Transcript For stars
Charting the Heavens Day 2 Going to the Stars Road at Logan Pass, Glacier National Park. This picture shows our view of the Milky Way in the night sky. Constellations – the 88 semi-rectangular regions that make up the sky • Northern constellations have Latinized Greek-mythology names: – Orion, Cygnus, Leo, Ursa Major, Canis Major, Canis Minor • Southern constellations have Latin names: – Telescopium, Sextans, Pyxsis Use the Summer Triangle to find constellations during summer evenings Use the winter triangle to find constellations during winter evenings Anyone recognize any shapes here? Star Names Betelgeuse Aldebaran Rigel SIRIUS Using Orion in to find other objects Pleiades Aldebaran Great Orion Nebula Sirius Pleiades Seven Sisters Subaru Use the Big Dipper in the northern sky as a way to find other groups of stars Astrology: The belief that the positions of the stars and planets as seen from Earth impact human events. Turn to your neighbor and discuss what Astrological sign you have been told you are. Sun signs • Are based on which constellation the sun was on the day of your birth • Moon sign: which constellation is the moon in at the time of your birth • Most astrological signs are incorrectly shown because they are based on your birth where the sun was during Greek times. Your Birth Sign ROUGHLY, it is the constellation that the Sun is covering up during the day you are born if you were born 2000 years ago. Ophiucus • • • • • The thirteenth zodiac sign Sun passes through Ophiucus’ foot November 30-Dec. 18 He is the serpent bearer also used as the medical symbol Local co-ordinate systems • Based on the objects above the plane of the horizon – Altitude is the angle above the horizon star altitude horizon NORTH STAR HAS AN ALTITUDE OF 0° IF YOU ARE ON THE EQUATOR THE ALTITUDE OF THE NORTH STAR=YOUR LATITUDE ON EARTH!!! Altitude • NORTH STAR HAS AN ALTITUDE OF 0° IF YOU ARE ON THE EQUATOR • THE ALTITUDE OF THE NORTH STAR=YOUR LATITUDE ON EARTH!!! A ROUGH WAY TO ESTIMATE ALTITUDE • PINKY =1° • 3 FINGERS=3° • FIST = 10° Figure out the altitude of the American flag in the room. How about the globe in the back of the room? Local Co-ordinate System • Azimuth – starts with north a 0° and south is 180° • Zenith is 90° zenith North Star • Even though Polaris is currently the North star, it doesn’t lie due North –and eventually will move and Vega will be our North Star, Why do you think this is happening? Discuss with your elbow partner, write down your thoughts on your white board, be ready to defend them. The North Star • Polaris, our current North Star is the 49th brightest star in the night sky!!!!! • To find it, locate the cup of the Big Dipper to the handle of the Little dipper. • It doesn’t appear to move in the night sky but the other stars rotate around it • North pole and Polaris are about 1° off from one another CIRCUMPOLAR STARS • STARS THAT NEVER GO BELOW THE HORIZON – CAN ALWAYS BE SEEN AT NIGHT – http://upload.wikimedia.org/wikipedia/commons /2/21/Zirkumpolar_ani.gif Earth’s Orbital Motion: what causes the North star to change? Precession: rotation of Earth’s axis itself; makes one complete circle in about 26,000 years With your table group try out the top, how does the top model precession? Precession • Wobbles in a 26,000 year cycle • Wobble is between Polaris, Vega and Thuban • Changes the position of the Vernal Equinox which will also change the co-ordinates of the stars Celestial Sphere The celestial sphere: Stars seem to be on the inner surface of a sphere surrounding the Earth They aren’t, but they can use two-dimensional spherical coordinates (similar to latitude and longitude) to locate sky objects Celestial Coordinates Right Ascension • Like longitude • Use units of time-hours instead of degrees • 0 hour is the vernal equinox Declination • Like latitude except use +/instead of north and south Terms related to the Celestial Sphere Terrestrial System • South Pole • North pole • Equator • Latitude – 0° at the Equator • Longitude – 0° at the Prime Meridian Celestial System • South Celestial Pole • North Celestial Pole • Celestial Equator • Declination 0° at celestial Equator • Right Ascension – 0 Hours at Vernal Equinox Angular Measure: A way to describe the amount of sky a celestial body takes up • Full circle contains 360° (degrees) • Each degree contains 60′ (arc-minutes) • Each arc-minute contains 60′′ (arc-seconds) • Angular size of an object depends on its actual size and distance from viewer What do you think? • Do the stars stay in the same position in the sky all day/night long? • Do we see the same stars all year round every night? What do you think? • What causes the stars move? • Do the stars actually move in the way they appear from Earth? • Is the daily motion of the Sun different from the stars? Consider the dome of the sky over our heads…. mixing bowl Consider the dome of the sky over our heads…. inverted mixing bowl …. Imagining a spinning Celestial Sphere surrounding Earth aids in thinking about the position and motion of the sky Imagining a spinning Celestial Sphere surrounding Earth aids in thinking about the position and motion of the sky Animation! Celestial Sphere Rotation Celestial Sphere Rotation Star B Star B 2 2 Star A Star A North Star 1 2 1 2 Celestial Sphere Celestial Sphere 3 3 1 1 4 4 3 3 Earth’s Equator 4 4 Celestial Sphere Rotation Celestial Sphere Rotation Figure 1 Figure 2 Horizon Is the horizon shown a real physical horizon, or an imaginary plane that extends from the observer and Earth out to the stars? Celestial Sphere Rotation Star B 2 Star A 1 Can the observer shown see an object located below the horizon? 2 Celestial Sphere Celestial Sphere 3 1 4 3 Is there a star that is in an unobservable position? When a star travels from being below the observer’s horizon to being above the observer’s horizon, is that star rising or setting? 4 Celestial Sphere Rotation Figure 2 Horizon Tutorial: Position – p.1 • Work with a partner • Read the instructions and questions carefully • Talk to each other and discuss your answers with each another • Come to a consensus answer you both agree on • If you get stuck or are not sure of your answer ask another group • If you get really stuck or don’t understand what the Lecture Tutorial is asking as one of us for help Did you get the Key Ideas from the Position Lecture Tutorial? Celestial Sphere Rotation Star B In what direction is the observer facing? 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 4 1. 2. 3. 4. toward the South toward the North toward the East toward the West Celestial Sphere Rotation Figure 2 Horizon Imagine that from your current location you observe a star rising directly in the east. When this star reaches its highest position above the horizon, where will it be? A. B. C. D. high in the northern sky high in the southern sky high in the western sky directly overhead Celestial Sphere Rotation Where would the observer look to see the star indicated by the arrow? A. B. C. D. High in the Northeast High in the Southeast High in the Northwest High in the Southwest Star B 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 4 Celestial Sphere Rotation Figure 2 Horizon Motion Earth’s Orbital Motion • Daily cycle, noon to noon, is diurnal—solar day and is based on the sun’s position. • Stars aren’t in quite the same place 24 hours later, though, due to Earth’s rotation around Sun; when they are once again in the same place, one sidereal day has passed SEASONAL CHANGES IN OUR NIGHT SKY • Summer triangle: Vega, Denab, Altair • Winter: Orion, Sirius (Dog Star) • The change occurs about 1°/night Earth’s Orbital Motion Seasonal changes to night sky are due to Earth’s motion around Sun Earth’s Orbital Motion The Twelve constellations (some say thirteen) that the Sun moves through during the year are called the zodiac; The view of the night sky changes as Earth moves in its orbit about the Sun. As drawn here, the night side of Earth faces a different set of constellations at different times of the year. The 12 constellations named here make up the astrological zodiac. Earth’s rotation causes the Sun, Planets, Moon and stars to appear to move when viewed from Earth Nightly Motion of the Stars • Imagine looking toward the East as a star rises above your horizon - what does it do after that? Nightly Motion of the Stars Celestial Sphere Rotation Star B 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 4 Celestial Sphere Rotation Figure 2 Horizon Nightly Motion of the Stars • For stars (the Moon and planets) that appear in the southern sky: Stars first rise near the eastern horizon, move upward and toward the south, and then move down and set near the western horizon. What direction is the observer facing in this picture? Nightly Motion of the Stars • Imagine looking toward the North. What do stars appear to do over the course of an evening? Nightly Motion of the Stars Celestial Sphere Rotation Star B 2 Star A 1 2 Celestial Sphere Celestial Sphere 3 1 4 3 4 Celestial Sphere Rotation Figure 2 Horizon Nightly Motion of the Stars • Looking North: Stars appear to move counterclockwise around the stationary North Star (Polaris) – we call these circumpolar stars. Looking North: Circumpolar Stars – Circumpolar stars seem to move counter-clockwise around the stationary North Star. – These constellations and stars are visible any night of the year in the NORTHERN sky because they never rise or set! – Examples: Ursa Major, Ursa Minor, Draco, Cepheus, and Cassiopeia What happens over time in the Northern Sky? Tutorial: Motion – p. 3 • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group. • If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help.