Where are we

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Where are we?
http//zebu.uoregon.edu/js/ast122/
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The Milky Way
We are here
Top view
Side view

• 200 billion stars.
• One revolution every 200 million years.

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Comparison of different stars
Stars come in a wide range of sizes
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And different emission temperatures

• Typical star b.b. temperatures range from 3000K
  to 20,000K.

• Some stars look bluer, some look redder.

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Getting closer
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The Sun
uv image
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Some details about the sun
Gravitational collapse - high pressure,
temperature Thermonuclear reaction 4H He
2e 2n 26.5MeV
(1eV 1.6 x 10-19J)
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(No Transcript)
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• Sun Facts I
• Diameter 1.4 million km
• Age 4.5 billion years (lifetime 11 billion
  years)
• Mass 2 x 1030 kg (330,000 x Earths)
• (99.8 of mass of solar system)
• Density 1.41 (water 1)
• Composition (by mass) Hydrogen 73, Helium
  25,
• Others 2

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• Sun facts II
• Distance from Earth 149.6 million km.
• Distance to nearest Star 9.46 million million
  km.
• Luminosity 4 x 1026 J s-1 (390 billion billion
  Megawatts).
• Solar Cycle 8 - 11 years.
• Temperature at Surface 5,800C (10,500 F).
• Temperature of Core 14 millionC (22.5 million
  F)
• Pressure at core 250 billion atmospheres (2.5 x
  1016 Pa)
• Every second 700 million tons of hydrogen
  converted to
• 695 million tons helium, and 5 million tons of
  energy.

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Sunspots and coronal loops jets of plasma
trapped by suns magnetic field
NASA (uv image from TRACE)
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We are very small!
(NASA, TRACE)
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Sunspots II
Royal Swedish Academy of Sciences Vacuum telescope
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Structure of the Solar System
Solar system formed from cloud of gas/debris from
supernova
Oort cloud - extends out 50,000 AU (1000 x
Plutos orbit) (nearly a light year, 25 of
distance to nearest star)
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Structure of the Solar System
Kuiper belt - Neptune to 55AU
gt 70,000 objects with radius gt1 km, including
dwarf planets gt 35,000 Kuiper Belt objects
greater than 100 km Largely composed of frozen
ices (volatiles - methane, water, amonia)
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Structure of the Solar System
Dwarf planet (plutoid) 1) is in orbit around
the Sun. 2) has sufficient mass for its
self-gravity to overcome rigid body forces so
that it assumes a hydrostatic equilibrium
(near-spherical) shape. 3) has not cleared the
neighborhood around its orbit. 4) is not a
satellite.
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Pluto Radius 1137 km Mass 1.3x1022 km Orbit
5.9x109 km Made of rock, ice Moons
1 Atmosphere tenuous CO2, CH4
(http//seds.lpl.arizona.edu/nineplanets)
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• Neptune
• Radius 24,766 km
• Mass 1.0x1026 kg
• Orbit 4.5 x 109 km
• Made of
• ices (H20, CH4, NH3),
• rock, hydrogen (15)
• helium
• Atmosphere yes
• Moons 13 known
• Internal heat source
• radiates twice the
• energy it receives
• Fastest winds in solar
• system gt 2000km/hr

(http//seds.lpl.arizona.edu/nineplanets)
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Neptunes fast winds? Under such conditions,
the methane found in Neptune's atmosphere also
decomposes, as the bonds holding methane's four
hydrogen atoms dissolve and the carbon atoms may
bind to one another in the extreme pressure to
form diamonds (according to a new hypothesis by a
team at the University of California at Berkeley
and experiments conducted by Robin Benedetti).
Hence, a rain of diamonds may be falling toward
Neptune's core, which release heat through
friction with its heavy atmosphere (Curtis Rist,
Discover, September 2000).
Random fact Scientists know diamonds can form in
other places in space, too, besides the Earth.
For example, the biggest diamond in the galaxy is
the entire crystallized core of a dwarf star,
2,500 miles across, that weighs 5 million
trillion trillion pounds, which translates to
approximately 10 billion trillion trillion
carats, or a one followed by 34 zeros.
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Uranus Radius 25,559 km Mass 8.7x1025
kg Orbit 2.9 x 109 km Made of ices, rock,
hydrogen, helium Atmosphere yes Moons
27 n.b. axis of rotation parallel to plane of
orbit!
(http//seds.lpl.arizona.edu/nineplanets)
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Saturn Radius 60,268 km Mass 5.7x1026
kg Orbit 1.4 x 109 km Made of hydrogen, helium
ice, and rock Atmosphere yes Moons 31 Least
dense planet 0.7 g cm-3 (water 1)
NASA, Hubble
(http//seds.lpl.arizona.edu/nineplanets)
Below molecular hydrogen and helium layer, a
layer of metallic hydrogen - a liquid soup of
ionized protons and electrons. - occurs for
pressures gt 4 x 109 Pa
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Jupiter Radius 71,492 km Mass 1.9x1027
kg Orbit 7.8 x 108 km Made of hydrogen (90),
helium (10), ice, and rock Atmosphere
yes Moons 61
Io
Europa
(http//seds.lpl.arizona.edu/nineplanets)
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The Asteroid belt Region where Jupiters gravity
prevented formation of planets Made of rock and
ice. Largest object Ceres (950 km radius)
Frequent asteroid collisions a major Earth hazard
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Mars Radius 3,397 km Mass 6.4x1023 kg Orbit
2.3 x 108 km Made of rock Atmosphere yes
(CO2) Moons 2
NASA (http//seds.lpl.arizona.edu/nineplanets)
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Biggest bump in the solar system Olympus Mons,
24km high!
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Mars contd- machines on Mars...
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Its a tough neighbourhood out there.
Phobos, moon of Mars
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Earth Radius 6,678 km Mass 5.9x1024 kg Orbit
1.5 x 108 km Made of rock Atmosphere yes
(nitrogen, oxygen, argon) Moons 1 Specific
density 5.52
Densest planet in solar system
(http//seds.lpl.arizona.edu/nineplanets)
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Venus Radius 6,052 km Mass 4.9 x 1024
kg Orbit 1.1 x 108 km Made of rock Atmosphere
yes (CO2) Moons No Surface pressure 90
atm Surface temperature 750K
Surface
Visible from space
Venera 10
(http//seds.lpl.arizona.edu/nineplanets)
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Mercury Radius 2,440 km Mass 3.3x1023
kg Orbit 5.8 x 107 km Made of rock Atmosphere
yes (unstable) Moons No Temperatures vary from
90K to 700K - largest range in solar system
(http//seds.lpl.arizona.edu/nineplanets)