Black&Holes The$point where all$laws of physics break$down Sascha$Hablützel$&$Samantha$Pafumi Outline 1. Definition 2. Detection of a-Black-Hole 3. Types and-Sizes 4. A-Thought Experiment 5. Theories 6. Open-Questions 7. Summary Black&Hole&– a&Concise Definition • Historical-Prediction: Einstein‘s General-Relativity (1915):-gravity is a-distortion of spacetime ! there are dense regions where not-even light-can escape • Simple-Definition: A-black hole-is a-region in-spacetime,-where there is so-much concentrated mass,-that gravity is so-strong-that not-even light-can escape its surface. Structure of a&Simple&Black&Hole • Event$Horizon:-where the escape velocity is equal to the speed of light • (Gravitational)$Singularity:-a-single small point with very high-density )*++→-./0(234356) )*++ !"#$%&' = = → %#?%#%&' 89:;)6→-./0(<6=9) > @ vs.- = A#!"?%#"! > • Schwarzschild$Radius$(Rs):-the size of the black hole Figure 1:-Black-Hole-Structure CDE C×M.MO×P>QRR×M×P>GS B = ! B HIJ&ℎ = ≈ 0.0090Y0 ≈ 9YY + FG + T×P>U G What is a&Black&Hole&Made&of? • We cannot see a-black hole,-but-it has three properties that can be measured: 1. Mass 2. Electric Charge 3. Angular-Momentum !But:-there is no way to distinguish black holes,-i.e.-matter-that forms a-BH-or falls-into it disappears ! this concept is called:-„a$black hole$has no hair“ Detection of Black&Holes • Cannot be directly detected Figure 2:-Star-being torn apart • Only their effects on-nearby matter-can be detected: 1. A-star gets torn apart-as it gets pulled towards the black hole 2. Cloud-of interstellar-matter-forms an-accretion disc and-emits x[rays 3. Stars-orbiting a-massive,-but-unseen object, e.g.-Sagittarius A 4. Gravitational lens effects Figure 3:-Sagittarius A Types and&Sizes&@ Two General&Types of BH 1. NonGrotating black holes (Schwarzschild) 2. Rotating black holes (Kerr) • Formed from a-rotating star (most common) • Static limit:-boundary between ergosphere and normal-space • Ergosphere:-egg[shaped,-distorted space around the event horizon • Inner &$outer event horizon:-caused by rotation of BH • Singularity:$formed like-a-donut Types and&Sizes – Four Sizes&of BH 1.$Stellar$Black$Holes • Mass:-5[20-Msol • Radius:-10[300-km • Formation:-when a-massive-star (> 30\+9:)0collapses • Location:-throughout the entire galaxy (the same-places where we find-stars) • Spaghettification Types and&Sizes – Four Sizes&of BH 2.$Supermassive$Black$Holes • Mass:-millions [ billions Msol • Radius:-3-mio – 30-bio km • Formation:-not-known [ probably a-byproduct of galaxy formation • Location:-likely exist in-the centers of nearly every large-galaxy • Other-characteristics:-continue to grow by sucking in-matter Types and&Sizes – Four Sizes&of BH 3.$Intermediate$Black$Holes • Mass:-100-– 1-million Msol • Radius:-300-– 3‘000‘000-km • Formation:-not-known • Location:-mostly in-star clusters or in-dwarf galaxies Types and&Sizes – Four Sizes&of BH 4.$Primordial$Black$Holes • Mass:-10P^gram • Radius:-10[15-m • Formation:-shortly after-the Big-Bang • Location:-are not-yet discovered General$Relativity Hawking-Radiation A&Thought Experiment String-Theory Quantum • What happens if Sascha-falls-into a-supermassive-black hole-and- Samantha-is watching her-from a-„safe“-distance?- Sascha-stays in- front-of the Event- Horizon forever No,-I-passed the Event-Horizon A&Thought Experiment • General'Relativity:'massive'objects warp'spacetime ! Gravitational time-dilation:-Sascha‘s clock runs slow relative-to distant clocks • Special'Relativity:'time'stops at'c ! at-the Event-Horizon time-will-stop for outside-observers • Gravitational redshift is infinite-! invisible Excursus – Wormholes and&White&Holes • White$Holes: Expel-matter-from-a-singularity But:-violation-of-the-2nd-law-of-thermodynamics • Wormholes: Link-two-seperate points-in-spacetime • Open-question:-What-if-a-black-hole-and-a-white-hole-collided? Open&Questions • How do-supermassive-black holes form? • Does the mass of a-black hole-change during time? • Do-all-black holes evaporate? • What happens inside a-black hole? • Black-hole-information paradox-(firewalls)- Summary • 2-types:-Schwarzschild-&-Kerr • 4-different-sizes,-only 3-existing:-supermassive,-stellar,-intermediate • Black-Hole-description 1. Mass 2. Electric-Charge 3. Angular-Momentum • Event-Horizon:-where-the-escape-velocity-is-equal-to-c • Singularity:-a-point-with-infinite-density For Interested Students… Movies: Links: • Interstellar • http://curious.astro.cornell.edu/the[ • Event-Horizon universe/black[holes[and[quasars • Battlestar:-Galactica • https://www.universetoday.com/46687 /black[hole[facts/ • Stargate-SG1 • PBS-Space-Time:-Black-Holes-Playlist- Books: https://www.youtube.com/watch?v=vN • Hawkings-Kosmos-einfach-erklärt-– aEBbFbvcY&list=PLtN[ Rüdiger-Vaas PHIoVLbGc7OVtjd[AT7qKxh7_rhNN • UNIVERSO-[ La-guia visual definitva from Cosar Editores References • Figure 1:-https://imagine.gsfc.nasa.gov/science/objects/black_holes1.html • Figure 2:-https://www.youtube.com/embed/hu6hIhW00Fk • Figure 3:-http://www.galacticcenter.astro.ucla.edu/animations.html • Sources-for types of black holes:- https://imagine.gsfc.nasa.gov/science/objects/black_holes1.html • Rotating black holes: https://universe[review.ca/R15[17[relativity04.htm • Evaporation:-https://en.wikipedia.org/wiki/Hawking_radiation • Firewalls:-https://phys.org/news/2016[04[hot[problem[black[hole[firewalls.html.