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Helio - and Asteroseismology

Helio - and Asteroseismology. b y Christine Do EPSC 330. Definition. Helio - and asteroseismology : The study of internal structures and dynamics of the Sun and other stars by means of their resonant oscillations. ( García , 2010). History. Helioseismology started about 50 years ago

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Helio - and Asteroseismology

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  1. Helio- and Asteroseismology by Christine Do EPSC 330

  2. Definition Helio- and asteroseismology: The study of internal structures and dynamics of the Sun and other stars by means of their resonant oscillations. (García, 2010)

  3. History • Helioseismology started about 50 years ago • 1962: Leighton, Noyes, and Simon noticed shifts in absorption lines (Doppler shift effect)

  4. Spectral Lines • A hot opaque body produces a continuous spectrum • A hot, transparent gas produces an emission line spectrum • A cool, transparent gas in front of a source of a continuous spectrum produces an absorption line spectrum

  5. History • 1970: Ulrich proposed that these waves were the surface manifestation acoustic oscillations (aka sound waves) • Types of solar oscillations: • P-mode (acoustic waves) • G-mode (gravity waves) • F-mode (surface gravity waves)

  6. P-mode Oscillations • Over a million oscillation modes in the Sun • http://ap.smu.ca/~guenther/seismology/seismology.html • http://ap.smu.ca/~guenther/seismology/pmodes.html

  7. Helioseismology • The Sun has a oscillation period of 5 minutes • Pulsation frequencies give density profile • Spectrum gives chemical composition • Reference point for other Sun-like stars.

  8. Detection • SOHO (Solar and Heliospheric Observatory) • GONG (Global Oscillation Network Group) • MOST (Microvariability and Oscillations of STars) • CoRoT (COnvectionROtation and planetary Transits) • Kepler • Vibrations are associated with small variations of stellar luminosity • The light signal is converted to sounds we can understand

  9. Stellar music • Listen here: http://news.bbc.co.uk/2/hi/science/nature/7687286.stm • Recorded by CoRoT • Repeating pattern indicate the pulsations • Varies for every star

  10. Alpha Centauri A • First star to be measured (besides our Sun). • Closest star visible to the naked eye • Almost the same size, colour, temperature and age as our Sun. • Oscillates at a 7 minute frequency. • Agrees with expectations based on the theoretical models of these stars

  11. Limitations:MOST’sProcyon Controversy • Recorded no oscillation

  12. Limitations:MOST’sProcyon Controversy • MOST data is possibly noisy at low frequency • The behaviour of convection is different from expectations • Difficult to see as luminosity variations but ground-based observations by WIRE can measure radial velocity

  13. Applications • Predict the eruptions of solar flares (GONG) • Studying sunspots • Infer helium abundance • Determine age, radii, density profile, internal rotation profile, evolution of stars, fundamental properties, etc.

  14. Conclusion • From helioseismology to asteroseismology • Only about 20 stars observed in details until now • Allows us to go beyond conventional astronomy • Broaden our understanding of stars and their systems

  15. References • http://ap.smu.ca/~guenther/MOST/MOST.htm • http://www.scientificamerican.com/article.cfm?id=the-gong-show • http://news.bbc.co.uk/2/hi/science/nature/7687286.stm • http://www.bbc.co.uk/news/science-environment-12507032 • http://www.scientificamerican.com/article.cfm?id=solar-flares-space-weather • http://news.bbc.co.uk/2/hi/science/nature/1641599.stm • http://news.bbc.co.uk/2/hi/science/nature/7687286.stm • Stellar pulsations of solar-like oscillators with CoRoT and KeplerRA Garcia - Arxiv preprint arXiv:1101.0236, 2010 • Asteroseismology: Oscillations on the star ProcyonFBouchy, A Maeder, M Mayor, D Megevand… - Nature, 2004 - nature.com • An Overview of Helio-and Asteroseismology • Christensen-Dalsgaard - SOHO 14 Helio-and …, 2004 - adsabs.harvard.edu

  16. References • A Precise Asteroseismic Age and Radius for the Evolved Sun-like Star KIC 11026764Astrophysical journal [0004-637X] Metcalfe yr:2010 vol:723 iss:2 pg:1583 • The non-detection of oscillations in Procyon by MOST: Is it really a surprise?T. R. Bedding, H. Kjeldsen, F. Bouchy, H. Bruntt, R. P. Butler, D. L. Buzasi, J. Christensen-Dalsgaard, S. Frandsen, J.-C. Lebrun, M. Martić and J. SchouA&A 432 (2) L43-L48 (2005) • Evidence for Granulation and Oscillations in Procyon from Photometry with the WIRE SatelliteH. Bruntt1, H. Kjeldsen2, D. L. Buzasi3 and T. R. Bedding4 • No stellar p-mode oscillations in space-based photometry of ProcyonJaymie M. Matthews1, Rainer Kusching1, David B. Guenther2, Gordon A. H. Walker1, Anthony F.J. Moffat3, Slavek M. Rucinski4, Dimitar Sasselov5 & Werner W. Weiss6

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