Popular in Course
verified elite notetaker
Popular in Department
This 6 page One Day of Notes was uploaded by Morgan Burleson on Wednesday September 17, 2014. The One Day of Notes belongs to a course at a university taught by a professor in Fall. Since its upload, it has received 172 views.
Reviews for Astronomy-Chapter1PDF.pdf
I'm a really bad notetaker and the opportunity to connect with a student who can provide this help is amazing. Thank you so much StudySoup, I will be back!!!
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/17/14
Wednesday September 3 2014 Astronomy Chapter 1 A Modern View of the Universe We shall not cease from exploration And the end of all our exploring Will be to arrive where we started And know the place for the first time TS Elliot 11 The Scale of the Universe What is our place in the universe Our Cosmic Address our solar system consists of the sun a star the planets and their moons asteroids comets etc located a little over halfway from the galactic center to the edge of the galactic disc milky way galaxy huge diskshaped collection of stars contains more than 100 billion stars one of the two largest in the local group galaxy great island of stars in space containing between a few hundred million and a trillion or more stars local group the group of about 40 galaxies to which the milky way galaxy belongs to located in the outskirts of the local supercluster galaxy clusters galaxies with more than a few dozen members superclusters regions in which galaxies and galaxy clusters are mostly tightly packed essentially clusters of galaxy clusters universe the sum total of all matter and energy encompassing the superclusters and voids and everything within them Astronomical Distance Measurements astronomical unit AU earth s average distance from the Sun approximately 150 million kilometers93 million miles lightyear ly distance light can travel in 1 year approximately 10 trillion kilometers 6 trillion miles unit of distance not time lightsecond distance that light travels in one second Wednesday September 3 2014 300000 kilometers Looking Back in Time Sirius the brightest star in the night sky located about 8 lightyears away because it is located 8 lightyears away we see it as it was 8 years ago rather than how it is now when we study the universe it is impossible to separate space and time Basic Astronomical Definitions Astronomical Objects star a large glowing ball of gas that generates heat and light through nuclear fusion in its core ex oursun planet a moderately large object that orbits a star and shines primarily by reflecting light from its star a object can only be considered a planet if it orbits a star is large enough for its own gravity to make it round has cleared most other objects from its orbital path an object that meets the first two criteria but not the last one is designated a dwarf planet pluto moonsatellite an object that orbits a planet satellite is also used more generally to refer to any object orbiting another object asteroid a relatively small and rocky object that orbits a star comet a relatively small and icerich object that orbits a star small solar system body an asteroid comet or other object that orbits a star but is too small to qualify as a planet or dwarf planet Collections of Astronomical Objects solar system the sun and all the material that orbits it including planets dwarf planets and small solar system bodies although the term technically refers only to our own star system it is often applied to other star systems as well star system a star sometimes more than one and any planets and other materials that orbit it galaxy a great island of stars in space containing from a few hundred million to a trillion or more stars all held together by gravity and orbiting a common center cluster or group of galaxies a collection of galaxies bound together by gravity small collections up to a few dozen galaxies are generally called groups while larger collections are called clusters Wednesday September 3 2014 supercluster a gigantic region of space in which many groups and clusters of galaxies are packed more closely together than elsewhere in the universe universecosmos the sum total of all matter and energy that is all galaxies and everything between them observable universe the portion of the entire universe that can be seen from Earth at least in principle the observable universe is probably only a tiny portion of the entire universe Astronomical Distance Units astronomical unit AU defined above lightyear ly defined above Terms Relating to Motion rotation the spinning of an object around its axis ex Earth rotates once each day around its axis which is an imaginary line connecting the North and South Poles orbit revolution the orbital motion of one object around another due to gravity ex Earth orbits the Sun once a year expansion of the universe the increase in the average distance between galaxies as time progresses The Observable Universe astronomers estimate that the universe is about 14 billion years old if we look at a galaxy that is 7 billion light years away we see it as it looked 7 billion years ago due to this the distance of 14 billion lightyears marks the boundary or horizon of the observable universe How big is the universe The Scale of the Solar System fitting our solar system onto a diagram with the sun being the size of a grapefruit including the orbits would require 300 football fields of space only the sun planets and a few moons would be big enough to see the rest of the space would just look empty Distances to the Stars the nearest star system to our own a threestar system called Alpha Centauri is about 44 lightyears away convenient interstellar travel remains well beyond our present technology The Size of our Milky Way Galaxy on a scale of 11 billion the 100000lightyear diameter of our milky way galaxy becomes about the length of a football field the size of our solar system becomes a microscopic dot located around the 20 yard line the number of stars in our galaxy is more than 100 billion Confusing Very Different Things solar system vs galaxy solar system single star system galaxy a collection of more than 100 billion star systems the size of our galaxy is about 100 million times larger in diameter than our solar system Wednesday September 3 2014 The Observable Universe the milky way is only one of about 100 billion galaxies in the observable universe if you count every single grain of dry sand on every single beach on earth that is comparable to the number of stars in the observable universe Order of Magnitude Estimation estimates good to about the nearest power of 10 are called order of magnitude estimates 12 The History of the Universe How did we come to be The Big Bang Expansion and the Age of the Universe telescopic observations of distant galaxies show that the entire universe is expanding average distances between galaxies are increasing with time galaxies must have been closer together in the past and if we go back far enough we must reach the point at which the expansion began the big bang which is calculated to have occurred 14 billion years ago the universe has continued to expand ever since the big bang on smaller scales the force of gravity has drawn matter together structures such as galaxies amp galaxy clusters occupy regions where gravity has won out against the expansion while the universe as a whole continues to expand individual galaxies and galaxy clusters as well as objects within them do not expand most galaxies including the milky way formed within a few billion years after the big bang Stellar Lives and Galactic Recycling within galaxies like the milky way gravity drives the collapse of clouds of gas and dust to form stars and planets a star is born when gravity compresses the material in a cloud to the point at which the center becomes dense enough and hot enough to generate energy by nuclear fusion the process in which lightweight atomic nuclei smash together and fuse to make heavier nuclei a star lives as long as it can shine with energy from fusion and it dies when it exhausts its usable fuel massive stars fie in explosions called supernovae the returned matter from the supernovas mixes with other matter floating between the stars in the galaxy eventually becoming part of new clouds of gas and dust from which new generations of stars can be born Star Stuff by studying stars of different ages we have learned that the early universe contained only the simplest chemical elements hydrogen and heium and a trace of lithium we and earth are made primarily of other elements carbon nitrogen oxygen and iron these elements were manufactured by stars some through the nuclear fusion that makes stars shine and others through nuclear reactions accompanying the explosions that end stellar lives by the time our solar system formed about 4 12 billion years ago earlier versions of stars had already converted about 2 of our gaaxy s original hydrogen and helium into heavier elements the cloud that gave birth to our solar system was about 98 hydrogen and helium and 2 other elements Wednesday September 3 2014 some of these elements became the raw ingredients of life ultimately blossomed into the great diversity of life on Earth today most of the material from which we and our plane are made from was created inside stars that lived and died before the birth of our sun How do our lifetimes compare to the age of the universe imagine the 14billionyear age of the universe compressed into a single year each month represents a little more than 1 billion years the big bang occurred on January 1st and the present is at 12am December 31st the milky way formed in February our solar system formed in September early dinosaurs December 26th dinosaurs extinct December 30th average college student was born 005 seconds ago 13 Spaceship Earth How is Earth Moving Through Space Rotation and Orbit rotation spin daily earth rotates once each day around its axis imaginary line connecting the north and south poles rotates from east to west counterclockwise why the sun and stars appear to rise in the east and set in the west orbit revolution yearly orbits the sun once each year average distance from the sun is 1 AU 150 million kilometers earth s orbital path defines a flat plane that we call the ecliptic plane earth s axis is tilted by 23 12 degrees from a line perpendicular to the ecliptic plane the axis tilt is oriented so that the axis points almost directly to a star called PolarisNorth Star in space up and down mean only away from the center of Earth or another planet and toward the center of Earth earth orbits the sun in the same direction that it rotates on its axis counterclockwise earth and the other planets were born in a spinning disk of gas that surrounded the sun when it was young earth rotates and orbits in the same direction that the disk was spinning Motion Within the Local Solar Neighborhood the stars in our local solar neighborhood move essentially at random relative to one another on average our sun is moving relative to nearby stars at a speed of about 70000 km per hour40000 miles per hour stars are so far away that their motions would be noticeable to the naked eye only if we watched them for thousands of years Galactic Rotation as we widen our view beyond the local solar neighborhood the seemingly random motions of its stars give way to a simpler and even faster motion rotation of the milky way galaxy Wednesday September 3 2014 our solar system located about 27000 Iightyears from the galactic center completes one orbit of the galaxy in about 230 million years stars at different distances from the galactic center orbit at different speeds most mass of the galaxy seems to be located outside of the visible disk occupying the galactic halo that surrounds amp encompasses the disk we know very little about the nature of this matter which has a lack of light hence the name dark matter we know even less about the dark energy that seems to make up much of the total energy content of the universe How Do Galaxies Move Within the Universe 14 The Human Adventure of Astronomy
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'