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Announcements Homework #10: due today Solutions and study guides will be posted online. Final Exam scheduled for May 22nd @ 12:15. Bring a scantron form 882-EZ Need extra help? Come to SCI 242 on Thursday, 5/17, at either 10AM or 3PM. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Stellar Remnants: White Dwarfs, Neutron Stars, & Black Holes (Chp. 14) 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Black Holes: • Progenitor mass: > 10-20 MSun • Schwarzscild Radius • Event Horizon • What is the event horizon for a 1 MSun object? • Observational Evidence for the existence of BH’s • X-Ray Binaries • Center of the Milky Way 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Eclipsing X-Ray Binaries Accretion disk emits x-ray radiation 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mass of central object: 3 Million MSun!! Orbit of S2: P=15.2 years; a=900 AU Mass according to Kepler’s laws: 3.5x106 MSun! Luminosity: below detection threshold Closest approach: 17 light-hours 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Milky Way Galaxy (Chp. 15) 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Looking up at the sky at night, we can see that the Sun is one of (at least) thousands of stars. We also see that the stars in the sky are not uniformly spread out. 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Very thin (100-1000 pc) 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Milky Way NGC 891 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display NGC 1232 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Angle between Solar System plane and Galactic plane 62 degrees 13 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 14 Artist’s depiction of solar system seen from Sedna Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display • Disk – Distribution of stars, gas, and dust with a diameter of about 30 kpc (100,000 light-years) and plane tilted with respect to Earth’s orbit around Sun – Rotation with all objects circling in the same direction – High density of stars near center (10 million stars per cubic light-year) to low density farther out (0.003 stars per cubic light-year at Sun) 15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display • Halo – Roughly spherical region (disk embedded) – Contains mainly old stars, such as globular clusters • Bulge – Flattened collection of stars surrounding dense core of galaxy – About 1/3 the diameter of the galaxy 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Spiral Density Wave: galactic traffic jam 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Milky Way: • Herschel’s star counts • Shapley’s work with globular clusters • size (50,000 pc across; 100-1000 pc thick) • location of Sun (8,000 pc from center) • Components: bulge, disk, halo • Motion • bulge versus disk • direction of Sun’s motion with respect to spiral arms • Angle between ecliptic and Milky Way • Spiral Structure • “traffic jam” • young stars found in spiral arms 21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 4 billion miles from home… 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Earth, Moon, and Jupiter as seen from Mars 23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 25 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Pale Blue Dot 27 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display