UNIT 2: ASTRONOMY

After Unit 2 you should be able to: Understand scaling: solar system, galaxy, universe Understand that we are a part of a spiral galaxy known as the Milky Way Know the approximate age of the universe and solar system Understand the Big Bang theory and supporting evidence such as cosmic background radiation and red-shift of light Understand the process of fusion taking place in the Sun Understand how the solar system formed, what layered the planets, and how they were separated into two distinct groups: Jovian and Terrestrial Differentiate between a comet and an asteroid Understand how moon phases are observed Understand the difference between the sidereal period and synodic period of the moon Understand what impacts the formation of high and low tides Differentiate between lunar and solar eclipses Use the Electromagnetic Spectrum, Characteristics of Stars, and Solar System Data charts in the ESRT

Unit 2 vocabulary you should be able to use and understand: Universe Star Sun Solar system Galaxy Milky Way galaxy Spiral galaxy Singularity Big Bang theory Cosmic background radiation Radiation Visible light Wavelength Electromagnetic spectrum Red-shift Blue-shift Doppler Effect Luminosity Supernova Massive Giant star White dwarf Main sequence star Fusion Atoms Gravity Density Terrestrial planet Jovian planet Gas giant Period of revolution Period of rotation Equatorial diameter Eccentricity Mass Moon Comet Asteroid Impact crater Celestial object Sidereal period Synodic period Waxing Waning Crescent Gibbous Tides High tide Low tide Spring tide Neap tide Solar eclipse Lunar eclipse

The universe is vast. Incredibly, incredibly vast The universe is vast. Incredibly, incredibly vast. Even with modern technology, humans are unable to leave even our solar system within the timeframe of their lives. Astronomy is therefore much more abstract and theoretical than other disciplines here on Earth.

Scaling the Universe The true dimensions of the universe are unknown, but it has been said (in an expression) that there are as many stars as grains of sand on all the beaches of the world. Our solar system surrounds a star known as the Sun Our solar system is a part of many solar systems that make up the Milky Way galaxy

Galaxies Galaxies take on a variety of shapes The Milky Way is known as a spiral galaxy, with our solar system located in one of the outer arms There are billions of galaxies that make up the visible universe

Age of the Universe Our universe is estimated to be about 13.7 billion years old This estimate is based on the projected expansion from a singularity (single point) based on current evidence

The Big Bang The Big Bang is the current accepted theory for the expansion of the universe Approximately 13.7 billion years ago there was a rapid expansion and differentiation of matter that created the universe

Evidence for the Big Bang The Big Bang is supported by two pieces of evidence: Cosmic background radiation Red-shift of visible light

To understand the evidence supporting the Big Bang, you must first understand radiation traveling through space. Electromagnetic radiation travels in waves Shorter wavelengths = higher energy Wavelengths of radiation can be stretched or compressed

Cosmic Background Radiation Radiation exists from an explosion, believed to be from a time period following the Big Bang

Red Shift of Visible Light Light from distant sources that are moving away from an observer experiences stretching in the wavelength towards the red end of the spectrum Light from distant galaxies is red-shifted so they are moving away This phenomenon of wavelength alteration is known as the Doppler Effect When an object is moving towards an observer, the waves are compressed and it is blue-shifted This is evidence that this matter was once together at a singularity

Stars Our Sun is a medium-sized yellow star Stars are classified by luminosity, color, and size Larger stars have a short lifespan and can explode in a violent supernova We see stars in the night sky that have burned out long ago but their light is still traveling towards us

Fusion The process of fusion unites lighter elements and produces heavier ones releasing massive amounts of energy and light Hydrogen atoms fuse into helium inside of our Sun heating Earth 93 million miles away

The Beginnings of Our Solar System Our solar system is approximately 5 billion years old. The force of gravity caused fragments of debris to begin clumping together within a spinning disc Our Sun would later begin the process of fusion in the center of the spinning disc

8 Planets 8 planets would form within this spinning disc The densest material was closest to the Sun This formed rocky, denser planets known as the Terrestrial planets The less dense, gaseous, and icy Jovian planets formed beyond the asteroid belt

Terrestrial Planets Mercury Venus Earth Mars Jovian Planets Jupiter Saturn Uranus Neptune

Other Components of Our Solar System Comets (primarily ice and dust) Asteroids (rocky and metallic) Impact evidence is recorded in the geologic record (as craters) along with mass extinctions but erosion and deposition have erased many craters on Earth

Additional Solar System Data Found in the ESRT

Our moon is critically important to life here on Earth Our moon is critically important to life here on Earth. In addition to our tides, the moon is responsible for maintaining Earth’s rate of rotation.

The Moon The Moon revolves around Earth once every 27.3 days (sidereal period) Coincidentally, the moon’s period of rotation is equal to its period of revolution meaning that we will only ever see one side of the moon

Moon Phases The Moon enters phases as it orbits Earth based on how we view the lit side of the moon The time for the moon to go through all phases once is slightly longer (29 days --- the synodic period) than its orbit due to Earth’s revolution around the Sun.

Tides The Moon exhibits gravitational pull on the Earth This pull bulges water towards the Moon as well as on the opposite side of the Earth (high tide) When the Sun, Moon, and Earth are aligned, the tides are the highest and the lowest on Earth (spring tides) The Moon has a more significant influence on tides even though it is smaller than the Sun because it is closer to Earth Tides are about 6 hours apart (high to low)

Eclipses Eclipses are named for the object that is being blocked from an Earth perspective Solar eclipse: Sun is blocked by the moon Lunar eclipse: the Moon is blocked from the Sun’s rays by the Earth