1. Survey of the Universe Tom Burbine tburbine@mtholyoke.edu

2. Next Quiz This Wednesday Quiz includes material covered up to and including April 8 th Cumulative You can bring in one 8 ½ by 11 inch piece of paper with anything written on it

3. If you are unhappy with any of your grades: You can write a 10 page paper on an astronomical subject to replace it 12 point font Times New Roman font Double space No figures or plots Due by May 1st

6. Type Ia Supernova Lightcurve

7. Type Ia Supernova are consistent with coming from exploding white dwarfs No signs of hydrogen in their spectra, consistent a star that have lost their outer atmospheres of hydrogen in a stellar wind Lightcurve matches theoretical predictions of exploding white dwarfs

8. Last Type Ia supernovas that occurred in our galaxy were observed by Tycho Brahe (1572) and Johannes Kepler (1604)

9. Standard Candles Type Ia supernovas make excellent standard candles because they have identical maximum luminosities Their collapse and explosion occur the same way each time

10. Products Type Ia Supernovas are rich in elements such as carbon, oxygen, silicon, and iron Magnetic fields in the expanding remnant can accelerate atomic nuclei to speed close to the speed of light, which are called cosmic rays

11. Massive Stars Greater than 8 Solar Masses Begins life on main sequence as Blue Star Follows the same path as a low mass star but everything occurs faster

13. Fate of Massive Stars

16. Light Curves of supernovae of stars undergoing core collapse Dashed red line is Type Ia supernova

17. How do you get a Core-Collapse Supernova? A high-mass star keeps on fusing elements into ones with larger atomic masses Is now a Red Supergiant Energy keeps on being released since the mass of the new nucleus is less than the original ones

19. This stops with Iron Fusion of Iron with another element does not release energy Fission of Iron with another element does not release energy So you keep on making Iron

21. Initially Gravity keeps on pulling the core together The core keeps on shrinking Electron degeneracy keeps the core together for awhile

22. Then The iron core becomes too massive and collapses The iron core becomes neutrons when protons and electrons fuse together

23. Type I are classified based on the lack of hydrogen lines in their spectra –Type Ia are due to collapsing white dwarfs –Type Ib and Ic are due to collapsing cores of stars that have lost their hydrogen atmospheres Type II have hydrogen lines in their spectra –Due to collapsing cores

24. Type Ia Supernova Type II Supernova

25. http://www.ifa.hawaii.edu/~barnes/ast110_06/tooe/1314a.jpg

26. Supernova 1987A that exploded in Large Magellanic Cloud (a small, nearby galaxy) 168,000 light-years away Could be seen with naked eye peak magnitude +2.9 http://en.wikipedia.org/wiki/File:SN1987a_debris_evolution_animation.gif

27. Type II Supernova remnants of different ages Cassiopeia A 300 years old Crab Nebula 1,000 years old Supernova Several thousand years old

28. Type II Supernova explosion

29. Hypernova explosion - Hypothetical supernova explosion of a star so massive that its core collapses directly into a black hole

30. 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

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

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

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

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

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

43. 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

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

46. 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

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

48. 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

49. How do calculate the radius of the Event Horizon? It is called the Schwarzschild Radius Radius = 2GM/c 2 This is a variation of the escape velocity formula Escape velocity = square root (2GM planet /R planet )

51. 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

52. Anything with mass curves space

54. Can you see a Black Hole?

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

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

58. Evidence 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. http://helios.augustana.edu/~dr/img/ngc4261.jpg

59. 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.

60. http://documentaryheaven.com/whos-afraid-of-a- big-black-hole/http://documentaryheaven.com/whos-afraid-of-a- big-black-hole/

61. Any Questions?