Survey of the Universe Tom Burbine tburbine@mtholyoke

1. Survey of the UniverseTom Burbinetburbine@mtholyoke.edu

2. Chemistry • The science of matter and the changes it undergoes.

3. Atoms • Atoms are made up of 3 types of particles • Protons – positive charge (+1) • Electrons – negative charge (-1) • Neutrons – neutral charge (no charge) • Protons and Neutrons are found in the nucleus

5. Elements • Different elements have different numbers of protons • The properties of an atom are a function of the electrical charge of its nucleus

7. Definitions • Atomic Number – Number of protons • Atomic Mass – Number of protons and neutrons • U235 – atomic mass 92- atomic number • Isotopes – Same number of protons but different numbers of neutrons

8. Periodic Table • A chart in which all known elements are listed in order of atomic number

10. Period – Horizontal row • Across any period, the properties of elements change • Group – Vertical column • Down any group, the properties of elements are very similar

12. Radioactivity • Radioactivity – decay of an atomic nucleus • All elements with an atomic number greater than 82 (lead) are radioactive

13. Bohr’s Planetary Model • Electrons orbit the nucleus in specific energy levels • Level n=1 is closest to nucleus • Level n=2 is second closest

14. Shell Model • Electrons behave as they are arranged in a series of concentric shells around the nucleus • Innermost shell can contain 2 electrons • The second and third shells can contain 8 electrons each • The fourth and fifth shells can contain 18 electrons each

15. Ion • Ion – an electrically charged particle created when an atom either loses or gains one or more electrons

16. 4 Forces that operate in the universe • Gravity • Electromagnetism • Strong Force • Weak Force

18. Examples of elementary particles • Quarks – make up protons and neutrons • Electrons • Neutrino – almost massless particle with no charge that travels almost at the speed of light • Photons – particles of light

19. Celestial Sphere • an imaginary sphere of infinite extent on which all celestial objects appear to lie

20. Celestial Sphere

21. Terminology for looking at the sky

22. What is a constellation?

23. Constellations • People refer to constellations as a pattern of stars • Astronomers refer to constellations as specific regions of the sky • In 1928, the IAU (International Astronomical Union) decided there were 88 constellations • Many of the constellation names go back thousands of years

24. Constellations • The constellations are totally imaginary things that poets, farmers and astronomers have made up over the past 6,000 years (and probably even more!). • The real purpose for the constellations is to help us tell which stars are which, nothing more.

25. What is this constellation?

26. Orion Bigger the star, the brighter it is

27. Orion was the son of the god of the sea, Poseidon and a great hunter. One story is that he made an enemy of Hera who sent a scorpion to sting him. Orion was restored to health by Ophiuchus, the first doctor of medicine. Another story is that Artemis was Tricked by Apollo to shoot an arrow at Orion. When he died, Poseidon asked Zeus to put him among the stars.

32. Ursa Major • Ursa Major, the Great Bear, was identified with a bear by native American Indians of the Northeastern United States and the ancient Greeks. • The name common in Britain, the Plough, seems to have a medieval origin, • Another common name among northern European cultures is the Wain, a shortened form of wagon

33. What are the constellations named after • 14 men and women • 9 birds • 2 insects • 19 land animals • 10 water creatures • 2 centaurs • one head of hair • a serpent • a dragon • a flying horse • a river • 29 inanimate objects

34. Why don’t all the constellations have ancient names?

35. Ancient cultures such as the Greeks and Egyptians could not see the constellations in the Southern Hemisphere

36. Polaris • Polaris is called the North Star • Brightest star in the constellation Ursa Minor • Does not appear to move in the night sky • It is very close to the north celestial pole, making it the current northern pole star. • 48th brightest star in the night sky

38. Any Questions?