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Charles Hakes
Fort Lewis College
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Charles Hakes
Fort Lewis College
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“Dead” Stars
Charles Hakes
Fort Lewis College
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Outline
• Test 3 Wednesday
• Dead (?) Stars
• Review (?)
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Fort Lewis College
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Test 3
• Review Spectroscopy (Wein, Stefan) and
Doppler Shift
• The Sun (structure, fusion)
• Magnitude
• Parallax
• Interstellar Medium
• Stellar Evolution
• Dead Stars
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Fort Lewis College
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More Precisely 12-1
The Cycle of Stellar Evolution
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Fort Lewis College
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Supernovae
• On-line images
• Supernova in M 74 http://www.rochesterastronomy.org/sn2003/n628s2.jpg
• Supernova in NGC 1448
http://members.optushome.com.au/edobosz/images/1448_sn.jpg
• Supernova in NGC 3169
http://www.astrooptik.com/Bildergalerie/PolluxGallery/NGC3169.htm
• Supernova in NGC 3190
•
•
http://www.astrooptik.com/Bildergalerie/PolluxGallery/NGC3190.htm
Supernova in NGC 5965 http://www.nordita.dk/~dahle/ngc5965_sub.gif
Supernova in NGC 918 http://antwrp.gsfc.nasa.gov/apod/ap091112.html
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Fort Lewis College
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Chapter 13
• What is left after a Supernova?
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Fort Lewis College
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Figure 12.21
Supernova Remnants
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Fort Lewis College
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Figure 13.1
Neutron Star - from a type II Supernova
• typically ~20 km
diameter
• mass > Msun
• thimbleful would
weigh 108 tons
• rotate very quickly
• have very strong
magnetic fields.
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Fort Lewis College
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Figure 13.2
Pulsar Radiation
• The first observed neutron star was a
pulsar
• Neutron stars rotate VERY quickly.
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Fort Lewis College
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Figure 13.3
Pulsar Model

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Fort Lewis College
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lighthouse model - if
the beam sweeps
past the Earth, we
see a pulse.
At a distance of 1 A.U., which would have the
greatest gravitational force?
A) A 1 solar mass main sequence star
B) A 1 solar mass white dwarf
C) A 1 solar mass neutron star
D) They all have the same force.
Charles Hakes
Fort Lewis College
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At a distance of 1 A.U., which would have the
greatest gravitational force?
A) A 1 solar mass main sequence star
B) A 1 solar mass white dwarf
C) A 1 solar mass neutron star
D) They all have the same force.
Charles Hakes
Fort Lewis College
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At the surface of the object, which would
have the greatest gravitational force?
A) A 1 solar mass main sequence star
B) A 1 solar mass white dwarf
C) A 1 solar mass neutron star
D) They all have the same force.
Charles Hakes
Fort Lewis College
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At the surface of the object, which would
have the greatest gravitational force?
A) A 1 solar mass main sequence star
B) A 1 solar mass white dwarf
C) A 1 solar mass neutron star
D) They all have the same force.
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Fort Lewis College
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• A neutron star cannot be more than 3 Msun.
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Fort Lewis College
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• A neutron star cannot be more than 3 Msun.
• Surface gravity will become so great that
not even light can escape. (Escape
velocity > c)
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Fort Lewis College
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• A neutron star cannot be more than 3 Msun.
• Surface gravity will become so great that
not even light can escape. (Escape
velocity > c)
• Stars that began with > 25 Msun will
probably become black holes.
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Fort Lewis College
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Black Holes
• Can black holes be made of things
other than neutron stars?
• Any object of any mass has a radius that
if it is compressed below that radius,
light cannot escape.
• This is called the Schwarzschild radius.
• rS = 3km x M(solar masses)
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Fort Lewis College
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Black Holes
• Example Schwarzschild radii :
• Sun = 3km
• 3MsolarCore = 9km
• Jupiter = 3m
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Fort Lewis College
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Black Holes
• Exercise - calculate the size required
to compress a 70 kg person to make
a black hole.
• recall:
rS = 3km x M(solar masses)
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Fort Lewis College
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Black Holes
• Example Schwarzschild radii :
•
•
•
•
•
•
Charles Hakes
Fort Lewis College
Sun = 3km
3MsolarCore = 9km
Jupiter = 3m
Earth = ~1cm
Person = ~1x10-25 m
Mobservable universe = ~robservable universe
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If the Sun were suddenly replaced by
a one solar mass black hole:
A) we would immediately escape into deep space,
driven out by its radiation.
B) our clocks would all stop.
C) life here would be unchanged.
D) we would still orbit it in a period of one year.
E) all terrestrial planets would fall in immediately.
Charles Hakes
Fort Lewis College
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If the Sun were suddenly replaced by
a one solar mass black hole:
A) we would immediately escape into deep space,
driven out by its radiation.
B) our clocks would all stop.
C) life here would be unchanged.
D) we would still orbit it in a period of one year.
E) all terrestrial planets would fall in immediately.
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Fort Lewis College
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Practice Problem
• You observe a binary star system where the two
stars are exactly the same temperature. The
diameter of one star is 1.2 times the diameter of
the second star. How many times more energy is
emitted by the brighter star?
Charles Hakes
Fort Lewis College
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Practice Problem
• You observe a binary star system where the two
stars are exactly the same temperature. The
diameter of one star is 1.2 times the diameter of
the second star. How many times more energy is
emitted by the brighter star?
A. 1.095x
B. 1.2x
C. 1.44x
D. 2x
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Fort Lewis College
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Practice Problem
• You observe a binary star system where the two
stars are exactly the same size. One star is 5500
K. The other star is 6100 K. How many times
more energy is emitted by the brighter star?
Charles Hakes
Fort Lewis College
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Practice Problem
• You observe a binary star system where the two
stars are exactly the same size. One star is 5500
K. The other star is 6100 K. How many times
more energy is emitted by the brighter star?
A. 1.11x
B. 1.23x
C. 1.51x
D. 600x
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Fort Lewis College
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Review Questions
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Fort Lewis College
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An ordinary star becomes a Red
Giant when:
A) A white dwarf companion star goes nova
B) There is no Hydrogen remaining in the star
C) Nutrino oscillations drive the outer layers
D) The core becomes almost entirely Helium
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Fort Lewis College
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An ordinary star becomes a Red
Giant when:
A) A white dwarf companion star goes nova
B) There is no Hydrogen remaining in the star
C) Nutrino oscillations drive the outer layers
D) The core becomes almost entirely Helium
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Fort Lewis College
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A main sequence star of 19 solar masses will
eventually be a:
A) A brown dwarf
B) A white dwarf
C) A type I supernova
D) A type II supernova
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Fort Lewis College
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A main sequence star of 19 solar masses will
eventually be a:
A) A brown dwarf
B) A white dwarf
C) A type I supernova
D) A type II supernova
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Fort Lewis College
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A supernova is observed with very little H in the
spectrum. It is most likely a:
A) type I
B) type II
C) type III
D) not enough information
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Fort Lewis College
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A supernova is observed with very little H in the
spectrum. It is most likely a:
A) type I
B) type II
C) type III
D) not enough information
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Fort Lewis College
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A source of light is approaching us at
3,000 km/s. All its waves are:
A) Red shifted by 1%
B) Blue shifted by 1%
C) Not affected, as c is constant in all reference
frames.
D) Red shifted out of the visible into the infrared
E) Blue shifted out of the visible into the ultraviolet
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Fort Lewis College
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A source of light is approaching us at
3,000 km/s. All its waves are:
A) Red shifted by 1%
B) Blue shifted by 1%
C) Not affected, as c is constant in all reference
frames.
D) Red shifted out of the visible into the infrared
E) Blue shifted out of the visible into the ultraviolet
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Fort Lewis College
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How could you determine the temperature
of the photosphere of the Sun?
A) only direct spacecraft measurement
B) Newton’s Law
C) Stefan’s Law
D) Wein’s law
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Fort Lewis College
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How could you determine the temperature
of the photosphere of the Sun?
A) only direct spacecraft measurement
B) Newton’s Law
C) Stefan’s Law
D) Wein’s law
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Fort Lewis College
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If a star has a parallax of 0.05”, then its
distance must be
A) 5 light years.
B) 5 parsecs
C) 20 light years.
D) 20 parsecs.
E) 200 parsecs
Charles Hakes
Fort Lewis College
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If a star has a parallax of 0.05”, then its
distance must be
A) 5 light years.
B) 5 parsecs
C) 20 light years.
D) 20 parsecs.
E) 200 parsecs
Charles Hakes
Fort Lewis College
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Assume your naked eye limiting magnitude
is 4. With a 70mm diameter telescope (100x
area of your pupil) which object would be
barely visible?
A) Seventh magnitude Titan, Saturn’s largest moon.
B) Eighth magnitude Uranus.
C) Ninth magnitude Barnard’s Star
D) Eleventh magnitude Tethys, another Saturn moon
E) Thirteenth magnitude Pluto
Charles Hakes
Fort Lewis College
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Assume your naked eye limiting magnitude
is 4. With a 70mm diameter telescope (100x
area of your pupil) which object would be
barely visible?
A) Seventh magnitude Titan, Saturn’s largest moon.
B) Eighth magnitude Uranus.
C) Ninth magnitude Barnard’s Star
D) Eleventh magnitude Tethys, another Saturn moon
E) Thirteenth magnitude Pluto
Charles Hakes
Fort Lewis College
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On the H-R diagram, red
supergiants like Betelguese lie:
A) top right
B) top left
C) about the middle
D) lower left
E) on the coolest portion of the main sequence
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Fort Lewis College
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On the H-R diagram, red
supergiants like Betelguese lie:
A) top right
B) top left
C) about the middle
D) lower left
E) on the coolest portion of the main sequence
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Fort Lewis College
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From inside out, which is the correct order?
A) core, convective zone, radiative zone
B) photosphere, radiative zone, corona
C) radiative zone, convective zone, chromosphere
D) core, chromosphere, photosphere
E) convective zone, radiative zone, granulation
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Fort Lewis College
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From inside out, which is the correct order?
A) core, convective zone, radiative zone
B) photosphere, radiative zone, corona
C) radiative zone, convective zone, chromosphere
D) core, chromosphere, photosphere
E) convective zone, radiative zone, granulation
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Fort Lewis College
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If Vega is apparent magnitude zero,
and Deneb first magnitude, then
A) Vega is about 100x brighter than Deneb..
B) Deneb is one magnitude brighter than Vega.
C) Vega appears 2.5x brighter than Deneb.
D) Deneb must be a main sequence star, and Vega a giant.
E) Vega must be 2.5x more luminous than Deneb.
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Fort Lewis College
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If Vega is apparent magnitude zero,
and Deneb first magnitude, then
A) Vega is about 100x brighter than Deneb..
B) Deneb is one magnitude brighter than Vega.
C) Vega appears 2.5x brighter than Deneb.
D) Deneb must be a main sequence star, and Vega a giant.
E) Vega must be 2.5x more luminous than Deneb.
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Fort Lewis College
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Three Minute Paper
• Write 1-3 sentences.
• What was the most important thing
you learned today?
• What questions do you still have
about today’s topics?
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Fort Lewis College
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