Models of the universe from Aristotle to Newton - HOW DID EACH VIEW THE STRUCTURE OF THE UNIVERSE? What is the current scientific thinking about the structure of the universe? Chronicle of the 20th Century (Space Exploration) Intro; War of the Worlds Soundtrack

2. The first minutes of the universe released energy which changed to matter, forming stars and galaxies What are quarks? What is the structure of the atom; features of subatomic particles? How did Hubble discover an expanding Universe? Who’s Friedmann? What are the stages of the ‘Big Bang’ theory? Energy? Matter? WHICH SET OF SPECTRAL LINES ARE RED SHIFTED - GREEN OR YELLOW?

Big Bang Cosmic ‘atom’ undergoes Big Bang Expanding universe is a ‘soup’ of quarks then protons, neutrons & electrons Gases coalesce to form stars and planets Cooling and expansion leads to atoms Stars gather to form galaxies Extreme energy concentration Energy transforming into matter. Energy dominant over matter E>m K.E decreasing, matter dominant m>E Increased gravitational attraction led to lumpy gas cloud Stars attracted by gravity

3. Stars have a limited life span and may explode to form supernovas Recall the inverse square Law, relate intrinsic luminosity,distance and brightness LUMINOUS STARS MAY APPEAR LESS BRIGHT WHEN FAR AWAY LESS LUMINOUS STARS MAY APPEAR BRIGHT BECAUSE THEY ARE CLOSER I = 1/r 2 LUMINOUS STARS MAY APPEAR LESS BRIGHT WHEN FAR AWAY LESS LUMINOUS STARS MAY APPEAR BRIGHT BECAUSE THEY ARE CLOSER

Temperature Ionised Hydrogen means there are no absorption lines in O and B stars (hot)( K). At lower than 10000K, Balmer absorption lines are produced, so Hydrogen absorption is a maximum in A2 stars Different elements produce strong absorption lines at different temperatures. Therefore, observing the strong absorption lines for elements indicates the temperature Using Wien’s Law we can calculate the surface temperature from the wavelength of maximum intensity Practical Activity 13.2 Jacaranda text or heat pencil lead (use safety glasses!)

Hertzsprung-Russell diagram Luminosity (incr.) vs colour or temperature(decr.) Where are red giants, white dwarfs, main sequence?

Energy sources of stars Nuclear energy Fission - atoms split apart e.g. reactor, bomb, but NOT STARS Fusion - atoms joined together (extremely high temp needed) - STARS!! What happens in a red giant, white dwarf, main sequence star?

Three Types of Emissions from Radioactive Sources Emissions from radioactive sources were initially called rays and included alpha, beta, and gamma rays. The properties of these rays were mysteriously different. Alpha rays (+ve), could be bent by a magnetic field, and were easily stopped by a sheet of paper. Beta rays (-ve), could be bent in the opposite direction by a magnetic field, and could penetrate paper but be stopped by an aluminium shield. Gamma rays (neutral), were not deflected by a magnetic field, and penetrated both paper and aluminium, but could be stopped by a heavy shield of concrete or lead. Alpha rays (generally called alpha particles) are the slow- moving nuclei of helium atoms. Beta rays (generally called beta particles) are electrons. Gamma ray,like all electromagnetic waves, can also be thought of as particles called photons. IONIZATION: ALPHA IS MOST IONIZING GAMMA IS LEAST IONIZING