Astronomy II Flash Cards -- Song 8th Grade Science H

Planets in Solar System (in order)

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Mercury

• terrestrial (rocky surface)

• smallest planet

• no moons

• thin atmosphere →heat doesn’t get trapped →opposite side is cold

• side that faces sun is very hot

Astronomical Unit (au)

• 1.5 × 10 ^11 m

• approximately avg distance btwn Earth & Sun

• WHY IT’S HELPFUL: VERY CONVENIENT & IS USED FOR THINGS IN SOLAR SYSTEM

Light year

• 9.46 × 10^15 m

• used for things OUTSIDE solar system

• very convenient for large distances

• the distance light travels in a year (MEASURING DISTANCE, NOT TIME)

Venus

• Terrestrial

• Hottest planet due to thick CO2 in atmosphere

• No moons

• Rotates clockwise (Sun sets towards east)

• Day on Venus > year on Venus

• Earth’s twin (similar size, close orbit)

Earth

• 1 moon

• Densest planet in solar system

• all 3 states of water

• Plate tectonics → earthquakes

Asteroid Belt

• Asteroids = rocky objects, diameter = usually <1 km

• Asteroids orbit btwn Mars & Jupiter

• Thought to be leftover pieces of early solar system that never formed a planet

Mars

• Terrestrial

• 2 moons

• Red planet due to iron oxide (rusted iron)

• Tallest mountain

• May have had water in the past

Jupiter

• Gaseous planet

• largest (in terms of mass & size)

• Rotates very fast (10 hrs per day)

• Great red spot : super storm, 3X the size of Earth

• 79 known moons

• 2 ½ times the mass of all the planets combined

Saturn

• Gas planet

• Less dense than water

• Over 30 rings made of ice, dust, and rocks

• 82 known moons: the largest moon, Titan, is larger than the planet Mercury

Uranus

• Ice Planet

• 27 moons

• 13 rings

• Tilted on side

• Blue-green color from METHANE GAS in atmosphere.

  • Sunlight passes thru atmosphere & reflected back out by Uranus' cloud tops

  • Methane gas absorbs red portion of light => blue-green color

Neptune

• Ice planet

• 14 moons

• 5 rings

• Blue due to methane gas

• LONGEST PERIOD OF REVOLUTION

  • Furthest from the Sun → takes longer to revolve

Beginning of universe

• Singularity

  • point in space in time which is:

    • infinitely hot

    • infinitely dense

    • infinitely small (SMALLER THAN PROTON!!)

    • CONTAINED EVERYTHING IN THE UNIVERSE

    • We do not know where it came from.

Big Bang Theory

• scientifically accepted theory of the beginning of the universe

• refers to when singularity began to expand & cool. A LOT HAPPENED

• Happened about 13.7 billion years ago

• Expansion, not explosion

• We do not know what caused it.

Hubble’s Law

• the farther galaxies are, the faster they are moving away from us

• strong support for Big Bang Theory

• Universe is still expanding

Newton’s 1st Law (its relation to this unit)

• From Big Bang Theory, all things in universe are moving.

• Once stars are moving, what will cause them to stop?

  • NOTHING. They will continue moving at a constant velocity, until an unbalanced force causes them to change their motion.

Nebula

• “Star nursery” - where stars are born

• Clouds of dust (Li) & gas (primarily H & He)

• GRAVITY keeps the particles together.

Law of Universal Gravitation

• All things w/ mass are attracted to each other.

• Based on 2 factors:

  • mass of objects

  • distance btwn objects

    • center to center

• Gravity & mass = directly related.

• Gravity & distance = inversely related.

• Fg = Gm1m2/r²

  • G = gravitational constant (doesn’t change)

  • r = radius (distance btwn 2 objects from center to center)

  • m = mass

Birth of a Star

• Stars begin in a nebula (clouds of dust & gas).

• Gravity pulls mass together → particles spin

  • Spins faster & faster → gets hotter

  • Reaches ~ 15 million degrees C = nuclear fusion begins & star is born.

    • Beginning of star’s life (when star will expand & release light / energy)

Nuclear Fusion

• When gasses get too hot, they turn into 4th state of matter (PLASMA)

  • Plasma = electrons are stripped & nuclei is left bare

• If nuclei in this state go fast enough, they will fuse into a new element

  • Hydrogen fuses into helium. 4 hydrogen nuclei → 1 Helium nucleus.

    • Difference in mass in nuclear reaction → energy

      • According to equation E=mc²

        • From mass, you get energy.

          • We see this energy in form of light → how star shines

• From the Sun, tension btwn 2 competing forces

  • Gravity - wants to pull everything together

  • Energy from fusion - wants to blow it all apart

Convert Venus’ distance from Sun (107.5 BILLION M) to AU & cm if 1 AU is 147.4 billion m.

0.7 AU or 70 CM

How are galaxies classified?

SHAPE & SIZE

Order this from smallest → largest:

Mars, USA, Cell, Jupiter, atom, Cerritos, dog, Sun, Mercury

• atom, cell, dog, Cerritos, USA, Mercury, Mars, Jupiter, Sun

How are galaxies different from nebulae?

• Nebulas are solely where stars are born

• Galaxies contain stars, as well as other things like planets, asteroids, etc

  • Galaxies are larger than nebulas

Mass of planets from smallest → largest

Mercury, Mars, Venus, Earth, Uranus, Neptune, Saturn, Jupiter

ACRONYM: Mighty Martians Visit Earth, Usually Not So Jovial

Inner planets

• Mercury, Venus, Earth, Mars

• Also called terrestrial planets

• Smaller in size & denser

• Few moons & no rings

• Rocky surface

• Close to Sun & each other

Outer planets

• Jupiter, Saturn, Uranus, Neptune

• Also called gas giants

• Larger in size

• Lots of moons & can have rings

• no solid surface

  • => no defined physical features

  • As a result of gaseous surface

What do planets with the most mass have in common?

• < density

• > period of rotation @ equator

• > period of revolution

• > distance from Sun

• Eccentricity of orbit

Why do outer planets not have craters?

Outer planets made of gas → asteroids have no solid surface to fall onto

True or false: less gravitational force = less size & less moons & rings (unable to support them w/ less Fg)

True

What is used to differentiate between inner & outer planets?

• Surface

• # of rings

• Distance from Sun

• # of moons

• Size

Kuiper Belt

• large region in cold, outer reaches of our solar system beyond orbit of Neptune.

• sometimes called "third zone" of solar system

• most likely has millions of small, icy objects

  • Some objects, including Pluto, are > 600 miles wide.

  • Objects have frozen compounds i.e. ammonia & methane

Oort Cloud

• lies beyond Pluto & most distant edges of Kuiper Belt.

• planets of our solar system orbit in a flat plane, but Oort Cloud is in giant spherical shell surrounding Sun, planets & Kuiper Belt Objects

  • like a big, thick bubble around solar system, made

    of icy, comet-like objects (can be large as mtns, or even larger)