Astronomy

Astronomy Study of objects in space such as the Sun, stars, planets, comets, gas, & galaxies. *Also, the Earth’s place in the universe. Universe = everything that exists

How long is one full revolution? Our revolution and rotation is determined by how close or how far we are from the sun In astronaut terms, this is determined by the astronomical unit -1 A.U. is the distance from Earth to the Sun -The Earth, like all planets, orbits (revolves around) the sun How long is one full revolution? 365.25 days = 1 year Go back and make easier to read.

DAY NIGHT The Earth rotates on its axis 1 full rotation = one day warmer NIGHT cooler

Earth’s axis is not straight Earth’s axis is tilted 23.5° from vertical 23.5° tilt

The Earth’s orbit actually looks like this This shows orbit

Earth’s Seasons = caused by the tilted axis (23.5o) Equinox = equal hours of daylight & darkness Solstice = longest day & shortest day Fall Sep. 21 SUN Dec. 21 Jun. 21 (shortest day) (longest day) Mar. 21 Spring

The angle of the sun’s radiation hitting the Earth impacts the climate or temperature.

EXAMPLE! warmer cooler

If the tilt were the only factor, then every location on Earth would have one season and it would never change.

When northern hemisphere is facing the sun: •Summer Solstice June 21st or 22nd

SUMMER SOLSTICE Most direct rays over Northern Hemisphere Striking at Tropic of Cancer 23.5° N Light = 15 hours (about 14.27 (NC) Dark = 9 hours

Antarctica is completely dark for 24 hours and the Arctic is completely light for 24 hours!!!

Fall Equinox (September 22 or 23)

Direct rays over Equator: EQUAL amounts of daylight and darkness everywhere. Direct rays over Equator: Light = 12 hours Dark = 12 hours

Winter Solstice - December 21-22 SHORTEST DAY !!! Most direct rays over Southern hemisphere •Striking at Tropic of Capricorn 23.5°S Light = 9 hours Dark = 15 hours

Spring Equinox (March 21 or 22)

Direct rays over Equator: EQUAL amounts of daylight and darkness everywhere. Direct rays over Equator: Light = 12 hours Dark = 12 hours

The Southern Hemisphere has opposite Seasons than us . . . WHY?

Big Bang Theory At one time, the universe was a dense, hot, supermassive ball. About 13.7 billion years ago, a violent explosion occurred sending material in all directions into space.

1. The Beginning- An Explosion 14 billion years ago a tightly packed, very dense, high temperature singularity exploded. The Big Bang

Universe Galaxies Cosmic Size Solar systems Stars Star clusters & Constellations Solar systems Stars Planets, moons Asteroids, meteors, meteorites, comets The “Big Dipper” constellation is a pattern made of 7 stars watch this! Powers of Ten Video

Geo-centric Helio-centric Earth-centered view of universe Sun-centered view of solar system C. Ptolomy 90-168 N. Copernicus 1473-1543 modern view of the solar system: “the Sun” is a star planets orbit the Sun

Galaxies = groups of billions of stars there are more than 100 billion galaxies they all have different shapes Spiral Elliptical Irregular

A cloud of space dust or gas. Nebula A cloud of space dust or gas.

Nebular Hypothesis cloud of mostly hydrogen & helium A. A. nebula A. cloud of mostly hydrogen & helium B. Started rotating & collapsing toward center because of gravity forming an accretion disk , also the Sun forms C. rocky & metallic materials form as nebula cools D. collisions of particles created asteroid-sized objects (protoplanets or planetesmals) E. Sun = most dense object, nuclear fusion Rock / Terrestrial planets = more dense, heavy material, closer orbit Gas / Jovian planets = least dense, lighter material, farther orbit B. accretion disk C. cooling D. protoplanets E. solar system

How the Solar System Form Summary Solar nebula collapsed. The nebula became denser and denser and the attraction between the particles increased. Due to the increase collisions the center of the cloud became very hot. The cloud flattened out into a rotating disk in which all of the planets still follow this rotation.

The Birth of a Star At the same time the planets were forming material kept pulling in toward the center of the nebula. Eventually temperature got so hot that fusion reaction began to occur between hydrogen atoms creating helium. Fusion reactions released large amounts of pressure balancing the inward pull of gravity.

The Birth of a Star As the gases became balanced, stabilization occurred, giving birth to a new star. The Sun

Energy Nuclear Fission Nuclear Fusion The splitting of an atom to create energy Produced in nuclear reactors The fusion of two atoms to create energy Happens within stars

The Expanding Universe 1929 – Edwin Hubble found that the universe is expanding Proof comes from Red Shifts: meaning wavelengths of light from other Galaxies are becoming longer and redder This proves these galaxies are moving Away from us  

Doppler Effect https://www.youtube.com/watch?v=kdiHmSWI2Ks

Support for the Big Bang Theory Cosmic background radiation Radio signals coming from every direction in space. Believed to be created by the big bang explosion.

The Earth in the Universe The Motion of our Home. . .

Earth’s Motions Rotation Revolution spinning of Earth from west to east on an axis results in day / night Earth makes one rotation in 24 hours Revolution Earth moves around the sun every 365¼ days

Earth’s Motions Precession The change in direction of the northern axis North star is different This will change the stars near the pole but will not change the seasons (as long as the angle of the tilt, 23.5 in the case of Earth, stays the same)

22.2 The Earth–Moon–Sun System Motions of Earth 22.2 The Earth–Moon–Sun System  Precession • Precession traces out a cone over a period of 26,000 years.  Earth–Sun Motion • The solar system speeds in the direction of the star Vega. • The sun revolves around the galaxy. • Earth is presently approaching one of its nearest galactic neighbors, the Great Galaxy in Andromeda.

3. Precession Precession- the change in the Earth’s rotational axis As we rotate (dashed lines), the axis rotates Add video showing precession

Nutation Slight wobble, or change, in Earth’s axis from 23.5° Very slow movement due to the gravity of the moon

Earth’s Motions Winter – closest to the sun Summer – farthest from the sun

22.2 The Earth–Moon–Sun System Motions of the Earth–Moon System 22.2 The Earth–Moon–Sun System  Phases of the Moon • The phases of the moon are the progression of changes in the moon’s appearance during the month. • Lunar phases are a result of the motion of the moon and the sunlight that is reflected from its surface.

Phases of the Moon Makes no sense without caption in book

22.2 The Earth–Moon–Sun System Motions of the Earth–Moon System 22.2 The Earth–Moon–Sun System  Lunar Motions • The synodic month is based on the cycle of the moon’s phases. It lasts 29 1/2 days. • The sidereal month is the true period of the moon’s revolution around Earth. It lasts 27 1/3 days.

22.2 The Earth–Moon–Sun System Motions of the Earth–Moon System 22.2 The Earth–Moon–Sun System  Lunar Motions • The difference of two days between the synodic and sidereal cycles is due to the Earth–moon system also moving in an orbit around the sun. • The moon’s period of rotation about its axis and its revolution around Earth are the same, 27 1/3 days. It causes the same lunar hemisphere to always face Earth.

Lunar Eclipses Occurs during full moon phases Do not see the moon because the Earth blocks light Sun, Earth, moon in a line

Solar Eclipses Occurs when sun is blocked by the moon Sun, moon, Earth If the moon is partially blocking the sun, a partial solar eclipse will occur

Results of the Earth’s Motions Other rare events include seeing other planets cross across the face of the Sun (like Venus did on June 5th, 2012, only time until 2117).

Results of the Earth’s Motions Tides- As the moon orbits the Earth we experience high and low tides as the Moon’s gravity pulls on the Earth High Tides happens when the Moon is straight above (and on the opposite side of Earth as well) and the water is pulled up by the Moon’s gravity.

Equatorial Bulge The Earth is not completely round There is a bulge at the equator because of rotation Video Link

Barycenter The point between two objects where they balance each other The actual center of our solar system The sun orbits around this point Barycenter Video Music :)

Kepler’s Laws 1st Law: orbital paths are ellipses (ovals) Sun is at one focal point Animation of Laws

Kepler’s Laws 2nd Law: a planet sweeps out equal areas in equal times

Planet moves FASTER in orbit when CLOSE to the SUN, and SLOWER in orbit when FAR FROM the SUN WHY? GRAVITATIONAL PULL

The closer a planet is to the sun, the FASTER it orbits around it!! Kepler’s 3rd Law The further the planet is from the Sun, the LONGER it will take for the planet to orbit the Sun. The closer a planet is to the sun, the FASTER it orbits around it!! Mercury – 88 days Venus – 225 days Mars – 687 days Jupiter – 4331 days Pluto – 90,582 days or 248 years!!

Kepler’s Laws 3rd Law: T2 = d3 T= time of orbit d = distance (avg) from the sun