FRONTIERS OF ASTROPHYSICS - giant telescopes, space missions and invisible wavelengths

1. FRONTIERS OF ASTROPHYSICS- giant telescopes, space missions and invisible wavelengths Michael Rowan-Robinson Imperial College London Institute of Physics, Liverpool

2. some frontier topics in astrophysics • Black holes • The dusty universe • - dramatic starbursts in colliding galaxies • Exoplanets • - the search for extraterrestial earths • Cosmology • - measuring the size and age of universe with 5% precision • - a universe of dark matter, dark energy Institute of Physics, Liverpool

3. first detection of electromagnetic radiation outside the optical band:Herschel (1800) detectedinfrared radiation from the sun Atmospheric transmission Institute of Physics, Liverpool

4. X-ray astronomy The first X-ray satellite, Uhuru (1970) detected X-rays from compact sources in binary systems (white dwarfs, neutron stars, black holes), from quasars (massive black holes) and from very hot gas in clusters of galaxies (100 million degrees) Institute of Physics, Liverpool

5. HOW TO OBSERVE BLACK HOLES? Black holes give off no light from within the event horizon Must observe effects on environment near horizon, in particular: VELOCITIES (matter speeds up near hole) ACCRETION (matter being sucked into hole and heated to X-ray temperatures) REDSHIFT (time slows down near hole) * Effect of Einstein’s General relativity * Institute of Physics, Liverpool

6. Cygnus X-1, a 10 solar mass black hole in our Galaxy Institute of Physics, Liverpool

7. X-ray spectra of black holes in Active Galactic nuclei Hypothesis: The nucleus of an Active Galaxy contains a black hole being fed by an accretion disk. X-rays illuminate the disk inducing emission from iron. Prediction: shape of line distorted by huge velocities and gravitational shifts Observer X-rays Institute of Physics, Liverpool

8. WE SEE THESE EFFECTS! X-ray iron spectrum from the ASCA satellite Clear broadening and redshift Requires black hole ASCA • Line profile depends on: • Inclination • Inner radius • Outer radius • X-ray illumination pattern Tanaka et al. (1995) Institute of Physics, Liverpool

9. Institute of Physics, Liverpool

10. Institute of Physics, Liverpool

11. AND THEY ARE COMMON Nandra et al. (2007) New spectra from XMM-Newton Institute of Physics, Liverpool

12. the dusty universe IRAS 1983 - SPITZER, 2003 Institute of Physics, Liverpool

13. IRAS - star forming regions constellation Orion LMC, the Large Magellanic Cloud Institute of Physics, Liverpool

14. Uultraluminous infrared galaxies IRAS discovered ultraluminous infrared galaxies, forming stars 100-1000 times faster than our Galaxy, probably caused by mergers between two galaxies this is an image of Arp 220 Institute of Physics, Liverpool

15. Sombrero galaxy- end product of a galaxy merger Institute of Physics, Liverpool

16. IC1396, the Elephant’s Trunk • a dark globule inside an emission nebula • a pair of newly formed stars have created a cavity • the animation shows how the appearance changes from the optical, where dust absorbs light to the infrared where the dust radiates Institute of Physics, Liverpool

17. Institute of Physics, Liverpool

18. IRAS - dust debris disks IRAS also discovered dust debris disks around stars, confirmed by imaging with the Hubble Space Telescope, evidence for planetary systems in formation. Today over 200 exoplanets are known. Institute of Physics, Liverpool

19. last week: HST image of exoplanet in Fomalhaut debris disk Institute of Physics, Liverpool

20. The Exo-Planet Discovery Era • <1995 Solar System planets • 1995 first extra-solar planet ( 51 Peg ) - Hot Jupiters! • 2008 ~300 exo-planets known • 2005-10 first Hot and Cool exo-Earths • 2010-15 Habitable Earths -- common or rare? • 2020-30 Extra-solar Life? Are we alone? Institute of Physics, Liverpool

21. Exoplanet Discovery Methods • Doppler Star Wobbles: ~230 • Transits: 39 • Microlensing: 7 Institute of Physics, Liverpool

22. 1995First Doppler Wobble Planet:51 Peg Discovered by accident: Mayor & Queloz (1995) Quickly confirmed: Marcy & Butler (1995) P = 4.2 days (!) a = 0.05 AU T ~2000K m sin(i) = 0.5 mJ New class of planet:“Hot Jupiters” (how did these form ?) Institute of Physics, Liverpool

23. Institute of Physics, Liverpool

24. WASP’s first 2 new Hot Jupiters UK WASP Consortium: Belfast, St.Andrews, Keele, Open, Leicester, Cambridge, IAC, SAAO Institute of Physics, Liverpool

25. brown dwarfs, gas giants and rocky planets Low-Mass Stars Gas Giant Planets Rock/Ice Planets Institute of Physics, Liverpool

26. How to find Earths ? • Hot Earths: Transits from Space • 2007-10 … CoRoT -- Launched 27 Dec 2006. • 2009-15 … Kepler • 2017 … PLATO • Habitable Earths:Hard to Find • Habitable Zone: T~300K liquid water on rocky planet surface • Cool Earths:Gravitational Lensing • 2004-14 … OGLE, PLANET/RoboNet, microFUN, MOA Institute of Physics, Liverpool

27. CoRoT (CNES) First CoRoT planet: 3 May 2007 Launch 27 Dec 2006 CoRoT-Exo-1b: P = 1.5 d m sin(i) = 1.3 mJ 6 months/field Institute of Physics, Liverpool

28. Space Transit Planet Catch A few Earth-like Planets may be found. hot habitable Jupiters Planet Size (rE) Too large? Earths Too small? Too hot? Planet Temperature (K) Institute of Physics, Liverpool

29. OB-03-235 / MB-03-053 first microlens planet 2003 MOA OGLE OGLE alert Bond et al. (2004) Institute of Physics, Liverpool

30. OB-05-390 smallest cool planet Aug 2005 OB-05-390 PLANET/RoboNet OGLE MOA Institute of Physics, Liverpool

31. ESA: Darwin ~ 2020-30?infrared space interferometer destructive interference cancels out the starlight snapshot ~500 nearby systems study ~ 50 in detail Institute of Physics, Liverpool

32. Life’s Signature:disequilibrium atmosphere(e.g. oxygen-rich) simulated Darwin spectrum Which planet is alive? Institute of Physics, Liverpool

33. The distances of the galaxies In 1924 Edwin Hubble used Cepheid variable stars to estimate the distance of the Andromeda Nebula. It clearly lay far outside the Milky Way System. This opened up the idea of a universe of galaxies. Institute of Physics, Liverpool

34. The expansion of the universe Five years later he announced, based on distances to 18 galaxies, that the more distant a galaxy, the faster it is moving away from us velocity/distance = constant, Ho (the Hubble law) This is just what would be expected in an expanding universe. The Russian mathematician Alexander Friedmann had shown that expanding universe models are what would be expected according to Einstein’s General Theory of Relativity, if the universe is homogeneous (everyone sees the same picture) and isotropic (the same in every direction). Institute of Physics, Liverpool

35. The Hubble Space Telescope Key Program Following the first HST servicing mission, which fixed the telescope aberration, a large amount of HST observing time was dedicated to measuring Cepheids in distant galaxies, to try to measure the Hubble constant accurately. Institute of Physics, Liverpool

36. The HST Key program final result Ho = 72 km/s/Mpc uncertainty 10% (Freedman et al 2001) logV Institute of Physics, Liverpool

37. Implications of the Hubble constant Ho is (velocity/distance) so has the dimensions of (1/time). 1/Ho is the expansion age of the universe (how old the Universe would be if no forces acting) = 13.6 billion yrs For simplest model universe with only gravity acting, age of universe would be 9.1 billion years (gravity slows expansion) Institute of Physics, Liverpool

38. The age of the universe We can use the colours and brightnesses of the stars in globular clusters to estimate the age of our Galaxy ~ 12 billion years Long-lived radioactive isotopes give a similar answer Allowing time for our Galaxy to form, the age of the universe is ~ 13 billion years Institute of Physics, Liverpool

39. The age of the universe problem • This is a problem for the simplest models, where gravity slows down the expansion • To get consistency between the HST Key Program value of Ho and the observed age of the universe, we need to reverse the deceleration of the universe • Something is pushing the galaxies apart Institute of Physics, Liverpool

40. The discovery of the Cosmic Microwave Background, 1965 The discovery of the Cosmic Microwave Background (CMB) by Penzias and Wilson in 1965, and the confirmation of its blackbody spectrum by COBE in 1991, showed that we live in a hot Big Bang universe, dominated by radiation in its early stages. Institute of Physics, Liverpool

41. How much matter is there in the universe ? The light elements D, He, Li are generated from nuclear reactions about 1 minute after the Big Bang. The abundances turn out to depend sensitively on the density of ordinary matter in the universe. density ~ 4.10-28 kg/cu m Wb ~ 0.04 Institute of Physics, Liverpool

42. Evidence for Dark Matter the speed at which stars orbit round a galaxy points to the existence of a halo of dark matter. sensitive surveys show that this can not be due to stars, or gas. Institute of Physics, Liverpool

43. Evidence for Dark Matter 2 images of clusters of galaxies with HST show arcs due to gravitational lensing. These can be used to weigh the cluster. Again, the cluster is dominated by dark matter. Abell 2218 Institute of Physics, Liverpool

44. Large scale structure The 3-dimensional distribution of galaxies shows structure on different scales. This can be used to estimate the average density of the universe. In dimenionless units: Wo~ 0.27 Institute of Physics, Liverpool

45. Need for Dark Matter So there is far more matter (Wo~ 0.27 ) out there than can be accounted for by the stuff we are made of (Wb ~ 0.04). 85% of the matter in the universe is ‘dark’ matter (the neutralino ?) Particle Physicists hope to detect this at the Large Hadron Collider Institute of Physics, Liverpool

46. Supernovae as Standard candles Type Ia supernovae (explosion of a white dwarf star in a binary system) seem to be remarkably uniform in their light curves. They behave like ‘standard candles’ and can be used to estimate distances. Institute of Physics, Liverpool

47. Distant Type Ia supernovae Recently a breakthrough in search techniques, using 4-m telescopes to locate new supernovae, and 8-m telescopes plus the Hubble Space Telescope to follow them up, has resulted in the detection of Type Ia supernovae at huge distances. Institute of Physics, Liverpool

48. Evidence for dark energy Over 100 Type Ia supernova have been found at redshifts 0.5-1.5 Comparing these to nearby supernova, we find that in cosmological models with matter only, the distant supernovae are fainter than expected for their redshift. ‘Dark energy’ is pushing the galaxies apart. Institute of Physics, Liverpool redshift, or distance

49. What is Dark Energy ? According to Einstein’s General Theory of Relativity, there can be an extra term in the equation for gravity, which on large scales turns gravity into a repulsive force (the ‘cosmological repulsion’) This extra term, denoted L, behaves like the energy density of the vacuum, hence ‘dark energy’ So far there is no particle physics explanation for this dark energy Institute of Physics, Liverpool

50. Mapping the Cosmic Microwave Background The CMB is incredibly smooth, to one part in 100,000, but the very small fluctuations, or ‘ripples’, first mapped by the COBE mission, are the precursors of the structure we see today. They also tell us about the matter and energy present in the early universe Institute of Physics, Liverpool