* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Galaxy
History of Solar System formation and evolution hypotheses wikipedia , lookup
Auriga (constellation) wikipedia , lookup
History of astronomy wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Fermi paradox wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Spitzer Space Telescope wikipedia , lookup
Aries (constellation) wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Gamma-ray burst wikipedia , lookup
Modified Newtonian dynamics wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
Space Interferometry Mission wikipedia , lookup
Corona Australis wikipedia , lookup
Stellar evolution wikipedia , lookup
Planetary system wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Globular cluster wikipedia , lookup
Observational astronomy wikipedia , lookup
Perseus (constellation) wikipedia , lookup
Open cluster wikipedia , lookup
Andromeda Galaxy wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Cosmic distance ladder wikipedia , lookup
Hubble Deep Field wikipedia , lookup
Timeline of astronomy wikipedia , lookup
Galaxies & Star Systems Astronomy 2 Star Systems Our solar system only has one star (our sun); however, most are grouped together to groups of two or more – called star systems Star systems with 2 stars are called double stars or binary stars – 3 stars are called triple stars Sometimes binary stars cannot be seen from Earth – only one star can be seen Star Systems When one star hides another star it is called an eclipsing star Astronomers know there are actually 2 stars by looking at the effects of gravity Our solar system is not the only solar system with planets revolving around a star In 2000, astronomers discovered a solar system about 10.5 light-years away with planets similar to our solar system Star Systems Scientists hypothesize that this solar system might contain life Since this discovery scientists have been sending out radio waves and looking for radio waves from unnatural sources hoping to discover extraterrestrial life However, this could take many years because radio waves travel much slower than light waves Galaxies Galaxy: A group of millions or billions of stars, gas, and dust held together by gravity Our sun and all visible stars are members of our galaxy, the Milky Way Galaxies There are 3 main categories of galaxies Spiral galaxies Elliptical galaxies Irregular galaxies Our Galaxy The Milky Way is visible as a band of light crossing the sky during summer and winter Represents the concentrated light of the billions of stars in our galaxy At night, we witness the view from within our galaxy Milky Way Galaxy A disk of stars that contains 100-200 billion stars 100,000 light years in diameter, about 3000 light years thick The center of the Milky Way (nuclear bulge), swells to about 10,000 LY thick Milky Way Diagram http://zebu.uoregon.edu/~imamura/123/images/mw-schematic.jpg Milky Way Infrared Milky Way (COBE) The view from within, in IR light http://www.astro.psu.edu/users/niel/astro1/slideshows/class21/slides-21.html Sun and Galaxy Sun located about 2/3 distance away from the center (30,000 light years) The entire Milky Way rotates around its center Sun orbits the center of the galaxy at 563,000 mph One galactic revolution takes 220 million years Sun’s Revolution http://www.envirotruth.org/images/graphics/suns_path.jpg Milky Way, a Spiral Galaxy Spiral galaxy, most are concentrated in a central nucleus Spiral arms of stars wind outward from the nucleus M101 Milky Way Map http://members.nova.org/~sol/chview/milkyway.jpg Formation of the Milky Way Milky Way appears to be about 13 billion years old MW likely represents one of the original galaxies created after the Big Bang Sun and planets are 4.5 billion years old Big Bang origin of universe 13.7 bya Elliptical Galaxies Elliptical Galaxies Look like flattened balls Contains billions of stars, but little dust and gas Due to the lack of dust and gas new stars rarely form Most elliptical galaxies contain only old stars Irregular galaxies Irregular galaxies Does not have a regular shape One of the closest neighboring galaxies to the Milky Way is an irregular galaxy It is about 160,000 light years away Star Clusters: Open Clusters A few dozen to thousands of stars loosely bound together by gravity Found mainly in the galaxy’s disk and spiral arms More than 1000 have been discovered in the Milky Way Young stars that recently formed from nebulosity Jewel Box open cluster (NGC 4755) Star Clusters: Globular Clusters Huge, concentrated balls of thousands to millions of stars Found in galactic halo, a spherical region centered on the nucleus Contain the oldest known stars About 150 globular clusters have been discovered Omega Centauri, globular cluster (NGC 5139) Cluster Summary Type Stars Location Age Open Cluster Dozens to thousands (Population I) Within galactic disk Globular Cluster Hundreds to millions (Population II) Orbit galaxy in halo Young, Among oldest thousands to known stars (billions millions of years of years) Open Clusters Pleiades—M45 M67 Which cluster is oldest? Note the star colors of the main stars in each cluster Globular Cluster M55 Colors indicate temperatures, red (cool) to blue (hot) The “turn off” area on the main sequence represents the cluster’s age Between the Stars Space between the stars in a galaxy is a vacuum, or empty space Also termed interstellar medium Matter between the stars is of gas and dust Between the Stars Interstellar matter 99% gas, 1% dust Gas consists of 75% hydrogen and 25% helium Interstellar dust similar in size to cigarette smoke In spiral galaxies, gas and dust is concentrated in the disk and spiral arms Pillars of Creation (M16) •In this iconic photo from the Hubble Space Telescope, a small portion near the center of M16, the Eagle Nebula, is revealed •Note the pink, newly formed stars within the nebula Barnard’s S Nebula A dark nebula represents interstellar dust that blocks the light of stars from behind http://www.astropix.com/HTML/D_SUM_S/B72.HTM Horsehead Nebula Famous dark nebula (B33) located near the Belt of Orion Messier Catalog All of the Messier objects are shown in this montage M1 starts the upper left, M110 ends the lower right Other Galaxies Until 1924, Milky Way was the “universe” Edwin Hubble proved that galaxies other than our Milky Way exist Hubble used Cepheid variable stars to measure the distances to galaxies Hubble also photographed stars in the Andromeda “Nebula” The universe contains an estimated 100 billion galaxies. Each of these galaxies contains about 100 billion stars Andromeda Galaxy Our nearest large neighbor Similar in size and shape to Milky Way Andromeda Galaxy is visible to the naked eye as a glowing spot in the constellation of Andromeda 2.3 million light years distant (wave!) Andromeda Galaxy (M31, M32, M110) Andromeda Constellation Locate M31 and M33 Triangulum Galaxy (M33) M33 The pink glow of emission nebulas can be seen in this photo Center of Virgo Cluster M86 Virgo Cluster near M84, M86 Sombrero Galaxy (M104) from HST Large-Scale Structure of the Universe Sheets & Voids: http://heasar c.nasa.gov/d ocs/cosmic/s heets_voids. html http://www.astro.princeton.edu/~cen/PROJECTS/p1/DARKallz0.jpeg Galactic Cannibalism Galaxies can merge together to form larger galaxies Elliptical galaxies may be the result of multiple galaxy collisions NGC 2207 (left) and IC 2163 (HST)