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The Magellanic System: A History of Discovery

The Magellanic System: A History of Discovery. Annie Hughes, Swinburne University of Technology. Resumen. Overview of The Magellanic System The MS in History (very abridged) Henrietta Leavitt and the SMC Cepheids WIMPs vs MACHOs Supernova 1987A Extended Stellar Populations in the MCs?

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The Magellanic System: A History of Discovery

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  1. The Magellanic System: A History of Discovery Annie Hughes, Swinburne University of Technology

  2. Resumen • Overview of The Magellanic System • The MS in History (very abridged) • Henrietta Leavitt and the SMC Cepheids • WIMPs vs MACHOs • Supernova 1987A • Extended Stellar Populations in the MCs? • Formation of the Magellanic Stream?

  3. Sky View

  4. The Local Group Sky View

  5. ~6° Sky View

  6. But galaxies are more than stars A galaxy is made of: • dark matter (>90% of galaxy mass) • stars • interstellar medium (ISM, <1% of mass)

  7. And dust: • <1% of ISM mass • < 0.1mm • heating/cooling • catalyst for molecule formation But galaxies are more than stars H2, cold The ISM consists of gas: • mostly hydrogen, some helium and traces of heavier elements, which astronomers call “metals” H, cool/warm H+, warm/hot

  8. Sky View

  9. Sky View

  10. Sky View

  11. Sky View

  12. Sky View

  13. Sky View

  14. Emu in the Sky

  15. Aboriginal Astronomy

  16. Al Sufi and ‘The White Ox’

  17. Cape Clouds

  18. John Herschel

  19. John Herschel

  20. Henrietta Leavitt Employed as “computer” at Harvard College Observatory in 1893 to catalogue the brighness of stars from Arequipa plates.

  21. Finding Cepheids in the SMC

  22. The Period-Luminosity Relation

  23. Hubble Discovers the Universe

  24. M100 Cepheids

  25. Zwicky ‘Discovers’ Dark Matter

  26. WIMPs: • Weakly Interacting Massive Particles • something really weird and tiny • particle physicists Dark Matter Candidates MACHOs: • Massive Compact Halo Objects • brown dwarfs, planets, black holes • astronomers

  27. Gravitational Lensing

  28. MACHO Microlensing

  29. The MACHO Project Question: What fraction of Milky Way’s halo consists of MACHOs? Experiment: Six years of photometric monitoring of 12 million stars in the LMC and 5 million stars in the SMC.

  30. MACHO Microlensing MACHO candidate LMC GPE #1 (05:14:44.5 -68:48:00)

  31. Conclusions from MACHO • Detected 13 to 17 events in LMC • 9 x 1010 M of MACHOs within 50 kpc of MW • MACHOs are objects with mass ~0.5 M • ~20% of MW’s halo is MACHOs • MACHOs cannot be all the “missing mass”

  32. Flashback to 1987

  33. Flashback to 1987

  34. What is a supernova?

  35. Stellar Evolution

  36. Stellar Evolution

  37. Flashback to 1987

  38. Confirmation!

  39. Formation of the Stream • Tidal interaction? • Ram pressure stripping? • Blow out from 30 Doradus?

  40. An extended stellar population RGB stars from LMC observed up to 23º from LMC optical centre What??! Majewski et al 2009

  41. A conclusion (sort of…) We still have a lot to learn about the Magellanic System!

  42. Cepheid Variables

  43. Pulsation • Pulsation mechanism is the “Eddington valve” • He++ is more opaque than He+ • Radiation pushes outwards; gravity pulls inwards He++ He+ He++ Dim Bright Dim

  44. Sky View

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