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Astronomy = the study of the universe. Astro = star Centr = center Geo = earth Retro = back Pre = before Peri = around Mar = ocean Terre = ground Sol = sun Chrom = color pro = first. Astronomical History!. Geocentric Model = moon, sun and planets orbit Earth.

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Astronomy = the study of the universe

Astro = star

Centr = center

Geo = earth

Retro = back

Pre = before

Peri = around

Mar = ocean

Terre = ground

Sol = sun

Chrom = color

pro = first

Astronomical History!

  • Geocentric Model = moon, sun and planets orbit Earth.

Astronomical History!

  • Heliocentric Model = Earth and other planets orbit sun.

Astronomical History!

  • Ptolemaic System = Planets orbit Earth, but seemed to exhibit retrograde motion.

Astronomical History!

Brahe: Yes, but my observations are much more precise.

Copernicus: Earth is a planet that orbits the sun.

Kepler: No, my 3 laws of planetary motionprove that Brahe is wrong.

Newton: The planets are held into a circle by the gravity of the sun.

Galileo: Well, here is how the planets and their satellites move.

Earth – Moon - Sun

Rotation = spinning

Revolution = going around another object

Earth Rotating






Plane of the Ecliptic = reference plane that runs from pole to pole.

Plane is tilted about 23.5o.

Seasons are result of the tilt.

More Earth Movement

Precession = very slow wobbling

Earth - Moon

Perigee = moon is closest to earth

Apogee = moon is farthest from earth

Phases of the Moon


Solar eclipse = moon is between earth and sun (like the background here!) and casts a shadow on Earth.

Lunar eclipse = Earth moves between sun and moon and casts shadow on moon.

Man on the Moon

Earth’s Moon

  • Gravity 1/6th that of Earth

  • 150 lb person = 25 lbs

  • The Only Natural Satellite

  • 1/4th diameter of Earth

  • Apollo moon mission 1969-1972

  • Craters

  • round depressions

  • produced by impacts

Compresses surface material.

Impact by meteor.

Rebound splash of ejecta.

Uplift of deep rock in center.

Major Topographic features of the Moon:

Highlands = light colored areas (almost as high as Mt. Everest!)

Mare (Maria, pl.) = dark smooth areas (ancient beds of lava)

Rilles are valleys or trenches.

Regolith = soil-like layer

Lunar History

When solar system was forming, a body the size of Mars impacted Earth and the debris shot into space. One piece was our Moon.

How the Moon Formed

Formation of the Solar System

Nebular Theory = sun and planets formed from a rotating disk of dust and gases.

Planetesimals = small, irregular-shaped bodies that collided and clumped together to form the planets.

The Solar System

Terrestrial Planet = small and rocky (inner planets)

Jovian Planet = large gaseous (outer planets)

Asteroids = small, rocky bodies floating in space

(Largest, Ceres, is about 1000 km in diameter!)

Comets = pieces of rocky and metallic materials held together

by frozen gases like water, ammonia, methane, etc.

(Some take hundreds of thousands of years to make one orbit.)

Small Pieces (w/Quiz)

Coma = the glowing head of a comet produced when the sun begins vaporizing the comet’s frozen gases.

Tail = stream of glowing vaporizing gases

Halley’s Comet


Kuiper Belt = disc-shaped region beyond Neptune where short-orbital comets originate.

Oort Cloud = area spreading in all directions from the sun where long-orbital comets originate.

  • Meteoroid

  • small, solid particle

  • travels through space

  • origination

    • interplanetary debris

    • asteroid belt material

    • remains of comets


  • Meteor

  • meteoroid that enters Earth’s atmosphere

  • Meteor Shower = a group of meteors traveling in the same direction

Meteor in Peru 2007


Photosphere = visible surface (90% hydrogen)

Chromosphere = thin layer of hot gases (can see during solar eclipse)

Corona= weak outermost layer (extends 1 million km)

Solar wind = streams of protons and electrons


Convective Zone

Radiative Zone





Activity of the Sun:

Sunspots= appear dark because they are cooler than the rest of the sun.

Prominences= large cloudlike structures consisting of chromospheric gases.

  • Solar Flares

  • explosive events

  • last about an hour

  • sudden brightening above a sunspot cluster

  • release enormous amounts of energy

  • ejects atomic particles

  • produce auroras (northern lights)

It’s how far??!!

1 Light Year = how far light travels in one year. Light travels at 299,792,458 m/s so in one year light goes 5.88 trillion (5.88 × 1012) miles.

1 A.U. (Astronomical Unit) is the distance from the Earth to the Sun which is 150 million km (93 million miles).

Earth’s diameter = 7,926 miles

Sun’s diameter = 870,000 miles

Sirius is the brightest star in the night-time sky. It is located in the constellation Canis Major. It is 8.5 light years away.

Pollux is 33.7 light years away.

Arcturus is 36.7 light years away.