The Discovery of the Neutron Star

1. The Discovery of the Neutron Star

2. The Neutron Predicted by Ernest Rutherford in 1920 Experimentally discovered by James Chadwick in 1932

3. The Neutron Star Fritz Zwicky and Walter Baade mathematically predicted the existence of a neutron star in 1934.

4. Massive Star Life Cycle

5. The Discovery of the Pulsar Jocelyn Bell discovers the first pulsating star (pulsar for short) using a radio telescope in 1967. The star pulsed once every 1.3 seconds.

6. Pulsars and Their Relation to Neutron Stars Crab Pulsar in the Crab nebula By 1968, with the discovery of the Crab and Vela pulsars in Supernova Remnants, MOST scientists believed that pulsars were in fact neutron stars.

7. How do Neutron Stars Form

8. What is a pulsar? A pulsar is a rapidly rotatingneutron star that beam radio waves towards Earth. This brings up some new questions... What is a neutron star? Why is it rotating? Why is it beaming radio waves?

9. Life of a Massive Star Stars spend most of their lives fusing hydrogen into helium • The star is literally blowing itself apart while gravity tries to crush it When a star runs out of hydrogen it tries to fuse heavier elements

12. Death of a Massive Star No energy can be extracted by fusing iron Without a source of energy, what do you think will happen to the star? Watch and see: http://www.youtube.com/watch?v=p8HcDnhkM3I

13. Supernovae Gravity causes the outer layers to collapse at super-sonic speeds When outer layers hit the Iron core, they pile up and “bounce back” Most of the star explodes

14. A Neutron Star is Born The star's core is left behind and goes through a wild transformation What was once a core of Iron is now a super-dense neutron star Write and equation to represent what is happening here.

15. Electron Capture (inverse Beta decay) Beta Decay Process

16. Neutron Star Facts – Diameter, Mass, Temperature and Rotation 1.4 times as massive as our Sun (500,000 Earth masses – 40% more massive than our Sun) About 12 miles across 1 teaspoon would weigh 5.5 billion tons 10 million ºF at birth Some spin several times a second or faster Why do neutron stars spin?

21. Stellar Remnant – Size Comparisons The more massive the Progenitor Star – the smaller the Remnant

22. Neutron Star: Mass and Diameter • 1.4 times as massive as our Sun (500,000 Earth masses – 40% more massive than our Sun) • About 12 miles across Calculate the density of a neutron star Density = Mass/Volume

24. Density • Extremely dense objects • 100,000,000,000,000,000 kg m-3 • Next thing down from a black hole

25. Your weight You can calculate your weight on Earth and any other planet or object using this formula. G is the universal gravitational constant

26. Calculate your weight on a neutron star applet • http://www.exploratorium.edu/ronh/weight/

27. Neutron star properties • Extremely rapid spin • Rotation rates in excess of 700 Hz • Speed at surface ~ significant fraction of c

28. Neutron Star Facts Neutron stars can also highly magnetized Fields thousands – billions times stronger than the strongest man made magnets This has an amazing effect Neutron stars can emit beams of radio waves

30. Do You See a Pulsar? Pulsars are like interstellar lighthouses If the beam points towards Earth, we see a pulse of radio waves

32. Sounds of Pulsars B0329+54 Spins 1.4 times every second Vela Spins 11 times every second B1937+21 Spins 714 times every second

33. What did you notice?

34. Pulsar Recycling Some pulsars spin faster than others When the pulsar period is a few milliseconds, we call it a millisecond pulsar MSPs are actually recycled pulsars and are the most exciting kinds

35. Pulsar Recycling Some pulsars spin faster than others When the pulsar period is a few milliseconds, we call it a millisecond pulsar MSPs are actually recycled pulsars and are the most exciting kinds

36. Millisecond Pulsars