The Stars .


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The Stars. The Sun is a Star. Surface of the Sun. Solar Prominence. Solar Corona. The Stars in the Sky. Vary in Brightness Distance Size Vary in Color Color = Temperature. Star Names. Proper star names mostly Arabic Greek Letters, Numbers Catalog Identifiers
Transcripts
Slide 1

The Stars

Slide 2

The Sun is a Star

Slide 3

Surface of the Sun

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Solar Prominence

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Solar Corona

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The Stars in the Sky Vary in Brightness Distance Size Vary in Color = Temperature

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Star Names Proper star names for the most part Arabic Greek Letters, Numbers Catalog Identifiers Faint stars more often than not have no name

Slide 8

Constellations 89 in number Based on Near Eastern myths by means of the Greeks Some 17 th - 18 th century Invented Constellations Now Have Formal Boundaries Every star is in one and stand out heavenly body Constellations are completely human creations. They are not "Generally" in the sky.

Slide 9

The Southern Cross

Slide 10

A Myth in the Autumn Sky

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A Star Map

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Western Constellations

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Chinese Constellations

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The Heavens Are Not Changeless The Stars Move Most of our groups of stars would have been unrecognizable to Neanderthal Man The Solar System Moves Very few of our adjacent stars would have been obvious to the main people Stars are Born, Live and Die Many of our brightest stars did not exist in the times of the dinosaurs

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Parallax and the Distances of Stars seem indistinguishable all over Earth They do indicate slight parallax move from inverse sides of Earth\'s circle

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Parallax: pre-1997 Parallax is minor - was once utilized as contention against movement of the Earth One second of circular segment = size of a quarter at 5 km (3 mi.) Parallax point of closest star (4.3 l.y.) is 0.75" Accuracy restricted by Earth\'s air Fairly precise to 30-40 l.y., unpleasant to 100

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Hipparcos Named for old Greek stargazer who indexed the stars Hi gh P recision Par allax Co llecting S ystem Launched by European Space Agency, 1989 Data Collection 1989-1993 Data Analysis 1993-1997

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The Hipparcos Data 118,218 stars measured: parallax and movement 22,396 exact to 10% - a 20-overlap change Stars out to 200-300 l.y. are known to inside 10% 30,000 more exact to 20% All pre-Hipparcos remove information is out of date

Slide 19

Brightness of Stars Variations in separation and inborn brilliance Scale in view of one by Hipparcos 500 B.C. Size: Large Numbers = Fainter One size = 2.5 x Five extents = 100 x

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Magnitudes Planet around close-by star: 30 Pluto: 13 Faintest Naked-Eye Star: 6 Big Dipper Stars: 2 Sirius (Brightest Star) -1.6 Venus -4 Full Moon -12 Sun -27

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Absolute Magnitude Altair and Deneb are about similarly splendid as observed from Earth Altair is 16 l.y. away, Deneb 1600 Hence Deneb must be around 10,000 times brighter

Slide 22

Absolute Magnitude How brilliant a star would be at a separation of 32.6 l.y. (10 parsecs) Sun: 4.5 (subtle bare eye star) Altair: 2.2 Deneb: - 7.1 (splendid as bow moon) Note: Deneb - Altair around 10 extents = 100 x 100 = 10,000 times

Slide 23

Black-Body Radiation Objects Emit Radiation Because They Are Hot Why "Dark"? Since None of the Radiation is Reflected from Some Other Source The Sun Emits Black-Body Radiation, the Moon Does Not

Slide 25

Color = Temperature

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Why Black-Body Radiation is so Important Color is specifically identified with Temperature is the main determinant of shading Energy per unit range is the same if temperature is the same If two stars have similar shading and separation, distinction in shine is because of contrast in size Dwarf and monster stars are actually midgets or mammoths

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Spectroscopy Different molecules retain or emanate particular wavelengths of light When light spread into a range, the ingested wavelengths appear as dim (missing) groups These phantom lines are pointers of: Chemical structure Physical conditions

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Atoms and Radiation

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The Solar Spectrum

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Spectral Lines are Affected By: Electrical and Magnetic Fields Number of Electrons Atoms Have Lost (Indicates Temperature and Pressure) Motion (Doppler Effect) Blue-moved if Motion Toward Observer Red-moved if Motion Away From Observer

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The Doppler Effect

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The Doppler Effect

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What the Doppler Effect Tells Us Radial Motion Rotation of Stars Approaching side of star blue-moved, subsiding side red-moved Unseen Companions (Stars or Planets) Star wavers around focus of mass Surface and Interior Motions Changes in Size Interior Oscillations

Slide 34

The Hertzsprung-Russell Diagram

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How Stars Form Collapsing gas and clean cloud Protostar - for the most part infrared

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Main Sequence Stars Brown Dwarf Red Dwarf Normal Star

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All Objects Exist Because of a Balance Between Gravity and Some Other Force People, Planets-Interatomic Forces Normal Stars-Radiation White Dwarfs-Electron Repulsion Neutron Stars-Nuclear Forces Black Holes-No Known Force

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How Stars Die Main Sequence Stars Brighten With Age The More Massive a Star, the Faster it Uses Fuel Giant Phase White Dwarf Supernova Neutron Star - Pulsar Black Hole

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Historical Supernovae 1006 - Chinese 1054 - Chinese, European, Anasazi? 1572 - Tycho\'s Star 1604 - Kepler\'s Star 1987 - Small Magellanic Cloud (170,000 l.y.)

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Life (Briefly!) Near a Supernova Sun\'s Energy Output = 77 billion megatons/second Let\'s relate that to human scales. What might that be at one kilometer remove? 77 x 10 15 tons/(150 x 10 6 km) 2 = 3 tons Picture a truckload of explosives a km away radiating a one-second burst of warmth and light to match the Sun

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Now Assume the Sun Goes Supernova Brightens by 100 billion times Our 3 tons of touchy gets to be 300,000 megatons Equivalent to whole Earth\'s atomic arms stockpile going off one km away - consistently This vitality yield would keep going for a considerable length of time

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Planetary Systems Protoplanetary Disks Accretion of Planets Expulsion and Migration of Planets About 120 extrasolar planets known Our Solar System might be uncommon?

Slide 43

Protoplanetary Disks in Orion

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