Astronomy 305/Frontiers in Astronomy

1. Astronomy 305/Frontiers in Astronomy Class web site: http://glast.sonoma.edu/~lynnc/courses/a305 Office: Darwin 329A and NASA E/PO (707) 664-2655 Best way to reach me: lynnc@charmian.sonoma.edu Prof. Lynn Cominsky

2. Group 10 Great job, Group 10! Prof. Lynn Cominsky

3. Where are the Sun’s neutrinos? • The Sun • A bit of history • Properties • Regions • Sub-atomic Particles • Solar neutrino problem • Neutrino oscillations Prof. Lynn Cominsky

4. The Solar Mass • History of the changing views of the Sun’s place in the Universe • Written and produced by Lynda Williams for the SFSU Planetarium Play real movie Prof. Lynn Cominsky

5. The Sun Song by the Chromatics • Astrocapella video Prof. Lynn Cominsky

6. … but high pressure and temperature encourage impact Electrostatic repulsion stops impact Solar Power • The Sun is powered by nuclear fusion reactions in its core • The gravity from the Sun’s mass squeezes the nuclei together so that they can overcome electrostatic repulsion and fuse Prof. Lynn Cominsky

7. Several Reactions End up with a “normal” helium nucleus, two gamma rays, two positrons and two neutrinos Start with 4 protons under enormous pressure and temperature Solar Power • Hydrogen nuclei fuse to Deuterium and then Helium, releasing about 7 MeV each • The released radiation keeps the Sun from collapsing due to its own gravity Prof. Lynn Cominsky

8. Sun Facts • Mass of Sun 1.989 x 1030 kg • Diameter of Sun 1,390,000 km • Distance to Sun 1 A. U. or 93 x 106 miles or ~1.5 x 1011 m • Rotation Rate of Sun 25.4 d (equator)36 d (poles) • Surface Temperature of Sun 5800 K (yellow visible light) Prof. Lynn Cominsky

9. Sun Facts • Power from Sun 3.86 x 1026 W • Composition of Sun 75% Hydrogen 25% Helium <0.1% other elements • Age of Sun 4.5 billion years …. with another ~5 billion years to go • Pressure at core 2.50 x 1011 atm • Magnetic Field of Sun a few Gauss (average) but up to 103.5 G connecting sunspots of opposite polarity Prof. Lynn Cominsky

10. Features of the Sun Prof. Lynn Cominsky

11. Regions of the Sun • Core– dense region consisting of plasma of electrons and protons which undergo nuclear fusion reactions to power the Sun. Temperature is greater than 15,000,000 K. • Radiation zone– region containing both plasma and atoms. The atoms slowly (170,000 y) absorb and reradiate the energy created in the core, transporting it to the outer layers. Temperature is around 5,000,000 K. • Convection zone– turbulent region where the solar material “boils” to quickly (1 week) move heat to the outer layers. T ~ 2,000,000 K Prof. Lynn Cominsky

12. Regions of the Sun • Photosphere–“surface” of the Sun that radiates visible light. Convection cells can be seen as granules – T ~ 5800 K • Sunspots–highly variable, dark, cool regions in the photosphere. T ~ 3500 K • Chromosphere - thin (2000 km) layer outside photosphere in which Hydrogen absorbs radiation and reemits it as red light (H-alpha). Jagged outer edge has dancing “flames” or spicules. Prof. Lynn Cominsky

13. Regions of the Sun • Transition region– very thin (100 km) layer in which temperature rises from 20,000 to 106 K • Corona - very sparse outer ionized gas region with loops and streamers of magnetic field. Temperature ~ 106 K Solar Movie shows: 1) Photosphere 2) Chromosphere 3) Corona Prof. Lynn Cominsky

14. Computer simulation Solar Interior • Sun has many oscillation modes • Helioseismology is used to study the interior of the Sun and to learn about the convection region • 3 SOHO instruments Prof. Lynn Cominsky

15. Sunspot and Convection Cells • Optical sunspot image from the Vacuum Tower telescope at the Sacramento Peak National Solar Observatory with100 km resolution • Shows granules from convection - each is about 1000 km across and lasts for about 10 minutes Prof. Lynn Cominsky

16. Solar Chromosphere • Maps of the solar chromosphere are made by observing light in the H-alpha line • Light is emitted in the H-alpha line when an electron jumps down from the n=3 shell to the n=2 shell in Hydrogen Prof. Lynn Cominsky

17. 4/26/98 Solar Transition Region • TRACE = Transition Region And Coronal Explorer • Blue = 360,000 K • Green = 900,000 K • Red = 2,700,000 K • White = sum of all 3 Prof. Lynn Cominsky

18. Solar Corona • Only easily visible during solar eclipse • Eclipses can be created artificially in coronographs • SOHO/LASCO movie Prof. Lynn Cominsky

19. Sun in X-rays • X-rays from corona, prominences, flares and sunspots Yohkoh movie Prof. Lynn Cominsky

20. nucleus Sub- Atomic Particles • Atoms are made of protons, neutrons and electrons • 99.999999999999% of the atom is empty space • Electrons have locations described by probability functions • Nuclei have protons and neutrons mp = 1836 me Prof. Lynn Cominsky

21. Leptons • An electron is the most common example of a lepton – particles which appear pointlike • Neutrinos are also leptons • There are 3 generations of leptons, each has a massive particle and an associated neutrino • Each lepton also has an anti-lepton (for example the electron and positron) • Heavier leptons decay into lighter leptons plus neutrinos (but lepton number must be conserved in these decays) Prof. Lynn Cominsky

22. Types of Leptons Prof. Lynn Cominsky

23. F = k q1 q2 r2 Atomic Forces • Electrons are bound to nucleus by Coulomb (electromagnetic) force • Protons in nucleus are held together by residual strong nuclear force • Neutrons can beta-decay into protons by weak nuclear force, emitting an electron and an anti-neutrino n = p + e + n Prof. Lynn Cominsky

24. Neutrinos in the Standard Model • The “standard model” of particle physics seeks to explain all the particles and forces that are observed • In this model, there are 3 flavors of neutrinos: electron, muon and tau • All three types of neutrinos are massless and travel at lightspeed • If neutrinos have mass, their mass could affect how the structure in the universe is formed Prof. Lynn Cominsky

25. Solar neutrino problem history • First experiments (1969) that detected solar neutrinos found about half the rate expected from models of nuclear reactions in the Sun • The neutrinos predicted from the models (and detected in the experiments) are all electron neutrinos – so either: • the models were wrong • something happened to the neutrinos on their way to the Earth • Many experiments in 1980s-1990s showed the perhaps the neutrinos were changing flavors (from electron neutrinos to some other type) Prof. Lynn Cominsky

26. Solar neutrino problem • 4p  4He + 2e+ + 2ne + 25 MeV • Chlorine atoms can capture neutrinos Prof. Lynn Cominsky

27. Homestake mine neutrino experiment • In an old mine in South Dakota (1967 – 1984) • 20 feet in diameter • 48 feet long, • held 100,000 gallons of tetrachloroethylene • located 4,900 feet below ground surface. Courtesy of Brookhaven National Laboratory Prof. Lynn Cominsky

28. Homestake mine neutrino experiment • Ray Davis Jr. takes a dip in the 300,000 gallons of water that surrounds the perchloroethylene tank • Water lowers background rates • Detects electron neutrinos only Photo courtesy of Brookhaven National Laboratory Prof. Lynn Cominsky

29. Sun in Neutrinos • Super Kamiokande neutrino observatory • 500 day image • 90 x 90 degrees centered on Sun Prof. Lynn Cominsky

30. SuperK detector SuperKamiokande • CAN DETECT ALL 3 TYPES OF NEUTRINOS • Water Cerenkov Detector • 41.4m (Height) x 39.3m (Diameter) • 50,000 tons of pure water • 1,000m underground • 11,200 photomultiplier tubes Prof. Lynn Cominsky

31. Where solar neutrinos come from Prof. Lynn Cominsky

32. Neutrino Oscillations • A pion decays in the upper atmosphere to a muon and a muon neutrino • Neutrinos oscillate flavors between muon and tau Prof. Lynn Cominsky

33. D (m2c4) = 0.005 eV2 Neutrino Oscillations • High energy neutrinos that travel a short distance do not change their flavor • Low energy neutrinos that travel a long distance have a 50% chance of changing flavors Prof. Lynn Cominsky

34. Neutrino Oscillations/KEK • K2K (KEK to SuperK) is the new experiment testing neutrino oscillation results • Neutrinos produced at KEK are measured at near detector and then shot 250 km across Japan to SuperK detectors • First events were detected in 1999 – confirm oscillations (56 seen, 80 expected by 2001) Prof. Lynn Cominsky

35. SuperKamiokande • Severely damaged in accident on 11/12/01 – over 5000 phototubes were destroyed • Is being rebuilt – online again by 2003 • First priority – resume K2K experiment by 2003 half of previous phototubes Bottom of SuperK detector covered with broken PMTs after accident Prof. Lynn Cominsky

36. Sudbury Neutrino Observatory • >2000 meters below ground, in active mine • Spherical detector, 12 m in diameter, filled with 1000 tons of heavy water, surrounded by 30 m cavity filled with normal water • 10,000 photomultipliers measure light flashes when heavy water catches neutrinos (e-) Prof. Lynn Cominsky

37. Comparing SuperK and SNO • SuperK detects all 3 types of neutrinos vs. SNO which detects e- neutrinos only • The numbers do not agree! • Use joint data set to predict total numbers of neutrinos reaching Earth • Prediction now agrees with solar models •  Neutrino oscillations now confirmed! •  Neutrinos have some mass!! •  Particle physics models must change Prof. Lynn Cominsky

38. Nobel Prize in Physics 2002 • “for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos” • Raymond Davis Jr. & Masatoshi Koshiba Prof. Lynn Cominsky

39. Nobel Prize in Physics 2002 • Raymond Davis Jr constructed a completely new detector, a gigantic tank filled with 600 tons of fluid, which was placed in a mine. Over a period of 30 years he succeeded in capturing a total of 2,000 neutrinos from the Sun and was thus able to prove that fusion provided the energy from the Sun. • With another gigantic detector, called Kamiokande, a group of researchers led by Masatoshi Koshiba was able to confirm Davis’s results. They were also able, on 23 February 1987, to detect neutrinos from a distant supernova explosion. They captured twelve of the total of 1016 neutrinos (10,000,000,000,000,000) that passed through the detector. • The work of Davis and Koshiba has led to unexpected discoveries and a new, intensive field of research, neutrino-astronomy. Prof. Lynn Cominsky

40. AMANDA • Antarctic Muon And Neutrino Detector Array • Purpose: high-energy (~ 1 TeV or 1012 electron volt) neutrinos from astrophysical point sources. • 302 PMTs on 10 strings at depths of 1500-2000 meters • Videotape of lecture about AMANDA Prof. Lynn Cominsky

41. Web Resources • Astro Capella Sun songhttp://www.pagecreations.com/astrocappella/sun.html • Sun Structurehttp://www.lmsal.com/YPOP/Spotlight/SunInfo/Structure.html • Clear Skies http://www.swin.au/astronomy • The Particle Adventurehttp://particleadventure.org/ • Nobel Prizeshttp://www.nobel.se • Ray Davis photoshttp://www.bnl.gov/bnlweb/raydavis/pictures.htm Prof. Lynn Cominsky

42. Web Resources • Sudbury Neutrino Observatoryhttp://www.sno.phy.queensu.ca/ • John Bahcall’s neutrino pageshttp://www.sns.ias.edu/~jnb/ • Homestake Neutrino Laboratory http://www.blackhillsdata.com/nusl/solar_neutrinos.htm • Super Kamiokande http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/ Prof. Lynn Cominsky