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Where are we?. http://zebu.uoregon.edu/~js/ast122/. The Milky Way. We are here. Top view. Side view. ~200 billion stars. One revolution every ~200 million years. Comparison of different stars. Stars come in a wide range of sizes. And different emission temperatures….

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Presentation Transcript
slide1

Where are we?

http://zebu.uoregon.edu/~js/ast122/

slide2

The Milky Way

We are

here

Top view

Side view

  • ~200 billion stars.
  • One revolution every ~200 million years.
slide3

Comparison of different stars

Stars come in a wide range of sizes

slide4

And different emission temperatures…

  • Typical star b.b. temperatures range from 3000K to 20,000K.
  • Some stars look bluer, some look redder.
slide6

The Sun

uv image

slide7

Some details about the sun:

Gravitational collapse - high pressure, temperature

Thermonuclear reaction: 4H+ He + 2e+ + 2n + 26.5MeV

(1eV = 1.6 x 10-19J)

slide9

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%
slide10

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: 5,800°C (10,500 °F).
  • Temperature of Core: 14 million°C (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.
slide11

Sunspots and coronal loops:

jets of plasma trapped by sun’s magnetic field

NASA (uv image from TRACE)

slide12

We are very small!

(NASA, TRACE)

slide13

Sunspots II

Royal Swedish Academy of Sciences Vacuum telescope

slide14

Structure of the Solar System

Solar system formed from cloud of gas/debris from supernova

Oort cloud - extends out 50,000 AU (1000 x Pluto’s orbit)

(nearly a light year, 25% of distance to nearest star)

Voyager 1: 125AU, edge of heliosphere, 17km/s, 36 years, = 17 light-hours from Earth

slide15

Structure of the Solar System

Kuiper belt - Neptune to ~55AU

> 70,000 objects with radius >1 km, including dwarf planets

> 35,000 Kuiper Belt objects greater than 100 km

Largely composed of frozen ices (volatiles - methane, water, amonia)

slide16

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.

slide17

Pluto (demoted 2006):

Radius: 1137 km

Mass: 1.3x1022 km

Orbit: 5.9x109 km

Made of: rock, ice

Moons: 5

Atmosphere: ~tenuous

CO2, CH4

Eliot Young (SwRI) et al., NASA

slide18

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 > 2000km/hr
  • 1 day = 16 hours
  • 1 year = 60,225 days

(http://seds.lpl.arizona.edu/nineplanets)

slide19

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!

Day: 17 hours

Year: 30,700 days

1 season = 1 year.

(http://seds.lpl.arizona.edu/nineplanets)

slide20

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: 62

Least dense planet

0.7 g cm-3 (water = 1)

NASA, Hubble

10832 days

Below molecular hydrogen

and helium layer, a layer of metallic hydrogen:

- a liquid soup of ionized protons and electrons.

- occurs for pressures > 4 x 109 Pa

(http://seds.lpl.arizona.edu/nineplanets)

1 year = 10832 days

1 day = 11 hours

slide21

Titan: Saturn’s largest moon

Radius: 2576km

Atmos. Pressure ~1.5 bar

Temp ~-200oC

Only known body (other than Earth) to have stable lakes

Huygens

Visible image

(on its way down)

Huygens

Visible

(landed)

Hydrocarbon lakes on

Titan (Cassini, radar)

slide22

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

Day: 9.8 hours

Year: 4,333 days

Io

Europa

(http://seds.lpl.arizona.edu/nineplanets)

slide23

An interior view

http://www.alienalley.com/andrew1.html

slide24

The Asteroid belt

Region where Jupiter’s gravity prevented formation of planets

Made of rock and ice.

Largest object: Ceres (~950 km radius)

Frequent asteroid collisions a major Earth hazard…

slide25

Mars:

Radius: 3,397 km

Mass: 6.4x1023 kg

Orbit: 2.3 x 108 km

Made of: rock

Atmosphere: yes (CO2)

Moons: 2

1 year = 78 days

1 day = 25 hours

Valles

Marineris

NASA & (http://seds.lpl.arizona.edu/nineplanets)

slide27

Mars contd:- machines on Mars...

Curiosity

Planetary Geology

slide29

Martian landscapes

dunes

Gullies in a crater

Dust devils

over dunes

Pockmarks

in dry ice at the poles

slide31

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

1 day = 25 hours

1 year = 365.25 days

(http://seds.lpl.arizona.edu/nineplanets)

slide32

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

1 year = 225 days

1 day = 243 days!

Surface

Visible from space

Venera 10

(http://seds.lpl.arizona.edu/nineplanets)

slide33

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

1 year = 88 days

1 day = 59 days!

(http://seds.lpl.arizona.edu/nineplanets)