Slide Number 1Guiding QuestionsTo understand the universe, astronomers use the laws of physics to construct testable theories and modelsiClicker QustionBy exploring the planets, astronomers uncover clues about the formation of the solar systemBy studying stars and nebulae, astronomers discover how stars are born, grow old, and dieBy observing galaxies, astronomers learn about the origin and fate of the universeSlide Number 8Astronomers use angles to denote the positions and apparent sizes of objects in the skySlide Number 10Slide Number 11Angular MeasurementsPowers-of-ten notation is a useful shorthand system for writing numbersCommon Prefixes for Powers of TenAstronomical distances are often measured in astronomical units, parsecs, or light-yearsParallaxSlide Number 17Careful measurements of the parallaxes of stars reveal their distances Barnard’s star has a parallax of 0.54 arcsec Slide Number 20The Small Angle FormulaSmall Angle Formula ExampleAstronomy is an adventure of the human mindDiscovering the Night Sky Part 2 Guiding QuestionsNaked-eye (unaided-eye) astronomy had an important place in ancient civilizationsSlide Number 27Eighty-eight constellations officially cover the entire sky Modern ConstellationsThe appearance of the sky changes during the course of the night and from one night to the nextSlide Number 31Slide Number 32Annual MotionSlide Number 34Slide Number 35Slide Number 36It is convenient to imagine that the stars are located on a celestial sphereSlide Number 38Slide Number 39Slide Number 40Slide Number 41Slide Number 42The seasons are caused by the tilt of Earth’s axis of rotationSlide Number 44Facts about the SeasonsSlide Number 46Slide Number 47Slide Number 48Regions of the Earth’s surface are marked by the Sun’s position in the sky throughout the yearThe Moon helps to cause precession, a slow, conical motion of Earth’s axis of rotationPrecession causes the gradual change of the star that marks the North Celestial PolePositional astronomy has played an important role in keeping track of timeSlide Number 53Slide Number 54Slide Number 55Astronomical observations led to the development of the modern calendarSlide Number 57Slide Number 58Astronomy JargonMore Astronomy Jargon1Discovering the Night Sky2Guiding Questions1. What methods do scientists use to expand our understanding of the universe?2. What makes up our solar system?3. What are the stars? Do they last forever?4. What are galaxies? What do astronomers learn by studying them?5. How does measuring angles help astronomers learn about objects in the sky?6. What is powers-of-ten notation, and why is it useful in astronomy?7. Why do astronomers measure distances in astronomical units, light-years, and parsecs?8. How does studying the cosmos help us on Earth?3To understand the universe, astronomers use the laws of physics to construct testable theories and models• Scientific Method– A reiterative process based on observations, logic, and skepticism• Hypothesis– A concept or idea that seems to explain a phenomenon or set of observations• Model– A set of hypotheses that have withstood observational or experimental tests• Theory– A set of related hypotheses can be pieced together into a self consistent description of natural observations• Laws of Physics– Theories that accurately describe the workings of physical reality, and have stood the test of time and been shown to have great and general validity4iClicker Qustion• What defines the scientific method?A A set of related hypotheses can be pieced together into a self consistent description of natural observationsB A concept or idea that seems to explain a phenomenon or set of observationsC A reiterative process based on observations, logic, and skepticismD A set of hypotheses that have withstood observational or experimental testsE Theories that accurately describe the workings of physical reality, and have stood the test of time and been shown to have great and general validity5By exploring the planets, astronomers uncover clues about the formation of the solar system– The star we call the Sun and all the celestial bodies that orbit the Sun• including Earth• the other seven planets• all their various moons• smaller bodies such as asteroids and comets6By studying stars and nebulae, astronomers discover how stars are born, grow old, and die7By observing galaxies, astronomers learn about the origin and fate of the universe89Astronomers use angles to denote the positions and apparent sizes of objects in the sky• The basic unit of angular measure is the degree (°).• Astronomers use angular measure to describe the apparent size of a celestial object—what fraction of the sky that object seems to cover• The angular diameter (or angular size) of the Moon is ½° or the Moon subtends an angle of ½°.10If you draw lines from your eye to each of two stars, the angle between these lines is the angular distance between these two stars11The adult human hand held at arm’s length provides a means of estimating angles12Angular Measurements• Subdivide one degree into 60 arcminutes– minutes of arc– abbreviated as 60 arcmin or 60´• Subdivide one arcminute into 60 arcseconds– seconds of arc– abbreviated as 60 arcsec or 60”1° = 60 arcmin = 60´1´ = 60 arcsec = 60”13Powers-of-ten notation is a useful shorthand system for writing numbers14Common Prefixes for Powers of TenFactor Name Symbol(billion) 109 Giga- G(million) 106Mega- M(thousand) 103kilo- k(hundredth) 10-2centi- c(thousandth) 10-3milli- m(millionth) 10-6micro-(billionth) 10-9nano- n15Astronomical distances are often measured in astronomical units, parsecs, or light-years• Astronomical Unit (AU)– One AU is the average distance between Earth and the Sun– 1.496 X 108 km or 92.96 million miles• Light Year (ly)– One ly is the distance light can travel in one year at a speed of about 3 x 105 km/s or 186,000 miles/s– 9.46 X 1012 km or 63,240 AU• Parsec (pc)– the distance at which 1 AU subtends an angle of 1 arcsec or the distance from which Earth would appear to be one arcsecond from the Sun– 1 pc = 3.09 × 1013 km = 3.26 ly16Parallax1718Careful measurements of the parallaxes of stars reveal their distances• Distances to the nearer stars can be determined by parallax, the apparent shift of a star against the background stars observed as the Earth moves along its