Astronomy

T: Earth-Moon-Sun

Why does Earth Have Seasons?

Moon Formation - The leading scientific theory approximates that the moon formed 100 million years (4.5 bya) after the Earth formed. - A planet sized object collided with Earth sending debris into orbit forming the moon. https://www.youtube.com/watch?v=mQAdYWcA7ig

Moon Facts - 384,401 km from Earth, 27% of Earth’s size (6784 km circumference). •127 °C during day and -173°C during night. - Impact craters from meteorites are visible. - Lava flows have cooled and blanket the moon.

Why doesn’t Earth have more craters?

Closer look at a crater.

Moon Phases Moon revolves around earth reflecting the sun towards earth. – “Far Side” of the moon because the rotation and orbit are both 27.3 days (29.5 days on Earth). 1.2 km/sec orbit speed Waxing = getting brighter Waning = getting darker

Eclipses Umbra = total shadow Penumbra = partial shadow - Lunar eclipses occur when the Earth is located between the Sun and the Moon at Full Moon Phase. - A solar eclipse occurs when the Moon comes between the Sun and Earth, and the Moon’s shadow hits Earth’s surface at New Moon Phase.

Tides Tides are the twice-daily rise and fall of water level that occurs because the Moon’s gravity attracts different parts of the Earth unequally. The two bulges stay in place as the Earth rotates under them. This produces two high tides and two low tides at a given place every day. http://ed.ted.com/on/Akt5TXox

Lab: Lunar Hats

T= Big Bang Theory

Scientific Theory Explanation of how natural phenomena work “the why”. Supported by evidence through observation. Tested many times. Widely accepted in the scientific community. May change over time with new technology or evidence.

Scientific Law Laws describes natural phenomenon world behavior (“what”). “Law describes what, and theories explain why.” Supported by evidence Repeatedly Tested Hubble Telescope Image

Universe Our sun is one of 1,ooo,ooo,ooo stars in the Milky Way Galaxy. The Milky Way Galaxy is one of 1,000,000,000 galaxies in Universe. Hubble Telescope Image

Big Bang Universe estimated at 13.7 billion years. - The most widely-accepted scientific theory on the beginning of our universe. Universe estimated at 13.7 billion years. Universe started as a dense, hot, super massive ball that exploded in all directions.

Supporting Evidence Other galaxies have a red shift in light showing that they are moving away from us. Doppler effect explains the change in the wave frequency. Cosmic background radiation has been discovered from the Big Bang, which is made up of faint radio signals.

Topic : Early Astronomy Topic : Early Astronomy (Chapter 22) Topic : Early Astronomy

Heliocentric Nicolaus Copernicus (1473-1543) – proposed a model of a solar system with sun in the middle (Heliocentric). Earlier model of the earth in the middle (Geocentric)

The Telescope Galileo Galilei (1564 – 1642) – used the first telescope. Discovered that the moon’s surface was not smooth. Sun spots found on sun. Four Satellites orbiting Jupiter.

Newton Sir Isaac Newton (1642 – 1727) – formulated the law of gravitational attraction. • Force of gravity combined with tendency of planet to stay in motion results in elipitical orbit. • Factors Affecting Planets Distance, Mass of Planet, and Gravity

Kepler’s 3 Laws Johannes Kepler (1571 – 1630) – discovered three laws of planetary motion.

Kepler’s 3 Laws Planets orbit in an ellipse. Equal area law, planets move faster when they are closer to the Sun and slower farther away.

Kepler’s 3 Laws 3. Period of Orbit2 = Distance away from the sun (astronomical units)3 (P2 = A3) 1 A.U. is the distance from Earth to the sun. 93,000,000 miles or 150,000,000 km

Topic: Sun and Solar System

The Nebular Hypothesis The most widely accepted scientific theory for the solar system. developed from a Nebula - a cloud of gas and dust particles. 4.7 Billion years ago. First, the heaviest elements contract towards the center of the cloud forming the sun.

Second, the nebula began to spin around the sun, and it flattened into a disk.

Third, particles in the cloud began to collide & stick together forming planetesimals (small early planets). What is expected from the student

Evidence - Meteorites. - Hubble telescope has captured other solar systems forming.

The Sun Average-sized star, Middle aged 4.7 billion years old (10 by is expectancy). 109 x bigger than Earth (332,000 more massive than Earth). One of over 1,000,000,000 stars in Milky Way Galaxy Like the cosmos is mainly made up of Hydrogen and Helium (99.9%).

Structure of Sun

Sun Spots Occur in chromosphere. Dark regions due to 1500 kelvin less than surrounding. Cycles every 11 years.

Solar Flares Occur at sunspots. Emits lots of energy in the form of UV rays, radio waves and x-rays and forms a solar wind. Day after larger flares can affect long distance communication. Causes auroras.

Auroras Aurora Borealis (northern lights) Aurora Australis (southern lights). Earth’s magnetic shield deflects solar flares to the poles where energized particles create a light show.

Nuclear Fusion Sun produces energy from Nuclear Fusion. Hydrogen atoms combine to form helium and the extra mass is converted to energy (gamma rays).

Topic: Stars

Spectroscopy - Study of light’s wavelength. Can study stars temperature and composition. Hubble Telescope

Characteristics of Stars Color of star is due to stars temperature. • Hot stars are towards blue spectrum. • Cold star are towards the red spectrum.

Stellar Brightness -Apparent magnitude, how bright a star looks from earth. • Factors include distance, temperature and size. Absolute magnitude, actual brightness adjusted for distance. **Light year (light travels in one year) is 9.5 x 1012 km

Hertzsprung-Russel Diagram Diagram compares magnitude and temperature of stars. Shows the evolution of stars (i.e. Life Cycle).

How are elements made? Nucleosynthesis is the building of atoms. When stars die they compress due to density and fuse atoms. • Larger star deaths result in heavier atoms.

We categorize planets into 3 groups: Inner Planets known as Terrestrial (Earth like) Outer Planets known as Jovian (Jupiter like) Exo Planets known as Dwarf (very small)

Inner Planets The inner planets are those found closest to the Sun: Mercury, Venus, Earth, and Mars. The inner planets are sometimes called the Terrestrial (Earth-like) planets. This is because all the inner planets have rocky crusts, dense mantle layers, and very dense cores.

Outer Planets The outer planets are those found beyond the asteroid belt: Jupiter, Saturn, Uranus, and Neptune. The outer planets are known as the Jovian (Jupiter-like) planets. They are much larger, are gaseous (outer layer is mostly hydrogen gas), & have a hot liquid core. These planets are less dense, & all four have ring systems.

Dwarf Planets The newest group is called dwarf planets: Ceres, Pluto, and Eris. More dwarf planets are expected to be announced in the coming months. The major reason these are considered dwarf planets is the fact that mass of these objects have not cleared the “neighborhood” around their orbit.