Survey of the Universe Tom Burbine tburbine@mtholyoke

1. Survey of the UniverseTom Burbinetburbine@mtholyoke.edu

2. Last HW (due this Wed.) • Go to http://www.galaxyzoo.org • Register • Classify 100 galaxies • Turn in a sheet of paper with evidence you classified 100 galaxies

3. Type II Supernova explosion

4. Neutron Star Neutron stars are usually ~10 kilometers across But more massive than the Sun Made almost entirely of neutrons Electrons and protons have fused together

5. How do you make a neutron star? Remnant of a Supernova

6. How do we know there are neutron stars? • The identification of Pulsars • Pulsars give out pulses of radio waves at precise intervals

8. Pulsars • Pulsars were found at the center of supernovae remnants • Fastest pulsars are called millisecond pulsars

9. Pulsars • Pulsars were interpreted as rotating neutron stars • Only neutron stars could rotate that fast • Strong magnetic fields can beam radiation out

11. Conservation of Angular Momentum (M x V x R) If Radius shrinks, Rotation Velocity must increase

17. X-ray pulsars – generate pulses of X-ray radiation • Magnetars – neutron stars with extremely intense magnetic fields that generate intense bursts of X-ray and gamma-ray radiation

19. Black Hole • A black hole is a region where nothing can escape, even light.

20. Black Hole • After a supernova if all the outer mass of the star is not blown off • The mass falls back on the neutron star • The gravity causes the neutron star to keep contracting

21. http://www.astronomynotes.com/evolutn/remnants.gif

22. Event Horizon • Event Horizon is the boundary between the inside and outside of the Black Hole • Within the Event Horizon, the escape velocity is greater than the speed of light • Nothing can escape once it enters the Event Horizon

23. How do calculate the radius of the Event Horizon? • It is called the Schwarzschild Radius • Radius = 2GM/c2 • This is a variation of the escape velocity formula • Escape velocity = square root (2GMplanet/Rplanet)

25. Black Hole Sizes • A Black Hole with the mass of the Earth would have a radius of ~0.009 meters • A Black Hole with the mass of the Sun would have a radius of ~3 kilometers

26. Anything with mass curves space

28. Can you see a Black Hole?

29. No • Black Holes do not emit any light • So you must see them indirectly • You need to see the effects of their gravity

30. Accretion disk – flat disk of gas or other material held in orbit around a body before it falls onto the body

32. The white area is the core of a Galaxy Inside the core there is a brown spiral-shaped disk. It weighs a hundred thousand times as much as our Sun. Evidence http://helios.augustana.edu/~dr/img/ngc4261.jpg

33. Evidence • Because it is rotating we can measure its radii and speed, and hence determine its mass. • This object is about as large as our solar system, but weighs 1,200,000,000 times as much as our sun. • Gravity is about one million times as strong as on the sun. • Almost certainly this object is a black hole.

34. Any Questions?