Catching the Waves with LIGO: Gravitational Waves & "Colliding Black Holes

1. Catching the Waves with LIGOBarry BarishWatson Lecture5-March-03

2. Gravitational Waves "Colliding Black Holes"Credit:National Center for Supercomputing Applications (NCSA)

3. Gravity a fundamental force

4. Universal Gravitation • Solved most known problems of astronomy and terrestrial physics • eccentric orbits of comets • cause of tides and their variations • the precession of the earth’s axis • the perturbation of the motion of the moon by gravity of the sun • Unified the work of Galileo, Copernicus and Kepler unified.

5. But, what causes the mysterious force in Newtons theory ? Although the equation explains nature very well, the underlying mechanism creating the force is not explained !

6. General Relativitythe essential idea Gmn= 8pTmn • Gravity is not a force, but a property of space & time • Spacetime = 3 spatial dimensions + time • Perception of space or time is relative • Objects follow the shortest path through this warped spacetime; path is the same for all objects • Overthrew the 19th-century concepts of absolute space and time • Concentrations of mass or energy distort (warp) spacetime

7. General Relativity Einstein theorized that a massive object warps the surrounding space

8. General Relativity Smaller objects travel through space that is warped by larger objects

9. After several hundred years, a small crack in Newton’s theory ….. perihelion shifts forward an extra +43”/century compared to Newton’s theory

10. A new prediction of Einstein’s theory … bending of light Observation made during the solar eclipse of 1919 by Sir Arthur Eddington, when the Sun was silhouetted against the Hyades star cluster A massive object shifts apparent position of a star

11. Confirming Einstein … Their measurements showed that the light from these stars was bent as it grazed the Sun, by the exact amount of Einstein's predictions.

12. Einstein’s Cross The bending of light rays gravitational lensing Quasar image appears around the central glow formed by nearby galaxy. The Einstein Cross is only visible in southern hemisphere.

13. A Conceptual Problem is solved ! Newton’s Theory “instantaneous action at a distance” Einstein’s Theory information carried by gravitational radiation at the speed of light

14. Einstein’s Theory of Gravitation • a necessary consequence of Special Relativity with its finite speed for information transfer • gravitational waves come from the acceleration of masses and propagate away from their sources as a space-time warpage at the speed of light gravitational radiation binary inspiral of compact objects

15. Russel A. Hulse Joseph H.Taylor Jr Binary Pulsars emit gravity waves The Evidence For Gravitational Waves The Discovered and Studied Pulsar System PSR 1913 + 16 with Radio Telescope Source: www.NSF.gov

16. Neutron Star Radio Pulsar

17. The evidence for gravitational waves • Neutron binary system • separation = 106 miles • m1 = 1.4m • m2 = 1.36m • e = 0.617 Hulse & Taylor 17 / sec · · • Prediction • from • general relativity • spiral in by 3 mm/orbit • rate of change orbital • period period ~ 8 hr PSR 1913 + 16 Timing of pulsars

18. “Indirect”evidence for gravitational waves

19. Direct Detection Gravitational Wave Astrophysical Source Terrestrial detectors LIGO, TAMA, Virgo,AIGO Detectors in space LISA

20. Gravitational wave detection in space The Laser Interferometer Space Antenna LISA • Center of the triangle formation is in the ecliptic plane • 1 AU from the Sun and 20 degrees behind the Earth.

21. Detection on Earth simultaneously detect signal LIGO Virgo GEO TAMA AIGO detection confidence decompose the polarization of gravitational waves locate the sources

22. The frequency range of astrophysics sources of gravitational waves Audio band • Gravitational Waves over ~8 orders of magnitude • Terrestrial detectors and space detectors Space Terrestrial

23. The frequency range of astronomy • EM waves studied over ~16 orders of magnitude • Ultra Low Frequency radio waves to high energy gamma rays

24. The effect of a gravitational wave passing through us … Leonardo da Vinci’s Vitruvian man stretch and squash in perpendicular directions at thefrequency of the gravitational waves

27. I have greatly exaggerated the effect!! If the Vitruvian man was 4.5 light years high, he would grow by only a ‘hairs width’ LIGO Interferometer Concept LIGO (4 km), stretch (squash) = 10-18 m will be detected at frequencies of 10 Hz to 104 Hz. It can detect waves from a distance of 600 106 light years

28. As a wave passes, the arm lengths change in different ways…. Suspended Mass Interferometer Concept • Arms in LIGO are 4km • Measure difference in length to one part in 1021 or 10-18 meters • Laser used to measure relative lengths of two orthogonal arms …causing the interference pattern to change at the photodiode

29. One meter ~ 40 inches Human hair ~ 100 microns Wavelength of light ~ 1 micron Atomic diameter 10-10 m Nuclear diameter 10-15 m LIGO sensitivity 10-18 m How Small is 10-18 Meter?

30. Robbie Vogt Kip Thorne Rai Weiss Ron Drever CALTECH 40 m LIGO Prototype

31. Today’s Caltech LIGO Group

32. DESIGN CONSTRUCTION OPERATION SCIENCE Detector R&D LIGO Laboratory MIT + Caltech ~140 people Director: Barry Barish LIGO Science Collaboration 44 member institutions > 400 scientists Spokesperson: Rai Weiss UK Germany Japan Russia India Spain Australia $ National Science Foundation LIGO Organization & Support

33. LIGOLaser Interferometer Gravitational-wave Observatory Hanford Observatory MIT Caltech Livingston Observatory

34. LIGO Livingston Observatory

35. LIGO Hanford Observatory

36. Beam Tube under High Vacuum • LIGO beam tube under construction in January 1998 • 65 ft spiral welded sections • girth welded in portable clean room in the field 1.2 m diameter - 3mm stainless 50 km of weld NO LEAKS !!

37. Vacuum Chambers

38. Optics Substrates: SiO2 25 cm Diameter, 10 cm thick Homogeneity < 5 x 10-7 Internal mode Q’s > 2 x 106 Polishing Surface uniformity < 1 nm rms Radii curvature matched < 3% Coating Scatter < 50 ppm Absorption < 2 ppm Uniformity <10-3

39. Core Optics Installation and Alignment

40. What Limits LIGO Sensitivity? • Seismic noise limits low frequencies • Thermal Noise limits middle frequencies • Quantum nature of light (Shot Noise) limits high frequencies • Technical issues - alignment, electronics, acoustics, etc limit us before we reach these design goals

41. LIGO interferometers are working better and better …. May 01 Jan 03 goal

42. Detecting Earthquakes From electronic logbook 2-Jan-02 An earthquake occurred, starting at UTC 17:38.

43. Detect the Earth Tide from the Sun and Moon

44. Compact binary collisions:“chirps” • Neutron Star – Neutron Star • waveforms are well described • Black Hole – Black Hole • need better waveforms • Search: matched templates Neutron Star Merger Simulation and Visualization by Maximilian Ruffert& Hans-Thomas Janka

45. Supernovae:“burst signals” The death of stars time evolution Images from NASA High Energy Astrophysics Research Archive

46. Stars Form • Collapsing gas clouds heat up and ignite nuclear burning, fusing hydrogen, helium to heavier elements • Stars Burn • Star becomes “layered”, like an onion, with heavy elements fusing yet heavier elements at center • Iron is the heaviest element that will fuse this way • Eventually, the atoms in the star “melt” into a sea of electrons and nuclei. This sea resists compression and might stop collapse  “dwarf” star. • In more massive stars, electrons and nuclei are crushed into pure nuclear matter  “neutron star”. This stiffer form of matter may halt collapse. • Stars Collapse • As the end of the fusion chain is reached, nuclear burning can no longer provide the pressure to hold the star up under gravity • The material in the star continues to crush together • No other form of matter exists to stop collapse in heavier stars  space and time warpage increase until an “event horizon” forms  “black hole”.

47. Spinning Neutron Stars: “periodic” Maximum gravitational wave luminosity of known pulsars An afterlife of stars

48. Early Universe: “correlated noise” ‘Murmurs’ from the Big Bang Cosmic Microwave background WMAP 2003

49. Gravitational waves from the early universe E7 results projected S1 S2 LIGO Adv LIGO

50. Advanced LIGOimproved subsystems Multiple Suspensions Active Seismic Sapphire Optics Higher Power Laser