12-Galaxies - Origin and Evolution of Galaxies Our Home...

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Origin and Evolution of Galaxies; Our Home Galaxy: The Milky Way Biology 190A Lecture 12 ‐‐‐ Prof. Steve Schneider Dept. of Astronomy
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Our Cosmic Address We belong to a series of successively larger groupings or systems: UMass Amherst assachusetts Massachusetts USA rth Earth Solar System Orion spiral arm Milky Way galaxy Local Group of galaxies Virgo Supercluster Universe #293,763,211,099??
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Our View Looking Out: The Milky Way & Magellanic Clouds
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Structure of the Milky Way We live in a disk shaped system of stars about 100,000 light years across. The Sun is located 25,000 ly out from the center. ost stars are Most stars are near the center, ut few stars are but few stars are forming there. as ust and star Gas, dust and star formation are ncentrated to our view of the nter and out through concentrated to the disk. center and out through the disk is blocked by dust
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Hubble’s Galaxy Classification Scheme There are three broad categories of galaxies: Irregulars Spirals llipticals dd l Ellipticals redder ––––––––––––––––––––––––– bluer no gas –––––––––––––––––––––– a lot of gas no star formation –––––– a lot of star formation
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Our Place in the Milky Way (photo of M61 – a similar type of galaxy as the Milky Way) X The Sun is just one of about 100,000,000,000 stars rcling the center of the Milky Way circling the center of the Milky Way. We live on the inner edge of the “Orion spiral arm.”
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Outward from the Milky Way ~150,000 ly istant An image of the whole sky at infrared wavelengths distant made with the 2-Micron All Sky Survey (2MASS), shows the “nearby” Magellanic Clouds.
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The Local The Andromeda galaxy is the Group largest in the Local Group ist ~ 000000 ~4 dozen Dist 2,000,000 ly The Milky Way is part of a group of about 50 galaxies, most of which are small irregulars
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Galaxy Clustering Most galaxies are found in clusters, from poor groups with only a few large galaxies, to rich groups with 100s or 1000s of large galaxies. Clusters are dynamic! The dense environment leads to galaxy interactions, galaxy mergers, “cannibalism” of small galaxies, … Rich clusters contain mostly ellipticals. hen galaxies llide with each ther stars are When galaxies collide with each other, stars are so far apart that they are unlikely to collide, but s n be ripped out of them possibly turning gas can be stripped out of them, possibly turning them into ellipticals.
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12-Galaxies - Origin and Evolution of Galaxies Our Home...

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