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Today’s Comments • • • • • Graded papers – see Raquel to get old papers or tests. Grades updated yesterday Lab Students: pickup notebooks this week; grades on website D2L Quizzes 9&10 available; do them to prepare for test 3 Observations – Binoculars available for Moon Craters on your own. Fill out loan form. • RETURN BINOCULARS BY RETURN DATE – Sunset Part 2. Work on this. Due Apr. 28 – Telescopes, Star Gazing & Moon Craters available at UMN, Macalester and Eagle Lake Observatory – see dates on calendar • Apr. 24, 25, 28 & May 1 – Space Exhibit at Science Museum of MN on 5:30-9pm, Thursday, May 7; Evite invitation coming tomorrow and you need to RSVP • Answer EVITE – if you didn’t get this, see Raquel Stars • • • • • • • • Binary Stars Open Star Clusters Globular Clusters Milky Way Galaxy Other Galaxies Colliding Galaxies The Local Group Galactic Clusters Binary Stars • Two stars orbiting each other • Very common Binary Stars • Important – Used to measure mass of stars (using Kepler’s Laws) Binary Stars • Three Main Types – Visual – see with telescope – Eclipsing – light dims periodically – Spectroscopic – Doppler shifts in spectra Visual binary – See with telescope Visual binary – See with telescope Visual binary – See with telescope Alcor A and B Mizar quadruple system Eclipsing binary – light dims periodically Demo at http://www.eso.org/public/usa/videos/eso1311b/ And http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html Eclipsing binary – light dims periodically Kepler Telescope looks for planets this way. Over 4000 planets discovered this way. What are these planets called? Exoplanets Spectroscopic binary – wobble in spectral lines Demos at http://csep10.phys.utk.edu/astr162/lect/binaries/spectroscopic.html or http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html or https://www.youtube.com/watch?v=1kFFwHkxBiI&list=PLJistbn1hLkxuwLpuOHbt PRJFETEgu1RO (best: 80% of stars in binary systems) Open Star Clusters • Few to a few thousand stars grouped by gravity in the same region of space • No particular shape • Generally younger stars • Located in plane of galaxy • Example - Pleiades http://www.spitzer.caltech.edu/images/2396-sig05-023-Star-Clusters-Found-in-the-MIlky-Way Pleiades M45 3000 stars ~400 LY away 13 LY across Brown dwarfs too Pleiades M45 3000 stars ~400 LY away 13 LY across Brown dwarfs too M39 800 LY away Cygnus M7 1000 LY away 25 LY across, Scorpius Perseus double cluster 7000 LY away few hundred LY across http://antwrp.gsfc.nasa.gov/apod/ap070314.html In Puppis M46 (upper left) 5,400 ly , 300 million years old, a few hundred stars, 30 ly across M47 (lower right) 1,600 ly. 80 million years old, 50 stars, 10 ly across. http://antwrp.gsfc.nasa.gov/apod/ap070314.html Globular clusters • • • • ~100 000 stars Spherical shape Generally older stars Surround the galaxy • Out of galaxy plane M13 25 000 LY away, 150 LY across 12 billion yrs old http://apod.nasa.gov/apod/ap120614.html Galaxy • Very large collection of gas, dust and stars orbiting a central mass • > 100 billion galaxies in the universe • Each has millions to billions of stars Milky Way Galaxy • • • • • ~300 billion stars ~100 000 LY across Think fried egg shape Spiral with arms 13 billion years old http://apod.nasa.gov/apod/ap140916.html http://apod.nasa.gov/apod/ap141031.html Milky Way - edge on IR COBE From a distance, MW might look like this M100 56 MLY away M100 Artist conception of Milky Way http://www.jpl.nasa.gov/news/news.php?release=2010-179 If this was the MW, where is Earth? 100 000 LY NGC 7331 Spitzer 50 MLY away Blue older stars If this was the MW… Downtown Milky Way You are here 30 000 LY 100 000 LY Other galaxies • Various shapes and sizes • Types – Elliptical – Spiral M87 • Ordinary spiral (Sa) • Barred spiral (Sb) M100 SA – Irregular NGC 1365 SB – Other • Dwarf Large Magellanic Cloud http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm Other galaxies • Most common – Elliptical • Oldest M87 – Elliptical • Youngest – Irregular M100 SA NGC 1365 SB Large Magellanic Cloud http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm Elliptical M87 Virgo 50MLY Ordinary Spiral Galaxies Ordinary Spiral (Sa) Whirlpool Galaxy M51 30 MLY away 60 KLY across Sa M33 Pinwheel or Triangulum Galaxy 3 MLY Sb M31 Andromeda 2.5 MLY 1 trillion stars (3X MW) NGC 4565 30 MLY away 100 000 LY across Needle Galaxy, 240 globular clusters In Coma Berenices (Sb) NGC 613 Sb 65 MLY Sculptor NGC 6946 Sc or Sab 10 MLY away Cepheus Sc M83 15 MLY Hydra Irregular Large Magellanic Cloud – southern hemisphere 180,000 LY away 15,000 LY across Irregular NGC 1569 7 MLY Camelopardalis Galaxies collide Stephen’s Quintet 300 MLY Pegasus 8 BLY NGC 4676 The Mice 300 MLY Coma Berenices Tadpole ARp188 420 MLY Tail is 280 000 LY. Intruder is 300 MLY behind galaxy in front. Antennae galaxies (NGC 4308, 4309) 63 MLY Binary black holes merging Galaxies merging 25 000 ly separation 1200 km/s through gas Image: http://antwrp.gsfc.nasa.gov/apod/ap 060412.html Watch Animation (from last lecture): http://chandra.harvard.edu/photo/2006/a40 0/animations.html Andromeda Galaxy has 2 nuclei http://antwrp.gsfc.nasa.gov/apod/ap061126.html 2 nuclei at center of Andromeda galaxy http://antwrp.gsfc.nasa.gov/apod/ap961011.html NASA video of MW and Andromeda Collision http://vimeo.com/43694515 The Local Group • ~50 members less than 4 million LY away from Milky Way • Milky Way, Andromeda Galaxy dominate • 2.5 million LY to Andromeda Galaxy Large and Small Magellanic Clouds Southern Hemisphere Triangulum Galaxy Canis Major Dwarf Nearest neighbor Canis Major Dwarf in red Milky Way in blue NGC 6712 Loses Stars into the Milky Way Halo (Artist’s impression) Source: European Southern Observatory ESR PR Photo 06c/99 (18 Feb 1999) Clusters of Galaxies Hercules, 650Mly Credit & Copyright: Jim Misti (Misti Mountain Observatory) Seyfert Sextet 190 MLY Serpens each < 35 000 LY Virgo Virgo Coma Bernices ~500 MLY Millions of LY to cross Coma 320 MLY http://antwrp.gsfc.nasa.gov/apod/ap070531.html Sloan + Spitzer (dwarfs, 1000s) Perseus 300 MLY Do clusters cluster? Yes, Superclusters! What is the large scale structure of the universe? What does that tell us about the origin and future of the universe? • • • • • • • • Stars Binary Stars Open Star Clusters Globular Clusters Milky Way Galaxy Other Galaxies Colliding Galaxies The Local Group Galactic Clusters • Next Lecture – Hubble’s Law and Galaxy Motion