Exploring the Planets: The Solar System

The solar system has X stars, X planets with X moons, X large asteroids, X dwarf planets with X moons and more than X Kuiper Belt objects

1, 8, 427, 12, 5, 9, 100

Mercury orbit

Off from the plane of the other planets's orbits by 7 degrees

Planetary alignment

Since the planets are in the same plane, they can sometimes be seen in a line in the sky

Which 3 planets are similar in size and density?

Venus, Mercury and Earth

Why are planetary alignments useful?

We can use them to recalibrate instruments and we can use gravitational assist for spacecrafts

Terrestrial planet similarities

1.Rotate slowly 2.Rocky 3.weak magnetic fields 4.Few moons

Terrestrial planet differences

1.Different atmospheres (Only earth has O2) 2.Rotation: Earth/Mars are similar, Mercury is slow, Venus is slow and retrograde

Jovian planet similarities

1.Large and gaseous 2.Rotate quickly 3.Strong magnetic fields 4.Many moons

Jovian planet differences

1. Gas giants vs ice giants 2.Jupiter is 2.5x bigger than all other planets combined 3.Different chemical compositions of their atmospheres give them different colours

Main asteroid belt

Interplanetary matter between Mars and Jupiter with small metallic and rocky material

Kuiper belt

Interplanetary matter just beyond Neptune made of small frozen volatiles

Oort cloud

Spherical shell of interplanetary matter made of icy bodies around the farthest parts of the solar system

Dwarf planets

Interplanetary matter that meet 2 of the 3 criteria for planets

Criteria for planets

1. Must orbit the sun 2. Must be spherical due to its own gravity 3. Must have cleared its orbit of other objects/debris

Pluto

Demoted to a dwarf planet because while it orbits the sun and is spherical due to its own gravity, it has not cleared its orbit of debris

Meteoroids

Interplanetary matter made of rock and metal, ranging in size from a grain of sand to 1m

Asteroids

Interplanetary matter made of rock and metal, ranging in size form 1m to hundreds of km eg Asteroid Vesta is 500km across

Comets

Interplanetary matter made of rock and ice that have not changed since the formation of the universe

Comet tails

Trails of gas (blue) and dust particles (yellow) stretching for millions of miles that appear when a comet gets too close to the sun

What colour would the sun be outside our atmosphere?

White, because it has enough energy for its waves to cross the entire visible spectrum

Solar system origin is discovered though…

motion, chemistry, age

Motion of the solar system

Everything spins in the same direction, in orbit and on axis’

Chemistry of the solar system

Metals and rocks are closest to the sun, carbon is in asteroid belt and H and He in outer solar system (temp gradient)

Age of solar system

Oldest rocks on earth are 4.43 billion years old and primitive meteorites are 4.5 billion years old so formed roughly the same tim

Our solar nebula formed shortly after___ and was made of __

The big bang (13.8Ga), dust and gas

Chemical elements in solar nebula

H and He

Solar system formation: 4.5Ga

Nebula starts spinning and acceleration flattens it into a disk with most material at the centre, and becomes hot enough to start nuclear fusion

Angular momentum

Momentum must be conserved, so as things become smaller, they spin faster

Density perturbations

Slightly higher density of mass than surrounding gas exterts a slight gravitational force

Dust accumulation

Dust particles stick together by electrostatic interaction

Condensation sequence

Order in which elements transition from gas to solid eg metals condense close to the sun and gases and water cannot condense due to high temperature

Frost line

Line in space at which gases can condense into ice due to distance from the sun

Planetary accretion: Dust conglomerate

Dust grains in a nebula stick together through electrostatic forces

Planetary accretion: Planetesimals

When the dust cloud is larger than 1km, it has enough gravity to pull objects in

Planetary accretion: Protoplanets

Planetesimals collide and form moon-Mars sized objects

Planetary accretion: Planets

Protoplanets undergo massive collisions and clear their orbits of debris

Rocky planet planetary accretion

Planetesimal impacts are hot enough to form a liquid core with denser materials at the centre

Comet/asteroid creation

Planetesimals that never became big enough to be protoplanets and still crash into other space objects

Homogenous accretion hypothesis

Earth started as an unlayered planets with metals and oxides mixed evenly throughout → Collisions and radioactive decay cause it to heat up and melt → Metals sink to the centre and silicates float to the top, forming the crust

Crust

Solid, rigid silicates with plate tectonics

Mantle

Silica rich, hotter, like malleable plastic

Core

Liquid outer core and solid inner core mostly F and N

Jovian planetary accretion

Protoplanets can hold onto gas due to massive gravity of cores made of H and He in the composition as the sun

What is responsible for Mercury's thin crust, Venus' odd rotation and Earth's large moon?

Protoplanet collisions

What happened to planetesimals in our solar system that did not form planets?

Ejected from the solar system, accreted by a planet or part of the kuiper/asteroid belt