000,000 K
What is the approximate average temperature of the Sun's surface?
5800 K
electron motion between energy levels
Each atom absorbs or emits a set of photon wavelengths unique to its element type.
Which mission is mapping the heliosphere's boundary?
Interstellar Boundary Explorer
Why aren't optical or radio telescopes used in particle astronomy, which studies cosmic waves and gravity waves?
Optical and radio telescopes can only detect electromagnetic radiation.
Why are X-rays and gamma rays considered dangerous forms of light?
Photons of these wavelengths have high energy.
The star Betelgeuse appears red; the star Rigel appears blue. What accounts for this difference?
The surface of Betelgeuse is cooler than the surface of Rigel.
Wien's Law
The wavelength of maximum intensity depends on the surface temperature of the star.
What is the function of the receiver antenna of a radio telescope?
To absorb the radio energy collected by the dish
Which telescope is the largest refracting telescope in the world?
Yerkes Observatory refractor telescope
The position of an absorption or emission line is useful in determining the ____.
chemical composition of an object
Violent bursts of ionized gas ejected from magnetic fields that flow outward in the solar wind
coronal mass ejection
Which type of nebulae are twisted and distorted clouds of gas and dust dense enough to obstruct the view of the more distant stars?
dark nebulae
Interstellar extinction and the reddening of light by the interstellar medium (ISM) are both caused by _____.
only dust in the ISM
What is the resistance of a gas to the flow of radiation?
opacity
A supergiant star's radii may extend out to the _____.
orbit of Saturn
An atom can only have orbits of certain sizes, called ---- orbits.
permitted
The layer in the Sun from which visible photons most easily escape
photosphere
The ---- is a thin layer of gas from which Earth receives most of the Sun's light.
photosphere
What characteristic of a telescope controls the amount of light captured by the telescope?
diameter of tube
The Babcock model of the solar magnetic cycle explains the sunspot cycle as primarily a consequence of the Sun's ____.
differential rotation
The _____ occurs when some of the energy in the convective motion of gas is converted into magnetic field energy.
dynamo effect
An atom must emit a photon when a(n) ____.
electron moves from a higher to a lower energy level
The Stefan-Boltzmann law relates the ____.
energy emitted from a surface every second to the temperature of the surface
Photons of light can be absorbed by an atom of an element ____.
if they match one of several possible wavelengths that are absorbed by that element
Where would you most likely find a large radio telescope?
in a mountain valley
Where is the Trapezium found?
in the Orion Nebula
When a large gas cloud starts to collapse in a free-fall due to gravity, the cloud will ____.
increase in temperature
Four of following are factors that must be overcome by a large molecular cloud before gravitational contraction can begin. Which one is the exception?
intense radiation from a nearby star
What is the upper limit of a brown dwarf's size?
less than 0.08 solar masses
What occurs on the surface of the Sun during a solar cycle minimum?
little to no sunspot activity
The most common type of star is a(n) ____.
lower-main-sequence star
As a blackbody becomes hotter it will radiate ____.
more energy, at a shorter wavelength of maximum intensity
The Doppler effect is useful in measuring the ____.
motion of an object toward or away from the observer
Electromagnetic waves are generated whenever the ____.
motion of any charged particle changes
The binding energy is the amount of energy ____.
needed to pull an electron completely away from the nucleus
Galileo proposed that the Sun is a rotating sphere after he ____.
observed sunspots move across the surface of the Sun
Which is the correct order of the Sun's atmospheric layers, from the innermost to outermost?
photosphere → chromosphere → corona
Arches of magnetic field visible in the chromosphere and corona
prominences
The type of element is determined by the number of ____.
protons in the atom
As the protostar contracts gravitationally, it will rotate faster and faster and produce a(n) ____.
protostellar disk
Stellar winds and _____ will eventually blow away the protostellar disk and remnant cocoons of a protostar apart.
radiation pressure
When two arches in a magnetic field encounter each other, ____ can cause powerful eruptions called ____.
reconnection events; flares
On the H-R diagram, lines of constant radius are illustrated as _____.
sloping downward from left to right
Which type of binary system have pairs of stars that are so close together that they look like one single point?
spectroscopic binary
Flame-like structures that extend upward into the lower corona
spicules
The wavelength of maximum intensity is useful in measuring the ____.
surface temperatures of an object from their colors
The pressure of a gas depends on the ____ and ____ of the gas.
temperature; density
Which trigger could start the gravitational contraction of a molecular cloud?
the collision of molecular clouds
A protostar will continue to collapse due to gravity until it reaches the main sequence, and then gravitational collapse will stop when _____ begins.
the fusion of hydrogen
A continuous spectrum is produced by ____.
the intensity of agitation of atoms in a hot gas
A shift in the position of an emission line of an element toward the red or blue is produced by ____.
the motion of an object toward or away from the observer
The arrangement of permitted orbits is ____.
unique for each element
The least common type of star is a(n) ____.
upper main sequence
Cepheid and RR Lyrae variable stars change their brightness by ____.
changing its period between pulses
What modern-day instrument do astronomers use to record images from telescopes?
charge-coupled device
A optical distortion of refracting telescopes called ---- causes a separation of colors, such as when you focus on one color, the other colors in an image are blurred.
chromatic aberration
Energy flows by radiation or convection inside normal stars but almost never by ----- because radiation or convection is much more efficient.
conduction
Variables of a certain type are called Cepheid variables because the first one discovered was in the ----- Cepheus.
constellation
The photons coming from blackbody radiation create a(n) ____ spectrum.
continuous
A hot blackbody emits a(n) ----- spectrum.
continuous
A spectrum that displays a smooth variation in intensity of all wavelengths without any breaks is a(n) ____ spectrum.
continuous
What process on the Sun's photosphere does this figure (Figure 8-1) represent?
convection currents
CCD images captured from telescopes are often ____ to be stored in a computer's memory for later analysis.
converted to numerical data
Space telescopes carrying long-wavelength infrared detectors must carry --- for their optics to avoid the insides of the telescope and instruments from blinding the detectors.
coolant
Recent discoveries of two types of brown dwarfs have placed these stars near which spectral type of star?
cooler than M stars
The outermost part of the Sun's atmosphere
corona
Of the following parts of the Sun, which is the hottest?
corona
Which component of the interstellar medium has the greatest temperature?
coronal gas
Violent bursts of ionized gas ejected from magnetic fields that flow outward in the solar wind
coronal mass ejection
The images produced by ----- reveal streamers in the corona that follow magnetic lines of force in the Sun's magnetic field.
coronographs
Astronomers can determine the interiors of main-sequence stars by _____.
creating stellar models
The Chandra observatory uses ----- mirrors in which the X-rays reflect at shallow angles from the polished inside of the mirrors to form images on X-ray detectors.
cylindrical
When a gas is so dense that most of its electrons are not free to change their energies, it is called
degenerate matter
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
The ____ of a radio telescope collects and focuses radiation.
dish
The formula can be used to calculate a star's _____.
distance
If luminosity depends on radius and temperature, what does flux depend on?
distance
The period-luminosity relation for Cepheid and RR Lyrae variable stars can be used for
distance measurements
v=A star's absolute visual magnitude depends only on the star's ______ and _____.
distance; magnitude
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
Which part of a telescope is responsible for magnifying an image?
Eyepiece
A star's absolute brightness is calculated at a standard distance of 10 parsecs.
True
What technique often requires the use of a laser guide star?
adaptive optics
If the photons from blackbody radiation pass through a cool gas, a(n) ____ spectrum is produced.
Absorption
Most of the mass of an atom is ____.
Concentrated in the nucleus
The lower limit for a main-sequence star is --- solar masses.
0.08
What is the average distance between the Sun and Earth?
1 AU
Absolute visual magnitude is calculated at a standard distance of ____.
10 parsecs
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
The chromosphere is roughly -----times fainter than the photosphere.
1000
Coronal gas emits x-rays and has temperatures of ____.
106K or higher
Observing at a wide range of wavelengths, astronomers have detected more than ______ different molecules in the ISM.
150
The ground state of hydrogen has two closely-spaced energy levels, where one-electron is spinning up and the other is spinning down. This energy transition corresponds to releasing excess energy as a photon at what wavelength?
21 centimeters
H I clouds can be observed using _____.
21 cm radiation
Consider the complete magnetic cycle of sunspot activity on the Sun. Approximately how many years is this cycle?
22 years
If telescope A is 160 cm in diameter, and telescope B is 32 cm in diameter, how much more light does telescope A gather than telescope B?
25 times
Our Sun took about ________ years from the collapse of its parent molecular cloud to become a main-sequence star.
30 million
The Sun, a one-solar-mass star, will take approximately how many years to go from protostar to main-sequence star?
30 million years
If λ = 2.90 × 106/T expresses the relationship between Kelvin temperature and the wavelength of maximum intensity in nanometers, what is the wavelength in nanometers of maximum intensity for a star with a surface temperature of 7 250 K?
400
Which equation represents the overall nuclear fusion process of the Sun?
41H →4He + energy
The stellar parallax limit for ground-based telescopes is accurate for stars closer than ____.
50 parsecs
The formula expresses the relationship between Kelvin temperature and the amount of radiated energy. If a star is three times the temperature of the Sun, how many times more intense is the energy radiated from an equal-sized area of its surface? (Answer with a number only.
81
Chandra
A space telescope that detects X-rays
HST
A space-based telescope that detects visible, UV, and infrared wavelengths
SOFIA
An airborne telescope that captures short infrared wavelengths
agitation and collision of atoms
An excited atom in which an electron is raised to a higher orbit.
Built in 1963, the ---- telescope in Puerto Rico is the largest single radio dish in the world.
Arecibo
Why does the temperature of the corona rise with latitude?
Atoms within the corona become more ionized at higher altitudes.
The ---- predicts that pairs of sunspots should occur where magnetic tubes burst through the Sun's surface.
Babcock model
What causes granulation on the photosphere?
Convection
What must be used to maintain the optics and operation of an infrared telescope?
Coolant
A(n) __________ is both an image-recording device and a photometer.
CCD
Which atom is the end result of the triple alpha process?
Carbon
Molecular clouds are mapped using _____ gas instead of the most-abundant hydrogen because it radiates at radio wavelengths more efficiently.
Carbon monoxide
Which type of focus is most common for larger telescopes?
Cassegrain focus
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
The instability strip on the H-R diagram is the location for what type of stars
Cepheid variables
After a protostar has progressed in its development, it will have a dense inner part and an outer envelope called a(n) ____.
Cocoon nebulae
What does chromatic aberration separate within refracting telescopes?
Color
----- is believed to be produced by supernova explosions.
Coronal gas
Highly ionized state
Coronal gas
The part of the ISM that can only be detected with X-ray telescopes have has temperatures of 106K or higher
Coronal gas
The force between charged particles is called the ---- force.
Coulomb
The proton-proton chain needs a high temperature because the protons must overcome the ----
Coulomb barrier
In order for nuclear fusion to occur, atomic nuclei must overcome the ____ by colliding violently.
Coulomb barrier
Light-gathering power and resolving power both depend on what characteristic of a telescope?
Diameter
The amount of energy needed to move an electron from a lower energy level to a higher energy level is the ____.
Difference in energy between the two levels
The particle in an atom that carries a negative charge is the ____.
Electron
Which type of electromagnetic wave is the shortest?
Gamma
What are the dark regions that give the Sun's photosphere a mottled appearance?
Granules
Groombridge 34is an M2 main-sequence star. Based on this information, which statement is true?
Groombridge 34is less luminous than the Sun.
A chaotic shape that is usually twisted, flattened, and tangled
H I cloud
ISM clouds of cool gas of only about 100 K and dust with densities ranging up to 100 atoms per cubic centimeter and observed only at infrared and radio wavelengths
H I cloud
------- are cool, with temperatures of about 100 K and densities of ten to a few hundreds of atoms per cubic centimeter.
H I clouds
----- require that a young hot star (T ≥ 25,000 K) be relatively nearby.
H II regions
What is the shape of the segmented mirrors of twin Keck Observatory telescopes, Gran Telescopio Canarias, and the James Webb Space Telescope (scheduled to be launched in late 2018)?
Hexagonal
The satellite __________ measures stellar parallaxes from orbit.
Hipparcos
Which is the longest surviving, and most successful, space telescope?
Hubble Space Telescope
Which two elements are most abundant within the Sun?
Hydrogen and helium
The hot space of ISMs with temperatures of a few thousand K and a density of only 0.1 atom per cubic centimeter found between the cool H I clouds
Intercloud medium
The Very Large Array radio telescope in New Mexico is an example of the use of which astronomical technique?
Interferometry
An atom that has lost or gained one or more electrons is called a(n) ____.
Ion
If a neutral atom gains or loses an electron, it ___________.
Is ionized
Atoms that have the same number of protons but a different number of neutrons are called ____.
Isotopes
The energy a photon carries is inversely proportional to __________.
It's wavelength
Which telescope will be launched into solar orbit and eventually replace observations made by the Hubble Space Telescope?
JWST
Jenny, who lives on a farm in a rural part of New York, calls her cousin, Karen, in Brooklyn, to tell her that she can see the Milky Way in tonight's night sky. However, Karen says she can't see it at all. What is preventing Karen from seeing the Milky Way in the night sky?
Karen lives in an area with light pollution.
The ---- temperature scale is used in astronomy because it is based on absolute zero.
Kelvin
To determine the structure of the interior of a star, astronomers must balance density, luminosity, and ____.
Mass and temperature
Historical records show that there were very few sunspots from about 1645 to 1715, a phenomenon known as the
Maunder minimum
Which form of radiation has the lowest frequency?
Microwave
Clouds of gas and dust with densities ranging from 100s to 1000s particles per cubic centimeter, found deep inside the ISM, where it is protected from UV photons
Molecular clouds
During nuclear fusion, four hydrogen nuclei fuse into how many helium?
One
The luminosity (L) of a star is the total energy the star radiates in
One second, 1 sec, 1 second, one sec
------ is the apparent angular motion of a star across the sky with respect to very distant stars.
Proper motion
Molecules in the interstellar medium emit radiation at what wavelengths?
Radio
Which form of electromagnetic radiation is able to easily reach Earth's surface through an atmospheric window?
Radio
Very Large Array
Radio interferometers in the desert of New Mexico
What telescope instrument is used to counter the eastward rotation of Earth?
Sidereal Drive
Visible light with wavelengths at the long-wavelength end (λ = 700 nm) appears as which color?
Red
All large astronomical telescopes built since the start of the 20th century have been ---- telescopes.
Reflecting
Diffraction, optical quality, and atmospheric conditions all contribute to the limitations of what power of a telescope?
Resolving power
The temperature of the Sun is determined by measuring the __________ of sunlight.
Spectrum
Which telescope imaged the center of the Milky Way Galaxy at a wavelength of 8 microns to reveal the distribution of the dusty interstellar medium?
Spitzer Space Telescope
The spacecraft ________ captured particles that scientists believe came from the ISM.
Stardust
Which of the natural forces bind atomic nuclei?
Strong force
Cool, relatively dark spots on the Sun's photosphere, usually appearing in group
Sunspots
Which star has the largest diameter?
Supergiant
The Balmer thermometer works because the strength of the Balmer lines depends on the _________ of the star's surface.
Temperature
The classification of stellar spectra started with the amount of hydrogen in the star's spectrum; however, now a better scheme uses the star's _____.
Temperature
the Doppler effect
The apparent change in the wavelength of a photon from a source caused by the relative motion of the source and the observer.
the Stefan-Boltzmann law
The energy output of a surface is proportional to the temperature of the surface.
Yerkes Observatory
The largest refracting telescope in the world
Arecibo Telescope
The largest single radio dish in the world
What is so unique about the mirrors of telescopes such as the Keck Observatory, Gran Telescopio Canaries, and the soon-to-be-built Giant Magellan Telescope?
The mirrors are segmented.
Why was the Davis experiment only able to detect one-third of the neutrinos originally predicted?
The neutrinos distributed evenly among three different flavors while traveling to Earth.
If a star has an apparent magnitude of +5 and an absolute magnitude of -10, what can we say about that star?
The star is farther than 10 parsecs away.
The hydrogen lines of spectral type A main-sequence stars are ____.
The strongest
How many nuclear reactions occur in a proton-proton chain?
Three
Keck Observatory
Twin telescopes atop Mauna Kea whose primary mirrors are made of 36 individual hexagonal segments
Cepheid variable stars are classified as either ____.
Type I or Type II
Vega is an A0 main-sequence star. Based on this information, which statement is true?
Vega has mass that is greater than the Sun
Which mission passed the bow shock in the Universe?
Voyager I
A spectrograph spreads out light according to ____ to form a spectrum.
Wavelength
Which star has the highest density (mass per unit volume)?
White dwarf
Coronal gas radiates energy at --- wavelengths
X-ray
What type of electromagnetic radiation does Chandra collect?
X-ray
Celestial objects with temperatures below 500 K are labeled _______ dwarfs.
Y
Magnetic fields on the Sun can be measured by observing the splitting of atomic spectral lines due to the ----effect.
Zeeman effect
Astronomers can measure the magnetic fields of sunspots using the ____, which splits spectral lines into multiple components.
Zeeman effect
Observing star clusters will give astronomers needed data for stellar evolution because all the stars in the cluster have the same ____.
age
During the first reaction of the proton-proton chain of nuclear fusion, a weak force causes one of the protons to transform into a neutron and emit ____.
a positron and a neutrino
Pre-main-sequence stars (not protostars) on the H-R diagram are _____.
above and to the right of the main sequence
Cepheid variables can be used to determine distances because their _____ can be determined from their _____________.
absolute magnitude
The apparent magnitude of a star observed from a distance of 10 pc is called
absolute visual magnitude
A spectrum that displays a smooth variation in intensity over a range of wavelengths with breaks where no energy is observed at specific wavelengths is a(n) ____ spectrum.
absorption
A star like the Sun emits a(n) ____ spectrum.
absorption
A neutral atom must have ____.
an equal number of protons and electrons
Light-gathering power is proportional to the ---- of a telescope's primary lens or mirror.
area
An object that acts as a blackbody emits photons because ____.
atoms in the object collide, changing the motion of charged particles
The Answer is the amount of energy needed to pull an electron completely away from the nucleus.
binding energy
An object that is a perfect absorber and emitter of radiation is called a(n) -----
blackbody
A open star cluster will have a(n) _____ turn-off point than an older star cluster.
blue
Interstellar dust scatters ------ light more than _____________light.
blue; red
How do large-mass stars in the upper region of the main sequence produce energy?
by fusing hydrogen using the CNO cycle (carbon-nitrogen-oxygen)
How do low-mass stars in the lower region of the main sequence produce their energy?
by fusing hydrogen using the proton-proton chain
How did astronomers discover the relationship between spectral type and mass for main-sequence stars?
by measuring the masses and spectral types of main-sequence stars in binary systems
The emission lines from O III are called ____ because they are not visible laboratories on Earth due to the much greater pressure of the gas on Earth.
forbidden lines
Stars, like our Sun, generate their energy by way of nuclear
fusion
Eighty percent of the stars on the H-R diagram are on the main sequence, and that is because the star is in hydrostatic equilibrium due to the _____.
fusion of hydrogen
What is released from the proton-proton chain and is immediately absorbed by the surrounding gas, thereby heating it?
gamma rays
Any star that is more luminous than the Sun, but has the same temperature as the Sun, is a(n) ____.
giant
Large molecular clouds will form into protostars because of ____.
gravitational contraction
The force responsible for the collapse of an interstellar cloud is
gravity
The solar wind extends to the ----, marking an outer boundary of the Solar System.
heliopause
What methodology do astronomers use to map the inside of the Sun?
helioseismology
During the main-sequence lifetime of a star of any mass, the core of the star will be composed mainly of ____
helium
The two elements a one-solar-mass star uses over the course of its entire evolution are ________ and _____________.
helium
As a one-solar-mass star evolves off the main sequence, it will probably undergo a _____.
helium flash
H II emission nebula regions are found around
high temperature stars
According to Wien's Law, a(n) ____.
hotter object will emit more short-wavelength (bluer) radiation
A zero-age main-sequence star burns ----- in its core through fusion reactions.
hydrogen
The most abundant gas making up the Sun's composition is
hydrogen
What is the most abundant element in the interstellar medium?
hydrogen
Where are the Cepheid and RR Lyrae variable stars located on the H-R diagram?
in the instability strip
When a large gas cloud starts to collapse in a free-fall due to gravity, the rotation rate will
increase
When a large gas cloud starts to collapse in a free-fall due to gravity, the temperature of the gas will
increase
A(n) ---- is an atom that has gained or lost one or more electrons.
ion
Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 93 hours. the star becomes dimmer for about 2 hours. The most likely explanation for this is that the star ________.
is a member of an eclipsing binary star system
Granulation is evidence that energy in the photosphere ____.
is flowing upward
Subatomic particles released from the proton-proton chain of nuclear fusion
neutrinos
What is a major selecting factor for astronomers looking to place a telescope atop a mountain?
non-turbulent airflow
What does a refracting telescope use to gather and focus light?
lens
Astronomers no longer build large observatories in populated areas in order to avoid ----
light pollution
The ----- of the solar disk is dimmer than the center, which is caused by the absorption of light in the photosphere.
limb
Which atom is not a part of the CNO cycle?
lithium
The --- is a high temperature, low density region in the interstellar medium around the Sun.
local bubble
The most common stars are Answer stars.
lower-main-sequence
The vertical axis (y-axis) of the Hertzsprung-Russell Diagram is labeled with
luminosity
It is a common misconception that the purpose of an astronomical telescope is to ----- images.
magnify
On the H-R diagram, 90 percent of all stars are ----
main-sequence stars
On the H-R diagram, 90 percent of all stars are ____.
main-sequence stars
The coolest temperature
molecular clouds
Hydrogen lines are weak in the spectra of hot O-type stars because ____.
most of the hydrogen is ionized to high energy levels
The interstellar medium is composed of mainly _____.
mostly gas and some dust
Hydrostatic equilibrium in a newborn star is regulated by a very unique thermostat called the ---- thermostat.
pressure-temperature
The nuclear reactions in a star's core burn steadily so long as the relationship between ----- and_____________ is stable.
pressure; temperature
Two devices that spread white light into a spectrum are ----- and __________.
prisms/gratings
Arches of magnetic field visible in the chromosphere and corona
prominences
Stars with masses equal to or less than 1.1 solar masses use the ---- to convert H into He for their energy source.
proton-proton chain
T Tauri stars are understood to be relatively low-mass __________.
protostars
Brown dwarfs are ____.
protostars that could not ignite the fusion of hydrogen at their core
The type of radiation that is emitted when the electron in a hydrogen atom experiences a spin flip is a(n)
radio wave
The Hertzsprung-Russell diagram can be labeled many different ways. Which coordinates CANNOT be used on an H-R diagram?
radius vs temperatures
An object moving away from the observer will exhibit a(n) ------ shift due to the Doppler effect.
red
The pink color of the chromosphere is produced by the combined light of three emission lines of hydrogen: ____.
red, blue, and violet
Which type of nebulae is produced when short-wavelength scatters from the dust and displays a blue hue?
reflection nebulae
One way to measure and compare the strength of the radio signal at various places in the sky is to produce a(n) --- in which each color marks areas of similar radio intensity.
representational-color image
Which power of a telescope reveals fine details within an image?
resolving power
The magnetic polarities of sunspots --- at the end of an 11-year cycle.
reverse
A breeze of low-density ionized gas streaming away from the Sun
solar wind
Gas flows away from the Sun in the ---, which can be considered an extension of the corona.
solar wind
Columns of gas in a nebula that point back toward a young, massive star are called
star-formation pillars
How do astronomers determine the distance to stars that are farther than 100 parsecs away?
subtracting absolute from apparent magnitudes
Cool, relatively dark spots on the Sun's photosphere, usually appearing in group
sunspots
The number of ---- visible on the Sun varies in a cycle with a period of 11 years.
sunspots
The horizontal axis (x-axis) of the Hertzsprung-Russell diagram is labeled with
temperature
Using Wien's law, you can measure the ____ of a distant object without having to travel to it.
temperature
A star's absolute visual magnitude depends on its -------- and _________
temperature, diameter
Blackbody radiation is caused by an object's ____.
thermal agitation
The luminosity of a star is the ____.
total energy radiated by the star in one second
Helium fusion is sometimes referred to as the ---- because three helium nuclei are needed to make a carbon nucleus, and because the helium nucleus is called an alpha particle.
triple alpha process
Large doses of Answer light can cause sunburn and skin cancers.
ultraviolet
Astronomers often record solar images in the ____ part of the electromagnetic spectrum because the gaseous layers high in the Sun's atmosphere are very hot and emit most of their light at short wavelengths.
ultraviolet
Astronomers refer to the dark center of a sunspot as a(n) ____
umbra
The least common stars are ---- stars.
upper-main-sequence
A(n) ---- star is any star that changes its brightness significantly and repeatedly.
variable
Optical telescopes are intended for the study of ---- light.
visible
The Balmer series of hydrogen absorption lines in stars is located in what part of the electromagnetic spectrum?
visible region
One type of binary star is --- binary.
visual
The interstellar reddening does not shift the ---- of spectral lines, as does the Doppler effect.
wavelength
The type of elements present in a gas can be determined by studying the ____.
wavelengths of photons absorbed or emitted from the gas
Hydrostatic equilibrium is the balance between ----- and radiation _____________.
weight; pressure