Download Ch 29 Our Solar System

Ch 28 Formation of the Solar System
Formation Theory: Based on direct observations and
data from probes. The theory has to explain all
observed facts such as the shape of the solar system,
differences among planets concerning composition,
size, and other solar system features such as
asteroids, and comets.
Ch 28 Formation of the Solar System
Overview of solar system formation:
When an interstellar cloud of hydrogen (nebulae)
collapses, it forms a star when the temperature and
pressure become high enough to fuse hydrogen into
helium. The remaining part of the cloud surrounding
the star became the rest of the solar system.
Formation of the Solar System
Formation of the Solar System
Formation Details: Initially the density of the
interstellar cloud is very low and the temperature is
very cold. When the cloud begins to collapse under its
own gravitational pull, it begins to:
1. Rotates
2. Accelerates
3. Contracts
4. Density increases
5. Pressure increases
6. Temperature increases
Think of the cloud in a bottle you made. As you squeezed the
bottle, the air molecules were forced to be closer together, and
as a result the pressure and temperature increased.
More details:
As you might suspect, the temperature was warmer in
the middle of this collapsing cloud. The differences in
temperature throughout the cloud can account for why
we have different elements throughout the solar
system. Different elements will form at different
temperatures. This is similar to Bowen’s reaction
series and how different minerals and rocks form at
different temperatures.
More details:
The planets that were closest to the warm center
(rocky inner planets) are richer in the higher melting
point elements while the outer planets are their moons
are composed mostly of the more volatile elements
(gasses and ice).
More details:
Before there were planets, there were the
planetesimals! These are smaller planet like bodies
that were orbiting the Sun. There were 100’s of them!
They collided into each other like a cosmic game of
pool, but when they hit, they ended up sticking
together to form larger bodies, and eventually the
planets.
Gas Giants form:
The first large giant to form was Jupiter. It increased
in size due to the merging of icy planetesimals that
contained mostly lighter elements. The larger it grew,
the more gravitational pull it had, and the more it mass
it could collect until it “cleared the neighborhood.”
The other gas giants Saturn, Neptune and Uranus
formed the same way.
Terrestrial Planets form:
The terrestrial planets also grew in size due to the
collisions of the planetesimals. However, the
planetesimals near the hot center of the disk were
made of elements that could resist vaporization.
Because of this, the inner planets are more dense.
Debris:
Material that remained after the formation of the
planets is called debris. The planets swept up this
debris in their path and became larger still. Some
debris never formed planets and became:
1. The main belt (Asteroid belt between Mars and
Jupiter.
2. The Kuiper Belt
3. The Oort cloud of comets
Ch 28 Our Solar System
I Early ideas
A) geocentric model (Earth centered)
1. Could not easily explain observations
a. Wandering planets (epicycle orbits)
i Retrograde motion
b. Speed of stars would be immense
Retrograde motion: The apparent motion of the
planets that makes them appear to move
backwards because the Earth is on the “inside
track” and passes other planets which are on more
distant orbit.
2. Aristotle and Ptolemy’s ideas for a Earth
centered universe beat out the Sun centered model.
Since the Royalty and Religious leaders liked this idea, it
became law, and to say otherwise could get you jailed,
killed or worse (to them at least) excommunicated.
B) Heliocentric model (Sun centered)
back
1. Aristarchus. Thousands of years ago around the
same time as Aristotle, this astronomer/mathematician
came up with the Sun centered model. He also theorizes
that the stars are like our Sun, but very far away.
Unfortunately his ideas were not largely accepted and
took until the renaissance period for it to gain credibility
through men like Copernicus and Galileo.
B) Heliocentric model (Sun centered)
back
2. Nicolaus Copernicus’s idea
a. Easily explained observations
b. Not accepted by the church
3. Support grew for this idea
a. Tycho Brahe made many observations for
decades
b. Kepler used Brahe’s data, made 3 laws
i)
Orbits in shape of ellipse with
the Sun at one foci
ii)
Equal areas on the orbital plane
are swept out in equal time.
iii)
P^2 = a^3 page 778 in text
Keplers first law:
The Earth’s orbit is in the shape of an ellipse
We will draw and ellipse and calculate the eccentricity
for the ellipse for a lab. The ellipse requires 2 foci
points to draw it. You will measure the difference
between the foci points in centimeters. Then you will
measure the length of the major axis in centimeters.
Next you will divide the foci point length by the major
axis length. This formula is on your ESRTs cover. All
values are between 0 and 1. A circle which looks like
a 0 is 0! A straight line which looks like a 1 is a 1!
2. Kepler’s second law:
An equal area is swept out in equal time.
Kepler’s third law
P^2 = a^3
The length of time it takes for
a planet or other body to travel
a complete orbit around the
Sun is called its orbital period
(P). The formula is shows the
mathematical relationship
between the size of the planets
ellipse and its orbital period.
“P” is time measured in Earth
years, and “a” is the length of
the semi major axis measured
in astronomical units.
Newton invents calculus
4. Galileo uses telescope to observe sky
back
a. Jupiter has its own moons (so not
everything revolves around the Earth).
b. Moon has craters (heavens not perfect)
c. Sun has spots (blemishes) and rotates
5. Newton uses physics to explain solar system
a. Quantifies (not discovers) gravity
b. Establishes relationship of tides to Moon
c. Creates calculus (Algebraic short cut)
d. Explains math problems with orbits
Newton discovered the relationship
between the Moon, Sun and tides
C. Gravity is explained by Newton
back
1. Formula : Force = G (m1m2)
pg 779 in text
r^2
a. G is a constant value
b. m1 and m2 are the two masses
c. r is the distance between the masses and
it is squared
The center of mass for two objects of equal
weight is half way between the two objects.
The center of mass moves closer to the object
that is heavier.
An astronomical
unit or AU is the
average distance
from the Earth to
the Sun (1.49 X
10^8 km)
28.2 Terrestrial Planets
Terrestrial Planets: The planets that are close to
Earth’s size and have a solid rocky surface.
Gas giant planets: Are the large and gaseous planets
which lack a solid surface.
Mercury: Closest to the Sun and revolves around the Sun the
fastest (hence its name). It has a very thin atmosphere (oxygen
and sodium atoms. Because the atmosphere is so thin it has
wild swings in temperatures and ranges 427 C to -173 C in one
of its days. An impact crater here would last a long time due
to a lack of weathering and erosion. Mercury has large scarps
on its surface, possibly due to the crust shrinking as the planet
cooled. It is fairly dense and likely as a large iron and nickel
core.
Venus highlights:
-Second planet from the Sun, it is the brightest in our sky
because it is the closest to us, and has a high albedo.
-Venus has a longer day than its year because it rotates so
slowly.
-Venus is the hottest planet with temps at 464 degrees C (even
though Mercury is closer to the Sun) due to having a thick
atmosphere with nitrogen CO2 so it has a major green house
effect.
-The clouds are made of sulfuric acid and the surface is too hot
for liquid water to exist.
Venus highlights:
-Venus also has retrograde rotation: rotates clockwise (most
planets rotate counter clockwise). This means the Sun appears
to rise in the west and set in the east. This retrograde rotation
may be the result of a major collision (this spin change can be
observed and used while playing pool!)
-The surface is smooth due to lava flows from 500 mya but
not likely tectonically active like the Earth is.
-Its size and density are similar to Earth so it is theorized that
the internal structure is also similar.
Earth:
-Third rock from the Sun.
-Vast amounts of liquid water on the surface.
-Currently only Confirmed life in the Universe.
-Signs of intelligent life.
Mars (AKA The Red planet due to iron oxides) highlights:
-Smaller and less dense than Earth
-Two moons
-We have landed rovers on Mars to explore
-Largest volcano in the solar system called Olympus Mons.
Its base is larger than the state of Colorado and it is 3 times
taller than mount Everest.
These volcanoes were created by a hotspot. There is no plate
movement.
Volcanoes such as this may have shot bacteria laced rocks into
space which have hit the Earth. Did our life come from Mars?
-Enormous canyons such as Valles
Marineris which is 10 times longer than
the Grand Canyon and 3 times deeper.
-Thin atmosphere with a similar
composition to Venus
-Long lasting wind storms (weeks)
-Erosional features show dried river and
lake beds, outflow channels, and runoff
channels. These suggest that liquid
water once existed on Mars.
Astronomers think that the climate used
to be warmer which allowed for a water
cycle. Currently the only know water on
Mars is in ice form at the poles. Most
of this ice is carbon dioxide aka dry ice.
Jupiter highlights:
-A gas giant and the largest planet in the
solar system. It has 1/10th the diameter
of the Sun and it is11 times larger than Earth in diameter
-Has over 60 moons, but 4 large ones called the Galilean
moons (Galileo discovered) Io, Europa, Ganymede, and
Callisto. All but Europa are bigger than our Earth’s Moon.
Europa may even have a sub surface ocean of liquid water due
to the squeezing and heating caused by Jupiter's gravitational
pull.
-Has a unique compound called liquid metallic hydrogen
which can only exist under really high pressure.
-These gases act like liquids under such high pressure.
-Jupiter has rings (not has large and defined as Saturns)
-The core is made of rock and ice (possibly the size of Earth)
-Jupiter has the shortest day (rotates the fastest 9 hours 50
minutes = one day)
-This rapid rotation causes the clouds to flow rapidly as well
And forms bands of alternating dark and light colors.
Belts: low level dark colored warm clouds  cools and sinks.
Zones: high level, light colored (more ammonia ice) cool
clouds that get warm and rise.
The Great Red Spot: A hurricane like storm that could fit three
Earth’s inside and has lasted for the last 400 years.
Saturn
-Gas giant slightly smaller than Jupiter.
-Its average density would allow it to float
in water (good luck finding a tub for that…)
-Also rotates rapidly and makes a layered cloud system.
-The atmosphere is made up of Hydrogen, helium with
ammonia ice.
-has a small solid core of rock and ice
Saturn's Magnetic field is 1,000 times stronger than Earth
And is aligned with its rotational axis (Rare among planets)
-Rings are broader and brighter than other gas giants.
These rings are made of pieces of ice that range from
microscopic to house sized chunks.
The particles to make these rings may have come from debris
left over from the collisions of asteroids, comets, or the break
up of a moon.
Saturn has over 55 moons.
-The largest is Titan which is larger than the planet Mercury.
-Titan is unique because it has methane which can exist as a
liquid, solid or gas on its surface.
-In 2005 Cassini released the Huygens probe and found ice
and water vapor which suggests geologic activity.
-Titan has lots and lots of oil and natural gas.
Uranus highlights:
-Gas giant discovered accidently in 1781 when a blusish
object was seen moving relative to the stars.
-Has at least 27 moons
-Dark and nearly invisible rings
-Average temp -215 degrees C
-4 times the diameter of Earth
-Atmosphere is mostly
hydrogen and helium
(colorless)
-Blue color due to Methane
gas in atmosphere
-No distinctive clouds or
belts and zones.
-Rotational axis is tipped
over to the point where the
north pole almost lies on its
orbital plane (likely knocked
sideways due to a collision.
-Thus, each pole spends 42
years in darkness.
Neptune
-The existence of this planet was predicted before it was seen
based on the laws of gravitation.
-Discovered in 1846 where astronomers predicted it would be.
-The last of the gas giants in our solar system.
-Slightly smaller and denser than Uranus
-Similar to Uranus in terms of atmospheric composition
-Unlike Uranus, it does has distinctive clouds, belts and zones
like that of Jupiter and Saturn.
Other solar system objects
-In the Early 2000’s, astronmers began to notice large objects
in the Kuiper belt. One such object, now named Eris is the
same size or larger than Pluto.
The Astronomical community then re-evaluated what the
definition of planet should be. They decided on a new
classification called Pluto and others like it a Dwarf Planet.
Others in this same region are called Sedna, 2005 fy9 (Easter
bunny), EL61 Haumea, Buffy, and Makemake, Quaoar.
-Ceres is another large object but not a Dwarf planet. It is not
found in the Kuiper belt, but the main belt (in between Mars
and Jupiter). In 1801 it was predicted that there would be a
planet found between Mars and Jupiter. Instead they found an
asteroid belt consisting of hundreds of thousands of objects.
Ceres is considered to be the largest Asteroid.
Small Solar System Bodies
-Objects between Mars and Jupiter are called asteroids and the
belt is called the Main Belt.
-Objects beyond the orbit of Neptune care called
trans-Neptunian objects or TNOs
-Kuiper belt objects are termed KBOs
-Comets belong to the Oort cloud
Asteroids: Left over rock from the formation of the solar
system.
-Some are large enough to have their own natural satellites.
-The total mass of all of the asteroids in the solar system is
equivalent to about 0.08% of the Earth’s mass.
-Meteoroid: Asteroid that enters the Earths atmosphere.
-Meteor: The streak of light produced by a particle as it burns
up in the atmosphere.
Meteorite: If a meteoroid does not completely burn up and hits
the ground.
Kuiper belt: Asteroid belt (bodies made of rocks and ice) that
lie beyond the orbit of Neptune (KBOs).
Comets: Small icy bodies (1-10 km in diameter) that have
highly eccentric orbits around the Sun. They are largely found
in the area from the Kuiper belt out to 100,000 AU. This is
known as the Oort cloud.
Comet structure: When a comet comes within 3 AU of the
Sun it begins to evaporate. As a result it forms a head and one
or more tails. The head is surrounded by glowing gas and has
a small solid core. The tail forms as the dust and gas are
pushed away from the comet by particles and radiation from
the Sun. This is why Tails always point away from the Sun.
Periodic comets: Comets can get bumped out of the Oort cloud
and head into the interior of the solar system. When they
return repeatedly, they are called periodic comets.
Halley’s comet comes back every 76 years. The last time was
1985 and the next time will be 2061.
Meteor shower: When Earth crosses the trail of a comet, the
particles burn in the atmosphere producing bright streaks of
light called a meteor shower. Most meteors we see are caused
by dust particles from comets. They are often named for the
area in the sky in front of the constellation they appear to
come from such as Leonids for the constellation of Leo or
Geminids from Gemini.
Meteor Shower Dates for 2016
Quadrantid Draco (NE) Jan. 4 60-100 2003 EH1
Lyrid* Lyra (E) April 22 10-20 Thatcher (1861 I)
Eta Aquariid Aquarius (E) May 5 20-60 1P/Halley
Delta Aquariid Aquarius (S) July 28 20 96P/Machholz
Perseid Perseus (NE) Aug. 12 90** 109P/Swift-Tuttle
Orionid* Orion (SE) Oct. 21 10-20 1P/Halley
Southern Taurid Taurus (S) Nov. 5 10-20 2P/Encke
Leonid* Leo (E) Nov. 17 10-20 55P/Tempel-Tuttle
Geminid* Gemini (S) Dec. 14 100-120 3200 Phaethon
- See more at: http://www.skyandtelescope.com/astronomynews/observing-news/meteor-showers-in-2016/#sthash.MhNAhkuj.dpuf
Ch 28 notes quiz
1. What is a nebulae?
2. Describe what happens in detail when the hydrogen cloud
begins to collapse under its own gravitational pull.
3. Describe what the main belt is and where it is located.
4. Why would impact craters on Mercury last a long time?
5. Describe one of the problems with the geocentric model.
6. Describe Retrograde motion.
7. List and describe two pieces of evidence that Galileo found
to support the heliocentric model.
8. List and describe Kepler’s three laws of planetary motion.
9. All values for eccentricity fall between what 2 numbers?
10. List And describe one of Isaac Newton’s contributions to
Astronomy.
11. If you tripled the distance between two masses, what
happens to the force of gravity between them?
12. Define an Astronomical unit.
13. Which planet has a longer day then its year?
14. Which planet has the shortest day?