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Phys/ Geog 182 – Week 7 The Deaths and Remnants of Stars

Phys/ Geog 182 – Week 7 The Deaths and Remnants of Stars. The evolution of intermediate-mass stars like the Sun. Planetary nebulae and the formation of white dwarf stars. Supernova explosions: two types Type I: due to “carbon detonation” of an accreting white dwarf in a binary.

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Phys/ Geog 182 – Week 7 The Deaths and Remnants of Stars

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  1. Phys/Geog 182 – Week 7 The Deaths and Remnants of Stars The evolution of intermediate-mass stars like the Sun. Planetary nebulae and the formation of white dwarf stars. Supernova explosions: two types Type I: due to “carbon detonation” of an accreting white dwarf in a binary. Type II: due to “core collapse” in a high-mass star. Compact objects: neutron stars, pulsars, and black holes.

  2. In an old star on the main sequence, hydrogen burning eventually builds up an “ash” core, which is mostly helium. The core temperature is about T = 10 million K and the star expands to become a red giant.

  3. Helium shell burning begins, and a core of carbon ash forms.

  4. Planetary Nebulae form when the core can’t reach 600 million K, the minimum needed for carbon burning.

  5. A Planetary Nebula shaped like a sphere, about 1.5 pc across. The white dwarf is in the center.

  6. A Planetary Nebula with the shape of a ring, 0.5 pc across, called the “Ring Nebula”.

  7. Cat’s Eye Nebula, 0.1 pc across, may be from a pair of binary stars that both shed envelopes.

  8. M2-9 has twin lobes leaving the central star at 300 km/sec, reaching 0.5 pc end-to-end.

  9. (See the slide show of planetary nebulae.) Many more examples of planetary nebulae are known: • NOAO: • http://www.noao.edu/image_gallery/planetary_nebulae.html • http://www.noao.edu/jacoby/pn_gallery.html • AAO:http://203.15.109.22/images/general/planetary_frames.html • ESO: http://www.eso.org/public/images/archive/category/nebulae/ • Hubble: http://hubblesite.org/gallery/album/nebula/planetary/ • ESO: http://www.eso.org/public/images/archive/category/nebulae/ • And for a list of the Messier Catalog, see the SEDS Messier database: http://messier.seds.org/

  10. Sirius Binary System: Sirius B is a white dwarf(this is also known as Alpha Canis Majoris B)

  11. White Dwarfformation on the H–R DiagramSome heavier elements are formed in the last years of the burning in the shells surrounding the carbon core. H, He, C, O, and some Ne and Mg are expelled from the star as a “planetary nebula”

  12. Sirius B has a high mass for a white dwarf, and probably came from a mass 4 Msolar star. Compare with Earth’s radius, 6371 km.

  13. Sirius B is at the 5 o’clock position.

  14. X-ray picture of Sirius A 11,000K and Sirius B 24,000K

  15. A Nova is an explosion on a white dwarf, but only a small amount of material on the surface of the white dwarf explodes. Nova Herculis 1934a) in March 1935b) in May 1935, after brightening by a factor of 60,000

  16. Nova Persei - matter ejection seen 50 years after the 1901 flash (it brightened by a factor of 40,000).

  17. Nova light curve – due to a nuclear flash on a white dwarf

  18. Supernova explosions • There are two types of supernova explosions: • Type I: due to “carbon detonation” of an accreting white dwarf in a binary star system. • Type II: due to “core collapse” in a high-mass star, forming a neutron star or black hole. • They have distinctive light curves (next slides).

  19. Artist’s drawing of a Close Binary System

  20. Type Ia supernovae • When enough carbon accumulates on the close binary white dwarf, it can suddenly start carbon fusion, and with no outer layers, it will completely explode. • This has about the same brightness for each explosion because it happens at a particular limit of the star’s mass (1.4 solar masses). • These can therefore be used to estimate distances to remote galaxies (109 ly away).

  21. High-Mass stellar evolutionary tracks (the top track)are quite different from the lower-mass stellar evolution tracks. Notice that the core can heat up so fast that the envelope of the star tends to lag behind. Carbon fusion can start before the red giant phase.

  22. Heavy Element Fusion- shells like an onion

  23. Supernova 1987A seen near nebula 30 Doradus

  24. SN2005cs in M51(Whirlpool galaxy) discovered June 27, 2005

  25. A type II Supernova is a “core collapse” and occurs when the core is finally pure iron, which cannot be fused to other elements. The core collapses to a big ball of neutrons (a neutron star), which causes a shock wave to bounce back outward, which blows off the entire envelope of the red giant, to form a supernova remnant.

  26. Supernova Remnants Crab nebula Vela supernova remnant Other examples: Cassiopeia A (link) (link) N63A (link)

  27. M1 – the Crab Nebula is from a supernova seen in year A.D. 1054 The remnant is 1800 pc away and the diameter is currently 2 pc.

  28. The Crab Nebula contains a pulsar: The Crab Pulsaris due to a spinning neutron star that rotates 30 times per second.

  29. The Crab Pulsar also blinks ON and OFF in X-rays. The Chandra observatory has seen some detail in the accretion disk of the Crab pulsar.

  30. Neutron Star: extremely compact and dense solid sphere, made of neutrons, about 25 km across, about one solar mass, density over 1018kg/m3 spins rapidly

  31. The Cycle of Stellar Evolution

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