# Unit 4- Astronomy - Earth and Environmental

Unit 1Astronomy Earth, Sun, and Moon Interactions Revolution Move around an object; to orbit A path the Earth follows around the sun Takes 1 year or 365.25 days for Earth to travel around the Sun Causes seasons

Rotation Spin/turn on an axis Earths tilt or axis is 23.5 from the equator One rotation = one solar day (24 hrs/day) Foucault Pendulum- evidence of Earths rotation on its axis Plane of Ecliptic = the plane in which Earth orbits around the Sun

Solstice Summer Solstice Sun directly overhead at Tropic of Cancer 23.5 north latitude

June 21 each year Maximum daylight hours in northern hemisphere Winter Solstice

Tropic of Capricorn 23.5 south latitude December 21 each year Minimum daylight hours in northern hemisphere Equinox Vernal (Spring) and Autumnal (Fall) Equinox Equal night- 12 hours of daylight, 12 hours of night

Earths axis is NOT pointed at the Sun Both hemispheres receive equal amounts of sunlight Stop to Summarize 1.) Whats the difference between rotation and revolution? 3.) How does the Earths tilt influence the equinoxes and solstices? Earths Shape

OBLATE SHEROID A sphere flattened along the axis from pole to pole such that there is a bulge around the equator. This bulge results from the rotation of the Earth, and causes the diameter at the equator to be 43 km (kilometer) larger than

the pole-to-pole diameter. Precession Precession a gravity-induced, slow and continuous change in the orientation of a Earths rotational axis Changes the stars near the Pole

axis is not fixed in space. Like a rotating toy top, the direction of the rotation axis executes a slow precession with a period of 26,000 years Nutation Nutation (WOBBLE) a small irregularity of the equinoxes.

makes a small change to the angle at which the Earth tilts with respect to the Sun, changing the location of the major circles of latitude that are defined by the Earth's tilt occurs over an 18 year period and caused exclusively by the moon

Barycenter is the center of mass of two or more bodies that are orbiting each other, or the point around which they both orbit

Center of gravity- The exact center of all the material (that is, mass) that makes up an objectwhether a planet or a pencil Earth and the Sun, both bodies orbit around the very center of the mass between them Stop to Summarize

1.) Do you think the Sun is stationary in our solar system? (think barycenter) 2.) Explain the difference between precession and nutation The Moon Our Nearest Neighbor A natural satellite

One of more than 96 moons in our Solar System The only moon of the planet Earth Movements of the Moon

Revolution Moon orbits the Earth every 27 and 1/3 days The moon rises in the east and sets in the west The moon rises and sets 50 minutes later each day Rotation Moon turns on its axis every 27 days

Same side of Moon always faces Earth Its Just a Phase Moonlight is reflected sunlight Half the moons surface is always

reflecting light From Earth we see different amounts of the Moons lit surface The amount seen is called a phase FOUR MAIN SHAPES

FULL QUARTER CRESCENT GIBBOUS

Phases of the Moon Tides Moon affects Earth by the formation of tides Moons gravity pulls on Earth along imaginary line connecting Earth and the Moon creates bulges of ocean water on both the near

and far sides of the Earth Earths rotation contributes to tide formation As Earth rotates, these bulges align with the Moon Tides

Spring=Str ong High tides are called spring tides and they are high when Moon is nearest Earth and Earth is nearest the Sun Tides Neap=

Weak Solar Eclipses Lunar Eclipses The Closest StarOur Sun

History of Our Sun Worshipped as a deity (god) by many cultures throughout history Called Helios by the Greeks Called Ra by the Egyptians

Helios, Greek god carrying the Sun to its position in the sky Ra, the god of the Sun HELIO-centric=the Sun is at the center of our solar system NOT

GEO-centric= the Earth is at the center of our solar system Keplers Laws 1.) The orbit of a planet is an ellipse with the Sun at one of the two foci. 2.) A line segment joining a planet and the Sun sweeps out

equal areas during equal intervals of time. Why is the Sun important? Temperature: supports most life on earth by providing warmth required for survival (exception:

underwater hydrothermal vent ecosystems) Photosynthesis: plants grow which in turn absorb carbon dioxide and create oxygen How does the Sun produce light and

heat? Deep in the sun's core, nuclear fusion reactions convert hydrogen to helium, which generates energy. Hydrogen atoms are fused together to create a helium and release a tremendous

amount of energy Suns Layers How does the Sun produce light and heat? Radioactive Zone: energy is

transported from the superhot interior to the colder outer layer by photons, includes the core (85% of the Suns radius) Convection Zone: more ions are able to block the outward flow of photo radiation (15% of the Suns radius) LAVA LAMP- boiling motions of gases

transfer the energy to the surface. This journey takes about 100,000 years. Outer Layers of the Sun 1.) Photosphere: bottom layer of outer sun 2.) Chromosphere: next layer above the

photosphere 3.) Corona: crown of light from the Sun Features of the Sun Prominence Prominences are arcs of gas that are anchored in the photosphere layer of the Sun

Prominences extend through the corona layer of the Sun Features of the Sun Sunspots Sunspots are small, dark spots seen on the surface of the Sun Sunspots are caused by strong magnetic fields on the Suns

surface One sunspot has North magnetic polarity and one sunspot has South magnetic polarity. Caused by the Suns rotation Features of the Sun Solar Wind a stream of energized, charged

particles flowing outward from the Sun as plasma Our magnetic field protects the Earth from the solar wind Auroras are created as the solar winds charged particles interact with our magnetic field

Features of the Sun Solar Flares a sudden and intense variation in brightness from a magnetic energy build up IMPACT: radiation from past solar flares has been responsible for; disrupting satellites

stretching the visibility of the Aurora Borealis down to the tropics causing electronics and cellular devices to fail causing telegraph wires to burst into flames.

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