Astronomy PDF Notes (PDF)

# Parallax - the apparent shift in position of an object when viewed from different locations - used by astronomers to measure distance - Put your pointer finger in front of your face and begin opening and closing your eyes in an alternating manner. What do you notice about the your finger's posit...

# Parallax - the apparent shift in position of an object when viewed from different locations - used by astronomers to measure distance - Put your pointer finger in front of your face and begin opening and closing your eyes in an alternating manner. What do you notice about the your finger's position? # Parsec - unit of distance equal to about 3.26 light years (or 206,265 AU) - If one parsec equals 206, 265 AU, how many miles is it equal to? # Light Year - the distance that light travels in one year in a vacuum, which is about 9.5 trillion kilometers (6 trillion miles) - The Milky Way Galaxy is about 100,000 light years in diameter - the speed at which light travels this distance is about 300,000 km/sec (186,000 mi/sec) - The second closest star to the Earth is a little over four light years away. How far away (in miles) is the star? # Astronomical Unit (AU) - unit of distance equal to the average spacing between the Earth and the Sun - equal to about 150 million kilometers (93 million miles) - light takes about eight minutes to cover this distance # Hubble Space Telescope - reflecting telescope that was placed into orbit in 1990 - sends images and measurements back to Earth electronically - What is one of the main benefits of having the Hubble Space Telescope in orbit, as opposed to it being here on Earth? # Meteoroid, Meteor, Meteorite - **Meteoroid** - solid debris from space (asteroids) that are moving towards Earth - **Meteor** - a brief streak of light produced by a small particle entering Earth's atmosphere at high speed - often referred to as "shooting stars" or "falling stars" - travel at speeds between 11-72 kilometers per second (6.8 – 44.7 miles per second) - **Meteorite** - a small object from outer space that passes through Earth's atmosphere and reaches the surface - Freehold Meteorite - MSNBC - Freehold Meteorite - USA-Today - What causes a meteor shower to occur? # Telescope - a device that gathers electromagnetic radiation - **Types:** - Visible, infrared, ultraviolet – pick up visible, infrared, and ultraviolet waves - **Reflecting** - use mirrors that reflect the image being viewed - **Refracting** - using lenses, gathers light and focuses it near the opposite end of the tube, works like a magnifying glass - **Radio** - pick up radio waves emitted from space, not effected by variables like weather or clouds # Comet - a small body of ice and dust ("dirty snowball") that orbits the Sun - contain a head (coma) followed by a tail(s) of gas and dust - the tail always points away from the sun and can be millions of kilometers long (but the amount of matter it contains can be very small) # Solar System - the sun and all things orbiting around it, including the eight major planets, their satellites, and all the smaller pieces such as asteroids and comets - formed around 4.6 billion years ago - What is incorrect or misleading about this visual? # Planet - derived from a Greek word that means "wanderer" - a major object which orbits around a star - in our solar system, there are eight such objects which are traditionally called "planets" # Satellite - an object that orbits a more massive object (i.e. - moons) - probes we launch into orbit around the Earth are called "artificial satellites" # Asteroids - small, solid, rocky bodies that orbit close to the Sun - most found between the orbits of Mars and Jupiter in the "Asteroid Belt" - thought to be leftover material from the formation of the solar system - range in size from 1000 km or 621 miles (Ceres) to the size of pebbles # Constellation - a group of stars that form a pattern in the sky - stars of a constellation are often far apart from each other, but they appear grouped together when viewed from Earth - one of 88 sectors into which astronomers divide the sphere of the sky - named after a traditional constellation in that sector - patterns of constellations are dynamic; therefore, the constellations of 100,000 years ago are quite different from today's - a part of a constellation that forms its own pattern in the sky is known as an asterism (ex. - The Big Dipper) - Why is it not possible to see all constellations at once? # 3 Types of Galaxies - **Spiral** - have arms of stars, gas, and dust that curve away from the center of the galaxy in a spiral pattern - Ex. - Milky Way - **Elliptical** - shaped like spheres or eggs; have almost no dust or gas between stars; contain old stars - **Irregular** - faint galaxies without a definite shape; smaller than the other types of galaxies; contain fewer stars - The process of galaxies colliding to create a larger galaxy is known as "galactic cannibalism." # Edwin Hubble - determined that other galaxies exist, besides the Milky Way - observed that galaxies were moving away from each other - Hubble Law - the farther away a galaxy is, the faster it is moving away from us; supports the Big Bang Theory # Galaxy - a large assemblage of stars (and often gas and dust), typically containing millions to hundreds of billions of member stars - Star - a large hot ball of gas which generates energy in its core by nuclear reactions - around 100 billion in the universe - held together by the gravitational attraction of all its member stars on one another - formed around 200 million years after the "Big Bang" - most large ones seem to have super-massive black holes at their centers - sometimes contain very bright centers called quasars - 3 major types: - Spiral - Elliptical - Irregular # "Big Bang" Theory - the primeval explosion of space, time, matter and energy that most astronomers think gave rise to the universe as we see it today. - occurred about 13.7 billion years ago - thought to have expanded within a second from something the size of a spec of dust to the size of our solar system - Misconception Alert: Describing this theory as the "Big Bang" is a misnomer because there really was not an explosion, just a release of energy # Cosmology - the branch of astronomy that deals with the origin, large-scale properties, and the evolution of the observable universe # The Universe - in astronomy, the sum total of all things which can be directly observed or whose physical effects on other things can be detected - in simpler terms, space and all the matter and energy in it - major components: - galaxies - solar systems - planets