Universe 1

Astronomy 25 1

The Milky Way

Our home galaxy.

Astronomy 25 2

Milky Way

The Milky Way

The Milky Way over the Alps

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Milky Way

Changing Ideas

!Galileo (1610): the Milky Way is stars

!Herschel (1800): the Big Wheel

!Shapley (1917): the Sun isn't at the center

!Trumpler (1930): interstellar "dust" absorbs light

William Herschel

Universe 2

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Milky Way

The Sun is Not in the Center

!Shapley plottedglobular clusters.

!Center of Galaxy is8 kpc away

!Re-affirmed theCopernicanPrinciple

Harlow Shapley

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Milky Way

The Milky Way From Earth

North American Nebula Galactic Center

Great Sagittarius

Star Cloud

Cygnus Loop

The Great Rift

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Milky Way

Structure of the Galaxy

Galaxy in infrared.

Universe 3

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Milky Way

A Spiral Galaxy

Spiral arms

Central bulge

M83 in Hydra

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Milky Way

Structure

!Halo

"No gas

"Old starsDark matter

!Bulge

"Some gas

"Old stars

!Disk

"Gas + dust

"Young starskpc = kiloparsec

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Milky Way

Halo

!Globular clusters

!Single old stars

e.g. Arcturus

M4 in ScorpiusCharles Messier

Universe 4

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Milky Way

Globular Clusters

!About 200 known

!100,000 - 1,000,000 stars

!20-100 pc in diameter

!>10 billion years old

!Most toward center ofgalaxy

M3 in Canes Venatici

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Milky Way

Globular Clusters

47 Tucanae

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Milky Way

Globular Clusters

Omega Centauri

Universe 5

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Milky Way

The Disk

Based on radio

observations

of H at 21 cm

!Spiral arms

"Bright O and B stars

"Dust and gas

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Milky Way

Density Wave Theory

!Stars move faster than waves

!Traffic jam

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Milky Way

A Barred Spiral!

Universe 6

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Milky Way

Contents of Disk

! Open Clusters

! Diffuse Nebulae

"Emission nebulae

"Reflection nebulae

"Dark nebulae

! Planetary Nebulae

! Mass ejection nebulae

! Supernova Remnants

NGC 6559

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Milky Way

Open Clusters

Jewelbox Cluster

in Crux

•10-100s of stars

•Young

•Irregular shape

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Milky Way

Open Clusters

M7 in Scorpius

Universe 7

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Milky Way

Open Clusters

M50 in Monoceros

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Milky Way

Diffuse Nebulae

Great Orion Nebula (M42)

•Star formationregions

•Hot and coldgas clouds

•Red light is Ha

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Milky Way

Emission Nebulae

Lagoon Nebula

Trifid Nebula

Universe 8

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Milky Way

Emission Nebulae

Trifid Nebula (M20)

Sagittarius

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Milky Way

Emission Nebulae

Lagoon Nebula

(M8)

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Milky Way

Emission Nebulae

Center of Lagoon Nebula

(HST)

Universe 9

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Milky Way

Emission Nebulae

Eagle Nebula (M16)

In Serpens

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Milky Way

Emission Nebulae

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Milky Way

Reflection Nebulae

M78 in Orion

Universe 10

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Milky Way

Dark Nebulae

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Milky Way

Dark Nebulae

NGC281

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Milky Way

Diffuse NebulaeAntares

M4

Universe 11

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Milky Way

Planetary Nebulae

Ring Nebula (M57)

in Lyra

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Milky Way

Planetary Nebulae

Dumbbell Nebula (M27)

in Vulpecula

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Milky Way

Planetary Nebulae

Universe 12

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Milky Way

Planetary Nebulae

NGC 3132 in Antlia

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Milky Way

Mass Loss Nebulae

HD 44179 (HST)

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Milky Way

Mass Loss Nebulae

Universe 13

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Milky Way

Supernova Remnants

Crab Nebula (M1)

in Taurus

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Milky Way

Supernova Remnants

Supernova 1006

in Lupus

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Milky Way

Supernova Remnants

Tycho's Supernova

Universe 14

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Milky Way

Supernova Remnants

Gum Nebula

in southern

Milky Way

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Milky Way

Supernova Remnants

S147 in

Taurus

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Milky Way

The Center of the Galaxy

Center of

Galaxy

M22

Lagoon

Neb.

Sagittarius

Universe 15

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Milky Way

The Center at 1 Meter

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Milky Way

The Center of the Galaxy

5 pc

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Milky Way

The Center of the Galaxy

Speed of orbiting stars-> supermassive blackhole 3 million Msun

Universe 16

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Milky Way

The Center in X-Rays

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Milky Way

The Center in IR

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Milky Way

Our Galaxy