2. LIGO-G0500XX-00-Z 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)

3. LIGO-G0500XX-00-Z Searching for Gravitational Waves2 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

4. LIGO-G0500XX-00-Z Searching for Gravitational Waves3 Gravity: the Old School Sir Isaac Newton, who invented the theory of gravity and all the math needed to understand it

5. LIGO-G0500XX-00-Z Searching for Gravitational Waves4 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 Sun perihelion Image from Jose Wudka Urbain Le Verrier, discoverer of Mercury’s perihelion shift anomaly Image from St. Andrew’s College

6. LIGO-G0500XX-00-Z Searching for Gravitational Waves5 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.

7. LIGO-G0500XX-00-Z Searching for Gravitational Waves6 The New Wrinkle on Equivalence 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 A massive object shifts apparent position of a star

8. LIGO-G0500XX-00-Z Searching for Gravitational Waves7 Gravitational Waves 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:

9. LIGO-G0500XX-00-Z Searching for Gravitational Waves8 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.

10. LIGO-G0500XX-00-Z Searching for Gravitational Waves9 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

11. LIGO-G0500XX-00-Z Searching for Gravitational Waves10 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

12. LIGO-G0500XX-00-Z Searching for Gravitational Waves11 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

13. LIGO-G0500XX-00-Z Searching for Gravitational Waves12 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

14. LIGO-G0500XX-00-Z Searching for Gravitational Waves13 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

15. LIGO-G0500XX-00-Z Searching for Gravitational Waves14 Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral:

16. LIGO-G0500XX-00-Z Searching for Gravitational Waves15 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

17. LIGO-G0500XX-00-Z Searching for Gravitational Waves16 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

18. LIGO-G0500XX-00-Z Searching for Gravitational Waves17 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

19. LIGO-G0500XX-00-Z Searching for Gravitational Waves18 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

20. LIGO-G0500XX-00-Z Searching for Gravitational Waves19 Sensing the Effect of a Gravitational Wave Laser signal Gravitational wave changes arm lengths and amount of light in signal Change in arm length is 10 -18 meters, or about 2/10,000,000,000,000,000 inches

21. LIGO-G0500XX-00-Z Searching for Gravitational Waves20 How Small is 10 -18 Meter? Wavelength of light, about 1 micron One meter, about 40 inches Human hair, about 100 microns LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter

22. LIGO-G0500XX-00-Z Searching for Gravitational Waves21 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory 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.

23. LIGO-G0500XX-00-Z Searching for Gravitational Waves22 The LIGO Observatories 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). LIGO Hanford Observatory (LHO) H1 : 4 km arms H2 : 2 km arms LIGO Livingston Observatory (LLO) L1 : 4 km arms 10 ms

24. LIGO-G0500XX-00-Z Searching for Gravitational Waves23 Part of Future International Detector Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

25. LIGO-G0500XX-00-Z Searching for Gravitational Waves24 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

26. LIGO-G0500XX-00-Z Searching for Gravitational Waves25 Core Optics Suspension and Control Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100 th inch diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

27. LIGO-G0500XX-00-Z Searching for Gravitational Waves26 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

28. LIGO-G0500XX-00-Z Searching for Gravitational Waves27 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

29. LIGO-G0500XX-00-Z Searching for Gravitational Waves28 Simulation: Gravitational Waves Seen & Heard Play Me (AM & FM modulation greatly exaggerated) Power vs sky position Power vs frequency

30. LIGO-G0500XX-00-Z Searching for Gravitational Waves29 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

31. LIGO-G0500XX-00-Z Searching for Gravitational Waves30 : Data from detector

32. LIGO-G0500XX-00-Z Searching for Gravitational Waves31 : Data from detector : “Guess” at signal

33. LIGO-G0500XX-00-Z Searching for Gravitational Waves32 : Data from detector

34. LIGO-G0500XX-00-Z Searching for Gravitational Waves33 : Data from detector : “Guess” at signal

35. LIGO-G0500XX-00-Z Searching for Gravitational Waves34 : Data from detector : “Guess” at signal

36. LIGO-G0500XX-00-Z Searching for Gravitational Waves35 : Data from detector : “Guess” at signal

37. LIGO-G0500XX-00-Z Searching for Gravitational Waves36 : Data from detector : “Guess” at signal

38. LIGO-G0500XX-00-Z Searching for Gravitational Waves37 : Data from detector : “Guess” at signal Match!!

39. LIGO-G0500XX-00-Z Searching for Gravitational Waves38 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

40. LIGO-G0500XX-00-Z Searching for Gravitational Waves39 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

41. LIGO-G0500XX-00-Z Searching for Gravitational Waves40 Einstein@home 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 Public Launch date: Feb 19, 2005

42. LIGO-G0500XX-00-Z Searching for Gravitational Waves41 What might the sky look like?