Charles Hakes

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• Dead Stars

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Outline

• Test 3 Wednesday
• Dead (?) Stars
• Review (?)

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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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More Precisely 12-1The Cycle of Stellar Evolution
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Supernovae

• On-line images
• Supernova in M 74 http//www.rochesterastronomy.or
  g/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/Bi
  ldergalerie/PolluxGallery/NGC3169.htm
• Supernova in NGC 3190 http//www.astrooptik.com/Bi
  ldergalerie/PolluxGallery/NGC3190.htm
• Supernova in NGC 5965 http//www.nordita.dk/dahl
  e/ngc5965_sub.gif
• Supernova in NGC 918 http//antwrp.gsfc.nasa.gov/
  apod/ap091112.html

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Chapter 13

• What is left after a Supernova?

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Figure 12.21Supernova Remnants
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Figure 13.1Neutron Star - from a type II
Supernova

• typically 20 km diameter
• mass gt Msun
• thimbleful would weigh 108 tons
• rotate very quickly
• have very strong magnetic fields.

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Figure 13.2Pulsar Radiation

• The first observed neutron star was a pulsar
• Neutron stars rotate VERY quickly.

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Figure 13.3Pulsar Model

• lighthouse model - if the beam sweeps past the
  Earth, we see a pulse.

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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.

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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.

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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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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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• A neutron star cannot be more than 3 Msun.

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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 gt c)

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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 gt c)
• Stars that began with gt 25 Msun will probably
  become black holes.

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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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Black Holes

• Example Schwarzschild radii
• Sun 3km
• 3MsolarCore 9km
• Jupiter 3m

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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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Black Holes

• Example Schwarzschild radii
• 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.

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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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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?

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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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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?

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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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Review Questions
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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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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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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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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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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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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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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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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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How could you determine the temperature of the
photosphere of the Sun?

• A) only direct spacecraft measurement
• B) Newtons Law
• C) Stefans Law
• D) Weins law

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How could you determine the temperature of the
photosphere of the Sun?

• A) only direct spacecraft measurement
• B) Newtons Law
• C) Stefans Law
• D) Weins law

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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

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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

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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, Saturns largest
  moon.
• B) Eighth magnitude Uranus.
• C) Ninth magnitude Barnards Star
• D) Eleventh magnitude Tethys, another Saturn moon
• E) Thirteenth magnitude Pluto

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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, Saturns largest
  moon.
• B) Eighth magnitude Uranus.
• C) Ninth magnitude Barnards Star
• D) Eleventh magnitude Tethys, another Saturn moon
• E) Thirteenth magnitude Pluto

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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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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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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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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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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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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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Three Minute Paper

• Write 1-3 sentences.
• What was the most important thing you learned
  today?
• What questions do you still have about todays
  topics?