Review Session 10 Celestial Sphere Imaginary sphere on

Review Session 10

Celestial Sphere • Imaginary sphere on which we see all objects in the sky. (Like a Planetarium)

Motion of celestial objects • Motion of Celestial Objects- (Sun, oon, planets, stars, and any other visible objects) – most objects appear to move in circular paths from east to west. – Move at a rate of 15 0/hr. – The speed is a result of the rotation of the Earth.

• http: //2. bp. blogspot. com/va. Wh 7 tr. DSRE/T_v. ED 9 i 2 id. I/AAAADak/794 j 62 I 83 G 4/s 1620/ sun+going+down+basketball+hoop. jpg

Star Paths and star trails • Stars in the east, south and the west appear to move from east to west and appear to rise and set like the sun. • Stars in the north appear to follow a ircular path around Polaris (North Star) – Polaris does not appear to move because it is on the axis of rotation. • Circumpolar stars - stars that do not ppear to rise or set but follow a circular path around Polaris. • Ursa Major (Big Dipper) • Ursa Minor (Little Dipper) • Cassiopeia (W) • https: //www. youtube. com/watch? v=s. AJi. Kk. Ob. Pzc

Constellations • figures that people have observed n the sky. • Signs of the Zodiac – called your sun sign because they are on the ecliptic. • Ecliptic – the path of the sun on the celestial phere. • Seasonal Constellations-certain constellations are only visible at specific times of the year hen they are not behind the sun. – Spring – Leo – Summer – Cygnus the Swan – Fall – Adromeda(V) – Winter – Orion the Hunter

Models of the celestial sphere • Geocentric – Earth centered – Early observers believed that the Earth was the center of the universe. – Observed all celestial objects moving from east to west and they did not feel the Earth move. – After detailed observations of the other planets orbits were made, a new model was created to xplain these motions better.

Models of the celestial sphere • Heliocentric – Sun centered – The Eight Planets(Pluto not included anymore) orbit the sun – This model includes the two motions of the Earth. • Two pieces of evidence: a. Coriolis effect-winds curve to the right in the northern hemisphere b. Focault Pendulum-a pendulum swinging n a north south orientation will change irection clockwise. • this was interpreted as the Earth rotating underneath the pendulum. • https: //www. youtube. com/watch? v=iqp. V 1236_Q 0 • https: //www. youtube. com/watch? v=V 87 VXA 6 g. Pu. E

Retrograde motion – Mars appears to move backwards for a period of its orbit. – https: //www. youtube. com/watch? v=72 Fr. Zz_z. JFU – https: //www. youtube. com/watch? v=c. SU 5 Vw. IQTNI

Apparent motions of the sun • Called apparent because the sun doesn't move it is a result of the motion of the Earth. • Earth's Rotation – rotates on its axis once in 24 hours – results in day and night • Earth's Revolution – the Earth revolves around the sun in 365 days. – this motion results in the change in the angle and duration of insolation = seasons – http: //astro. unl. edu/classaction/animations/coordsmoti on/eclipticsimulator. swf

Angle and duration of the sun’s rays • The duration and angle of the suns rays depends on an observers latitude and the season. • The seasons are a result of the parallelism of the Earth's axis throughout the year.

Summer solstice June 21 st-the first day of summer is the longest period of day light - direct rays are at the tropic of Cancer-23 1/2 0 N highest angle of insolation for the year = shortest shadow at noon. -the sun appears to rise north of East and set north of west.

Equinoxes Sept 23 rd and March 21 st Fall and Spring Equinox -12 hours of day light and 12 hours of darkness for all locations on the Earth the direct rays of the sun are at the Equator. the sun appears to rise due east and set due west.

Winter solstice December 21 st-the first day of winter - shortest day of the year - the direct rays of the sun are at the tropic of Capricorn -23 1/2 0 S - the lowest angle of insolation - the longest shadow of the year at noon -the sun appears to rise south of east and sets south of west

The moon Phases and eclipses

The Moon • Closest celestial object to the Earth •

Theory of the Formation of the Moon • As the Earth was cooling a large meteor mpact released the mass of debris that we know as our Moon. • • https: //www. youtube. com/watch? v=ib. V 4 Md. N 5 wo 0

The Moon • The Period of Rotation is the same as the eriod of Revolution = only one side of the Moon ver faces the Earth

Phases of the Moon • The Moon does not produce light, it reflects the light from the sun. – The Moon orbits the Earth in 27 days but it akes 29 ½ days for all the phases of the oon because the Earth is also moving so it akes an extra 2 ½ days – the different phases are a result of how much f the illuminated side we can see. • https: //www. youtube. com/watch? v=79 M 2 l. SVZi. Y 4

• http: //ww 2. valdosta. edu/~cbarnbau/astro_demo s/frameset_moon. html

Eclipses of the Sun and Moon • Lunar Eclipse - occurs when the Earth is between he sun and the Moon = the Earth's shadow falls on he Moon – 2 Parts to a shadow • umbra-inner darker part • penumbra-outer part, not as dark – occurs during the Full Moon, and not every ull Moon because the orbital plane of the arth and sun is not aligned with the orbital lane of the Earth and the Moon

Eclipses of the Sun and Moon • Solar Eclipse: When the moon is between the Earth and the sun = Moon's shadow falls on the Earth. – this will occur during a new moon.

Tides

What are tides? • Tides are the cyclical rise and fall of the oceans

What causes the tides? • The gravity of the moon and sun pull on the earth’s oceans – The moon’s effect is larger because it is closer • This gravitational force causes the oceans to move toward the moon and/or sun a little bit • http: //wwwtc. pbs. org/wgbh/nova/ venice/media/tides. swf Moon Gravity EARTH

How many tides do we have a day? • Every day there are two high tides and two low tides Moon – For example: High Tide Low Tide EARTH High Tide Low Tide • • 6: 00 AM – low 12: 00 PM – high 6: 00 PM – low 12: 00 AM – high • High tides happen when the moon is at its highest point in the sky or is on the opposite side of the Earth

How much do the tides change? • the average change is about 1 meter – maximum is the Bay of Fundy= 15 meter tidal change. • https: //www. youtube. c om/watch? v=OP 0 cp. Xp w 8 yk

What is the difference between a spring and neap tide?

Spring Tides • High Tides are especially high and Low Tides are especially low (Think: highest high tide and lowest low tide) • Occurs during a new moon and full moon phase!

Neap Tides • The smallest difference between high and low tides (Think: height of the two tides are very similar) • Occurs during a 1 st and 3 rd quarter moon

Spring and Neap Tide Occurrences

Geometry of Orbits

Ellipses • An ellipse is a flattened circle – Foci – 2 fixed points that are on either side of the center. – Major axis – line through the widest part of he ellipse • the sun is located at a focus for all the lanets

Shape of an Ellipse • The farther apart the foci are the flatter the ellipse or the higher the eccentricity. • Formula for eccentricity = distance between the foci divided by the length of the major axis. – This is on the Front page of ESRT under formula!

Eccentricity • Eccentricity has to be a value between 0 and 1. – 0 = a perfect circle and 1 = a straight line – Reference Tables!

Aphelion • Aphelion- when an object is furthest from the oci-the orbital velocity is slowest.

Perihelion • Perihelion= when an object orbiting around n object is closest to that object- the orbital elocity will be faster at this point.

Kepler’s Laws • 1 st Law-All orbits are ellipses with the primary at one focus – Primary = object that a satellite orbits around • 2 nd Law-the radius of a satellite will cover equal areas in equal times whether it is at erihelion or aphelion. • 3 rd Law- the closer a satellite is to the primary the faster it moves in its orbit. – the closest planets move fastest.

Gravity, the Universe, and Stars

Gravity • The force of attraction between two objects – Depends on the mass of the objects and the istance between them. – increase mass = increase gravity – increase distance = decrease gravity • Gravity is what is responsible for keeping the lanets in their orbits. – attraction between the planet and the sun – satellite-an object that orbits another object – Inertia-reason that the planets are moving

The Universe • Everything that exists , more than 10 billion years old and possibly up to 17 billion. – Began with the big bang-all matter started out concentrated in a small area. – large explosion – matter began to organize into subatomic particles. • https: //www. youtube. com/watch? v=YJJK 9 x 1 F fhw

The Universe • The universe is expanding – Doppler shift(Red shift) • light that is going away will appear red because the wavelengths are stretched. – if it were shrinking the rays would be compressed and would appear blue.

Galaxies • Large clusters of billions of stars • Milky way Galaxy – our galaxy, spiral galaxy that looks like a fried egg and the yolk is a ulge in the middle – we are located on one wing of the galaxy – http: //www. space. com/14249 -milkyway-galaxy -photos. html

The Milky way

Solar System • Made up of the sun the planets and their moons.

Solar System - Planets – Planets are divided into two major groups: • Terrestrial= rocky -Mercury, Venus, Earth and Mars – planets are small and very dense – (density in ESRT)

Solar System • Gas Giants or Jovian – made mostly of compressed gasses and a liquid or rocky core – Examples: Jupiter, Saturn, Uranus and Neptune – much larger in size

Solar System • Earth is the only planet with abundant liquid water and free oxygen, therefore it is the only planet that can support life (as we know it). • The sun is also orbited by objects other than the planets.

Asteroids, Meteors, and Comets • Asteroids – large cluster located between Mars and Jupiter. – asteroids have hit the Earth • extinction of the dinosaurs about 65 mya. https: //www. youtube. com/watch? v=alv 5 ybol. FE

Asteroids, Meteors, and Comets • Meteors – Smaller objects in space that can be dragged down by the Earth's gravity = shooting star. – most would be burned up by friction rom the atmosphere. – if it survives the fall through the tmosphere it is called a meteorite. – https: //www. youtube. com/watch? v=dpm. Xy. Jrs 7 i. U

Asteroids, Meteors, and Comets • Comets-masses of frozen gasses that have highly eccentric orbit. – when they come close to the sun the rozen gasses vaporize forming a visible tail – the tail is not behind the comet it is ointing opposite the sun.

Stars • Self-luminous body that creates its own energy through the process of nuclear fusion. – H+H= He (Hydrogen into Helium) • The sun is the closest star but is only ofaverage size and brightness.

Stars • Hertsprung-Russel diagram in the reference table shows the life cycle of a star. – on the chart in the ESRT (page 15) the two axis are luminosity and temperature, which is etermined by the color. – the chart is simplified because it is missing the diagonal axis which is the solar radi • http: //ww 2. valdosta. edu/~cbarnbau/astro_de mos/stellar_evol/birth. html