Astrophysics and Cosmology

1. Astrophysics and Cosmology Some of the biggest ideas of the last 100 years Of the Stars, the Universe and Everything!!! (the answer is 42. . . )

2. Star Life Cycle: Birth • Stars are born out of a cloud of dust • Dust Collapses together due to gravity • When sufficient heat and pressure, nuclear fusion starts • Atoms combine • Releasing lots of Energy • Star shines

3. Star Life Cycle: Life • Our sun is a typical star • Typical lifetime is 10 billion years for sun-sized star • Combines Hydrogen into Helium • Hotter stars burn brighter, Blue • Colder stars burn Red

5. Star Life Cycle: Deaththe form star-death takes depends on star’s size

6. Star Life Cycle: Supernova • Heavy stars can collapse in a Supernova • Two types of Supernova • Small star eats bigger star (Ia) • Massive star collapse (IIa)

7. Some History • Supernovae observed by Chinese and Arab astronomers (1006 ACE, possibly others) • Tycho observed a supernova in 1572 • Convinced him that stars change • A nail in the coffin of Aristotelian “spheres” • Most recent in Milky Way observed by Kepler in 1604 • Nova means “new” • Supernovae are “new” stars – they appear suddenly • Are brightest in sky for a month • Visible during daytime • Visible at night for a year or two • Leave behind a Nebula

8. Supernova Part of Cycle • Shockwave drives nebular gas together • Creating more dense clumps of gas • Igniting new stars • Supernovae produce and spread heavy elements • So we are “star stuff”

9. Star Life Cycle: Black Hole • Large enough star collapses • So dense, that light’s path is bent by gravity as it travels • Gravity so strong • Light can’t escape: • Black Hole

10. Black Holes – Very Weird • Center – Singularity • Edge: “Event Horizon” • Anything falling in is gone forever • Time slows to a stop inside • Inside event horizon, forces rip matter apart • “Rip” in Space-Time • Gravity can swallow other stars or planets • Making Black Hole bigger

11. Cosmology: The Big Bang

13. Cosmology: The Big Bang • Edwin Hubble (of Hubble telescope) big name • Saw galaxies moving away from each other • Tracing backwards, then. . . • All matter in the universe starts off at one point -- “singularity” • Expands outward rapidly – “Inflation” • Matter at first “hot soup” of particles

14. The Process • Expands, cools into atoms • Atoms clump up into gas • Gas clumps up into stars and galaxies • Process currently theorized to take place over 13.75 billion years

15. Cosmology: Evidence – Universe Expanding

16. Arno Penzias and Robert Wilson 1965:Cosmic Microwave Background • Had Antenna to measure microwaves • Looking for point sources (Stars!) • Found constant buzz through all of sky • Thought there was a problem • Cleaned out bird poo • Buzz still there • Evidence for: the Big Bang

17. What does it mean? • Radiation released when matter first formed • Went in all directions • Universe expanded • This light is only getting to us now • 13.75 billion years later! • From the edge of the Universe • Uneven parts are clumps • That later became galaxies

18. Dark Matter • The Galaxies are rotating faster than predicted • What force causes the galaxies to rotate? • What does it mean if they rotate fast? • And what does that imply? • Dark Matter • Acts like matter in terms of gravitational pull • Unlike normal matter (stars, dust), emits no radiation • Hence “Dark”, we can’t see it • It’s a “Conceptual Placeholder”

19. Dark Matter is a “Conceptual Placeholder” • If we stick with Newton’s Theory of Gravity, we need it • Might be made of new particles • Or just lots of planets we can’t see • According to Newton/Einstein theory, 83% of matter in the Universe is Dark Matter • Or maybe the Theory’s just insufficient as it is . . . We don’t really know