Survey of the Solar System. Introduction The Solar System is occupied by a variety of objects, all maintaining order around the sun The Solar System is

Survey of the Survey of the Solar SystemSolar System

IntroductionIntroduction

• The The Solar SystemSolar System is occupied by is occupied by

a variety of objects, all a variety of objects, all

maintaining order around the sun maintaining order around the sun

• The planets in the solar system The planets in the solar system

form two main families: solid form two main families: solid

rocky inner planets and rocky inner planets and

gaseous/liquid outer planetsgaseous/liquid outer planets

Survey of the Solar System 2

Origin of the Solar SystemOrigin of the Solar System• Age of the Solar SystemAge of the Solar System– All objects in the Solar System All objects in the Solar System seem to have formed at nearly seem to have formed at nearly the same timethe same time

– Radioactive dating of rocks Radioactive dating of rocks from the Earth, Moon, and some from the Earth, Moon, and some asteroids suggests an age of asteroids suggests an age of about 4.6 billion yearsabout 4.6 billion years

– A similar age is found for the A similar age is found for the Sun based on current Sun based on current observations and nuclear observations and nuclear reaction ratesreaction rates


Origin of the Solar SystemOrigin of the Solar SystemSolar nebula hypothesisSolar nebula hypothesis – current – current theory explaining the Solar Systemtheory explaining the Solar System’’s s originorigin• Solar System evolved from a rotating, Solar System evolved from a rotating, flattened disk of gas and dust (an flattened disk of gas and dust (an interstellar cloudinterstellar cloud), the outer part ), the outer part of the disk becoming the planets and of the disk becoming the planets and the inner part becoming the Sunthe inner part becoming the Sun

• This hypothesis naturally explains This hypothesis naturally explains the Solar Systemthe Solar System’’s flatness and the s flatness and the common direction of motion of the common direction of motion of the planets around the Sunplanets around the Sun

–Interstellar clouds are common Interstellar clouds are common between the stars in our galaxy and between the stars in our galaxy and this suggests that most stars may this suggests that most stars may have planets around them have planets around them


Origin of the Solar SystemOrigin of the Solar System

• Formation of the Solar NebulaFormation of the Solar Nebula

– A few million years passes for a A few million years passes for a

cloud to collapse into a rotating cloud to collapse into a rotating

disk with a bulge in the centerdisk with a bulge in the center

– This disk is called the This disk is called the solar solar

nebulanebula with the bulge becoming the with the bulge becoming the

Sun and the disk condensing into Sun and the disk condensing into

planetsplanetsSurvey of the Solar System 5

Origin of the Solar SystemOrigin of the Solar System• PlanetesimalsPlanetesimals– Next step is for tiny particles Next step is for tiny particles to stick together into bigger to stick together into bigger pieces through collisions pieces through collisions

– As long as collision are not too As long as collision are not too violent, objects, called violent, objects, called planetesimalsplanetesimals, ranging in size , ranging in size from millimeters to kilometers, from millimeters to kilometers, may formmay form

• Formation of the PlanetsFormation of the Planets– Planets formed from Planets formed from ““gentlegentle”” collisions of the planetesimals, collisions of the planetesimals, which dominated over more violent which dominated over more violent shattering collisionsshattering collisions


Origin of the Solar SystemOrigin of the Solar System• Formation of the PlanetsFormation of the Planets– Simulations show that Simulations show that planetesimal collisions planetesimal collisions gradually lead to gradually lead to approximately slightly approximately slightly elliptical planetary orbitselliptical planetary orbits

– As planetesimals grew in As planetesimals grew in size and mass their size and mass their increased gravitational increased gravitational attraction helped them grow attraction helped them grow faster into clumps and faster into clumps and rings surrounding the Sunrings surrounding the Sun


Origin of the Solar SystemOrigin of the Solar System• Direct Formation of Giant PlanetsDirect Formation of Giant Planets

– It is possible the outer regions of the It is possible the outer regions of the solar nebula were cold and dense enough solar nebula were cold and dense enough for gravity to pull gas together into for gravity to pull gas together into the giant planets without the need to the giant planets without the need to first form cores from planetesimalsfirst form cores from planetesimals

• Formation of MoonsFormation of Moons– Moons of the outer planets were Moons of the outer planets were probably formed from planetesimals probably formed from planetesimals orbiting the growing planetsorbiting the growing planets

• Final Stages of Planet FormationFinal Stages of Planet Formation– Rain of planetesimals cratered surfacesRain of planetesimals cratered surfaces– Remaining planetesimals became small Remaining planetesimals became small moons, comets, and asteroidsmoons, comets, and asteroids


Origin of the Solar SystemOrigin of the Solar System• Formation of AtmospheresFormation of Atmospheres

– Atmospheres were the last planet-forming processAtmospheres were the last planet-forming process

– Outer planets gravitationally captured their Outer planets gravitationally captured their

atmospheres from the solar nebulaatmospheres from the solar nebula

– Inner planets created their atmospheres by Inner planets created their atmospheres by

volcanic activity and perhaps from comets and volcanic activity and perhaps from comets and

asteroids that vaporized on impactasteroids that vaporized on impact

• Cleaning up the Solar SystemCleaning up the Solar System

– Residual gas and dust swept out of the Solar Residual gas and dust swept out of the Solar

System by young SunSystem by young Sun’’s intense solar winds intense solar wind


Components of the Solar SystemComponents of the Solar System• The SunThe Sun– The Sun is a star, a ball of The Sun is a star, a ball of incandescent plasma whose output is incandescent plasma whose output is generated by nuclear fusion in its generated by nuclear fusion in its corecore

– Composed mainly of hydrogen (71%) and Composed mainly of hydrogen (71%) and helium (27%), it also contains traces helium (27%), it also contains traces of nearly all the other chemical of nearly all the other chemical elementselements

– It is the most massive object in the It is the most massive object in the Solar System – 700 times the mass of Solar System – 700 times the mass of the rest of the Solar System combinedthe rest of the Solar System combined

– ItIt’’s large mass provides the s large mass provides the gravitational force to hold all the gravitational force to hold all the Solar System bodies in their orbits Solar System bodies in their orbits around the Sunaround the Sun


Components of the Solar SystemComponents of the Solar System

• The planetsThe planets

– Planets shine primarily by reflected Planets shine primarily by reflected

sunlightsunlight

– Orbits are elliptical, lying in nearly Orbits are elliptical, lying in nearly

the same plane –All the planets travel the same plane –All the planets travel

(revolve) counterclockwise around the (revolve) counterclockwise around the

Sun Sun

– Six planets rotate counterclockwise; Six planets rotate counterclockwise;

Venus rotates clockwise, and Uranus Venus rotates clockwise, and Uranus

appears to rotate on its sideappears to rotate on its sideSurvey of the Solar System 11

Components of the Solar SystemComponents of the Solar System• Two types of planetsTwo types of planets– Inner planetsInner planets

• Mercury, Venus, Earth, MarsMercury, Venus, Earth, Mars• Small rocky (mainly silicon and oxygen) Small rocky (mainly silicon and oxygen) bodies with relatively thin or no bodies with relatively thin or no atmospheresatmospheres

• Also referred to as Also referred to as terrestrial planetsterrestrial planets– Outer planetsOuter planets

• Jupiter, Saturn, Uranus, NeptuneJupiter, Saturn, Uranus, Neptune• Gaseous, liquid, or icy (HGaseous, liquid, or icy (H22O, COO, CO22, CH, CH44, , NHNH33))

• also referred to as also referred to as Jovian planetsJovian planets• Jovian planets are much larger than Jovian planets are much larger than terrestrial planets and do not have a terrestrial planets and do not have a well-defined surfacewell-defined surface


The Demise of Pluto

• Pluto is no longer part of the big

8, but considered a dwarf planet

since 2006 IAU reclassification of

it

• There have been several other dwarf

planets discovered after Pluto such

as MakeMake and Eris

• It is a Kuiper Belt objectSurvey of the Solar System 13






Components of the Solar SystemComponents of the Solar System

• SatellitesSatellites

– The number of planetary satellites has The number of planetary satellites has

changed frequently over the last several changed frequently over the last several

years; years;

• Most recent count is broken down as follows: Most recent count is broken down as follows:

Jupiter 63, Saturn 60, Uranus 27, Neptune 13, Mars Jupiter 63, Saturn 60, Uranus 27, Neptune 13, Mars

2, Earth 1, and Mercury and Venus are moonless2, Earth 1, and Mercury and Venus are moonless

– The moons generally follow approximately The moons generally follow approximately

circular orbits that are roughly in the circular orbits that are roughly in the

planetplanet’’s equatorial plane, thus resembling s equatorial plane, thus resembling

miniature solar systemsminiature solar systems


Components of the Solar SystemComponents of the Solar System• Asteroids and cometsAsteroids and comets– Their composition and sizeTheir composition and size

• AsteroidsAsteroids are rocky or metallic bodies are rocky or metallic bodies ranging in size from a few meters to 1000 ranging in size from a few meters to 1000 km across (about 1/10 the Earthkm across (about 1/10 the Earth ’’s s diameter)diameter)

• Comets Comets are icy bodies about 10 km or less are icy bodies about 10 km or less across that can grow very long tails of across that can grow very long tails of gas and dust as they near the Sun and are gas and dust as they near the Sun and are vaporized by its heatvaporized by its heat

– Their location within Solar SystemTheir location within Solar System• Most asteroids are in Most asteroids are in asteroid beltasteroid belt between Mars and Jupiter indicating that between Mars and Jupiter indicating that these asteroids are the failed building-these asteroids are the failed building-blocks of a planetblocks of a planet

• Comets are from a region located past Comets are from a region located past Pluto called the Oort CloudPluto called the Oort Cloud


Fig. 14.4


Documents

Survey of the Solar System. Introduction The Solar System is occupied by a variety of objects, all maintaining order around the sun The Solar System is