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Lecture 4

Introduction to Astronomy-Lecture 4 Notes!.docx

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PCS 181
Margaret Buckby

Galaxies:  Recall the COBE satellite which was launched to confirm the CMB ~ 3 K (2.728 K).  COBE was LATER asked to seek VERY small temperature variations in the CMB.  COBE found tiny temperature deviations of +/- 0.0003 K. Galaxy Formation 1:  Pink regions = 2.278 + 0.0003 K.  Blue regions = 2.278 – 0.0003 K.  Galaxy theorists hypothesize that galaxies “condensed” at the interface between warmer and cooler volumes of space. *NOTE: THE HISTORY OF THE UNIVERSE IS ON TEST # 1. E.G. 100 YEARS, 4 S. Galaxy Formation 2:  The first stars to form after the Big Bang were extremely massive…hundreds of times the mass of our sun.  These stars only lived a few million years and exploded as supernovae, leaving Black Holes as remnants.  These massive Black Holes attracted gas/dust into orbit.  Overtime, the system attracted more matter until a galactic mass was present.  Massive Black Holes are found at the centers of most galaxies. Properties:  A galaxy is a gravitational-bound collection of stars, gas, dust, radiation.  Galaxies range from thousands to hundreds-of-thousands of light years across.  Galaxies contain from thousands to trillions of stars.  Galaxies usually gather into groups.  Many groups = a galaxy Cluster.  Our own galaxy, the Milky Way, is about 100,000 to 120,000 light years across.  Our Milky Way is in the LOCAL GROUP which consists of about 40 member galaxies.  Our sun lies about 8 Kpc ~ 26,000 light years from the center of the Milky Way.  Our sun travels around the Milky Way galaxy at ~ 220 Km/s. Globular Clusters:  A globular cluster is a spherical distribution of ~10 to 10 stars.  Typically only a few hundred light years across.  Formed early in the life of a galaxy and contain the oldest stars known.  Follow RANDOM paths through their home galaxy = do NOT move ~ circularly in the plane (disk) of the galaxy as most stars do.  They are found above, below and within their galaxy. The Hubble Classification System: See Handout for Characteristics on Galaxies! You can assist the SOLOAN Galaxy survey: *NOTE: GALAXY PROPERTIES BY TYPE ON SHEET ON TEST # 1! –
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