Chapter 19 - Solar System

Front 1

revolve

Back 1

To physically move around something. A planet revolves around the sun.

Front 2

rotate

Back 2

To turn. A planet rotates on its axis.

Front 3

terrestrial planets

Back 3

Earth-like planets. They are small, dense, rocky worlds with little or no atmosphere. Mercury, Venus, Earth, and Mars.

Front 4

Jovian planets

Back 4

Jupiter-like planets. They are large, low-density world's with thick atmospheres and liquid or ice interiors. Jupiter, Saturn, Uranus, and Neptune.

Front 5

asteroids

Back 5

Small, rocky worlds, most of which orbit the sun in a belt between the orbits of Mars and Jupiter.

Front 6

Kuiper Belt

Back 6

Over a thousand small, icy bodies orbiting in the outer fringes of the Solar system beyond Neptune. Named after astronomer Gerard Kuiper.

Front 7

comets

Back 7

Ice-rich bodies a few to 10 km in diameter, similar to asteroids. Comets provide evidence that at least some parts of the Solar system had abundant icy material when it formed.

Front 8

radiation pressure

Back 8

Exerted by sunlight

Front 9

meteors

Back 9

Sometimes called shooting stars because they are small bits of rock and metal that collide with earth's atmosphere and burst into incandescent vapor and flash across the sky in momentary streaks of light.

Front 10

meteoroid

Back 10

A meteor before it's fiery plunge.

Front 11

meteorite

Back 11

Any part of a meteoroid that survives the fiery passage to earth's surface.

Front 12

half-life

Back 12

The time it takes for half of the parent isotope atoms to decay into daughter isotope atoms.

Front 13

Passing Star Hypothesis

Back 13

Hypothesis that the planets were formed when a passing comet collided with or passed close to the sun and pulled matter out of the sun gravitationally. Proposed by Georges-Louis Leclerc.

Front 14

Evolutionary hypothesis

Back 14

Involved common, gradual processes to produce the sun and planets. Proposed by René Descartes.

Front 15

Catastrophic hypothesis

Back 15

An unlikely, sudden event produced the solar system, and thus implies that planetary systems are very rare.

Front 16

Nebular hypothesis

Back 16

Mathematical - that a spinning cloud could contract under its own gravity and produce a disk of material that might condense into planets orbiting a central mass, the sun. As this disk grew smaller, it had to conserve angular momentum and spin faster. When the disk was spinning as fast as it could, it would shed it's outer edge to leave behind a ring of matter. Then the disk would contract further and leave another ring, producing a series of rings which could become planets circling the newborn sun.

Front 17

angular momentum problem

Back 17

According to the nebular hypothesis, the sun should be spinning rapidly and have most of the Solar systems angular momentum. However, the sun actually spins relatively slowly and the planets move more quickly, even though the sun has most of the Solar systems mass.

Front 18

Solar Nebula Theory

Back 18

Supposes that planets form in rotating disks of gas and dust around young stars.

Front 19

uncompressed densities

Back 19

Densities the planets would have if their gravity did not compress them

Front 20

frost line

Back 20

A boundary far from the sun beyond which water vapor could freeze to form icy particles.

Front 21

condensation sequence

Back 21

The sequence in which the different materials would condense from the gas as a function of nebular temperature.

Front 22

planetesimals

Back 22

Larger bodies of metal, rock, and ice that eventually made the planets.

Front 23

accretion

Back 23

The sticking together of solid particles

Front 24

protoplanets

Back 24

Massive objects destined to become planets

Front 25

gravitational collapse

Back 25

The rapid accumulation of large amounts of infalling gas from the nebula.

Front 26

heat of formation

Back 26

Violent impacts of infalling particles release this energy

Front 27

differentiation

Back 27

The separation of material according to density

Front 28

outgassing

Back 28

The accumulation of gases from a planets interior to create an atmosphere

Front 29

Jovian Problem

Back 29

How Jovian planets can form quickly enough before the disks of raw material evaporate.

Front 30

direct collapse

Back 30

Massive planets are able to form by skipping the slower step of forming a dense core by condensation and accretion of solid material.

Front 31

heavy bombardment

Back 31

The last of the debris in the solar nebula was swept up by the planets.

Front 32

debris disks

Back 32

Tenuous dust disks. Cold, low-density disks around stars much older than Orion, old enough to have reached the main sequence.

Front 33

transit

Back 33

When an orbiting planet passes in front of a star.

Front 34

microlensing

Back 34

An extrasolar planet passes precisely between Earth and a background star, briefly magnifying the distant stars brightness by gravitational lensing.

Front 35

hot Jupiters

Back 35

Big planets near their stars