How We See Ourselves In The Universe: A Look At The Galaxies That Surround Us

How High Can You Count? Our solar system contains the following items: 1 star (the sun) 8 planets 1-3 dwarf planetoids a few hundred natural satellites (moons) gases, asteroids, dust, etc. Well, Guess What? Our solar system is only one of billions of star systems that make up the Milky Way Galaxy, which is only one of several dozen galaxies that makes up our Local Cluster, and our Local Cluster group is only one of many in a collection called superclusters… Welcome to the Universe!

What are galaxies? Galaxies contain millions or billions of stars held together by gravity Gravity holds galaxies together in clusters Clusters of galaxies can form even larger groups called superclusters How do we see galaxies? We can see our own Milky Way without the use of a telescope Telescopes (far-seeing) allow us to see distant galaxies Spyglasses let us see further at sea and into the skies With new technology comes new discovery

Optical TelescopesRadio Telescopes Very Large Array (VLA) New Mexico Refracting Telescope Nice, France - Uses combinations of lenses to see distant light sources Reflecting Telescope, Los Angeles, CA - Uses combinations of mirrors to see distant light sources - Detects radio signals from space

Hubble Telescope (1990) Hubble repairs (2001) Infrared Telescopes Chandra Observatory (1999) X-Ray Telescopes

Messier 100 Pillars of Creation, Eagle Nebula Tarantula Nebula in Large Magellanic Cloud Supernova 1604 Crab Nebula caused by 1054 supernova

Spiral Galaxies Milky Way NGC 7331 “Pinwheel” - A flat, rotating disc of mainly young (blue) stars and interstellar matter - A central “bulge” of mainly older (red) stars - A spherical “halo” of stars, including many in globular clusters - A super-massive black hole at the center of the central bulge NGC 1672 AndromedaNGC 1365

Elliptical Galaxies ESO-325M 59NGC Have no spiral arms and are spherical or egg shaped - Contain mostly older (red) stars and little interstellar matter - Range from dwarf to giant galaxies based on number of stars M 87 M 105 M 32

Irregular Galaxies - Lack regular shapes and do not have well-defined structure - Some contain large amounts of interstellar matter, others do not - More dwarf irregular galaxies than large ones - Most irregular galaxies found near spiral or elliptical galaxies, so gravity may affect shapes IC 10 M 82 “The Cigar”NGC 1569 Large Magellanic CloudNGC 4449 NGC 1427A

Hubble Deep Field, 13 million years ago Are galaxies stationary? - Galaxies are on the move, due to gravity, inertia and early forces at the time of the Big Bang - If the spectral lines in light from a galaxy shift toward the red end of the spectrum, the galaxy is moving away from us (red shift) - If the spectral lines in light from a galaxy shift toward the blue end of the spectrum, the galaxy is moving toward us (blue shift) Artistic depiction of a quasar; a new galaxy?