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The Solar System (Cont.)
Chapter 4
Ingredients?
The Sun
● Planets
● Moons and Rings
● Comets
● Asteroids (size > 100 m)
● Meteoroids (size < 100 m)
● Kuiper Belt
● Oort cloud
● Zodiacal dust
● A lot of nearly empty space
●
Solar System Formation Video – Bring up Quicktime
Result from computer simulation of planet growth
Shows growth of terrestrial planets. If Jupiter's gravity not included, fifth
terrestrial planet forms in Asteroid Belt. If Jupiter's gravity included, orbits
of planetesimals there are disrupted. Almost all ejected from Solar System.
Simulations also suggest that a few Mars-size objects
formed in Asteroid Belt. Their gravity modified orbits of
other planetesimals, before they too were ejected by
Jupiter's gravity.
Asteroid Ida
Clicker Question:
In the leading theory of solar system
formation, the planets:
A: were ejected from the Sun following a close encounter
with another star.
B: formed from the same flattened, swirling gas cloud that
formed the sun.
C: were formed before the Sun.
D: were captured by the Sun as it traveled through the
galaxy.
Clicker Question:
We can tell something of the composition of
the planets by looking at their:
A: spectra
B: radius
C: mass
D: magnetic fields
Zodiacal Dust
What is it?
•
•
•
Cosmic dust in the solar system between the planets
Thin pancake cloud of dust in the plane of the planets
Dust band is distributed evenly across the ecliptic
What causes it?
•
•
Fragmentation of comets near Jupiter
Dust enters into elliptical orbits around the sun
Seen?
•
Appears as a triangular cloud best seen just after sunset (West Spring) or before sunrise (East - Autumn)
Zodiacal dust
Dust particles on the plane of the orbits of the planets. (size: 1 to 300 x 10-6 m)
What Killed the Dinosaurs?
The dinosaurs
may have been
killed by the
impact of a large
meteor or small
asteroid.
The larger an
impact is, the less
often we expect it
to occur.
Dinosaur Killer Impact 65 million
years ago: an asteroid
with diameter roughly 10 km
High levels of iridium in Raton
Pass (I25)
The Fossil Record is Marked by Mass
Extinction Events
Extinction
Genus loss
End Ordovician
60%
End Devonian
57%
End Permian
82%
End Triassic
53%
End Cretaceous
47%
From Solé & Newman 2002
Interplanetary Matter: Earth Impacts
The impact of a large meteor can create a
significant crater.
The Barringer meteor crater in Arizona
Interplanetary Matter: Earth Impacts
The Manicouagan
reservoir in Quebec
Clicker Question:
An asteroid impact like the one that killed
off the dinosaurs is expected once every:
A: year
B: hundred years
C: thousand years
D: hundred thousand years
E: hundred million years
The Structure of the Solar System
L3
L5
L4
~ 5 AU
~ 45 AU
Lagrange Points
Interplanetary Matter: Asteroids
The inner solar
system, showing
the asteroid belt,
Earth-crossing
asteroids, and
Trojan asteroids
Interplanetary Matter: Asteroids
Large picture:
The path of
Icarus, an Earthcrossing asteroid
Inset: Ceres, the
largest asteroid
Interplanetary Matter: Asteroids
Asteroids and meteoroids have rocky composition;
asteroids are bigger.
(below)
Asteroid
Gaspra
(above) Asteroid
Ida with its
moon, Dactyl
(above)
Asteroid
Mathilde
Interplanetary Matter: Asteroids
Asteroid Eros
Interplanetary Matter: Comets
Comets are icy, with some rocky parts.
The basic components of a comet
Interplanetary Matter: Comets
The solar wind means the
ion tail always points away
from the Sun.
The dust tail also tends to
point away from the Sun,
but the dust particles are
more massive and lag
somewhat, forming a
curved tail.
Interplanetary Matter: Comets
The internal structure of the cometary nucleus
Oort Cloud
The size, shape, and orientation of cometary orbits
depend on their location. Oort cloud comets rarely
enter the inner solar system.
Meteor Showers
Meteor showers are
associated with comets –
they are the debris left
over when a comet
breaks up.
Meteor Showers
Stellar Spectra
Spectra of stars are different mainly due to temperature and composition differences.
'Atmosphere', atoms and
ions absorb specific
wavelengths of the blackbody spectrum
Interior, hot and
dense, fusion
generates radiation
with black-body
spectrum
Star
We've used spectra to find planets around other stars.
Star wobbling due to gravity of planet causes small Doppler
shift of its absorption lines.
Amount of shift depends on velocity of wobble. Also know period of
wobble. This is enough to constrain the mass and orbit of the planet.
As of today ~400 extrasolar planets known. Here are the first few discovered.
Molecules
Two or more atoms joined together.
They occur in atmospheres of cooler stars,
cold clouds of gas, planets.
Examples
H2 = H + H
CO = C + O
CO2 = C + O + O
NH3 = N + H + H + H (ammonia)
CH4 = C + H + H + H + H (methane)
They have
- electron energy levels (like atoms)
- rotational energy levels
- vibrational energy levels
Searching for Habitable
planets around other
stars
Molecule vibration and rotation