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Chapter 13: Chapter 13: The Deaths of Stars The Helix Nebula.

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Presentation on theme: "Chapter 13: Chapter 13: The Deaths of Stars The Helix Nebula."— Presentation transcript:

1 Chapter 13: Chapter 13: The Deaths of Stars The Helix Nebula

2 Planetary Nebulae NGC 7293, Helix Nebula NGC 6826Menzel 3

3 From Supergiants to White Dwarfs

4 Structure of an Old Low-Mass Star Near the end of its life, a low-mass star like the Sun travels up the AGB and becomes a supergiant.

5 Structure of an Old High-Mass Star

6 Supernovae Proceed Irregularly Computer simulations showing how chaotic the supernova is deep inside the star as it begins to explode.

7 Supernova 1987A

8 Rotating, Magnetized Neutron Star Charged particles are accelerated near a neutron star’s magnetic poles and produce two oppositely directed beams of radiation.

9 WHAT DO YOU THINK? Will the Sun someday stop shining? If so, how? What is a nova? Where do heavy elements on the Earth like carbon, silicon, oxygen, iron, and uranium come from? What are cosmic rays? What is a pulsar?

10 You will discover… what happens to stars when core helium fusion ceases how heavy elements are created the characteristics of the end of stellar evolution why some stars go out relatively gently, while others go with a bang the incredible densities of neutron stars and how they are observed

11 Post–Main-Sequence Evolution of Low-Mass Stars

12 Bipolar Planetary Nebula

13 Sirius and White Dwarf Sirius B, a white dwarf, at the five o’clock position Both are hot blackbodies and strong emitters of X rays

14 Nova Herculis 1934 Shortly after peak brightness as a magnitude –3 star. Two months later, magnitude +12.

15 Nova Cygni 1975

16

17 Supernovae Proceed Irregularly Chaos helps account for the lopsided distribution of all elements in this supernova remnant. X-ray images of a supernova remnant taken by Chandra.

18 Gum Nebula The Gum Nebula, created by a supernova 11,000 years ago, is the largest known supernova remnant. It now has a diameter of about 2300 ly.

19 Cassiopeia A An X-ray picture of Cassiopeia A taken by Chandra Radio image produced by the Very Large Array (VLA)

20 Cosmic Ray Shower

21 Shells of Gas Around SN 1987A

22 Supernova Light Curves

23 Recording a Pulsar PSR

24 Crab Nebula and Pulsar Observations at different wavelengths give astronomers information about the nebula’s chemistry, motion, history, and interactions with preexisting gas and dust.

25 Crab Nebula and Pulsar The Crab’s visible flashes and X-ray pulses have identical periods of seconds.

26 How Magnetic Field Strengths Increase As a star collapses, it carries the magnetic field inward, thereby increasing its strength.

27 Neutron Star’s Interior The neutron star has a superconducting, superfluid core 9.7 km in radius, surrounded by a 0.6-km-thick mantle of superfluid neutrons. The neutron star’s crust is only 0.3 km thick.

28 Glitch & the Vela Pulsar’s Spindown Rate

29 Double Pulsar Artist’s conception of PSR J

30 X-Ray Pulses from Centaurus X-3 X ray intensity as detected by Uhuru

31 Model of a Pulsating X-Ray Infalling gas is funneled down onto the neutron star’s magnetic poles, where it strikes the star with enough energy to create two X-ray–emitting hot spots.

32 X Rays from an X-Ray Burster

33 Summary of Stellar Evolution The evolution of isolated stars depends on their masses.

34 Summary of Stellar Evolution

35 WHAT DID YOU THINK? Will the Sun someday cease to exist? If so, how? The Sun will shed matter as a planetary nebula in about 6 billion years and then cease nuclear fusion. Its remnant white dwarf will dim over the succeeding billions of years. What is a nova? A nova is a relatively gentle explosion of hydrogen gas on the surface of a white dwarf in a binary star system. What are the origins of the carbon, silicon, oxygen, iron, uranium, and other heavy elements on Earth? These elements are created during stellar evolution, by supernovae, and by colliding neutron stars. What are cosmic rays? Cosmic rays are high-speed particles (mostly hydrogen and other atomic nuclei) in space. Many of them are believed to have been created as a result of supernovae. What is a pulsar? A pulsar is a rotating neutron star in which the magnetic field’s axis does not coincide with the rotation axis. The beam of radiation it emits sweeps across our region of space.

36 Key Terms asymptotic giant branch (AGB) star Chandrasekhar limit cosmic ray cosmic ray shower glitch helium shell flash helium shell fusion lighthouse model neutron degeneracy pressure neutron star nova (plural novae) photodisintegration planetary nebula pulsar quark secondary cosmic ray supernova Type Ia supernova Type II supernova white dwarf X-ray burster


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