Exploring the Cosmos: Solar System, Part I Flashcards
(33 cards)
Name all the planets in order from the sun.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Where is the asteroid belt located?
Between the terrestrial and Jovian planets, between the orbits of Mars and Jupiter.
Three things that define a planet
1- Must be in orbit around the Sun
2- Must be large enough to take on nearly
spherical shape
3- Must have “cleared its orbit”
Name the terrestrial Planets and describe their densities and surfaces
Mercury, Venus, Earth, Mars:
•have high density
•have solid rocky surfaces and dense metal cores
Name the Jovian planets and describe their densities and surfaces
Jupiter, Saturn, Uranus, Neptune:
•Large, gaseous, low density, no well-defined surface
Name the five dwarf planets in our solar system and where are they found.
1- Ceres: largest object in Asteroid Belt (diam = 975 km)
2- Pluto: largest object in Kuiper Belt (diam = 2306 ± 20 km)
3- Eris (2003 UB313): largest object in Scattered Disk
(diam = 2326 ± 12 km)
4- Haumea
5- Makemake
Where is the Kuiper belt located?
just beyond the orbit of Neptune
What forces shape the solar system?
Gravity:
Dominant force over long distances (by a big margin!)
•Electrical and Magnetic Fields:
Very weak effect on planets etc:
affect only very small electrically charged particles
•Radiation Pressure and Solar Wind:
Affect only atoms, molecules and small dust particles
Which direction are orbits when seen from north?
All orbits are anti-clockwise about the Sun when seen from the north.
What shape are orbits and what is meant by eccentricities?
Most orbits are almost circular with eccentricities less than 0.1. Exceptions are Mercury (0.2056) and Pluto (0.2484).
Orbit shape classified by eccentricity (e). If circular, eccentricity is zero. If very elongated, eccentricity is close to one.
What planetary object has the most anomalous orbit?
Pluto has the most anomalous orbit. Its orbital plane is rotated 17 degrees from the plane of Earth’s orbit.
What are Kepler’s three laws?
1- Planets move in an ellipse with the Sun at a focus.
2- The line between the planet and Sun sweeps out an area at a constant rate.
3- The period of the orbit is proportional to a3/2, where a is the semi-major axis of the ellipse
According to Kepler’s 2nd law, when would a planet travel faster?
A line between the planet and Sun sweeps out an area at a constant rate :
•Close to aphelion (furthest from Sun), planets travel slower
•Close to perihelion (closest to Sun), planets travel faster
Which directions do planets rotate? And what are the exceptions?
When viewed from the north most planets rotate in an anti-clockwise direction about their axes
In the same direction as the general motion around the Sun and the rotation of the Sun.
The rotation axes of the planets are approximately at right angles to the plane of the orbit (obliquity).
Exceptions – Venus, Uranus and Pluto
What is obliquity? And how large are the planets obliquity angles, exceptions?
Obliquity: This is the angle that the axis of rotation makes with the normal to the plane of the orbit
Most planets have small obliquity angles.
•Exceptions: Venus, Uranus (and dwarf planet Pluto)
•Venus: retrograde rotation (opposite to other planets)
What is De Buffon’s Passing Star Model?
Planets formed from material pulled from the Sun by another star passing close by.
Is De Buffon’s Passing star model a catastrophic or evolutionary model?
An example of a catastrophic model – the result of a singular, peculiar event.
Why was De Buffon’s model unlikely and what problems would arise from it?
Stars are very far apart: likely to be a very rare event, though this does not mean that it could never happen.
Suggests very few stars have planets.
Problems-
The material pulled from the Sun would be very hot and unlikely to form planets.
Stable, almost circular, orbits would be unlikely.
It is difficult to explain the varying properties of the different planets.
Is the Solar Nebula Hypothesis an catastrophic or evolutionary model?
An example of an evolutionary model in which process occurred slowly without requiring an unusual event
Describe stage 1 of The Solar Nebula Hypothesis
Stage 1: Cloud of Gas and Dust
The Sun and the planets formed at the same time from a contracting rotating cloud of gas
Describe stage 2 of The Solar Nebula Hypothesis
Stage 2: Disc Rotation
As the cloud rotated it became smaller. The disc speeded up and flattened.
Gravity caused a concentration at the centre of the disc which became the Sun.
Further from the centre, grains of dust and molecules of gas start to form other bodies by a process of accretion.
Describe stage 3 of The Solar Nebula Hypothesis
Stage 3: Formation of Planetesimals
Initially, accreting bodies too small for gravity to be effective.
Clumps of matter acted as condensation nuclei.
Through electrostatic forces and collisions, the clumps started to coalesce and grow (like a growing snowball)!
Accretion of matter made clumps grow into bodies, ranging in size from a few centimetres to several kilometres - planetesimals.
Gravity began to play an important role.
Describe stage 4 of The Solar Nebula Hypothesis
Stage 4: Formation of Protoplanets
Clumps coalesced into larger bodies, about 100 km in size.
These continued to grow to form protoplanets, more massive objects that were the next stage in the formation of the planets.
Largest protoplanets had greatest gravitational attraction: collected other bodies more effectively.
They grew fastest by sweeping up smaller bodies.
Planet sized bodies formed.
What does The Solar Nebula Hypothesis successfully explain?
Disc shape of solar system
Why almost everything rotates in the same direction
