Earth Science Chapter 27: Planets of the Solar System

solar system

the sun and all of the planets and other bodies that travel around it; consists of the sun, planets, dwarf planets, and all of the other bodies that revolve around the sun

planets

the primary bodies that orbit the sun; a celestial body that orbits the sun, is round because of its own gravity, and has cleared the neighborhood around its orbital path

nebular hypothesis

hypothesis that states that the sun and the planets condensed at about the same time out of a nebula; created in 1796 by the French mathematician Pierre-Simon, marquis de Laplace

nebula

a rotating cloud of gas and dust

solar nebula

the rotating cloud of dust and gas from which the sun and planets formed; also any nebula from which stars and exoplanets may form

planetesimal

a small body from which a planet originated in the early stages of formation/development of the solar system

protoplanets

larger bodies than planetesimals; formed when planetesimals join together through collisions and through the force of gravity; eventually became large enough to form planets and moons

moons

the smaller bodies that orbit the planets; planets and _____ are smaller and denser than the protoplanets

inner planets

planets close to the sun; Mercury, Venus, Earth, and Mars

gas giants

huge planets that are composed of mostly gases, have low density; a planet that has a deep, massive atmosphere, such as Jupiter, Saturn, Uranus, or Neptune (the outer planets)

outer planets

the four planets farthest from the sun which are Jupiter, Saturn, Uranus, and Neptune; formed in colder regions of the solar nebula far away from the sun

ice giants

Uranus and Neptune are different from Jupiter and Saturn and are sometimes called ___ ______ because they have more frozen gases

dwarf planets

any object that orbits the sun, is round because of its own gravity, has not cleared the region around its orbit, and is not a satellite of another planet; Pluto is best described as an ice ball made of frozen gases and rock and has a very tilted orbit. M

differentiation

process during a planets developing stages; denser materials sink to the center and less dense materials are forced to the outer layers; caused Earth to form three distinct layers

core

dense center layer of Earth composed of mostly iron and nickel

mantle

very thick layer of Earth around the core composed of iron and magnesium-rich rock

crust

the outermost layer of Earth composed of less dense, silica-rich rock

outgassing

formed a new atmosphere; process of volcanic eruptions releasing large amounts of gases, mainly water vapor, carbon dioxide, nitrogen, methane, sulfur dioxide, and ammonia

ozone

a molecule that contains three oxygen atoms; collected in a high atmospheric layer around Earth and shielded Earth's surface from the harmful ultraviolet radiation of the sun

geocentric

Earth-centered or __________ model of the solar system; suggested by the Greek philosopher Aristotle; in this model the sun, the stars, and the planets revolved around Earth

retrograde motion

a pattern of planets that sometimes appeared to move backwards in the sky relative to the stars

epicycles

Claudius Ptolemy, a Greek astronomer, suggested in 150 CE that planets moved in small circles called _________ as they revolved in larger circles around Earth

heliocentric

sun-centered or ____________ model of the solar system suggested by a Polish astronomer named Nicolaus Copernicus in 1543 CE; in this model the planets revolved around the sun in the same direction but at different speeds and distances from the sun; fast

law of ellipses

Kepler's first law; states that each planet orbits the sun in a path called an ellipse, not a circle

ellipse

a closed curve whose shape is determined by two points, or foci, within an _______; the shape of the planet's orbits

eccentricity

the degree of elongation of an elliptical orbit (symbol, e); determined by dividing the distance between the foci of the ellipse by the length of the major axis

parabolic orbit

the eccentricity of this type of extremely elongated orbit is e=1

law of equal areas

Kepler's second law; describes the speed at which objects travel at different points in their orbits; states that equal areas are covered in equal amounts of time as an object orbits the sun; Kepler calculated that a line from the center of the sun to the

law of periods

Kepler's third law; describes the relationship between the average distance of a planet from the sun and the orbital period of the planet; the cube of the average distance (a) of a planet from the sun is always proportional to the square of the period (p)

orbital period

the time required for a body to complete a single orbit

inertia

the tendency of an object to resist a change in motion unless an outside force acts on the object; Isaac Newton hypothesized that a moving body will remain in motion and resist a change in speed or direction until an outside force acts on it

gravity

an outside force that causes a planet's orbit to curve; this attractive force exists between any two objects in the universe; named by Newton

terrestrial planets

the inner planets are also called ___________ _______ because they are similar to Earth; highly dense planets nearest to the sun; Mercury, Venus, Mars, and Earth; consist mostly of solid rock and have metallic cores; number of moons per planet varies from

impact craters

bowl-shaped depressions that occur on the surfaces of inner planets; caused by collisions of the planets with other space objects

greenhouse effect

type of heating; occurs when the high concentration of carbon dioxide in the atmosphere blocks most of the infrared radiation from escaping; on Earth, it warms Earth enough for organisms to live on the planet

runaway greenhouse effect

phenomenon that makes Venus' surface temperature the highest known in the solar system (464degC)

evening star or morning star

what Venus is called because it is usually visible in the early morning or evening; Venus has sulfur dioxide droplets in its upper atmosphere, which forms a cloud layer that reflects light so strongly that from Earth, Venus appears to be near the sun and

Magellan

satellite that orbited Venus for four years in the 1990s before the satellite was steered into the planet to collect atmospheric data; bounced radio waves off Venus to produce radar images of Venus' surface, which found landforms such as mountains, volcan

Venus Express

European Space Agency's spacecraft that orbited Venus between April 2006 and May 2009

Viking

landing craft that detected two geological events that produced seismic waves on Mars

marsquakes

geological events on Mars that produced seismic waves; may indicate that volcanoes on Mars are more active

Spirit and Opportunity

mars rovers which landed on Mars in 2004; found liquid evidence that water did exist on Mars' surface in the past

Phoenix

lander that confirmed in 2008 that water also exists as ice just below the Martian surface of Mars

asteroid belt

a ring of debris that separates the inner planets from the outer planets

Great Red Spot

Jupiter's most distinctive feature; a giant rotating storm, similar to a hurricane of Earth, that has been raging for at least several hundred years

Galileo

spacecraft that dropped a probe on Jupiter which measured wind speeds of up to 540 km/h on Jupiter

Cassini

scientist are learning more about Saturn and its moons from this spacecraft which reached Saturn in 2004

Huygens

carried by Cassini, this probe landed on Titan, Saturn's largest moon

Hubble Space Telescope

has taken images that show changes in Uranus' atmosphere; images taken has also indicated that Neptune has an active weather system

Voyager 2

space probe that passed by Uranus and helped in the discovery of the rotation rate of Uranus; data from this probe indicate that Neptune's atmosphere is made up of mostly hydrogen, helium, and methane; images taken by this probe indicate that Neptune has

Great Dark Spot

a storm the size of Earth that appeared and disappeared on Neptune's surface

trans-Neptunian objects

(TNOs) hundreds of objects in our solar system beyond Neptune's orbit; some are similar to Pluto in size and composition, but most are simply small chunks of ice; scientists think that these bodies are the remnants of material that formed the early solar

Kuiper Belt

the region beyond Neptune's orbit where TNOs exist; a region of the solar system that starts just beyond the orbit of Neptune and that contains dwarf planets and other small bodies made mostly of ice

plutoids

trans-Neptunian dwarf planets such as Eris, Makemake, and Haumea

exoplanets

several hundred planetlike objects that circle stars other than Earth's sun; most known __________ circle stars like the Earth's sun therefore, the existence of __________ leads some scientists to wonder if life could exists in another solar system; most