Peer Led Team Learning. Tycho Brahe in his observatory His careful observations and records are his most important legacy

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1 Birth of Modern Astronomy Celestial Motion Lab starts this week NS 017 Bring lab manual to lab Do Prelab 1 before you go! Peer Led Team Learning Tuesday 5:45 to 7:45 PM Library Room 205 Add ES104X CRN Can add before or during Oct. 8 session Helps with vocabulary, concepts, confidence Will have exam review sessions Sit in to see if it is for you Nicolaus Copernicus Earth rotates on an axis, instead of everything orbiting Earth Earth orbits Sun like the planets, so it a planet too On the Revolution of the Heavenly Spheres, Tycho Brahe Detailed observations of movement of planets Tycho Brahe in his observatory His careful observations and records are his most important legacy Tycho s 1572 Nova observations Tycho s comet of Tycho s model of solar system Discounted Copernicus model because he could not discern stellar parallax It does exist, he didn t have tools to see it Johannes Kepler Tycho s assistant and successor Used Tycho s data to determine planetary orbits are elliptical 1

2 First Law of Planetary Motion Orbit of planet is ellipse Sun at one Focus Kepler s 2 nd Law Kepler s third law of planetary motion p 2 =d 3 p=period (time to orbit Sun) in Earth years d=distance in Astronomical Units: 1 A.U.=distance from Earth to Sun Equal areas in equal time intervals accounts for the uneven speeds Galileo Galilei Strong supporter of Copernican model of planetary movement Built 30x telescopes (from descriptions of the devices) and looked at planets and Moon starting in Galileo s notes on Jupiter s moons Telescope used to see that another body in solar system is a center of orbital movement These moons are not left behind, and Earth s Moon is not either Ptolemaic version of Venus Phases of Venus Galileo s explanation of Venus phases Moon s surface has texture 2

3 Galileo s Astronomical Discoveries When viewed by telescope, planets look like discs, not points of light as stars do Jupiter has moons Venus has phases Moon s surface has texture Sun rotates on an axis Foucault s Pendulum 1851 Proved Earth does rotate on its axis Copernicus hypothesis Isaac Newton Invented the calculus to simplify calculations Explained the orbital motion of planets as the interaction of inertia and gravity Orbital motion of planets Brief Review Sun is at the center of the solar system Published by Copernicus Supported by Galileo s telescopic observations of Jupiter and Venus Kepler determined orbits are ellipses Newton determined orbits created by interaction of inertia and gravity Constellations Star groups 88 recognized Stars names by brightness in them Orion Southern Sky Hunter White Tiger Star names in Orion Orion s place in the sky Bright star to lower left of Orion is Sirius

4 Sirius The Dog Star Brightest star in sky In Canis Major Arcturus Second brightest in northern sky Very large Rather cool Celestial position Earth turns pointed at Polaris Polaris and Big Dipper Polaris and Big Dipper Polaris and Big Dipper Polaris and Big Dipper each 8 hours Mean Solar Day What is a day? 4

5 Sidereal Day What is a day? What is a day? Mean Solar Day 24 hours Sidereal Day 23 hours, 56 minutes Plane of the ecliptic Incredibly distant stars closest is 60,000+ times further than Sun Animation of equinox and solstice Equinox and solstice related to the plane of the ecliptic Constellations on the ecliptic Earth Movement Revolution (orbit) around Sun Proposed by Copernicus: prediction that other planets would have phases like Moon Galileo found phases of Venus with telescope observations Rotation on axis Tested with pendulum swing over a 24-hour day, by Foucault, in 1851 Precession of axial direction Axial wobble-- precession Phases of Moon Animation link

6 Moon s Motion Takes 29 ½ days to proceed through its phases Synodic month Same side always faces Earth Rotates on axis once each 27 1/3 days Sidereal month No atmosphere extreme temperature variation: 127 o to -173 o C Sidereal vs. Synodic Month Sidereal with reference to a distant star Note the directions of view are parallel Lunar Eclipse Moon is in Earth s shadow during Lunar eclipse Solar Eclipse Solar Eclipse Eclipse geometry Earth is in Moon s shadow during Solar eclipse Moon s orbital plane around Earth at an angle to Earth s orbital plane around Sun Favorable for eclipse twice each year Moon 3475 km diameter Density ~ Earth s mantle Meteor Impact Compression Wave 6

7 Ejecta Rim Euler Crater Lunar Features Maria dark colored lowlands basalt Terra pale colored highlands anorthosite More craters indicated older surfaces No weathering and erosion like on Earth Maria Formation Flood Basalt Lunar Exploration Footprint in lunar regolith Moon formation Impact of asteroid 7

8 Ejecta from impact Coalesced to form Moon Moon was initially hot Moon by Apollo 17 Crew Right part of photo is dark side that cannot be seen from Earth Rayed Crater Lab Starts this Week Room NS 017 Down the south stairs Do not miss class the first week Buy your lab manual and read the first lab Do the prelab questions, because your lab instructor may want you to hand them in 8