Astronomy Chapter 14
Any spectrum can be displayed either in photographic form as shown to the left or as a graph. Which of the following graphs could represent a portion of the Sun's visible light spectrum?
(looks like a hill w/ cuts)
Approximately what is the parallax angle of a star that is 20 light-years away
0.16 arcsecond
Nuclear fusion of hydrogen doesn't occur for Temperatures less than about 10 Million K roughly what is the radius of the core?
0.2 R sun
Roughly what is the radius at which the temperature of the sun is about 2 million K?
0.7 Rsun
Which of the following must be true if we are to infer (calculate) a star's luminosity directly from the inverse square law for light?
1)We have measured the star's apparent brightness 2)We have measured the star's distance 3)No interstellar gas or dust absorbs or scatters light between us and the star.
If the sun had a luminosity of 10 lsun and a mass of 10msun its life span would be ?
10 billion years. Sun would have 10x as much fuel, but the rate of hydrogen burning would also be 10x higher, so it would run out of fuel in the same amount of time.
Some stars have a luminosity equal to 500 L sun and a mass of 5m sun. What is their lifespan?
100 million years Since massive stars are so luminous, they have relatively short life spans (50 billion divided by 500=100 million)
Every time four protons fuse into one Helium nucleus, the sun loses about 4.76 x 10^-29 kg of mass. About how much energy does this mass loss release?
10^-12 joules
For what temperature is the average speed of the protons roughly 5 x 10^5 m/s?
10^7 K. If the temperature is about 10 million kelvin, the average speed will be high enough for fusion of hydrogen to occur.
What is the temperature near the center of the Sun?
15 million Kelvin
Suppose that a star had a parallax angle of exactly 1 arcsecond. Approximately how far away would it be, in light-years?
3.3 light-years
Roughly how close do two protons get to each other if their initial speed is 200,000m/s?
3x10^-12 meters
The force when the protons are 1.0nm apart is __ than when they are 2.0 nm apart.
4x as high. Just like gravity, the magnitude of the electromagnetic repulsion is inversely proportional to the distance sqared. However, unlike gravity, the force depends on the charges of the particles, not their masses.
Roughly how fast must the protons initially be moving so that they get within 5 x 10^-13
5 x 10^5 m/s
The diagrams below show the same set of energy levels as in Parts A and B, but with a different set of electron transitions (notice that the arrows are now different). Assuming that these electron transitions were caused by the absorption of a photon, rank the atoms based on the energy of the absorbed photon, from highest to lowest.
5.30, 2o'clock(longer than 1 o'clock), 6, 1 o'clock
The mass that is lost is converted into other forms of energy, such as heat, and light. Ultimately this energy is radiated by the Sun. Every second, about 4x10^26 joules of energy is radiated away. About how much mass must the Sun be loosing every second?
5x10^9 kg
Jupiter's temp is too low for fusion. To have a higher core temp it would need much greater pressure on the core, and to have such pressure Jupiter would need to have?
A greater mass
Five stars are shown on the following H-R diagrams. Rank the stars based on their surface temperature from highest to lowest. If two (or more) stars have the same surface temperature, drag one star on top of the other(s)
All of them are stacked on top of each other.
Five stars are shown on the following H-R diagrams. Rank the stars based on their luminosity from highest to lowest; notice that these are the same five stars shown in Part D. If two (or more) stars have the same surface temperature, drag one star on top of the other(s).
All stacked on top of each other.
Which of the following changes would cause the fusion rate in the Sun's core to increase? Check all that apply.
An increase in the core temperature A decrease in the core radius
Suppose we want to know what the Sun is made of. What should we do?
Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory
In which region is the pressure of the Sun the highest?
Core
Rank the following layers of the Sun based on the pressure within them, from highest to lowest.
Core, radiation zone, convection zone, photosphere
Rank the following layers of the Sun based on their temperature, from highest to lowest.
Core, radiation zone, convection zone, photosphere
Which of the following is the correct list of regions of the Sun in descending order of temperature?
Core, radiation zone, convection zone, photosphere
We can see the Sun's _________ most easily during total solar eclipses
Corona
If the maximum distance between two protons such that they stick together (fusion) were considerably higher than the actual required distances, then fusion in the sun:
Could occur at much lower temperatures
When two protons fuse together in the first step of the proton-proton chain, what is produced?
Deuterium, containing one proton and one neutron.
Five stars are shown on the following H-R diagrams. Rank the stars based on their surface temperature from highest to lowest. If two (or more) stars have the same surface temperature, drag one star on top of the other(s).
Dots closest to the left at the left (highest)....dots closest to the right(lowest)
What is the cause of stellar parallax
Earth's orbit around the sun
Each diagram below shows a pair of spectra with a set of spectral lines. The top spectrum always shows the lines as they appear in a spectrum created in a laboratory on Earth ("Lab") and the bottom spectrum shows the same set of lines from a distant star. The left (blue/violet) end of each spectrum corresponds to shorter wavelengths and the right (red) end to longer wavelengths. Rank the five stars based on the Doppler shifts of their spectra, from largest blueshift, through no shift, to largest redshift
Follow the last lines on the right.
The following figure shows how four identical stars appear in the night sky seen from Earth. The shading is used to indicate how bright (white) or dim (dark gray) the star would appear in the sky from Earth. Rank the stars based on their distance from Earth, from farthest to closest.
For stars of the same luminosity, apparent brightness decreases with distance. Dimmest to brightest.
How does the force depend on the distance?
Force increases as the distance decreases. Like gravity(except gravity is attractive and this force is repulsive) , the force gets weaker w/ increasing distance
Listed following are the different layers of the Sun. Rank these layers based on their distance from the Sun's center, from greatest to least
From greatest to least-outer to inner- Corona, Chromosphere, photosphere, convection zone, radiation zone, core
Rank the layers of the Sun based on their density, from highest to lowest.
From highest to lowest- Core, radiation zone, convection zone, photosphere, chromosphere, corona
Five stars are shown on the following H-R diagrams. Rank the stars based on their surface temperature from highest to lowest. If two (or more) stars have the same surface temperature, drag one star on top of the other(s).
HIGHEST TO LOWEST: dot at the highest to the left/dot lowest to the left, dot in the middle, highest dot to the right/lowest dot to the right
Five stars are shown on the following H-R diagrams; notice that these are the same five stars shown in Part F. Rank the stars based on their luminosity from highest to lowest. If two (or more) stars have the same luminosity, drag one star on top of the other(s).
HIGHEST TO LOWEST: two highest dots, middle dot, two lowest dots
The core of a star more massive than the Sun that is burning hydrogen in its core should have a ____ temperature and a ___ pressure
Higher temperature, higher pressure
Five stars are shown on the following H-R diagrams; notice that these are the same five stars shown in Part B. Ranks the stars based on their luminosity form the highest lowest. If two (or more) stars have the same luminosity, drag one star on top of the other(s).
Highest to Lowest: Highest dot to the lowest dot.
Which of the following is a valid way of demonstrating parallax for yourself
Hold of your hand in front of your face, and alternately close your left and right hands
Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate? Check all that apply.
If the fusion rate initially increases, then the core expands. If the fusion rate initially decreases, then the core contracts
The diagrams below each show the motion of a distant star relative to Earth (not to scale). The red arrows indicate the speed and direction of the star's motion: Longer arrows mean faster speed. Rank the stars based on the Doppler shift that we would detect on Earth, from largest blueshift, through no shift, to largest redshift.
Largest Blueshift - Longer red arrow straight toward Earth - Shorter red arrow straight toward Earth - Red arrow pointed 90 degrees from Earth - Shorter red arrow pointed away from Earth - Longer red arrow pointed away from Earth Largest Redshift
. Rank these stages based on the central temperature, from highest to lowest.
Main-sequence star, Protostar w/ jets, Contracting cloud trapping infrared light, Molecular-cloud fragment
The following figures show four stages that occur during the formation of a one-solar-mass star. Rank these stages based on their rotation rate, from fastest to slowest.
Main-sequence star, Protostar w/ jets, Contracting cloud trapping infrared light, Molecular-cloud fragment
What is the most important reason that the sun is a star and Jupiter is not?
Mass
A solar model is used to calculate the expected temperature and density at all depths within the Sun. These results are then used to calculate the expected fusion rate within the Sun. We have confidence that the model is correct because it agrees with the observed characteristics of the Sun. Which of the following observations can be used to check that we really do know the Sun's internal fusion rate?
Measurements of the Sun's total energy output into space, Observations of neutrinos coming from the Sun
he following figures show four stages that occur during the formation of a one-solar-mass star. Rank these stages based on the order in which they occur, from first to last.
Molecular-cloud fragment, Contracting cloud trapping infrared light, Protostar w/ jets, Main-sequence star
the temperature in the inner region of Jupiter is roughly 30,000K(3x10^4 K). Is there a significant fraction of the protons having a speed of high enough for fusion to occur?
NO
Can an atmosphere in which the temperature and the density are increasing with elevation be in gravitational equilibrium?
No
To understand the interplay of observations and models you must first be able to distinguish between things that we observe and things that we infer from models. Consider the following statements about the Sun. Classify each statement as an observation or as an inference based on the current, accepted model for the Sun.
OBSERVATION: The photosphere is made mostly of hydrogen and helium,The photosphere emits mostly visible light,The corona is hotter than the photosphere, The Sun emits neutrinos. INFERENCES: The Sun generates energy by fusing hydrogen into helium,The core temperature is 10 million k, The convection zone is cooler than the radiation zone,The composition of the photosphere is the same as that the gas cloud that have birth to our solar system.
Consider a relatively nearby, single star, that is, a star that is not a member of a binary system and has no known orbiting planets. Listed below are a few properties of this star. Classify each property as either something that we can observe or measure directly (with the aid of a telescope and instruments such as cameras or spectrographs) or something that we must infer indirectly (and hence is correct only if all of our assumptions are correct).
Observe Directly- color, parallax angle, spectral type, apparent brightness Infer Inderectly - luminosity, surface temperature, mass, radius
Roughly how much higher is the pressure in the center of the Sun Compared to the pressure at the outer edge of the radiation zone?
Over 20 times as high the pressure in the center of the sun is over a 100 time as high as the pressure at the outer edge of the radiation zone.
Which of the following procedures would allow you to make a spectrum of the Sun similar to the one shown, though with less detail?
Pass a narrow beam of sunlight through a prism
Listed following is a set of statements describing individual stars or characteristics of stars. Match these to the appropriate object category.
RED GIANT OR SUPERGIANT STARS: Very cool but very luminous, Found in the upper right of the H-R diagram MAIN SEQUENCE STARS: The majority of the stars in our galaxy, The hottest and most luminous stars, The Sun, for example WHITE DWARFS Not much larger in radius than the Earth, Very hot but very dim
The source of energy ultimately responsible for the sun shining so brilliantly is
Rest-mass energy
We divide the electromagnetic spectrum into six major categories of light, listed below. Rank these forms of light from left to right in order of increasing wavelength. To rank items as equivalent, overlap them.
Shortest to Longest wavelength: gamma rays, x-rays, ultraviolet, visible light, infrared, radio waves
The more distant a star, the
Smaller its parallax angle
Listed following are various physical situations that describe how light interacts with matter. Match these to the appropriate category
TRANSMISSION: Visible light meets clear glass, Cell phone signals=wall pass through walls ABSORPTION: Visible light dose not pass through black wall, Blue light hits red shirt. REFLECTION or SCATTERING: Red light hits a red shirt, White light hits piece of paper. EMISSION: Light comes from a light bulb, light comes from your computer screen
Before we can use parallax to measure the distance to a nearby star, we first need to know
The Earth-Sun distance
What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?
The Sun's core would start to heat up and the rate of fusion would increase even more.
Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?
The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.
Where is the temperature of the Sun the highest?
The core
One statement about the Sun from Part A is "The corona is hotter than the photosphere." Which of the following statements provides observational evidence for this claim?
The corona primarily emits X rays while the photosphere primarily emits visible light.
Roughly how much higher is the pressure in the center of the sun compared to the pressure at the out edge of the core?
Three times as high.
Now consider the statements in Part A that are inferred from models. A solar model is used to calculate interior conditions based on certain "known" characteristics of the Sun, such the Sun's total mass. How do we know the Sun's mass?
We can calculate it by applying Newton's version of Kepler's third law with Earth's orbital period (1 year) and Earth's average distance from the Sun (1 AU).
You should now see that the reason the mass of the star in Part A must be inferred is that the star has no known orbiting objects, which means we cannot apply Newton's version of Kepler's third law. Which of the following must be true if the star's inferred mass is to be accurate?
We have determined that the star is a main-sequence star; We have measured the star's spectral type
Recall the relationship between the wavelength of thermal radiation and the temperature of a gas. What type of radiation is the most prevalent in the radiation zone?
X-rays, gas having a temperature of millions of degrees emits mostly X-rays.
Consider the four stars shown following. Rank the stars based on their surface temperature from highest to lowest.
a blue-white dwarf star, Sun, an orange main-sequence star, a red supergiant star
(Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________.
a shorter wavelength
What type of visible light spectrum does the Sun produce?
an absorption line spectrum
The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________.
be an emission line spectrum
Most of the Sun's ultraviolet light is emitted from the narrow layer called the ____________ where temperature increases with altitude.
chromosphere
Which of the following layers of the Sun can be seen with some type of telescope? Consider all forms of light, but do not consider neutrinos or other particles.
chromosphere, photosphere, corona
Energy moves through the sun's ______________ by means of the rising of hot gas and falling of cooler gas.
convection zone
compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are
cooler and larger in radius
Nuclear fusion of hydrogen into helium occurs in the __________.
core
Overall (not counting protons that go free) how many hydrogen nuclei proton does it take to produce on helium nucleus?
four
The mass of four hydrogen nuclei is __ then mass of a helium nucleus.
greater than. When hydrogen fuses into helium the mass of the Sun decreases.
if the sun were more massive the pressure in ts core would be?
higher
Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R digram are
hotter and smaller in radius-
However, we can measure a star's mass directly if
it is a member of an eclipsing binary system.
Compared to a main-sequence star with a short lifetime, a main-sequence star with a long lifetime is
less luminous, cooler, smaller, and less massive
If the sun has the same mass but a lower luminosity its lifespan would be?
longer than 10 billion years. a lower luminosity would mean that the sun's hydrogen is fused into helium at a slower rate, so it would take longer to run out of hydrogen.
In the illustration of the solar spectrum, the upper left portion of the spectrum shows the __________ visible light.
lowest frequency
Rank the forms of light from left to right in order of increasing energy. Lowest to highest
lowest to highest energy: radio waves, infrared, visible light, ultraviolet, x-rays, gamma rays
Rank the forms of light from left to right in order of increasing frequency. To rank items as equivalent, overlap them.
lowest to highest frequency: radio waves, infrared, visible light, ultraviolet, x-rays, gamma rays
Rank the forms of light from left to right in order of increasing speed. To rank items as equivalent, overlap them.
lowest to highest speed: they all in the middle or have the same speed
How much hydrogen fuses into helium every second?
more than 5 billion kg. the amount of mass lost when hydrogen fuses into helium is only about 0.7%, the initial mass, roughly 8x10^11 kg of hydrogen must fuse in order for the Sun to lose 5x10^9 kg every second.
If helium had exactly the same mass as four hydrogen atoms the luminosity of the sun would be
much lower than its actual value.
The neon "OPEN" sign appears reddish-orange because __________.
neon atoms emit many more yellow and red photons than blue and violet photons
Listed following is the same set of fictitious stars given in Part A. Rank the stars based on how bright each would appear in the sky as seen from Jupiter, from brightest to dimmest
nismo shelby, ferdinand (equal) enzo lotus
listed following are several fictitious stars with their luminosities given in terms of the sun's luminosity and their distances from earth given in light-years. rank the stars based on how bright each would appear in the sky as seen from earth, from brightest to dimmest.
nismo shelby, ferdinand (equal) enzo lotus
Nearly all the visible light we see from the Sun is emitted from the ___________.
photosphere
The ______________ is the layer of the Sun between its core and convection zone
radiation zone
How many gamma ray photons are produced for each helium-4 nucleus created ?
six
The diagrams below are the same as those from Part A. This time, rank the atoms based on the wavelength of the photon emitted as the electrons change energy levels, from longest to shortest.
small arrow on outer rings, small arrow innner rings, long arrow, longest touching center and outer layer.
What must we measure directly so that we can infer a star's surface temperature?
spectral type
Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us __________.
the approximate temperature of the Sun's surface.
How many neutrinos are produced for every helium-4 nucleus created?
two
