Transcript Powerpoint - Physics and Astronomy

Chapter 12 Clickers
Astronomy: A Beginner’s
Guide to the Universe
Seventh Edition
Stellar Evolution
© 2013 Pearson Education, Inc.
Question 1
Stars like our Sun will end their lives as
a) red giants.
b) pulsars.
c) black holes.
d) white dwarfs.
e) red dwarfs.
© 2013 Pearson Education, Inc.
Question 1
Stars like our Sun will end their lives as
a) red giants.
b) pulsars.
c) black holes.
d) white dwarfs.
e) red dwarfs.
Explanation:
Low-mass stars eventually swell into
red giants, and their cores later contract
into white dwarfs.
© 2013 Pearson Education, Inc.
Question 2
Elements heavier than hydrogen and helium were created
a) in the Big Bang.
b) by nucleosynthesis in massive
stars.
c) in the cores of stars like the Sun.
d) within planetary nebula
e) They have always existed.
© 2013 Pearson Education, Inc.
Question 2
Elements heavier than hydrogen and helium were created
a) in the Big Bang.
b) by nucleosynthesis in massive
stars.
c) in the cores of stars like the Sun.
d) within planetary nebula
e) They have always existed.
Explanation:
Massive stars create enormous core
temperatures as red supergiants,
fusing helium into carbon, oxygen,
and even heavier elements.
© 2013 Pearson Education, Inc.
Question 3
The Sun will evolve away from the main sequence when
a) its core begins fusing iron.
b) its supply of hydrogen is used up.
c) the carbon core detonates, and it explodes as a Type I
supernova.
d) helium builds up in the core, while the hydrogen-burning shell
expands.
e) the core loses all of its neutrinos,
so all fusion ceases.
© 2013 Pearson Education, Inc.
Question 3
The Sun will evolve away from the main sequence when
a) its core begins fusing iron.
b) its supply of hydrogen is used up.
c) the carbon core detonates, and it explodes as a Type I
supernova.
d) helium builds up in the core, while the hydrogen-burning
shell expands.
e) the core loses all of its neutrinos,
so all fusion ceases.
Explanation:
When the Sun’s core becomes unstable and
contracts, additional H fusion generates extra
pressure, and the star will swell into a red giant.
© 2013 Pearson Education, Inc.
Question 4
The helium flash occurs
a) when T-Tauri bipolar jets shoot out.
b) in the middle of the main sequence stage.
c) in the red giant stage.
d) during the formation of a neutron star.
e) in the planetary nebula stage.
© 2013 Pearson Education, Inc.
Question 4
The helium flash occurs
a) when T-Tauri bipolar jets shoot out.
b) in the middle of the main sequence stage.
c) in the red giant stage.
d) during the formation of a neutron star.
e) in the planetary nebula stage.
Explanation:
When the collapsing core of a
red giant reaches high enough
temperatures and densities,
helium can fuse into carbon
quickly – a helium flash.
© 2013 Pearson Education, Inc.
Question 5
Stars gradually lose mass as they become white dwarfs
during the
a) T-Tauri stage.
b) emission nebula stage.
c) supernova stage.
d) nova stage.
e) planetary nebula stage.
© 2013 Pearson Education, Inc.
Question 5
Stars gradually lose mass as they become white dwarfs
during the
a) T-Tauri stage.
b) emission nebula stage.
c) supernova stage.
d) nova stage.
e) planetary nebula stage.
Explanation:
Low-mass stars forming white dwarfs
slowly lose their outer atmospheres,
and illuminate these gases for a
relatively short time.
© 2013 Pearson Education, Inc.
Question 6
Astronomers determine the age of star clusters by observing
a) the number of main sequence stars.
b) the ratio of giants to supergiants.
c) the luminosity of stars at the turnoff point.
d) the number of white dwarfs.
e) supernova explosions.
© 2013 Pearson Education, Inc.
Question 6
Astronomers determine the age of star clusters by observing
a) the number of main sequence stars.
b) the ratio of giants to supergiants.
c) the luminosity of stars at the turnoff point.
d) the number of white dwarfs.
e) supernova explosions.
Explanation:
The H–R diagram of a cluster
can indicate its approximate age.
© 2013 Pearson Education, Inc.
Turnoff
point from
the main
sequence
Question 7
The source of pressure that makes a white dwarf stable is
a) electron degeneracy.
b) neutron degeneracy.
c) thermal pressure from intense core temperatures.
d) gravitational pressure.
e) helium-carbon fusion.
© 2013 Pearson Education, Inc.
Question 7
The source of pressure that makes a white dwarf stable is
a) electron degeneracy.
b) neutron degeneracy.
c) thermal pressure from intense core temperatures.
d) gravitational pressure.
e) helium-carbon fusion.
Explanation:
Electrons in the core cannot be
squeezed infinitely close, and
prevent a low-mass star from
collapsing further.
© 2013 Pearson Education, Inc.
Question 8
In a white dwarf, the mass of the Sun is packed into the
volume of
a) an asteroid.
b) a planet the size of Earth.
c) a planet the size of Jupiter.
d) an object the size of the Moon.
e) an object the size of a sugar cube.
© 2013 Pearson Education, Inc.
Question 8
In a white dwarf, the mass of the Sun is packed into the
volume of
a) an asteroid.
b) a planet the size of Earth.
c) a planet the size of Jupiter.
d) an object the size of the Moon.
e) an object the size of a sugar cube.
Explanation:
The density of a white dwarf is about
a million times greater than normal
solid matter.
© 2013 Pearson Education, Inc.
Question 9
In a young star cluster, when more massive stars are
evolving into red giants, the least massive stars are
a) ending their main-sequence stage.
b) also evolving into red giants.
c) forming planetary nebulae.
d) barely starting to fuse hydrogen.
e) starting the nova stage.
© 2013 Pearson Education, Inc.
Question 9
In a young star cluster, when more massive stars are
evolving into red giants, the least massive stars are
a) ending their main-sequence stage.
b) also evolving into red giants.
c) forming planetary nebulae.
d) barely starting to fuse hydrogen.
e) starting the nova stage.
Explanation:
More massive stars form much faster,
and have much shorter main-sequence
lifetimes.
Low-mass stars form more slowly.
© 2013 Pearson Education, Inc.
Question 10
A star will spend most of its “shining” lifetime
a) as a protostar.
b) as a red giant.
c) as a main-sequence star.
d) as a white dwarf.
e) evolving from type O to type M.
© 2013 Pearson Education, Inc.
Question 10
A star will spend most of its “shining” lifetime
a) as a protostar.
b) as a red giant.
c) as a main-sequence star.
d) as a white dwarf.
e) evolving from type O to type M.
Explanation:
In the main-sequence stage,hydrogen
fuses to helium.
Pressure from light and heat pushing
out balances gravitational pressure
pushing inward.
© 2013 Pearson Education, Inc.
Question 11
A nova involves
a) mass transfer onto a white dwarf in a binary star
system.
b) repeated helium fusion flashes in red giants.
c) rapid collapse of a protostar into a massive O star.
d) the explosion of a low-mass star.
e) the birth of a massive star
in a new cluster.
© 2013 Pearson Education, Inc.
Question 11
A nova involves
a) mass transfer onto a white dwarf in a binary star
system.
b) repeated helium fusion flashes in red giants.
c) rapid collapse of a protostar into a massive O star.
d) the explosion of a low-mass star.
e) the birth of a massive star
in a new cluster.
Explanation:
Sudden, rapid fusion of new fuel dumped
onto a white dwarf causes the star to flare up,
and for a short time become much brighter.
© 2013 Pearson Education, Inc.
Question 12
What type of atomic nuclei heavier than helium are
most common, and why?
a) those heavier than iron, because of supernovae
b) iron, formed just before massive stars explode
c) odd-numbered nuclei, built with hydrogen fusion
d) even-numbered nuclei, built
with helium fusion
© 2013 Pearson Education, Inc.
Question 12
What type of atomic nuclei heavier than helium are
most common, and why?
a) those heavier than iron, because of supernovae
b) iron, formed just before massive stars explode
c) odd-numbered nuclei, built with hydrogen fusion
d) even-numbered nuclei, built
with helium fusion
Explanation:
Helium nuclei have an atomic
mass of 4; they act as building
blocks in high-temperature fusion
within supergiants.
© 2013 Pearson Education, Inc.
Question 13
A white dwarf can explode when
a) its mass exceeds the Chandrasekhar limit.
b) its electron degeneracy increases enormously.
c) fusion reactions increase in it’s core.
d) iron in its core collapses.
e) the planetary nebula stage ends.
© 2013 Pearson Education, Inc.
Question 13
A white dwarf can explode when
a) its mass exceeds the Chandrasekhar limit.
b) its electron degeneracy increases enormously.
c) fusion reactions increase in it’s core.
d) iron in its core collapses.
e) the planetary nebula stage ends.
Explanation:
If additional mass from a
a companion star pushes
a white dwarf beyond 1.4
solar masses, it can
explode in a Type
supernova.
© 2013 Pearson Education, Inc.
Question 14
A Type II supernova occurs when
a) hydrogen fusion shuts off.
b) uranium decays into lead.
c) iron in the core starts to fuse.
d) helium is exhausted in the outer layers.
e) a white dwarf gains mass.
© 2013 Pearson Education, Inc.
Question 14
A Type II supernova occurs when
a) hydrogen fusion shuts off.
b) uranium decays into lead.
c) iron in the core starts to fuse.
d) helium is exhausted in the outer layers.
e) a white dwarf gains mass.
Explanation:
Fusion of iron does not
produce energy or provide
pressure; the star’s core
collapses immediately,
triggering a supernova
explosion.
© 2013 Pearson Education, Inc.
Question 16
As stars evolve during their main-sequence lifetime
a) they gradually become cooler and dimmer (spectral type
O to type M).
b) they gradually become hotter and brighter (spectral type
M to type O).
c) they don’t change their spectral type.
© 2013 Pearson Education, Inc.
Question 16
As stars evolve during their main-sequence lifetime
a) they gradually become cooler and dimmer (spectral type
O to type M).
b) they gradually become hotter and brighter (spectral type
M to type O).
c) they don’t change their spectral type.
Explanation:
A star’s main-sequence characteristics of surface temperature and
brightness are based on its mass.
Stars of different initial mass become different spectral types on the
main sequence.
© 2013 Pearson Education, Inc.
Question 17
More massive white dwarfs are ______ compared
with less massive white dwarfs.
a) hotter
b) smaller
c) larger
d) cooler
e) identical in size
© 2013 Pearson Education, Inc.
Question 17
More massive white dwarfs are ______ compared
with less massive white dwarfs.
a) hotter
b) smaller
c) larger
d) cooler
e) identical in size
Explanation:
Chandrasekhar showed that more mass will squeeze a white dwarf
into a smaller volume, due to electron degeneracy pressure.
© 2013 Pearson Education, Inc.