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80 terms

AST EXAM #2 Chapter 9-11

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The most abundant element in the sun (at the moment) is hydrogen.
True
The density in the solar corona is much higher than in the photosphere.
False
Sunspots appear dark because they are much hotter than the surrounding gas in the photosphere.
False
The proton-proton chain reaction releases energy because mass is created in the process.
False
The sun spins on its axis roughly about
once a month
What is the meaning of the solar constant?
the amount of energy the earth receives per unit area and unit time
The Sun's average density is almost exactly the same as
Jupiter
What two energy transport mechanisms, in order from outside the core to the surface, is found in the Sun?
radiative diffusion, convection
The solar winds blow outward from
coronal holes
A loop of gas following the magnetic field lines between sunspots' poles is
a prominence
As the Sun rotates, an individual sunspot can be tracked across its face. From eastern to western limb, this takes about
two weeks
A maximum in solar activity should next occur about
2012
What natural barrier must be overcome for two protons to collide and fuse together?
electrostatic repulsion
In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the lost mass?
it is converted to energy (E = mc2)
(E equals the velocity of light times the mass squared.)
The solution to the solar neutrino problem which won a Nobel Prize in 2002 was
2/3 of the neutrinos decay into a new form in the 8 minutes to Earth
The stars α Cygni and β Cygni are in the constellation Cygnus. Which statement can we claim is true?
α Cygni appears brighter
The spectral type of a star is primarily a measure of its
Temperature
Which of these stars would be the hottest?
B0
What can be said with certainty about a red star and a blue star
The blue star is hotter than the red star.
Which of these pairs of binaries would appear most similar in color telescopically?
M1V and K9V
In general, what can be said about type O and B stars compared to type K and M stars
They are hotter and younger
The stars with masses comparable to our Sun's, but sizes like the earth are
white dwarfs
In the H-R diagram, what are the two most important (common) types of data plotted
spectral classes (and/or temperature) and absolute magnitude (and/or luminosity)
On the H-R diagram, our Sun lies
about the middle
On the H-R diagram, red supergiants like Betelguese lie
at the top right
Compared to the size of the Sun, stars of all types range from approximately
0.01 to 1,000 solar radii
Binary stars separated enough to be resolved in a telescope are called
visual binaries
If we know the average separation and period of revolution for a binary system, we can then determine
the total mass of the system
What information can be gained from the light curves of eclipsing binaries
their relative sizes and period of orb
Interstellar gas is composed mainly of
90% hydrogen, 9% helium
Which statement about the dark nebulae is true?
They can be penetrated only with longer wavelengths such as radio and infrared
Due to absorption of shorter wavelengths by interstellar dust clouds, distant stars behind the clouds appear
redder
Emission nebulae like M42 occur only near stars that emit large amounts of
ultraviolet radiation
What is the primary visible color of an emission nebula?
red due to ionized hydrogen atoms
What two things are needed to create an emission nebulae
hot stars and interstellar gas, particularly hydrogen
What information does 21 cm radiation provide about the gas clouds?
all of the above
The average temperature of the typical dark dust cloud is about
100 K
When an electron in H changes its spin from the same to the opposite direction as the proton, it
a radio wave photon
On a H-R diagram, a protostar would be
above and to the right of the main sequence
The single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar is its
mass
How long does it take an M class star to reach the main sequence, compared to a solar type star
about twenty times longer
Which is characteristic of globular star clusters?
old age and hundreds of thousands of stars, only about 30 ly wide
A star's luminosity is
The total amount of energy radiated from its surface per second.
The inner core of the sun where there is no nuclear fusion and no convection is
called the
Radiation zone
What features or structures of the sun can be seen during a total solar eclipse?
The corona and solar flares
What keeps the Sun from exploding or imploding?
Hydrostatic equilibrium between gravity and radiation
The process that we think powers the sun involves what?
The fusion of six initial protons that result in two final protons plus a helium nucleus.
What kind of a "telescope" would you build to make a neutrino detector.
A gigantic container of fluid far under the Earth's surface with some kind of
photodetectors lining the wall, all in total darkness.
How long will a one-solar mass star live on the main sequence?
About 10 billion years
For measuring distances using spectroscopic parallax, what is one of the steps in
the method
The absolute luminosity of the star is inferred from the H-R diagram using "OBAFGKM".
Our Sun has which spectroscopic label?
G2
In any orbiting binary star system, what can the period of the orbit and its
semimajor axis tell you?
the total mass of the binary system
What is the approximate age of a star cluster if its turn-off point is at the position of our sun on the H-R diagram?
about 10 Billion years
Noting the turnoff mass in a star cluster allows you to determine its
age
Approximately how much power could a 1 square meter solar collector receive?
About 1 kilowatt.
The "boiling" effect that characterizes the Sun's surface is described as
Granulation
Open magnetic field lines (pointing out away from the Sun) in low density regions of the corona lead to
Solar wind and coronal mass ejections.
Going out from the center from the Sun, in sequence we have
the core, radiation zone, convection zone, photosphere, chromosphere, corona.
If a one kilogram melon were to be completely turned into energy, how much energy would it produce
9 x 1016 joules E=mc2 = 1kg*(3 x 108 m/s )2 = 9 x 1016 J.
The solar neutrino problem refers to what
The observation that only about 1/3 of the expected neutrino flux from the sun was initially observed, for instance by Davis
The star Altair has a parallax of 0.20 seconds of arc. How far away is it?
5 parsecs d = 1/p = 1/0.2 = 5 parsecs
We see the apparent magnitude of a star from its observed brightness. How is the absolute magnitude of a star defined?
It is the apparent magnitude it would have it were 10 parsecs from us.
Name two main regions where stars appear away from the main sequence in the H-R diagram:
The white dwarf and red giant regions.
If 2.00 kg of mass is converted to energy, how much energy will be produced?
1.80 × 1017 J
If spectroscopic luminosity classification gives us an estimated distance to the faint star SAO 47552 of about 3300 light years, then its parallax would be only
0.001 arcseconds
A star has a parallax of .05 arc seconds, its distance is
20 parsecs
If a 100 kg zombie were to suddenly be completely turned into energy, how much
energy would it produce?
e) 9 x 1018 joules. E = mc2 = 100(3x108)2 = 1009x1016 = 9x1018.
The star Botox 959A has a parallax of 0.01 arc seconds. How far away is it from
Earth?
100 parsecs. d = 1/p = 1/0.01 = 100
A star has a parallax of .05 arc seconds, its distance is
20 parsecs (d = 1/p = 1/0.05 = 20 pc)
Assume that the relationship between the lifetime of a star (in solar lifetimes) is
proportional to the inverse of the mass of a star (in solar masses) cubed, that is:
Eight solar lifetimes. Lifetime = 1/(1/2)3 = 1/(1/8) = 8.
If spectroscopic luminosity classification gives us an estimated distance to the faint star SAO 47552 of about 3300 light years, then its parallax would be about
0.001 arcseconds (note that 3300 LY = 1000 pc, so 1/1000 = 0.001)
The star Lacaille 9352 is 3.58 parsecs from Earth. What is its parallax?
0.279 arcseconds
If a two metric ton (2000 kg) car were to be completely turned into energy, how much energy would it produce?
1.8 x 1020 Joules
The speed of light is 3.00 × 108 m/s. If 2.00 kg of mass is converted to energy, how much energy will be produced
a) 1.80 × 1017 J
Two stars both have parallaxes of 0.023 arseconds, but star A has apparent magnitude 2.3, while star B has apparent magnitude 7.3. Which statement is true?
one magnitude unit corresponds to a change of 2.5 in brightness. So, a difference of 5 in magnitude corresponds to a difference of 100 in brightness, i.e. 2.5*2.5*2.52.52.5agnitude unit corresponds to a change of 2.5 in brightness. So, a difference of 5 in magnitude corresponds to a difference of 100 in brightness, i.e. 2.5*2.5*2.5*2.5*2.5 ~ 100
Assume that the relationship between the lifetime of a star (in solar lifetimes) is proportional to the inverse of the mass of a star (in solar masses) cubed, that is:
Lifetime = 1/Mass3. So, if a star has a mass that is ten times that of our Sun, how long does it live?
One thousandth of a solar lifetime.
If a star has a parallax of 1 arcsecond, how far away is it?
1 parsec
The closest star to the sun is
Proxima Centauri
Star clusters are good for studying
stellar evolution
The turn off point on the main sequence of a H-R diagram tells us
the average age of a star cluster