Searching for Gravitational Waves with LIGO, GEO and Einstein@home

1. Searching for Gravitational Waves with LIGO, GEO and Einstein@home Michael Landry LIGO Hanford Observatory California Institute of Technology "Colliding Black Holes"Credit:National Center for Supercomputing Applications (NCSA)

2. Here’s what we’ll go through • What are gravitational waves? • Newton’s theory of gravity • Einstein’s theory of gravity • Go figure: space is curved! • What might make gravitational waves? • Collisions of really cool and exotic things like black holes and neutron stars • Single, isolated neutron stars spinning (wobbling?) on their axes • How do we search for them? • LIGO: Laser Interferometer Gravitational Wave Observatory • What kind of computer analysis do you have to do to see a signal? • How can you search for them from your own home?! • All you need is a home PC, internet access, and Einstein@home Searching for Gravitational Waves

3. Gravity: the Old School Sir Isaac Newton, who invented the theory of gravity and all the math needed to understand it Searching for Gravitational Waves

4. Newton’s theory: good, but not perfect! • Mercury’s orbit precesses around the sun-each year the perihelion shifts 560 arcseconds per century • But this is 43 arcseconds per century too much! (discovered 1859) • This is how fast the second hand on a clock would move if one day lasted 4.3 billion years! Mercury Urbain Le Verrier, discoverer of Mercury’s perihelion shift anomaly Sun Image from St. Andrew’s College Searching for Gravitational Waves perihelion Image from Jose Wudka

5. Einstein’s Answer: General Relativity • Space and time (spacetime) are curved. • Matter causes this curvature • Space tells matter how to move • This looks to us like gravity Picture from Northwestern U. Searching for Gravitational Waves

6. Not only the path of matter, but even the path of light is affected by gravity from massive objects Einstein Cross Photo credit: NASA and ESA The New Wrinkle on Equivalence A massive object shifts apparent position of a star Searching for Gravitational Waves

7. Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy Rendering of space stirred by two orbiting neutron stars: Gravitational Waves Searching for Gravitational Waves

8. Important Signature of Gravitational Waves Gravitational waves shrink space along one axis perpendicular to the wave direction as they stretch space along another axis perpendicular both to the shrink axis and to the wave direction. Searching for Gravitational Waves

9. Here’s what we’ll go through • What are gravitational waves? • Newton’s theory of gravity • Einstein’s theory of gravity • Go figure: space is curved! • What might make gravitational waves? • Collisions of really cool and exotic things like black holes and neutron stars • Single, isolated neutron stars spinning (wobbling?) on their axes • How do we search for them? • LIGO: Laser Interferometer Gravitational Wave Observatory • How can you search for them from your own home?! • All you need is a home PC, internet access, and Einstein@home Searching for Gravitational Waves

10. Supernova: Death of a Massive Star • Spacequake should preceed optical display by ½ day • Leaves behind compact stellar core, e.g., neutron star, black hole • Strength of waves depends on asymmetry in collapse • Observed neutron star motions indicate some asymmetry present • Simulations do not succeed from initiation to explosions Credit: Dana Berry, NASA Searching for Gravitational Waves

11. Supernova: Death of a Massive Star • Spacequake should preceed optical display by ½ day • Leaves behind compact stellar core, e.g., neutron star, black hole • Strength of waves depends on asymmetry in collapse • Observed neutron star motions indicate some asymmetry present • Simulations do not succeed from initiation to explosions Credit: Dana Berry, NASA Searching for Gravitational Waves

12. Gravitational-Wave Emission May be the “Regulator” for Accreting Neutron Stars • Neutron stars spin up when they accrete matter from a companion • Observed neutron star spins “max out” at ~700 Hz • Gravitational waves are suspected to balance angular momentum from accreting matter Credit: Dana Berry, NASA Searching for Gravitational Waves

13. Gravitational-Wave Emission May be the “Regulator” for Accreting Neutron Stars • Neutron stars spin up when they accrete matter from a companion • Observed neutron star spins “max out” at ~700 Hz • Gravitational waves are suspected to balance angular momentum from accreting matter Credit: Dana Berry, NASA Searching for Gravitational Waves

14. Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral: Searching for Gravitational Waves

15. The “Undead” Corpses of Stars:Neutron Stars and Black Holes • Neutron stars have a mass equivalent to 1.4 suns packed into a ball 10 miles in diameter, enormous magnetic fields and high spin rates • Black holes are the extreme edges of the space-time fabric Artist: Walt Feimer, Space Telescope Science Institute Searching for Gravitational Waves

16. The “Undead” Corpses of Stars:Neutron Stars and Black Holes • Neutron stars have a mass equivalent to 1.4 suns packed into a ball 10 miles in diameter, enormous magnetic fields and high spin rates • Black holes are the extreme edges of the space-time fabric Artist: Walt Feimer, Space Telescope Science Institute Searching for Gravitational Waves

17. Here’s what we’ll go through • What are gravitational waves? • Newton’s theory of gravity • Einstein’s theory of gravity • Go figure: space is curved! • What might make gravitational waves? • Collisions of really cool and exotic things like black holes and neutron stars • Single, isolated neutron stars spinning (wobbling?) on their axes • How do we search for them? • LIGO: Laser Interferometer Gravitational Wave Observatory • What kind of computer analysis do you have to do to see a signal? • How can you search for them from your own home?! • All you need is a home PC, internet access, and Einstein@home Searching for Gravitational Waves

18. End Mirror End Mirror Beam Splitter Laser Screen Sketch of a Michelson Interferometer Viewing Searching for Gravitational Waves

19. Gravitational wave changes arm lengths and amount of light in signal Sensing the Effect of a Gravitational Wave Change in arm length is 10-18 meters, or about 2/10,000,000,000,000,000 inches Laser signal Searching for Gravitational Waves

20. One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron Atomic diameter, 10-10 meter Nuclear diameter, 10-15 meter LIGO sensitivity, 10-18 meter How Small is 10-18 Meter? Searching for Gravitational Waves

21. The Laser Interferometer Gravitational-Wave Observatory LIGO (Washington) LIGO (Louisiana) Brought to you by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide. Searching for Gravitational Waves

22. The LIGO Observatories LIGO Hanford Observatory (LHO) H1 : 4 km arms H2 : 2 km arms • Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov • NASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights). 10 ms LIGO Livingston Observatory (LLO) L1 : 4 km arms Searching for Gravitational Waves

23. Part of Future International Detector Network Simultaneously detect signal (within msec) Virgo GEO LIGO TAMA detection confidence locate the sources decompose the polarization of gravitational waves AIGO Searching for Gravitational Waves

24. Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter Searching for Gravitational Waves

25. Core Optics Suspension and Control Optics suspended as simple pendulums Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100th inch diameter wire to 1/100th degree of arc Searching for Gravitational Waves

26. Here’s what we’ll go through • What are gravitational waves? • Newton’s theory of gravity • Einstein’s theory of gravity • Go figure: space is curved! • What might make gravitational waves? • Collisions of really cool and exotic things like black holes and neutron stars • Single, isolated neutron stars spinning (wobbling?) on their axes • How do we search for them? • LIGO: Laser Interferometer Gravitational Wave Observatory • What kind of computer analysis do you have to do to see a signal? • How can you search for them from your own home?! • All you need is a home PC, internet access, and Einstein@home Searching for Gravitational Waves

27. Detecting a signal • We’ve talked about gravity waves and about sources… now let’s talk about detection! • If our detector was not moving with respect to a star, gravity waves would sound like a single tone • Gravity waves from dense spinning stars are Doppler shifted by the motions of the Earth relative to the star (FM) • Gravity waves are also amplitude modulated because interferometer sensitivity varies with direction (AM) Waves get Doppler shifted from relative motion Searching for Gravitational Waves

28. Simulation:Gravitational Waves Seen & Heard Power vs frequency Play Me Power vs sky position (AM & FM modulation greatly exaggerated) Searching for Gravitational Waves

29. Detecting a signal • Steps in detection: • Guess at what the signal might look like • Compare your guess to your data from your interferometer • This is called matched filtering • If you don’t find a signal, keeping guessing and comparing Searching for Gravitational Waves

30. : Data from detector Searching for Gravitational Waves

31. : Data from detector : “Guess” at signal Searching for Gravitational Waves

32. : Data from detector Searching for Gravitational Waves

33. : Data from detector : “Guess” at signal Searching for Gravitational Waves

34. : Data from detector : “Guess” at signal Searching for Gravitational Waves

35. : Data from detector : “Guess” at signal Searching for Gravitational Waves

36. : Data from detector : “Guess” at signal Searching for Gravitational Waves

37. : Data from detector : “Guess” at signal Match!! Searching for Gravitational Waves

38. Here’s what we’ll go through • What are gravitational waves? • Newton’s theory of gravity • Einstein’s theory of gravity • Go figure: space is curved! • What might make gravitational waves? • Collisions of really cool and exotic things like black holes and neutron stars • Single, isolated neutron stars spinning (wobbling?) on their axes • How do we search for them? • LIGO: Laser Interferometer Gravitational Wave Observatory • What kind of computer analysis do you have to do to see a signal? • How can you search for them from your own home?! • All you need is a home PC, internet access, and Einstein@home Searching for Gravitational Waves

39. Why distributed computing? • e.g. searching 1 year of data, you have 3 billion frequencies in a 1000Hz band • For each frequency we need to search 100 million million independent sky positions • pulsars spin down, so you have to consider approximately one billion times more “guesses” at the signal • Number of templates for each frequency: ~100,000,000,000,000,000,000,000 • Clearly we rapidly become limited in the analysis we can do by the speed of our computer! Einstein@home!!! a.k.a. Distributed computing Searching for Gravitational Waves

40. Einstein@home Public Launch date: Feb 19, 2005 http://einstein.phys.uwm.edu/ • Like SETI@home, but for LIGO/GEO data • Goal: pulsar searches using ~1 million clients. Support for Windows, Mac OSX, Linux clients • From our own clusters we can get thousands of CPUs. From Einstein@home hope to many times more computing power at low cost Searching for Gravitational Waves

41. What might the sky look like? Searching for Gravitational Waves