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Unit 8: The Sun and the Stars,
Review Game Questions
1) What kind of pressure supports a white dwarf?
2) What is the upper limit to the mass of a white dwarf?
3) How much would a teaspoonful of neutron star material weigh on Earth ?
4) What happens when the gravity of a massive star is able to overcome neutron
degeneracy pressure?
5) No stars have been found with masses greater than 100 times our Sun because
6) What happens when a star exhausts its core hydrogen supply?
7) What is a planetary nebula?
8) List the sequences correctly describing the stages of life for a low-mass star.
9) What is the smallest mass a newborn star can have?
10) When does a protostar become a true star?
11) What happens to the rotation of a molecular cloud as it collapses to form a star?
12)From the center outward, list the "layers" of the Sun in the correct order.
13) What are coronal holes?
14) How can cluster ages can be determined ?
15) On the main sequence, stars obtain their energy by
16) What is granulation in the Sun?
17) What do we mean when we say that the Sun is in gravitational equilibrium?
18) Briefly explain why sunspots are cooler than surrounding regions of the Sun and
why they look dark in photos.
19) Briefly explain why high-mass stars have shorter lifetimes than low-mass stars.
20) Which apparent magnitudes is the brightest +25.7 or - 23?
21) The ________ magnitude of a star depends directly upon its luminosity and distance.
22) The Hertzsprung-Russell Diagram plots ________ against the spectral type or
temperature.
23) What are the two most important intrinsic properties used to classify stars?
24) A nearby star has a parallax of 0.2 arc seconds. What is its distance?
25) What physical property of a star does the spectral type measure?
26) A balance between gravity and ________ is a factor which determines the interior
structure of a star.
27) In the H-R Diagram, the Main Sequence is basically a sequence of stars with
different:
28) The Main Sequence is the first stellar stage in which energy produced by ________
balances the energy lost by radiation from the surface of the star.
29) The youngest open clusters lie in the galactic plane and appear ________ in color.
30) If a protostar's mass is too low, instead of forming a star, it will become a ________
dwarf.
31) Dense clouds of ________ and gas are probably the birthplaces of stars.
32) The solar photosphere is not uniform in brightness, but has a mottled appearance
termed:
33) On the main sequence, type ________ stars will be stable only a million years or so.
34) The age of a star cluster may be estimated by determining the ________ of the Main
Sequence at which stars are just in the process of evolving away to become giant
stars.
35) From hottest to coolest, the seven letters for the star types are:
36) A relatively common type of stellar outburst, ________, are believed to be the result
of close binary systems in which matter from one star is dumped onto a companion.
37) A neutron star collapsed to city-sized dimensions when its protons and ________
fused.
38) An object compacted to such a small size that light cannot escape from its
gravitational field is called a:
39) The spherical surface of space which defines the "surface" of a black hole is the:
40) White dwarfs, like Sirius B, would be found to the ________ on the H-R diagram.
41) A red supergiant, like Betelguese, would lie to the ________ on the H-R diagram.
42) Stars that have masses like that of the Sun and radii like that of the Earth are:
43) Two stars which differ by one magnitude in apparent brightness have the same
parallax; thus, one star must be intrinsically ________ times as luminous as the
other.
44) A cluster where the turn-off point fell in spectral type B must be very:
45) ________ is the means of transport of energy outward by circulating currents of
material between hotter and cooler regions inside a star.
46) Collapsed white dwarfs are typically about as big as the:
47) A neutron star is one which has collapsed to a size of:
48) The ________ star clusters are the oldest and richest, over ten billion years old.
49) Energy transport as hot gases rise can occur by large-scale motions of the solar
material in regions called:
50) Energy from the core is first outwardly transported by gradual outward diffusion of
photons in the ________ zone, then these are absorbed closer to the surface.
51) In the photosphere, ________ shows that convection cells transport energy upward
immediately below the photosphere.
The following questions refer to the sketch below of an H-R diagram for a star cluster.
Figure 17.2
52) Based on its main-sequence turnoff point, the age of this cluster is
Unit 8: The Sun and the Stars
Review Game Answers
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electron degeneracy pressure
1.4 solar masses
more than Mt. Everest.
The core contracts and becomes a black hole.
they would generate so much power that they would blow themselves apart.
Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
the expanding shell of gas that is no longer gravitationally held to the remnant of a lowmass star
protostar, main-sequence, red giant, white dwarf
80 times the mass of Jupiter
when nuclear fusion begins in the core
The rotation rate increases and results in a disk of material around a protostar.
core, radiation zone, convection zone, photosphere, chromosphere, corona
areas of the corona where magnetic field lines project into space, allowing charged particles
to escape the Sun, becoming the solar wind
main sequence turnoff.
by converting hydrogen to helium.
the bubbling pattern on the photosphere produced by the underlying convection
There is a balance within the Sun between the outward push of pressure and the inward
pull of gravity.
They are cooler because their strong magnetic fields suppress convection and prevent
hotter material from flowing into them. Because they are cooler, they emit less thermal
radiation per unit area and therefore look dark in contrast to brighter surrounding regions.
High-mass stars have 10 to 100 times more mass (fuel) than a typical low-mass star. This
greater mass produces a much higher downward gravitational pressure, leading to much
higher core temperatures and higher rates of fusion. The luminosity of such stars is
therefore 1,000 to 1 million times greater than in low-mass stars. So, although high-mass
stars have more fuel to burn, they burn it at a much higher rate and therefore run out of
fuel much more quickly.
-23
apparent
luminosity or absolute magnitude
luminosity and surface temperature
5 parsecs
temperature
radiation pressure
masses.
fusion (of hydrogen into helium) or nuclear reactions
blue
brown
dust
granulation.
O
turn-off point
OBAFGKM.
novae
electrons
black hole.
39)
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event horizon.
lower left
top right
white dwarfs.
2.5
young.
Convection
Earth.
a city (about 20 km).
globular
convective zones.
radiative
granulation
about 10 billion years.