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SunStar around which the planets gravitate;represents over 99.8% of the total mass

of the solar system.

JupiterFifth planet from the Sun, also the

largest; Jupiter is 1,330 times the sizeof Earth.

SaturnSixth planet from the Sun, also thesecond largest planet; Saturn isencircled by rings forming a bandabout 120,000 mi in diameter.

Kuiper beltCircular region of the solar systemabout 50 astronomical units from theSun; thought to be a repository ofsmall icy bodies, the source of comets.

NeptuneEighth planet from the Sun; its atmosphere,

composed of hydrogen, helium and methane,gives Neptune its bluish color. Features four

rings.

UranusSeventh planet from the Sun, also the thirdlargest planet; Uranus is composed mainly

of rock, ice and hydrogen and features11 rings.

50 astronomical unitsCorresponds to about 50 times the

Earth-Sun distance.

C E L E S T I A L B O D I E S

solar systemRegion of our galaxy under the influence of the Sun; includes eight planets and their natural satellites as well asone dwarf planet, two plutoids, asteroids and comets.outer planetsPlanets located beyond the asteroid belt; theseare known as the gas giants.

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asteroid beltCircular region between Mars and Jupiter

containing the greatest number ofasteroids; marks the boundary between the

inner and outer planets.

inner planetsRocky planets closest to the Sun;

located inside the asteroid belt.

MercuryThe planet closest to the Sun; devoid ofatmosphere, heavily cratered andmarked by extreme variations intemperature (-300°F to 800°F).

VenusSecond planet from the Sun; its densityand chemical composition are similarto those of Earth.

MarsFourth planet from the Sun; its crustcontains iron oxide, giving Mars its

reddish color.

EarthThird planet from the Sun, inhabited byhumankind; up to now, the only planet withevidence of life.

1 astronomical unitUnit of distance equal to the mean

distance between Earth and the Sun,equivalent to about 93 million mi.

C E L E S T I A L B O D I E S

solar system

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planets and satellitesPlanets, dwarf planets and plutoids orbit the Sun, satellites orbit the planets. They are represented from left toright from the Sun, based on their relative sizes.

CeresDiscovered in 1801, it was promoted to

status of dwarf planet in 2006.

MarsFourth planet from the Sun; its crustcontains iron oxide, giving Mars itsreddish color.

EarthThird planet from the Sun, inhabited byhumankind; up to now, the only planet

with evidence of life.

VenusSecond planet from the Sun; its densityand chemical composition are similarto those of Earth.

MercuryThe planet closest to the Sun; devoid of atmosphere,heavily cratered and marked by extreme variations intemperature (-300°F to 800°F).

GanymedeSatellite of Jupiter; the largest naturalsatellite in the solar system; its glacialsurface is thought to cover an oceanand a mantle.

CallistoSatellite of Jupiter; its heavily crateredsurface indicates that Callisto is very old.

EuropaSatellite of Jupiter; displays a surface

layer of ice that might cover liquidwater.

IoSatellite of Jupiter; the celestial body

with the greatest number of activevolcanoes.

JupiterFifth planet from the Sun, also the

largest; Jupiter is 1,330 times the sizeof Earth.

SunStar around which the planets gravitate;represents over 99.8% of the total mass

of the solar system.

MoonEarth’s only natural satellite; devoid of

water and atmosphere andcharacterized by a highly uneven

surface.

C E L E S T I A L B O D I E S

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SaturnSixth planet from the Sun, also thesecond largest planet; Saturn isencircled by rings forming a bandabout 120,000 mi in diameter.

TitanSaturn’s largest satellite, 1.5 times thediameter of the Moon.

UranusSeventh planet from the Sun, also the thirdlargest planet; Uranus is composed mainly

of rock, ice and hydrogen and features11 rings.

PlutoDiscovered in 1930, it was long considered

the ninth planet of the solar system. Since2008, it has been classified as a plutoid.

CharonPluto’s only satellite; almost equal in

size and mass to the planet itself.

ErisPlutoid discovered in 2005, with a

diameter bigger than Pluto’s. It has asatellite, Dysnomia.

TritonNeptune’s largest satellite; together

with Pluto, Triton is the coldest objectin the solar system.

NeptuneEighth planet from the Sun; its atmosphere,

composed of hydrogen, helium and methane,gives Neptune its bluish color. Features four

rings.

RheaSatellite of Saturn; its cratered surfaceis covered with ice as hard as rock.

DioneSatellite of Saturn; its cratered surface

features ice deposits.

TethysSatellite of Saturn thought to be

composed of ice; visible on its surfaceis an immense impact crater named

Odysseus.

TitaniaThe largest satellite of Uranus; itssurface displays numerous valleys andfaults.

ArielSatellite of Uranus; its cratered surface iscomposed of numerous long valleys and

extremely high escarpments.

C E L E S T I A L B O D I E S

planets and satellites

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flareViolent projection of extremely hot gasinto space, provoking polar auroras on

Earth a few days later.

faculaeLuminous region of the photosphere.

chromosphereThe lowest level of the solar

atmosphere, with a temperature of18,000°F.

spiculesA narrow jet of gas in the form of a

plume observed in the solarchromosphere.

photosphereVisible surface of the Sun, with atemperature of 10,000°F.

coronaThe outermost layer of the solar

atmosphere, visible in the form of a haloduring a total eclipse; corona

temperatures can reach 1,800,000°F.

convection zoneRegion where hot gas currents

circulate between the hot regions of thecore and the cool surface.

radiation zoneRegion where energy produced in the

core cools before migrating in the formof light and heat.

coreThe innermost part of the Sun wherehydrogen is converted into helium by

nuclear fusion; core temperaturesreach 27,000,000°F.

structure of the SunFrom the center to the periphery are the core, theradiation and convection zones, the photosphere, thechromosphere and the corona.

SunStar composed of 92.1% hydrogen atoms and 7.8% helium atoms, around which the planets gravitate;represents more than 99.8% of the solar system’s total mass.

sunspotA dark, slightly cooler zone of the

photosphere where the magnetic fieldis more intense.

prominenceGas that erupts from the chromosphereand solar corona, contrasting with the

darkness of space.

C E L E S T I A L B O D I E S

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solar eclipseObscuration of the Sun brought about by thepassage of the Moon between Earth and the

Sun.

MoonNatural satellite of Earth.

SunLight source eclipsed by the Moon.

Moon’s orbitElliptical path of the Moon revolving

around Earth under the effect ofgravitation.

EarthThird planet from the Sun, Earth takesa full day to rotate once on itself, oneyear to revolve once around the Sun.

umbra shadowOn Earth, the observer in this region will

see a total or annular eclipse.

penumbra shadowOn Earth, the observer in this region

will see a partial eclipse.

Earth’s orbitElliptical path of Earth revolving around the

Sun under the effect of gravitation.

total eclipseOccurs when the lunar disk completely covers the

solar disk and only the Sun’s corona remainsvisible.

annular eclipseOccurs when the Moon comes between Earth and

the Sun, reducing the latter to a luminous ring.

partial eclipseObserved by anyone within the penumbra zone

during an eclipse.

types of eclipsesThere are three types of solar eclipse, based on

the degree of obscuration.

C E L E S T I A L B O D I E S

Sun

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MoonEarth’s only natural satellite; devoid of water and atmosphere, it displays a highly uneven surface.

cliffSteep rock face shaped by a sea.

baySmall plain of hardened lava located

along the edges of a sea.

oceanA very large sea.

craterCircular basin dug out by the impact of

a meteorite.

wallMountain usually surrounding a cirque.

mountain rangeVestiges of the walls of a once-largecrater; semicircular in shape, it can

span hundreds of miles.

seaDesignates the vast plains of hardenedlava forming the dark regions; youngerthan the highlands, these cover 15% of

the surface.

lakeSmall isolated plain of hardened lava.

lunar featuresAspect of the Moon determined by past volcanic activity,meteorite impact and soil fractures. highland

Designates bright regions riddled withcraters; these oldest regions cover

85% of the surface.

crater rayBand that radiates from a young crater,

the result of matter ejected during ameteorite impact.

cirqueVast crater characterized by remarkablerelief; varies between 12 and 120 mi in

diameter.

C E L E S T I A L B O D I E S

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types of eclipsesThere are two types of eclipse based on the degree

of obscuration: partial or total.

partial eclipseWhen the Moon enters the umbra

shadow, its bright side diminishes littleby little.

total eclipseOccurs when the Moon is completelywithin the umbra shadow and takes on

a reddish appearance.

SunLight source eclipsed by Earth.

lunar eclipseEclipse during which the Moon enters Earth’s umbra

shadow in part or in full.

Moon’s orbitElliptical path of the Moon revolving

around Earth under the effect ofgravitation.

Earth’s orbitElliptical path of Earth revolving

around the Sun under the effect ofgravitation.

umbra shadowWhen the Moon is completely in this

region, the Sun’s light no longerreaches it; the eclipse is therefore total.

MoonNatural satellite of Earth.

penumbra shadowWhen the Moon enters this region, it

slowly ceases to be illuminated by theSun.

EarthOur planet, by coming between the

Sun and the Moon, gives rise tolunar eclipses.

C E L E S T I A L B O D I E S

Moon