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Black Hole Event Horizon

Black Hole Event Horizon. Event Horizon. A Black Hole has a truly unique property: it possesses an Event Horizon A “ virtual ” surface One-way membrane --- matter/energy can fall in, but nothing gets out, not even light. Singularity. A Black Hole is Amazingly Simple. Mass: M

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Black Hole Event Horizon

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  1. Black Hole Event Horizon Event Horizon • A Black Hole has a truly unique property: it possesses an Event Horizon • A “virtual” surface • One-way membrane --- matter/energy can fall in, but nothing gets out, not even light Singularity

  2. A Black Hole is Amazingly Simple • Mass: M • Spin: a* (J=a*GM2/c) • Charge: Q Even though it is a macroscopic object, a BH is as simple as an elementary particle!

  3. Can We Test These Features? • Confirm that astrophysical BHs actually do have Event Horizons • Measure the two fundamental parameters of BHs • Mass (relatively easy) • Spin (much harder) • Ramesh Narayan, Jeff McClintock

  4. Do Black Hole Candidates Have Event Horizons? • Are Black Hole Candidates really BHs? • Can we find independent evidence that our BH candidates actually possess Event Horizons

  5. X-ray Binaries Image credit: Robert Hynes (2002)

  6. The Idea • Find BH X-ray Binaries in which the accretion flow radiates very little • Objects with surfaces (NSs) will then be much brighter than objects with event horizons (BHs) • Look for a huge difference in luminosity Narayan, Garcia & McClintock (1997)

  7. Large difference in luminosity between BHs and NSs is dramatically verified (Narayan, Garcia & McClintock;Garcia et al. 2001; McClintock et al. 2003; …) • Black Holes are really black!! Event Horizon

  8. Black Hole Spin • The material from which a BH is formed almost always has angular momentum • Also, accretion adds angular momentum • So we expect astrophysical BHs to be spinning: J = a*GM2/c, 0  a*  1 • Can we measure a*?

  9. The Basic Idea Measure radius of hole by estimating area of the bright inner disk (Zhang et al. 1997; Shafee et al. 2006; McClintock et al. 2006)

  10. Black Hole Parameters

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