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YOU ARE HERE… The Sun is located on the Orion Arm of the Milky Way The Sun is located on the Orion Arm of the Milky Way If you look toward the constellation Sagitarius, you are looking toward the center of the galaxy. If you look toward the constellation Sagitarius, you are looking toward the center of the galaxy. ~10,000 parsecs from the center of the galaxy. ~10,000 parsecs from the center of the galaxy.
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A Long Time Ago in a A Long Time Ago in a Galaxy Far, Far Away…Galaxy Far, Far Away…
The Milky Way Galaxy: The Milky Way Galaxy: Home Sweet Home!!Home Sweet Home!!
Our home Galaxy is called the MILKY WAY (like Our home Galaxy is called the MILKY WAY (like the candy bar the candy bar ))
So named because early stargazers thought the So named because early stargazers thought the stars looked like milk spilled across the sky. stars looked like milk spilled across the sky.
YOU ARE HERE…YOU ARE HERE… The Sun is located on the Orion Arm of the Milky WayThe Sun is located on the Orion Arm of the Milky Way If you look toward the constellation Sagitarius, you are looking If you look toward the constellation Sagitarius, you are looking
toward the center of the galaxy. toward the center of the galaxy. ~10,000 parsecs from the center of the galaxy. ~10,000 parsecs from the center of the galaxy.
How huge is the Milky Way?How huge is the Milky Way?
Milky Way Dimensions:Milky Way Dimensions: 75,000 light years from end to end75,000 light years from end to end 3,300 light years thick3,300 light years thick ~33,000 light years from the center of the galaxy to ~33,000 light years from the center of the galaxy to
the Sunthe Sun Mass: 4 x 10Mass: 4 x 101111 Solar Masses Solar Masses
“If there’s a bright center to the galaxy, you’re on the planet that it’s farthest from. “ ~Luke Skywalker, Star Wars
3,300 LY
75,000 LY
SUN
33,000 LY
Galactic Galactic AnatomyAnatomy
NUCLEUS:NUCLEUS: Bright Center Bright Center of the galaxy. of the galaxy.
NUCLEAR BULGE:NUCLEAR BULGE: Flattened cloud about 3 pc Flattened cloud about 3 pc in radius around center of in radius around center of the galaxy. the galaxy.
HALO:HALO: Area surrounding Area surrounding galaxy that contains some galaxy that contains some scattered globular clusters. scattered globular clusters.
DISK:DISK: Contains most of the Contains most of the stars in the galaxy. stars in the galaxy.
Jump to Hyperspace?Jump to Hyperspace? By looking at the By looking at the
radial velocities of radial velocities of surrounding stars, we surrounding stars, we can estimate the can estimate the Sun’s velocity to be Sun’s velocity to be about 220 km/s. about 220 km/s.
It takes about 240 It takes about 240 million years for the million years for the Sun to orbit the center Sun to orbit the center of the galaxy! of the galaxy!
Like Spinning a Like Spinning a Pizza…Pizza…
Clouds of hydrogen and helium Clouds of hydrogen and helium from the Big Bangfrom the Big Bang
Star motion within causes it to Star motion within causes it to rotate and contractrotate and contract
Cloud begins to flatten into a Cloud begins to flatten into a diskdisk
Older stars are left behind in Older stars are left behind in the halothe halo
The galaxy is now nearly flat The galaxy is now nearly flat
Spiral ArmsSpiral Arms Home to hot bright stars Home to hot bright stars
(O and B) (O and B) Used to trace the path of Used to trace the path of
our spiral armsour spiral arms Star formation is Star formation is
continuously renewed in continuously renewed in spiral armsspiral arms
Journey to the CenterJourney to the Center Nucleus is the most Nucleus is the most
mysterious partmysterious part Evidence of a Evidence of a
Supermassive Black Hole Supermassive Black Hole in Saggitarius: in Saggitarius: High Intensity Radio High Intensity Radio
SourceSource Orbits of surrounding Orbits of surrounding
objectsobjects Huge Mass (2.6 million Huge Mass (2.6 million
solar masses)solar masses) Small size (3 pc)Small size (3 pc) Event Horizon is smaller Event Horizon is smaller
than a period!than a period! Too massive to be the Too massive to be the
remains of a star: possibly remains of a star: possibly formed when galaxy didformed when galaxy did
Hubble Deep Field:Hubble Deep Field:
Millions of Galaxies!Millions of Galaxies!
Elliptical GalaxiesElliptical GalaxiesSpheres or EllipsesSpheres or Ellipses
Spiral GalaxiesSpiral Galaxies
Barred SpiralsBarred Spirals
Irregular GalaxiesIrregular Galaxies
Galactic Hugeness and Other Galactic Hugeness and Other Amazing Stuff Amazing Stuff
Mega parsec = 3.26 Mega parsec = 3.26 million light years!million light years!
Estimate distance using Estimate distance using indicators (clusters, indicators (clusters, Cepheids, supernovae)Cepheids, supernovae)
Dark Matter: Measured Dark Matter: Measured mass is much larger than mass is much larger than predicted mass, predicted mass, Gravitational lensingGravitational lensing
Massive Black Holes: Massive Black Holes: evidence in orbits of stars evidence in orbits of stars in the centerin the center
When Galaxies When Galaxies Collide…Collide…
Formation of spiral Formation of spiral armsarms
Distortion or Distortion or tearingtearing
Galactic Galactic CannibalismCannibalism
Firestorms of Star Firestorms of Star FormationFormation
Galactic MergersGalactic Mergers High Speed High Speed
CollisionsCollisions
Local Group: Local Group: Our Galaxy’s NeighborsOur Galaxy’s Neighbors
The Milky Way is one of about 35 galaxies The Milky Way is one of about 35 galaxies that are clumped close together. This that are clumped close together. This clump is called the clump is called the LOCAL GROUP.LOCAL GROUP.
M33: Triangulum Galaxy
M31: Andromeda Galaxy
Large Magellanic Cloud
Small Magellanic Cloud
Milky Way Galaxy
