Transcript A tour of the solar system.

ES 023
Planet Earth: Shaken and Stirred
•Quick review of last class
•Hertzsprung-Russell diagram (star
classification)
•A tour of the solar system
•How did the solar system form?
•Are we alone?
ES 123 The Dynamic Earth
Mendeleev’s Periodic Law
• Periodic variations in the properties of elements
led Dimitri Mendeleev to organize the elements into
the Periodic Table
Atomic Isotopes
Mass
number
(A)
Number of
protons (Z)
Number
of
neutrons
Hydrogen (1H)
Deuterium (2H)
Tritium (3H)
1
2
3
1
1
1
0
1
2
Uranium-235
(235U)
Uranium-238
(238U)
235
92
143
238
92
146
Composition of the universe
Helium
(7.8%)
Hydrogen
(92%)
Carbon (.03%)
and Oxygen (.06%)
All other elements (.11%)
Interior of the Sun
• The sun has multiple
layers (like an onion)
• The sun’s energy
source is generated by
H fusion at the core
• Heat escapes the
core by radiation
• In the outer part of
the sun, heat is
transferred by
convection
Evolution of a 15 solar-mass star
Element
fused
Hydrogen
Helium
Carbon
Neon
Fusion
product
Helium
Carbon
O, Ne, Mg
O, Mg
Oxygen
Silicon
Si, S
Iron
Time
Temp. (K)
1010 years
> 106 years
1000 years
A few
years
1 year
A few days
4x106
1x108
6x108
1x109
Source: In Quest of the Universe, Kuhn, 1998
2x109
3x109
Star Classification:
Hipparchus of Rhodes
190 BC to 120 BC
•Created a catalog of 850 stars,
classified by brightness
• His brightness scale counts
backwards, from 1st magnitude
(brightest) to 6th magnitude
(dimmest)
Apparent Stellar
Magnitude (m)
• In 1856, Oxford
astronomer Norman R.
Pogson invented an
apparent magnitude scale
based on Hipparchus’ visual
magnitudes
• According to this scale,
an increase of 5 units
corresponds to an object
that is 100 times brighter
• An increase of 10 units
corresponds to 10,000
times brighter (100x100)
Absolute Magnitude
• Definition: Absolute
stellar magnitude (M) is
the apparent magnitude
that a star would have if it
were 32.6 light years from
the Earth.
• Absolute magnitudes for
stars generally range from
-10 to +17.
• The Sun has an absolute
magnitude of 4.83, quite
average
Hertzsprung-Russell diagram
•Classification chart
for stars
•Shows absolute
magnitude versus
temperature (colour)
•Developed in the
early 20th century by
Danish astronomer
Ejnar Hertzsprung
and American
Astronomer Henry
Russell
Hertzsprung-Russell diagram
Super Giants
Giants
Sun
White Dwarfs
Stellar Evolution
•Stars on the main sequence are fueled by H fusion
•Near the end of its life, a star gets hotter and
bigger (i.e., main -> giant), as it switches to He
fusion, etc.
•Ultimately, a star may explode (nova) then become
a white dwarf, a neutron star or a black hole
A tour of the solar system
The inner solar system
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
A tour of the solar system
The outer solar system
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
A tour of the solar system
Pluto
Jovian planets
Neptune
Uranus
Saturn
Mars
Jupiter
Earth
Venus
Mercury
Terrestrial planets
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
Terrestial planets vs. Jovian planets
Terrestrial
Jovian
Diameter < 13000 km
Diameter > 48000 km
Two or fewer
satellites
8 or more known
satellites
No rings
All have ring systems
Density > 3.9 g/cm3
Density < 1.8 g/cm3
Solid surface
Primarily liquid
Mercury
•Smallest planet
•Heavily cratered surface,
like the moon’s.
• Studied by Mariner 10
spacecraft (1974 and 1975).
• Each day lasts 1.5 years
• Surface temperature
variations are most extreme
in the solar system (90 K to
700 K*)
*To get degrees Celsius from degrees
Kelvin, subtract 273.15.
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
Venus
• Most similar to Earth in
size (95% of diameter, 80%
of mass)
•Surface temperature 740 K,
pressure = 90 bars
• Studied by Mariner 2 in
1962, and more than 20
spacecraft since
• Each day lasts longer than
one year, retrograde rotation
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
Mars
• Surface area is about the same
as the land surface area of Earth
•Most spectacular
topography in the solar
system
• Olympus Mons: 24 km high
• Valles Marineris: canyons 2 to
7 km deep
•Mariner 4 (1965), Viking (1976),
Mars Pathfinder (1997), Mars
Expedition (2004), 3 orbiters
currently.
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
Jupiter
• More massive than the rest of
the planets combined
• In 1994, Comet ShoemakerLevy 9 collided with Jupiter
•Great red spot has persisted
for > 300 years
•16 known moons
•Since Pioneer 10 (1973) visited
by 5 missions including Galileo
probe (1995-2003).
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
Saturn
• 2nd largest planet in the solar
system
•Rings are > 250,000 km in
diameter, but only 1 km thick
•Less dense than water
•18 known moons
•Pioneer 11 (1979), then Voyager
1 and Voyager 2. Cassini (20042008)
http://seds.lpl.arizona.edu/nineplanets/nineplanets/
Formation of the solar system
Two theories:
1. Solar system
evolved from a
nebula (dust cloud)
2. Solar system
formed by
catastrophic event
Orion nebula - “stellar nursery”
Catastrophic theories for the
formation of the solar system
Georges de Buffon (1745) – A
comet collided with the Sun,
expelling matter which accreted
to form planets.
Forest Moulton & Thomas
Chamberlin (1900) – A star
passed close to Sun, pulling away
huge filaments of material.
Problems: such events are
extremely rare. Also material is
so hot that it would dissipate
into space and not accrete.
Formation of the solar system
Nebular theory is more
consistent with
observations
e.g., All planets rotate
in same direction and
almost in the same plane
(plane of the ecliptic)
The Best Prospects for Life
Name
Why
Earth
Mars
Europa
Titan
Io
Jupiter
:-)
most Earth-like; more so in the past
may have liquid water
atmosphere like early Earth, liquids likely
complex chemistry, warmer than most
long shot: warm, plenty of organic material
http://seds.lpl.arizona.edu/nineplanets/nineplanets/gif/NinePlanets.jpg