 Geocentric vs. Heliocentric Model  Geocentric Model- astronomers assumed that the Sun, planets, and the stars orbited around a stationary Earth  Heliocentric Model-the Sun is the center of our solar system(Copernicus). Earth and the other planets orbit around the sun

 Our Cosmic Neighborhood  the collection of eight planets and their moons in orbit around the sun, together with smaller bodies in the form of asteroids, meteoroids, and comets.

 Johannes Kepler in the 1600’s proposed 3 laws of planetary motion.  Kepler was able to summarize the carefully collected data of his mentor - Tycho Brahe - with three statements that described the motion of planets in a sun-centered solar system.

 The path of the planets around the sun is elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses)

 An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time. (The Law of Equal Areas)

 The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of Harmonies)

(Orbital period)

 In this equation P represents the period of revolution for a planet and R represents the length of its semimajor axis. The subscripts "1" and "2" distinguish quantities for planet 1 and 2 respectively. The periods for the two planets are assumed to be in the same time units and the lengths of the semimajor axes for the two planets are assumed to be in the same distance units. Kepler's Third Law implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit. Thus, we find that Mercury, the innermost planet, takes only 88 days to orbit the Sun but the outermost planet (Pluto) requires 248 years to do the same.

 The law states that every pair of bodies in the universe attract each other with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them.  Newton also determined that each planet orbits a point between it and the sun called the center of mass.

 The center of mass between 2 celestial bodies that orbit each other.

 We are located in the Milky Way Galaxy  The Milky Way is a great disk made of stars orbiting a central point in the disk  The Sun is just one of the BILLION stars that make up the Milky Way

What is it? How did it form?

 The formation of the planets is viewed as a by-product of the formation of the Sun.  The Solar nebula collapsed until the sun was several times larger than it is now surrounded by a disk of dust and gas.  A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, including galaxies beyond the Milky Way  Solar magnetic fields may have transferred the angular momentum of the sun into the disk.  The disk itself then fragmented into the planets 

 The Big Bang Theory  The Steady-State Theory  The Inflationary Theory

 The theory that the universe began as a point and has been expanding ever since is call The Big Bang Theory.

 The night sky presents the viewer with a picture of a calm and unchanging Universe. So the 1929 discovery by Edwin Hubble that the Universe is in fact expanding at enormous speed was revolutionary. Hubble noted that galaxies outside our own Milky Way were all moving away from us, each at a speed proportional to its distance from us. He quickly realized what this meant that there must have been an instant in time (now known to be about 14 billion years ago) when the entire Universe was contained in a single point in space. The Universe must have been born in this single violent event which came to be known as the "Big Bang."

 The Steady-State Theory proposes that the universe looks the same on large scales to all observers, and that it has always looked that way.  The steady-state universe does NOT change with time.

 The Inflationary Theory (Inflationary Model) states that the universe began as a fluctuation in a vacuum and expanded very rapidly for a fraction of a second, before settling into a more orderly expansion.

 Convection  Conduction  *Radiation

 Energy is transferred by electromagnetic radiation (energy travels in waves).  Electromagnetic radiation (light)- electric and magnetic disturbances, traveling through space as waves.

 Visible Light- the limited range of all the various wavelengths of electromagnetic radiation that is seen by the human eye.  Electromagnetic Spectrum- all types of electromagnetic radiation arranged according to wavelength and frequency.

 Wavelength- is the distance between peaks on a wave.  Frequency- what is the number of waves occurring per second. C=λf C=Speed of light (3.0 x 10^8 m/s) f=frequencyλ= Wavelength

 The sun is the LARGEST object in the solar system in both size and mass.  The Sun’s mass controls the motions of the planets and other objects  The sun is made up of about 70.4% hydrogen and 28% helium (gaseous interior).

Did you know the sun is not technically “stationary?” The gravitational pull of the other celestial bodies that orbit it cause the Sun to orbit its barycenter. So the Sun actually moves!

 The Sun’s magnetic field disturbs the solar atmosphere and creates new features to appear on the sun, like sunspots.  Sunspots- dark spots on the surface of the photosphere of the Sun.  The number of sunspots changes regularly and reaches a maximum number every 11.2 years. (The Solar Activity Cycle)

 Highly Active solar flares are associated with sunspots.  Solar Flares (“storms”) are violent eruptions of particles of radiation from the surface of the Sun.

 Solar Wind- Wind of charged particles that flows throughout the solar system and begins as gas flowing outward from the Sun’s corona at high speeds.  The charged particles emitted by the sun shower the planets in our solar system.  The Earth’s Magnetosphere deflects them.

 The Van Allen Belts-two large rings in Earth’s magnetic field, where the charged particles emitted from the Sun are trapped.  The highly energized particles within the Van Allen Belts combine with the gases in Earth’s atmosphere and emit light known as the Auroras. (Seen at the Poles)

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 Mercury, Venus, Earth, and Mars are called the terrestrial planets.  These planets lost most of their gases during development, therefore they have a more rocky composition.

 The planets that formed further from the Sun, were cool and massive enough to keep most of their hydrogen.  Jupiter, Saturn, Uranus, and Neptune are known as the Jovian Planets or the gas Giants

Revised by Claire Anne Baird Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, My Very Energetic Mother Just Served Us Nectarines

 In the Universe we are relatively small.  Specifically, Earth is located in the Solar System which is located within the Orion Spiral Arm of the Milky Way Galaxy. The Milky Way Galaxy is a part of the Local Galactic Group. The Local Galactic Group is within the Virgo Supercluster of galaxies within the Universe.