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

Alcor A and B Mizar quadruple system Visual binary – See with telescope

Eclipsing binary – light dims periodically Demo at And

Eclipsing binary – light dims periodically Kepler Telescope looks for planets this way. Over 4000 planets discovered this way. What are these planets called? Exoplanets

Demos at or or PRJFETEgu1ROhttps:// PRJFETEgu1RO (best: 80% of stars in binary systems) Spectroscopic binary – wobble in spectral lines

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

Pleiades M stars ~400 LY away 13 LY across Brown dwarfs too

Pleiades M stars ~400 LY away 13 LY across Brown dwarfs too

M LY away Cygnus

M LY away 25 LY across, Scorpius

Perseus double cluster 7000 LY away few hundred LY across

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.

Globular clusters ~ stars Spherical shape Generally older stars Surround the galaxy Out of galaxy plane

M LY away, 150 LY across 12 billion yrs old

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 ~ LY across Think fried egg shape Spiral with arms 13 billion years old

IR COBE Milky Way - edge on

M MLY away From a distance, MW might look like this

M100 Artist conception of Milky Way

LY NGC 7331 Spitzer 50 MLY away Blue older stars If this was the MW, where is Earth?

LY You are here If this was the MW… Downtown Milky Way LY

Other galaxies Various shapes and sizes Types –Elliptical –Spiral Ordinary spiral (Sa) Barred spiral (Sb) –Irregular –Other Dwarf Large Magellanic Cloud NGC 1365 SB M100 SA M87

Other galaxies Most common –Elliptical Oldest –Elliptical Youngest –Irregular Large Magellanic Cloud NGC 1365 SB M100 SA M87

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 MLY away 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 MLY Camelopardalis

Galaxies collide

Stephen’s Quintet 300 MLY Pegasus

8 BLY

NGC 4676 The Mice 300 MLY Coma Berenices

Tadpole ARp MLY Tail is LY. Intruder is 300 MLY behind galaxy in front.

Antennae galaxies (NGC 4308, 4309) 63 MLY

ly separation 1200 km/s through gas Image: html html Watch Animation (from last lecture): 0/animations.html Binary black holes merging Galaxies merging

Andromeda Galaxy has 2 nuclei

2 nuclei at center of Andromeda galaxy

NASA video of MW and Andromeda Collision

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)Misti Mountain Observatory

Seyfert Sextet 190 MLY Serpens each < LY

Virgo

Coma Bernices ~500 MLY Millions of LY to cross

Coma 320 MLY 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