1 / 17

Trip to a Black Hole I

Extraordinary Concepts in Physics. Lecture 4. Trip to a Black Hole I. by  Robert J. Nemiroff  Michigan Tech. Physics X: About This Course. Officially "Extraordinary Concepts in Physics" Being taught for credit at Michigan Tech Light on math, heavy on concepts Anyone anywhere is welcome

Download Presentation

Trip to a Black Hole I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Extraordinary Concepts in Physics Lecture 4 Trip to a Black Hole I by  Robert J. Nemiroff  Michigan Tech

  2. Physics X: About This Course • Officially "Extraordinary Concepts in Physics" • Being taught for credit at Michigan Tech • Light on math, heavy on concepts • Anyone anywhere is welcome • No textbook required • Wikipedia, web links, and lectures only • Find all the lectures with Google at: • "Starship Asterisk" then "Physics X"  • http://bb.nightskylive.net/asterisk/viewforum.php?f=39

  3. Trip to a Black Hole: Overview • Schwarzschild black hole only • It's the easiest • It's what I know best • Based partly on my paper: •  "Visual distortions near a neutron star and black hole" • American Journal of Physics 1993, 61, 619 • And my web page:   • Virtual Trips to Black Holes and Neutron Stars

  4. Trip to a Black Hole: Key Distances • r = infinity: space is flat: aN = GM/r2 • Near the black hole: a = aN / (1 - rs/r)1/2 • r = 3 rs: last stable orbit • r = 1.5 rs: photon sphere • r = rs: event horizon • r = rc: Compton radius • r = 0: GR singularity

  5. Trip to a Black Hole: Far Away • r -> infinity: space is "flat" • all (1 - rs/r) terms go to 1. • gravity is Newtonian:  aN = GM/r2 •  black holes attract the same as normal matter • curved universe NOT flat as r -> infinity • can see lensing effects with a telescope  • orbiting the same as spinning in place

  6. Trip to a Black Hole: Approaching • black hole appears black • excludes evaporation effects • blackness everywhere inside photon sphere • cannot see to the event horizon • outside, average surface brightness unchanged • appears fuzzy as star images merge • distant universe  • speeds up • appears bluer

  7. Background: Gravitational Lensing • gravity bends light: "null geodesics"

  8. Gravitational Lensing:Einstein Ring • Actual Einstein ring: APOD 2008 July 28

  9. Gravitational Lensing:Einstein Ring • Detailed image of Einstein ring from AJP paper

  10. Trip to a Black Hole: Orbiting Nearby

  11. Trip to a Black Hole: Orbiting at 10 rs  • Stars CANNOT cross the Einstein ring • Einstein ring mapped point behind BH center • Einstein ring divides complete image sets • Angular speeds diverge at the Einstein ring • One can see oneself  • All stars have two discernible images • One outside the ER, one inside • Observers also have two images • Actually, an infinite number of images exist

  12. Trip to a Black Hole: Orbiting at 10 rs  • Distant stars appear slightly bluer • Distant clocks appear to run faster • This also occurs for stars that appear next to the black hole • Objects ACTUALLY nearer to the black hole • Appear redder • Clocks appear to run slower

  13. Trip to a Black Hole: Orbiting at the Photon Sphere

  14. Trip to a Black Hole: Orbiting at the Photon Sphere • Everything below you is black • because those light paths fall into the BH • The whole sky appear above you • because those light paths escape the BH • The Einstein ring appears above the horizon • Stars still CANNOT cross the Einstein ring • Stars still speed up near the Einstein ring

  15. Trip to a Black Hole: Orbiting at the Photon Sphere • Other image sets between other Einstein rings • "The" Einstein ring actually "First Sky Einstein ring" • There are infinitely many Sky Einstein rings • Every radius from the BH has  • its own infinite set of Einstein rings • its own redshift (or blueshift)

  16. Gravitational Lensing:Einstein Ring • Einstein rings near a black hole

More Related