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The Last Epoch. Sections 39.4-39.5. Reminders & Update. There are no more Mallard-based quizzes . The final examination will be on December 13, Thursday, from 7 :50 AM - 9:50 AM.

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The last epoch

The Last Epoch

Sections 39.4-39.5


Reminders update
Reminders & Update

  • There are no more Mallard-based quizzes.

  • The final examination will be on December 13, Thursday, from 7:50 AM - 9:50 AM.

    • deals with Chs. 29, 37–39 (23 points) and review (12 points) plus extra credit based on questions from earlier chapters (6 points)– max. score 117%

    • 5 questions are mathematical; perhaps two other questions have mathematical components that do not require actual numberical problem solving.

  • Course evaluation begins momentarily...


Galaxy formation uncertain
Galaxy Formation Uncertain

  • Did galaxy or star formation come first?

  • Unclear, and problem is confounded by the presence of dark matter the nature of which is completely unknown.

  • Its presence is deduced from rotation curves.


Birth of a star
Birth of a Star

  • Gravity, with a bit of help from various collisions, forms stars.

  • At the center of a cloud, T increases to 10 million Kelvin and the P-P cycle starts.

  • Gravity balanced by radiation pressure for a long period of time depending on mass.


Death of a star
Death of a Star

  • 6P–>3He–>C–>N–>O–>

  • Near the end of their life spans, stars become red giants.

  • Three possible end states determined by the mass of the star:

    • White dwarf (low mass)

    • Neutron star (medium)

    • Black hole (high mass)


White dwarfs
White Dwarfs

  • Produced in planetary nebula phase where atmosphere begins a run away process.

  • An earth-sized core is revealed at 100,000K +


Neutron stars
Neutron Stars

  • Produced during a supernova explosion resulting in a pulsar.

  • Protons and electrons are crushed to produce neutrons.


Black holes
Black Holes

  • Produced in supernova explosions but neutron degeneracy cannot stop collapse.

  • Gravity is so strong that even light cannot escape.

  • Accretion disk (such as Cygnus X-1) often found in binary star systems.


Black hole detection
Black Hole Detection

  • X-ray sources

  • Gravitational effects on binary star companion

  • Gravitational lensing

  • Gravitational ripples

  • Accretion disk jets


Review ch 12
Review: Ch 12

  • Evidence for + and – charges.

  • Coulomb’s law:

    • F = kq1q2/r2

    • Parallel to Newton’s law of gravitation

  • Electric fields:

    • replace “action at a distance”

    • Forces propagated at the speed of light

  • Field lines and the “test particle”

  • F = Eq (E is measured in N/C)


Review ch 13
Review: Ch 13

  • Faraday – first produced electricity from magnetism and introduced magnetic field

  • Örsted – discovers that flowing electrical charges produce a magnetic field.

  • Earth’s magnetic field:

    • Earth’s south magnetic pole in northern hemisphere

    • Produced by a poorly understood dynamo effect

  • Electricity is produced by spinning a coil of wire in the presence of a magnetic field.

  • Current flow is related to the time-rate change of flux.


Review ch 14
Review: Ch14

  • Maxwell “updates” and modifies work of Coulomb, Örsted, Faraday, and Ampère to produce what are now known as Maxwell’s laws.

  • Maxwell’s laws govern all electromagnetism.

  • Maxwell predicts EM waves with v = c

  • Electromagnetic spectrum includes radio and microwaves, infrared, visible light, UV, X rays, etc.

  • EM waves are produced via the oscillation of electric charges.