Test 6
Our sun will become a white dwarf with a mass of about half its original mass and a size of about
1/100 its original diameter
The surface temperature of a newly formed white dwarf can be about
100,000 K
According to Phil, the method of measuring parallax angle allows us to determine the postions of stars out to about
1000 light years
The precise value of the Astronomical Unit is
149,597,870.7 km
Which of the following is closest to the core temperature of the sun?
15,000,000 Kelvin
CH.12 H I Clouds
21-cm wavelength spectral lines form the majority of spiral arms neutral atomic hydrogen
A magnetar has incredibly powerful magnetic fields. as much as a quadrillion times the magnetic field strength of our sun. Occasionally these will have star quakes, like earthquakes that can release energy in a flare a trillion times stronger than a typical solar flare. The amount of energy released in one of these events is the same as the sun releases in
250,000 years
If you could magnify an atom to be 100 meters across (the size of a football field), then the nucleus would be about the size of
a marble
Because they are incredibly dense objects, 1 cubic centimeter of a white dwarf mass (about the size of a six-sided die) is about
a million grams (one metric ton)
A star with a mass between 8 and 20 solar masses will undergo nuclear fusion in the core all the way up to iron (Fe) before exploding in a supernova explosion. If the remaining core mass is more than 1.4 solar masses and less than 2.8 solar masses then this incredibly dense object will form
a neutron star
CH.4 Larger lenses in telescopes offer better resolution. Resolution is defined as the closest angular distance two objects can be apart from one another before their light merges together and they look like just one object. Therefore, smaller resolutions are better (closer objects can be separated). The resolution of the human eye is 1 arcminute, or 1/60th of a degree. If the light of two street lamps in the distance is separated by 0.5 arcminute, what will you see with your eyes?
a single light, with the combined brightness of each street lamp
A neutron star packs a mass of more than our sun into the size of
a small city
A really low mass red dwarf can live as long as
a trillion years
A star with 8 Solar Masses will fuse hydrogen for
about 100 Million Years
Planetary nebula typically glow for
about 1000 years
The density of neutron stars matter, neutronium, is about 400 million metric tons per cubic inch. Phil tells us this is like squishing _________________ into one single six-sided die.
all of the automobiles in North America
When carbon fuses, it will produce all of the following EXCEPT
aluminum (Al)
CH.11 What is the definition of a standard candle?
an object whose luminosity is known without needing to know its distance
Sunspots
are cooler than their surroundings
A star with a mass of about 8 solar masses will
be able to fuse carbon in the core
Hotter stars tend to put out more __________ light than __________ light.
blue, red
CH.11 Eclipsing
brightness changes repeatedly over time binary orbit must be seen nearly edge-on
CH.12 Which of the following places the objects in increasing order of radius?
brown dwarf, Sun, protostar, Solar System, GMC
White Dwarfs emit ultraviolet and even x-ray radiation,
but have low magnitudes because they do not produce a lot of light
When comparing photons of light, the photons with a higher frequency
carry more energy
All of the following are layers within the sun EXCEPT
conduction zone
CH.10 Choose the correct order of the Sun's layers from the center outward
core, radiative zone, convective zone, photosphere, chromosphere, corona
In order to determine (indirectly measure) the distances from the other planets to the sun, first required us to know the
distance between the Earth and the Sun
This force is what prevents a white dwarf from collapsing any further under the influence of gravity.
electron degeneracy pressure
Most of the elements on the periodic table are produced by the expanding shockwave from a type II supernova. This process is known as
explosive (supernova) nucleosynthesis
The number of waves produced per second is called the ___________________ and is measured in units called the Hertz (Hz)
frequency
A star spends most of its life on the Main Sequence
fusing hydrogen into helium in the core
CH.4 Based on the above graph, which of these types of light from astronomical sources are not observable from the ground?
gamma ray ultraviolet at 100nm X-ray Infrared at 100 micrometer (10^-4m)
Our sun is "powered" by the fusion of hydrogen atoms into
helium atoms
The temperature of an object affects the color of light that is emitted by that object. The hotter the object is, the
higher the frequency of the light it will emit
The brilliant astronomer Cecelia Payne Gaposhkin found that stars are mostly made of
hydrogen and helium
The two most abundant elements in the sun are
hydrogen and helium.
Human beings emit light in which of the following color ranges?
infrared
A parsec is a distance used by astronomers to describe distance. Theoretically a star which is one parsec away would have a parallax angle of one arc second. A parsec is also
3.26 light years
Lower mass stars cannot ever achieve a high enough temperature and pressure to ignite Carbon fusion. What is the temperature needed to fuse carbon in a star core?
500,000,000K
Every second, the sun is converting 700 million tons of hydrogen gas into
695 million tons of helium
A "low mass star" has a mass less than **(1 solar mass = mass of our Sun)**
8 solar masses
CH.4The presence of dark lines at specific wavelengths in an otherwise continuous spectrum can be explained most easily by which of the following?
A cool gas between observer and source is absorbing light at the wavelengths corresponding to the missing photons.
CH.4 The light from objects that glow because they are warm (like people, planets, and stars) is distributed by wavelength in a particular way, called a blackbody spectrum. Using this interactive figure (requries Flash), experiment with how a blackbody spectrum changes with an object's surface temperature. Note that flux increases as an object gets brighter, and that the scale of the graph may be changing to indicate this, even if the curve doesn't appear to change. See the hint for tips on using the figure. Based on your observations, which one of the following is correct?
A hotter star will be brighter and bluer than a cooler star
CH.4 Which of the following can astronomers determine from the spectrum of an object?
Composition Speed toward or away from an observer Temperature
CH.10 Say you are trying to study the nuclear reactions in the Sun's core by observing photons coming off its surface. How will this random walk affect your results?
Each photon may be a different color than it was when it was created in the nuclear reactions Each photon would have been created a long time ago: it would be impossible to use them to study nuclear reactions as they are happening right now in the Sun's interior.
Which one of the following types of binaries would best be studied by watching the light curve of the system (the total light from the system).
Eclipsing binary
CH.10 The solar neutrino problem is accurately described in which of the following statements?
Experimental results found fewer neutrinos than models of nuclear fusion suggested would exist
CH.10 The mass of hydrogen is 1.6726 x 10-27 kg, and the mass of helium is 6.6465 x 10-27 kg. Given this, which of the following nuclear reactions would result in a decrease of total mass, and thus a release of energy, while keeping the same number of particles involved?
Four hydrogen nuclei combine into one helium nucleus
The stellar classification system has each letter broken down into 10 different classifications. The precise classification of our sun is
G2
CH.10 In the Sun, four hydrogen nuclei do not fuse directly into a helium nucleus. The overall reaction involves several steps, and other particles are also produced in the process. Study this animation of the reactions that occur in the Sun, and then select all the particles/elements that are created by the reaction.
Gamma ray Neutrino Helium Positron
CH.10 Which of these actions would improve our chances of seeing this reaction and thus detecting the presence of a solar neutrino?
Go to a place where there are a lot of solar neutrinos Build a detector made of a large amount of chlorine
Stars were initially classified in terms of the strength of their
Hydrogen lines
CH.12 H II
Hα emission lines surround young massive stars created by photoionization
CH.4 Study the figure, which shows how someone on Earth can view Jupiter's moon's eclipses when Earth is closer to or farther from Jupiter, and determine which of the following are correct.
If light has infinite speed, an eclipse would be seen to happen at the same time regardless of how far away Earth is from Jupiter If light has finite speed, it would take longer for it to travel from Jupiter to Earth when Earth is farther from Jupiter
CH.11 Wien's law tells us that
In blackbodies, temperature and peak radiation wavelength (color) are related
CH.12 A star has a mass of 0.7 MSun. Which statement about it is true?
It is using the P-P process of nuclear fusion
CH.4 A spectrum of a distant object reveals a sequence of known absorption lines that are all shifted to shorter wavelengths. What can be concluded about the object?
It must be moving towards us
When the hydrogen in our sun's core runs out, it will begin to collapse and heat up. What will happen in the shell around the core as a result?
It will get hot enough to fuse hydrogen
CH.4 If the integration time is long enough to collect the light from this entire animation, what effect would seeing have on the image of the object?
It would blur the light from the object, effectively increasing the angular resolution of the telescope.
CH.11 How would parallax measurements of stars made from Jupiter differ from those made from Earth?
Parallax for a given star would be greater
For a short while, astronomers were unsure of the source of regular radio pulses from space and gave them the name LGMs. What does LGM stand for?
Little Green Men
CH.4 The resolution of radio telescopes suffers greatly from the large wavelengths of the light they are observing. What can be done to a radio telescope to improve its angular resolution?
Make its dish bigger.
CH.12 Which phase of the ISM is most opaque to visible light?
Molecular cloud
The brightness of a star follows in inverse square law in relation to the distance from the star, very similar to the formula for
Newton's Universal Law of Gravitation
The mnemonic, Oh Be A Fine Guy/Girl Kiss Me gives the correct order of stellar classification as O,B,A,F,G,K,M. Which star is the hottest star in this classifaction system?
O
Mizar and Alcor (also called the horse and rider) have been known since ancient times. Which of the following statements is NOT true about them.
One of the stars will be exploding (supernova) soon.
When multiple star systems are first formed, they may not be fully stable, causing one or more stars to eventually be ejected. Only the stable arrangements survive for a long period of time. Which of the following stars does Phil say "might have" had a companion but we will never really know
Our sun
CH.4 Besides adding adaptive optics to a telescope, what else can be done to reduce the effects of seeing?
Put the telescope at a higher altitude (the height above sea level).
CH.4 Rank these types of light in order of increasing energy.
Radio Infrered Orange Green Ultraviolet Gamma ray
CH.11 what other property can we use to further classify stars?
Radius
CH.11 Study how the various properties of a main-sequence star are related to one another in the figure. Then select the properties in the list that would increase if the mass of a main-sequence star is increased.
Radius Temperature Luminosity
CH.4 Star I is observed to be brighter than Star II. Which of the following is/are true?
Star II may be bigger than Star I. If they are the same size and distance from the observer, Star I is hotter If their luminosity is the same, Star I must be closer.
Eratosthenes was able to determine the size of the Earth by knowing that at noon on the Summer Solstice, that light hit the bottom of the well in the city of
Syene
Herzsprung and Russell created a chart which compared the Luminosity of a star to its ______________ and discovered that there was a pattern.
Temperature
If a pair of binary stars are so close together that we cannot see them as separate even with the largest telescope, then we can use spectroscopy to determine that two or more stars are present. Spectroscopic binaries rely on which of the following principles to distinguish the two stars.
The Doppler effect. One of the stars will be moving away and its light red-shifted, while one will be moving toward us and its light will be blue-shifted.
When the sun is a red giant, what will happen to the Earth?
The Earth may move out to a larger radius because the sun will exert a weaker force of gravity, but will become a molten ball much like when it was formed.
If we study the light curve, we can see that the dips in brightness are not always the same "depth". What is the cause for a deeper dip?
The cooler star passes in front of the hotter star
CH.12 How do molecular clouds provide protection from ultraviolet photons that can dissociate molecules?
The dense gas and dust in their interiors shield molecules from interstellar ultraviolet radiation.
CH.4 The nature of light is rather unique: It acts like both a particle (called a photon) and a wave that can propagate energy even through empty space. Navigate to the interactive figure in Section 2 of this animation, as shown below, to see how changing the amplitude, wavelength, speed, and frequency of a light wave affects its properties.Choose all of the effects that would automatically happen if the wavelength of light were increased.
The energy of the light would decrease The frequency of the light would decrease
CH.4 When a telescope takes an image of an astronomical object, a shutter above the detector is opened to allow light to enter at the start of an exposure, and it is left open for a specified integration time. After the exposure is complete, the shutter closes and all the light that was gathered during that time is combined into a single image. The integration time of the human eye is about 0.1 second. If you had a telescope with the same-sized lens (and same focal length) as the human eye, what would be the benefit of taking an exposure of a steady light source with an integration time of 10 seconds?
The light source would appear brighter in the image
CH.4 Why do stars twinkle?
The motion of the earth
CH.4 Compare the spectra of blackbodies with different temperatures. Which of the following is true?
The peak of the emission in the spectrum of the cooler object is at a longer wavelength.
CH.10 Which statement about energy from nuclear fusion is correct?
The proportion of hydrogen converted to energy in nuclear fusion is 0.7 percent
CH.4 If there were two telescopes with the same diameter, but one is a visible light telescope and the other a radio telescope, how would the resolution of the images from each telescope compare? The wavelength of visible light is several hundred nanometers (1 nanometer = 10-9 meters), and radio can be several centimeters (1 cm = 10-2 meters) or several meters.
The radio telescope would have much worse angular resolution.
CH.4 Space telescopes that exist in orbit above most of Earth's atmosphere are expensive, so they must therefore be supported with a very compelling motivation. If you were trying to justify funding for a space telescope in orbit around the Earth, which of the following would be the best argument to use?
The telescope could observe wavelengths of light that are not visible from the ground.
CH.10 Which statement about the inputs to and outputs from nuclear fusion in the Sun is true?
The total mass of outputs is less than the corresponding inputs
CH.11 Choose the statement about variable stars that is not true.
Their luminosity may be continually increasing
CH.10 How will the composition of the Sun change over the next billion years?
There will be less hydrogen and more helium.
CH.4 The specific wavelength of a set of spectral lines depends not only the type of material that is creating them but also on the relative speed of that material to the observer. This is caused by the Doppler effect, which is demonstrated in this interactive figure (requires Flash). For tips on using the interactive figure, click on the hint. Experiment with this figure and use your observations to select all of the correct answers below. Note that blueshifted spectral lines appear shorter in wavelength than they otherwise would, and redshifted wavelengths appear longer.
There will be no change in the spectral lines of an object that is moving transversely from an observer An object moving toward an observer will have its spectral lines blueshifted
CH.4 which of the following are implications of the finite speed of light?
There would be a noticeable delay in communications at the speed of light between Earth and astronauts on the Moon. If the light of the Sun were suddenly extinguished, we wouldn't notice it from Earth for over 8 minutes When we gaze at the Andromeda Galaxy, we are looking back in time to the way it used to appear millions of years ago
Optical Double Stars are two or more stars that appear next to each other in the sky. Which of the following statements is true about them?
They could be close together in space, but more carfeul observation is needed to determine if they are.
Which of the following statements is true about high mass stars
They have a higher mass, but fuse at much higher rate than lower mass stars so they have shorter lives.
CH.10 Which of the following statements about sunspots is true?
They occur in predictable cycles
CH.11 Two neighboring stars are seen with significant differences in composition. What is not likely to be true of these stars?
They were born together
CH.10 As neutrinos travel through the Sun's dense interior, how will their path change due to the presence of the gravitational, electromagnetic, and nuclear strong forces around them?
They will not change at all
CH.11 Astrometric
Two separate stars are seen in an image binary orbit may be viewed nearly face-on
The largest known star is 2 Billion km in diameter, and is known as a hypergiant. What is the name of the largest known star?
VY Canis Majoris
In the 1960s, astronomers were able to bounce radar pulses off of ______________ to establish a precise value for the Astronomical Unit
Venus
CH.12 What kinds of photons are absorbed by typical dust grains?
Visible
CH.12 Coronal Gas
X-ray emission lowest density gas temperature about 1 million Kelvin
The brightest star in the night sky, Sirius, has a very faint companion star that can be seen with a telescope. Which of the following telescopes can see the binary actually appear as brighter than Sirius?
X-ray telescope
CH.10 Can this new information solve the neutrino problem and confirm that our models of nuclear reactions in the Sun are correct?
Yes. The existence of three different types of neutrinos would account for the missing neutrinos observed over the number that were predicted
CH.12 Which of the following is/are not a source of turbulence in the ISM?
infrared radiation from young stars
Instead of releasing energy, the fusion of _________________ absorbs energy and causes the core to collapse completely.
iron (Fe)
The reason a low mass star can live so long is that
it fuses hydrogen fuel slowly and the region outside the core is convective so the fuel can make it back to the core where it will eventually be used
What happens when a white dwarf steals enough mass from its companion to exceed 1.4 solar masses?
it fuses nearly all of its carbon at once and becomes a supernova.
CH.10 If a star like the Sun did not have the ability to create energy by nuclear fusion
it would have exhausted its energy long ago
CH.11 A star's position on the main sequence does not tell us
its chemical composition
With higher pressure, the nuclear fusion process occurs more frequently, releasing more energy. The lower the mass of a star, the
longer its life will be
CH.11 Spectroscopic
looks like one constant-brightness star relies on the Doppler effect
A "high mass" star is a star which begins with
more than 8 Solar Masses
CH.4 When you turn on a lightbulb in a room, the entire room appears to flood with light at the same time. Your eyes cannot perceive light originating at the bulb and then moving outward from it. This either means that light has infinite speed (appears everywhere instantaneously), or it moves so fast that it is difficult to tell the difference. How might you improve your chances of detecting the motion of light if it moves at finite speed?
move farther away from the light source
When a neutron star is formed, this force is strong enough to oppose the incredibly strong force of gravity trying to collapse it further.
neutron degeneracy pressure
If a star has less than 20 Solar Masses when it collapses, then it will form a compact object about 20 km in diameter called a __________________ with part of the matter, and the rest of the matter will explode outward in a Type II supernova.
neutron star
Inside the core of a star, 4 protons (Hydrogen nuclei) join together to make
one helium nucleus
What is the number of white dwarfs that have been found in our galaxy?
over 10,000
Much of the red color in planetary nebulae comes from hydrogen. The green color in nebulae was originally thought to come from an unknown element, named Nebullium, but in the end it turns out it comes from ordinary
oxygen (O)
As the Earth goes around the sun in orbit, we can measure shifts in the position of nearby stars relative to their background stars. This is called
parallax
When the sun begins fusing helium in its core, the process is highly unstable and Phil says the sun will go through a series of
paroxysms
Most of the visible light we see coming from the sun originates from the
photosphere
The gases expelled by a low mass star in its red giant phase don't get very far (about 1 light year or so) by the time the star collapses to form a white dwarf. When the radiation excites the gases, they glow and we call them a
planetary nebula
The sun is more than 100 times the size of the Earth, over 300,000 times the mass of the Earth and able to fit more than 1 million Earths inside its volume. The Sun is made of
plasma
The sun's magnetic field is evident in the looped shapes of
prominences.
As a graduate student, Jocelyn Bell Burnell (and her advisor Antony Hewish who ultimately received a Nobel Prize for this work in 1974) is credited with the discovery of the first rapidly rotating neutron star, which she detected with a radio telescope array. The rapid rotation, together with the powerful magnetic field produces twin beams of energy whcih radiate away from the object. We call this a
pulsar
CH.12 Promote Collapse
radiating energy away gravity
CH.4 Arrange the following regions of the electromagnetic spectrum from lowest to highest frequency.
radio infrared optical ultraviolet x-ray gamma ray
After the main life of the sun, where it fuses hydrogen in the core, it will become a
red gient
A much larger, but cooler star than our sun would be a ____________________ star.
red supergiant
When a high mass star finishes fusing the hydrogen in the core and begins fusing helium in the core it will become a
red supergiant
Conservation of momentum is a law of physics that says that if a star is rotating before it collapses, then when it collapses it will
rotate faster after the collapse
How can we tell that two stars are nearly identical?
spectroscopy
Einstein's formula E = mc2 relates how the matter in the sun is converted into pure energy to support the sun. The letter c is the
speed of light
Two stars which are the same intrinsic brightness, but star A is twice as far away as star B. How do their brightnesses compare to our eyes?
star A is 1/4 as bright as star B
One possible explanation for the weird, beautiful and fantastic shapes of planetary nebulae is that they
swallowed some their planets which then stirred the interiors of the stars
CH.4 A typical amateur telescope is a 10-inch reflector (where "10-inch" refers to the diameter of the telescope's mirror). How does the light-gathering power of the Hooker 100-inch reflector on Mount Wilson compare with that of the amateur telescope?
t is 100× greater
CH.4 Observations of excited gas in the lab show that every element, molecule, and ion has its own unique set of possible electron energy levels, as shown in the emission spectra below.Based on this fact, what can we find from the wavelengths of absorption lines seen in the spectrum of a star?
the composition of any gas between the light-emitting "surface" of the star and the observer
As the high mass star fuses one fuel, the "ash" of the fusion reaction will accumulate in the core, and fusion in the core will stop. What happens to the core at that point?
the core shrinks and heats up until the ash is finally able to fuse
CH.11 What does the main sequence show?
the distribution of core hydrogen-fusing stars by mass
"Ionized" hydrogen gas means that
the electrons have been ripped away from their protons
CH.4 The formation of absorption lines in a spectrum emitted by a blackbody indicates which of the following?
the interaction of matter and light the specific elements of the atoms present in an intervening cloud the existence of an intervening cloud of material cooler than the emitting source
CH.10 What property of neutrinos allows them to mostly pass right through matter?
their low probability of interaction with other particles
Of the following types of light, which one travels the fastest: x-ray, visible, microwave, radio?
they all travel with the same speed
What happens when protons and electrons are pushed together under extreme pressures?
they merge and form a neutral neutron
CH.12 Halt Collapse
turbulence magnetic fields gas (thermal) pressure
CH.12 Which of the following is not a characteristic of molecular clouds?
uniform structure throughout
The distance from a wave crest to the next wave crest is called the
wavelength
According to Phil, the only way we know how to get accurate stellar masses is
when they are in a binary system
CH.12 Molecular
where stars form densest and coldest phase molecular emission and absorption lines
A star with a spectrum having a peak in the green part of the visible spectrum would appear ___________ to our eye.
white
The most bizarre binary system that Phil knows about is 4U 1820-30 which orbit each other with a period of only 685 seconds (11.4 minutes) and is composed of a neutron star and a
white dwarf
The sun will never be able to fuse carbon in the core, and the force of gravity will compress it into a small ball, only the size of the Earth called a
white dwarf
These are small but hot stellar remnants found in the lower left of the H-R diagram.
white dwarf
According to Phil, when compared to lower mass stars, higher mass stars go out
with a bang