Chapter 8 Flashcards
(20 cards)
Nebular Theory
that our solar system formed from the gravitational collapse of a
giant interstellar gas cloud
Close Encounter Hypothesis
A rival idea proposed that the planets formed from debris torn off the Sun by a close
encounter with another star
Galactic Cycling
Elements that formed planets were made in stars
and then recycled through interstellar space
We can see stars forming in other interstellar gas
clouds, lending support to the nebular theory
Conservation of Angular Movement
Rotation speed of the cloud from which our solar system
formed must have increased as the cloud contracted.
Flattening
Collisions between particles in the cloud caused it to flatten into a disk
Collisions between gas particles in cloud gradually reducerandom motions
Collisions between gas particles also reduce up and downmotions
Spinning cloud flattens as it shrinks
Frost Line
the distance from the Sun where the solar radiation makes hydrogen compounds into ices.
Accretion
Gravity eventually assembled these planetesimals into terrestrial planets
Solar Rotation
Friction between solar magnetic field and solar nebular probably slowed the rotation over time
Where did Comets and Asteroids come from?
Leftovers from the accretion process
Rocky asteroids inside frost line
Icy comets outside frost line
Heavy Bombardment
Leftover planetesimals bombarded other objects
in the late stages of solar system formation
Origin of Earths Water?
Water may have come to Earth by way of icy
planetesimals
Odd Rotation
Giant impacts might also explain the
different rotation axes of some
planets
What caused the orderly patterns of motion in our solar system?
Solar nebula spun faster as it contracted because of conservation of angular momentum.
Collisions between gas particles then caused the nebula to flatten into a disk
Why are there two major types of planets?
Terrestrial and Jovian
Where did asteroids and comets come from?
They are leftover planetesimals, according to the nebular theory
How do we explain “exceptions to the rules”?
Bombardment of newly formed planets by planetesimals may explain the exceptions
Radioactive Decay
Some isotopes decay into other nuclei.
A half-life is the time for half the nuclei in a
substance to decay
How do we know the age of the Solar System?
Radiometric dating tells us that oldest moon rocks are 4.4 billion years old
The Age of the Oldest Meteorites?
4.55 billion years old
When were probably planets formed?
4.5 billion years ago
