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Transcript of Martin D. Weinberg UMass Astronomy weinberg@astro. · PDF file Martin D. Weinberg UMass...

  • Read: S2, S3, Chap 18 10/30/14 – slide 1

    A100–Exploring the Universe: Black holes

    Martin D. Weinberg

    UMass Astronomy

    weinberg@astro.umass.edu

    October 30, 2014

  • Announcements

    ⊲ Announcements Forming BHs

    Energy

    Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 2

    The solar neighborhood visualized!

    http://stars.chromeexperiments.com

    Thanks to Raymond Phoung

    http://stars.chromeexperiments.com http://stars.chromeexperiments.com

  • Announcements

    ⊲ Announcements Forming BHs

    Energy

    Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 2

    The solar neighborhood visualized!

    http://stars.chromeexperiments.com

    Thanks to Raymond Phoung

    Exam #2: November 04

    ⊲ Covers Chaps: S4, 14, 15, (16), 17, 18

    http://stars.chromeexperiments.com http://stars.chromeexperiments.com

  • Announcements

    ⊲ Announcements Forming BHs

    Energy

    Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 2

    The solar neighborhood visualized!

    http://stars.chromeexperiments.com

    Thanks to Raymond Phoung

    Exam #2: November 04

    ⊲ Covers Chaps: S4, 14, 15, (16), 17, 18

    Today

    1. Black holes

    ⊲ What they are

    ⊲ What they are NOT

    ⊲ Theories of relativity

    http://stars.chromeexperiments.com http://stars.chromeexperiments.com

  • Announcements

    ⊲ Announcements Forming BHs

    Energy

    Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 2

    The solar neighborhood visualized!

    http://stars.chromeexperiments.com

    Thanks to Raymond Phoung

    Exam #2: November 04

    ⊲ Covers Chaps: S4, 14, 15, (16), 17, 18

    Today

    1. Black holes

    ⊲ What they are

    ⊲ What they are NOT

    ⊲ Theories of relativity

    Questions?

    http://stars.chromeexperiments.com http://stars.chromeexperiments.com

  • Stellar evolution ⇒ Black Holes

    Announcements

    ⊲ Forming BHs Energy

    Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 3

    A star with M > 18MSun would leave behind an iron core more massive than 2-3 MSun

    Neutron degeneracy pressure would fail with nothing to

    stop its gravitational collapse

    Core would collapse into a singularity!

    Gravity becomes so strong that nothing, not even light,

    can escape

    Infalling matter is shredded by powerful tides

    Black hole!

    ⊲ Black because they neither emit nor reflect light

    ⊲ Hole because nothing entering can ever escape

  • Energy is conserved: a quick review

    Announcements

    Forming BHs

    ⊲ Energy Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 4

    Definition:

    Energy is the capacity of a physical system to do work

    Definition:

    Work is application of force over a distance

  • Kinetic energy

    Announcements

    Forming BHs

    ⊲ Energy Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 5

    Example: kinetic energy from accelerating an object

    fv=v

    v=0

    d

    d

    m

    m

    ⊲ Push object with constant force over distance d

    ⊲ Final velocity vf

    ⊲ Average velocity: v̄ = vf 2

    = d

    t

    ⊲ Force required: F = ma = m vf t

    ⊲ Work done (energy): E = Fd = mvfd

    t =

    1

    2 mv2f

  • Kinetic energy

    Announcements

    Forming BHs

    ⊲ Energy Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 5

    Example: kinetic energy from accelerating an object

    fv=v

    v=0

    d

    d

    m

    m

    ⊲ Push object with constant force over distance d

    ⊲ Final velocity vf

    ⊲ Average velocity: v̄ = vf 2

    = d

    t

    ⊲ Force required: F = ma = m vf t

    ⊲ Work done (energy): E = Fd = mvfd

    t =

    1

    2 mv2f

  • Kinetic energy

    Announcements

    Forming BHs

    ⊲ Energy Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 5

    Example: kinetic energy from accelerating an object

    fv=v

    v=0

    d

    d

    m

    m

    ⊲ Push object with constant force over distance d

    ⊲ Final velocity vf

    ⊲ Average velocity: v̄ = vf 2

    = d

    t

    ⊲ Force required: F = ma = m vf t

    ⊲ Work done (energy): E = Fd = mvfd

    t =

    1

    2 mv2f

  • Kinetic energy

    Announcements

    Forming BHs

    ⊲ Energy Escape velocity

    Schwarzschild

    Sizes of black holes

    Thought question

    Laws of physics

    Special Relativity

    Consequences

    Photon clock

    More consequences

    General Relativity

    Back to Black holes

    Event horizon

    Gravity around a black hole

    Gravitational redshift

    Not really Black!

    Evaporating Holes

    Other Predictions

    Read: S2, S3, Chap 18 10/30/14 – slide 5

    Example: kinetic energy from accelerating an object

    fv=v

    v=0

    d

    d

    m

    m

    ⊲ Push object with constant force over distance d

    ⊲ Final velocity vf

    ⊲ Average velocity: v̄ = vf 2

    = d

    t

    ⊲ Force required: F = ma = m vf t

    ⊲ Work done (energy): E = Fd = mvfd

    t =

    1

    2 mv2f

  • Potential energy

    Read: S2, S3, Chap 18 10/30/14 – slide 6

    Example: potential energy is energy that can be converted to kinetic

    energy by moving in a force field

    Ground level

    v=0

    v=vf

    ⊲ Potential energy is p