Solar energy leaves the core of the Sun in the form of
Definition
Term
At the center of the Sun, fusion converts hydrogen into
Definition
helium, energy, and neutrinos.
Term
Scientists estimate the central temperature of the Sun usingmathematical models of the Sun.
Definition
mathematical models of the Sun.
Term
Which of these groups of particles has the greatest mass?
Definition
four individual protons
Term
Which of these things poses the greatest hazard to communications satellites?
Definition
Term
Definition
They are cooler than their surroundings.
Term
Definition
Solar winds can affect satellite communications.
Term
Where in the Sun do fusion reactions happen?
Definition
Only the core
Term
Which of the following quantities is equal to the energy per second generated by the Sun's nuclear reactions?
Definition
The luminosity of the Sun's photosphere
Term
The light radiated from the Sun's surface reaches Earth in about 8 minutes. However, the energy of this light was released by fusion in the Sun's core about
Definition
several hundred thousand years ago.
Term
Which of the following is not a method astronomers use to determine the physical conditions inside the Sun?
Definition
Observing X-ray images of the solar interior using satellites.
Term
Suppose you try to bring two protons close together. Because of the electromagnetic force, the two protons will
Definition
repel one another.
Term
Which of the following is the phase of matter in the Sun?
Definition
plasma
Term
Which is closest to the temperature of the Sun's core?
Definition
10 million K
Term
Based on its surface temperature of 6,000 K, most photons that leave the Sun's surface lie in which region of the electromagnetic spectrum?
Definition
Visible
Term
By what process does the Sun generate energy?
Definition
nuclear fusion
Term
By what process do nuclear power plants on the Earth generate energy?
Definition
nuclear fission
Term
Hydrogen fusion in the Sun requires a temperature (in Kelvin) of
Definition
millions of degrees.
Term
At the center of the Sun, nuclear fusion converts hydrogen into
Definition
helium, gamma rays, and neutrinos.
Term
The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about ________.
Definition
few hundred thousand years ago
Term
Why are neutrinos so difficult to detect?
Definition
They have a tendency to pass through just about any material without any interactions.
Term
Which of the following choices is not a way by which we can study the inside of the Sun?
Definition
We can send a space probe into the Sun's photosphere.
Term
The Sun's surface seethes and churns with a bubbling pattern. Why?
Definition
We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
Term
Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?
Definition
The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
Term
Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
Definition
Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
Term
An O-star has a hotter surface temperature than the Sun. Therefore, compared to the Sun...
Definition
its emission peaks in the blue part of the spectrum.
Term
Which main sequence star has the lowest mass?
Definition
M
Term
What is the approximate age of a star cluster where the brightest main sequence stars are G stars?
Definition
10 billion years
Term
If a star has a mass of 10 solar masses and a luminosity of 10,000 solar luminosities, how long is its lifetime? (The Sun's lifetime is 10 billion years.)
Definition
10 million years
Term
If the Sun-Earth separation was 10 AU instead of 1 AU, what would the flux of sunlight (energy per second per square meter) be at the Earth, compared to what it is today?
Definition
100 times less
Term
Which main sequence star will have the shortest lifetime?
Definition
O
Term
Which star is the hottest star?
Definition
O
Term
Which star cluster is the youngest star cluster? The one where the brightest main sequence stars are . . .
Definition
O stars.
Term
Which of the following stars has a spectrum that peaks at the highest frequency?
Definition
A blue star
Term
The age of stars in a cluster can be determined by
Definition
determining the main sequence turnoff point.
Term
Which of the following comparisons between low-mass stars and high-mass stars is true?
Definition
Term
A star of spectral type G lives approximately how long on the main sequence?
Definition
10 billion years
Term
Which of the following stellar properties has the greatest range in values?
Definition
luminosity
Term
Which of the following is the most numerous type of main-sequence star?
Definition
an M star
Term
On a Hertzsprung-Russell diagram, where on the main sequence would you find stars that have the greatest mass?
Definition
upper left
Term
You see two main-sequence stars with the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude, assuming there is no absorption of either star's light by interstellar gas or dust?
Definition
Star 1 is 10 times more distant than Star 2.
Term
The spectral sequence, in order of decreasing temperature, is
Definition
OBAFGKM.
Term
Which of the following statements about spectral types of stars is true?
Definition
The spectral type of a star can be used to determine its surface temperature
A star with spectral type F2 is hotter than a star with spectral type F3.
The spectral type of a star can be used to determine its color.
A star with spectral type A is cooler than a star with spectral type B.
Term
Which of the following correctly states the relationship between the apparent brightness, luminosity, and distance of a star?
Definition
[image]
Term
If the distance between us and a star is doubled, with everything else remaining the same, its luminosit
Definition
remains the same, but its apparent brightness is decreased by a factor of four.
Term
Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
Definition
mass they are formed with
Term
How is the lifetime of a star related to its mass?
Definition
More massive stars live much shorter lives than less massive stars.
Term
According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples?
Definition
Its apparent brightness will decrease by a factor of 9.
Term
The total amount of power (in watts, for example) that a star radiates into space is called its ________.
Definition
luminosity
Term
Which two processes can generate energy to help a star maintain its internal thermal pressure?
Definition
Nuclear fusion and gravitational contraction
Term
Our Sun is considered to be a ________.
Definition
low-mass star
Term
Angular momentum plays an important role in star formation. Which of the following characteristics of a protostellar system is probably not strongly affected by the star's angular momentum?
Definition
The onset of core hydrogen fusion
Term
[image]
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. During which stage is the star's energy supplied by primarily by gravitational contraction?
Definition
ii
Term
[image]
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. During which stage does the star have an inert (non-burning) helium core?
Definition
iv
Term
[image]
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. Which stage lasts the longest?
Definition
iii
Term
[image]
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. During which stage does the star have an inert (non-burning) carbon core surrounded by shells of helium and hydrogen burning?
Definition
viii
Term
[image]
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals. What will happen to the star after stage viii?
Definition
Its outer layers will be ejected as a planetary nebula and its core will become a white dwarf.
Term
Why is a 1 solar-mass red giant more luminous than a 1 solar-mass main sequence star?
Definition
Why is a 1 solar-mass red giant more luminous than a 1 solar-mass main sequence star?
Term
Carbon fusion occur in high-mass stars but not in low-mass stars because ________.
Definition
the cores of low-mass stars never get hot enough for carbon fusion
Term
Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, and so on) in a high-mass star is not true?
Definition
Each successive stage lasts for approximately the same amount of time.
Term
Which event marks the beginning of a supernova?
Definition
The sudden collapse of an iron core into a compact ball of neutrons
Term
A spinning neutron star has been observed at the center of a ________.
Definition
supernova remnant
Term
Which part of the electromagnetic spectrum generally gives us our best views of stars forming in dusty clouds?
Definition
Infrared
Term
Approximately what core temperature is required before hydrogen fusion can begin in a star?
Definition
10 million K
Term
The vast majority of stars in a newly formed star cluster are ________.
Definition
Less massive than the Sun
Term
What is the approximate range of masses that newborn main sequence stars can have?
Definition
0.1 to 300 solar masses
Term
Which of the following lists the stages of life for a low-mass star in the correct order?
Definition
Protostar, main-sequence star, red giant, planetary nebula, white dwarf
Term
What happens when a main-sequence star exhausts its core hydrogen fuel supply?
Definition
The core shrinks while the rest of the star expands.
Term
The main source of energy for a star as it grows in size to become a red giant is ________.
Definition
hydrogen fusion in a shell surrounding the central core
Term
What is a planetary nebula?
Definition
Gas ejected from a low-mass star in the final stage of its life
Term
The ultimate fate of our Sun is to ________.
Definition
become a white dwarf that will slowly cool with time
Term
In order to predict whether a star will eventually fuse oxygen into a heavier element, you mainly want to know what fact about the star?
Definition
Its mass
Term
What type of star is our Sun?
Definition
A low-mass star
Term
What did Carl Sagan mean when he said that we are all "star stuff"?
Definition
that the carbon, oxygen, and other elements essential to life were created by nucleosynthesis in stellar cores
Term
What percentage of a star's total lifetime (before it becomes a white dwarf or explodes in a supernova) is spent on the main sequence?
Definition
90%
Term
Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission?
Definition
iron
Term
What types of stars end their lives with supernovae?
Definition
stars that are at least several times the mass of the Sun
Term
The more massive a white dwarf, the ________.
Definition
smaller its radius
Term
Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?
Definition
Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4-solar-mass limit.
Term
The white dwarf that remains when our Sun dies will be mostly made of ________.
Definition
carbon
Term
Which of the following is not true about differences between novae and supernovae?
Definition
Supernovae eject gas into space but novae do not.
Term
Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?
Definition
No, because it is not orbited by another star.
Term
According to present understanding, a nova is caused by ________.
Definition
hydrogen fusion on the surface of a white dwarf
Term
Which statement about pulsars is not thought to be true?
Definition
Pulsars can form only in close binary systems.
Term
Which statement concerning black hole masses and Schwarzschild radii is not true?
Definition
In a binary system with a black hole, the Schwarzschild radius depends on the distance from the black hole to the companion star.
Term
Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?
Definition
Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted.
Term
Which of statement below about black holes is not true?
Definition
A spaceship passing near a 10 solar mass black hole is much more likely to be destroyed than a spaceship passing at the same distance from the center of a 10 solar mass main-sequence star.
Term
A white dwarf is ________.
Definition
what most stars become when they die
Term
A typical white dwarf is ________.
Definition
as massive as the Sun but only about as large in size as Earth
Term
The maximum mass of a white dwarf is ________.
Definition
about 1.4 times the mass of our Sun
Term
Degeneracy pressure stops the crush of gravity in all the following except:
Definition
a very massive main-sequence star.
Term
Which of the following is closest in mass to a white dwarf?
Definition
the Sun
Term
What is the ultimate fate of an isolated white dwarf?
Definition
It will cool down and become a cold black dwarf.
Term
Suppose a white dwarf is gaining mass because of accretion from a binary companion. What happens if its mass reaches the 1.4 solar mass limit?
Definition
The white dwarf (which is made mostly of carbon) suddenly detonates carbon fusion and this creates a white dwarf supernova explosion.
Term
Which of the following statements about novae is not true?
Definition
Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now.
Term
What kind of pressure supports a white dwarf?
Definition
electron degeneracy pressure
Term
What is the upper limit to the mass of a white dwarf?
Definition
1.4 solar masses
Term
Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?
Definition
The 1.2 solar mass white dwarf has a smaller radius.
Term
Observationally, how can we tell the difference between a white-dwarf supernova and a massive-star supernova?
Definition
The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not.
Term
After a massive-star supernova, what is left behind?
Definition
Either a neutron star or a black hole
Term
From an observational standpoint, what is a pulsar?
Definition
An object that emits flashes of light several times per second (or even faster), with near perfect regularity.
Term
From a theoretical standpoint, what is a pulsar?
Definition
a rapidly rotating neutron star
Term
Why is nuclear fusion necessary to power the Sun(why other energy sources, such as chemical energy or gravitational contraction, don’t work).
Definition
Nuclear fussion is the one energy source that you get the most energy per unit mass. AND the age. The sun is OLD, that means you need a lot of ENERGY.
Term
What is Jupiter being powered by?
Definition
Gravitational contraction
Term
Name some of the the total inputs and outputs
of the main fusion process that powers that Sun.
Definition
Inputs - Hydrogen (1 proton, 1 electron)
In the Sun, all you get is protons, 4 protons needed
Output - Helium (1 helium)
Plus energy, add nutrino. This powers the sun
Term
What is the difference between fusion and fission?
Definition
Fusion is things coming together and Fission is breaking them apart.
Fission has to do with massive radioactive elements (found in powerplants).
Term
What are the requirements for nuclear fusion to occur?
Definition
Needs to be high temperatures and high density
High density AND high particle movement
Term
What is the Sun’s age and how long it is expected to live on the main sequence?
Definition
The sun is about 5 billion years old. It is expected to live another 5 or 6 billion years. It is about halfway through its main sequence life (1010)
Term
Explain how long it takes for the energy produced by fusion to diffuse out of the Sun’s center.
Definition
Gamma rays come out of the center of the sun. Photons bounce in the sun for A WHILE (10,000 years).
When they diffuse out and are reemitted, it takes 8 minutes for them to reach Earth.
Term
Explain how the solar thermostat works.
Definition
This is the energy production at the center of the sun. The sun keeps it regulated.
Fast = heat + expand
Slow = cool and shrink
Term
Explain the relationship between mass, luminosity, and lifetime for main sequence stars.
Definition
O- type: More massive = brighter, live shorter.
M- type: Less massive = dim, live longer.
Term
What is the definition of luminosity?
Definition
All of the energy put out by something compared to its apparent brightness.
Term
the relationship between luminosity and apparent
brightness (the inverse-square law)
Definition
GO LOOK THIS UP.
Term
Compare 2 stars with different luminosities.
One is a 10 solar mass star (10 MSUN).
It also contains 1000 solar luminosities (1000 LSUN).
The Lifetime is 50 Million Years.
Calculate the lifetime of a star with
20 MSUN and 4000 LSUN.
Definition
It is twice as massive... So multiply by 2, you get 100 Million Years. THEN, applying the 4x luminosity, you divide 100 by 4... and get a lifetime of 25 Million Years.
Term
What are the basic stages of evolution for low-mass stars?
Definition
Main sequence vs. Low mass
THE SUN is on it's main sequence for 90% of its life (the time for most stars). THEN
The run out of fuel in the center
It then wants to start fusing helium
But the core is not hot enough to begin
This is when it is labeled as a "Sub-Giant Star"
Then it becomes BIG
Then the SUN is reborn
It fuses helium into carbon
THEN becomes giant ONCE MORE!
Finally becomes a white dwarf
It's luminosity and mass both decrease
Term
What are the basic stages of evolution for high-mass stars?
Definition
Fusion KEEPS happening with them.
Layers of elements inside are formed. The core of elements, like iron, is formed and here is where it stops.
The iron core is massive
It collapses - a supernova insues
A black hole or neutron star is formed
USUALLY fusion stops
High mass star = IRON requires not produces energy
Low mass star = temperature isn't high enough
Term
List the spectral types of stars and their interpretation.
Definition
OBAFGKM
(Our Best Alien Friends Give Kids Milk)
This is a TEMPERATURE sequence. Only on the MAIN SEQUENCE is there a relationship between TEMP. and MASS.
Term
Use H-R diagrams of star clusters to age-date stars.
Definition
With graphs that have a STRAIGHT LINE ... it means they are all giant stars, and YOUNG
With graphs that CURVE or are weird ... it means they
are only main sequence and with LOW MASS.
A LACK of BRIGHT BLUE stars mean that is is an older star cluster.
Term
Explain the frequency of different kinds of stars.
Definition
This is the OBAFGKM. Imagine the O starting at the top left of the diagram and the M at the bottom right.
The most frequent stars are M.
The most rare are O.
Term
What are novae and supernovae? (Compare)
Definition
Novae = White dwarf and other stars ... it is when a star dumps its mass, has a little explosion.
Supernova = White dwarf burns up in day ... when the IRON CORE collapses and EXPLODES. Happens to MASSIVE stars.
Term
What do supernova and novae similarily produce?
Definition
Iron (Supernovas produce others, too) mostly.
ALL elements in our body are from supernovas.
Term
What are the remnants of high and low-mass stars?
Definition
Low = White Dwarf
High = Neutron Star or Black Hole
Term
What are the basic properties of white dwarfs, neutron stars, and black holes?
Definition
White Dwarf: Size of Earth
Neutron Star: Size of a City
Black Hole: massive but with NO SIZE
Term
What are the properties of accreting neutron stars and black holes (X-ray binaries)?
Definition
When you have a black hole in a BINARY SYSTEM, it will form an accreting DISK and start to glow on an X-Ray... that is how we find neutron stars and black holes.
