Celestial Coordinate Systems K12 Coordinate Curriculum Karen Lancour

Celestial Coordinate Systems K-12 Coordinate Curriculum Karen Lancour Chandra Resource Agent and Mark Van Hecke Chandra Resource Agent

Night Sky • Sky appears as inside of a very large sphere • 88 constellations • Important to specify positions of objects in the sky in relation to one another • Coordinate systems

Appearance of the Night Sky • 3 -dimensional space appears as a 2 dimensional flat surface • Like a photograph or drawing • Different methods are used to determine distance from earth

Spherical Coordinates • Geographic & Celestial systems are spherical coordinate systems • 2 -dimensional systems • Fundamental Plane – Equator • Polar Axis • North & South Poles

Celestial Sphere • Huge, hollow, imaginary sphere • Infinite radius • Appears to rotate east to west • Earth is actually rotating west to east • Celestial Equator • North Celestial Pole and South Celestial Pole

Coordinate Systems – Different Reference Planes • Major Coordinates Systems • Different reference planes for Celestial Sphere • North-South Axis perpendicular to reference plane • Developed to facilitate different perspectives

Coordinates – Angular Measurements • Angular measurements • Latitude-like coordinates • Longitude-like coordinates • Zero point of longitude • Local meridian

Latitude and Longitude • Circles of latitude • Same latitude • Meridians of longitude • Same longitude • Zero point or prime meridian

Geographic System • Equator is 0 degrees • North Pole is 90 degrees N. • South Pole is 90 degrees S. • Greenwich meridian • 0 to 180 degrees east • 0 to 180 degrees west

Geographic Coordinates • 360 degrees of arc in a circle • Each degree has 60 minutes of arc • Each minute of arc has 60 seconds of arc

Geographic and Celestial Coordinate Systems Spherical Coordinate System Geographic Latitude Longitude Earth vs. Sky Based System Earth Great Circle of Fundamental Plane ( x-y plane) Equator Polar Axis (z axis) Horizon Alt-AZ Equatorial RA-Dec Ecliptic Longitude-Latitude Galactic Longitude-Latitude Earth – Local Sky Sky Astronomical Horizon Celestial Equator Ecliptic Galactic Plane North and South Earth Poles Zenith, Nadir North and South Celestial Poles North and South Ecliptic Poles North and South Galactic Poles Latitude-Like Coordinates N is + 90 S is – 90 Latitude (L, lat) Altitude (Alt) Latitude of Observer 0 to + 90 Declination (Dec) Ecliptic Latitude (Lat) Galactic Latitude (B) Longitude. Like Coordinates 360 Longitude (long) 0 to 180 E and 0 to 180 W Azimuth (AZ) N=0 , E=90 S=180 , W=270 Clockwise - LH (E to W) Hour Angle (HA) 0 – 24 Hrs. Clockwise - LH (E to W) Right Ascension (RA) 0 to 24 hr or 0 to 360 Counterclockwise. RH (W to E) Ecliptic Longitude (Lon) 0 to 360 Counterclockwise. RH (W to E) Galactic Longitude (L) 0 to 360 Counterclockwise-RH (W to E) Longitude (Zero Point) Prime Meridian North Point of Horizon Celestial Meridian Zero-Point Affixed to Earth Vernal Equinox Zero-Point Affixed to Sky Vernal Equinox Galactic Center Physical Basis Circumference of the Earth Direction of Gravity Earth’s Rotation Earth’s Orbital Motion Galactic Plane Used For: Determining Geographic Location Personal Observation and Some telescopes Setting of Telescopes To Track Objects Cataloging Positions and to Determine Locations Solar System Structure Milky Way and Other Galactic Structures 0 to 90 N 0 to 90 S Earth - Local Equatorial HA – Dec 0 to +90 (N) 0 to – 90 (S) 0 to +90 (N) 0 to – 90 (S)

Horizon System • For Personal Observation • Plane of local horizon • Zenith – 90 degrees above horizon • Nadir – 90 degrees below horizon • Horizon affected by the latitude of the observer.

Horizon System - Alt-AZ • Altitude – angle of object above the horizon • Azimuth – angle of object around the horizon clockwise from north

Horizon System - Alt-az • Altitude = 0 to 90 deg • Azimuth = 0 to 360 deg • North point defined • North = 0 deg • East = 90 deg • South = 180 deg • West = 270 deg

Horizon System • Observer’s view • Geography dependent • Altitude of NCP = latitude of observer. • Time and Season dependent • Same object has different coordinates at different times

Local Horizon – North Pole • View from North Pole • Zenith is North Celestial Pole • Local horizon is parallel to Celestial Equator • Stars rotate parallel to horizon (celestial equator) • Stars never rise and set

Local Horizon – Fairbanks • View from Fairbanks • Altitude of NCP equals latitude of observer. • Stars move parallel to the celestial equator • As one moves south, the NCP moves away from zenith toward the north point of horizon

Local Horizon - Seattle • View from Seattle • Stars rise in east and set in west • NCP moves further away from Zenith • Arc of star movement above horizon gets steeper

Local Horizon – Los Angeles • View from Los Angeles • 34 deg latitude • NCP at 34 deg above the horizon and 56 deg from zenith • All observers on 34 th parallel see the same star path • Star path is steeper

Local Horizon – Equator • View from equator • NCP is parallel to local horizon • Celestial Equator is perpendicular to local horizon • Zenith is on celestial equator • Stars rise and set perpendicular to horizon

Local Equatorial System • Stars rise in east and set in west • Motion of each star = parallel of declination on the Celestial Sphere • Celestial Equator is half way between NCP and SCP • Related to sidereal “star” time • Used to track motion of stars

Local Equatorial System “HA-dec” • Used to track objects • Latitude (Declination) is from the Celestial Sphere • Longitude uses Hour Angle • Follows star path from east to west • Is still time dependent at local meridian

Hour Angle • Time before and after star reaches zenith of its path

Equatorial System “RA-dec” • Used to catalog objects • Celestial Sphere • Celestial Equator • NCP and SCP • Declination (latitude) • Right Ascension (longitude) • Vernal Equinox

Declination • Angle above Celestial Equator • Parallels of Declination • CE = 0 deg • NCP = 90 deg • SCP = - 90 deg

Right Ascension • Hour circles or “meridians” • Equator = 360 arc deg circumference • Measured as hours (24 hours) • 1 hr = 15 arc degrees • Counterclockwise • 0 h = vernal equinox

Ecliptic From Earth, 1. Sun ‘s apparent path 2. Inclined 23. 5 deg to Celestial Equator 3. Vernal Equinox 4. Autumnal equinox 5. Winter Solstice 6. Summer Solstice

Ecliptic System • Earth revolves around sun = ecliptic • Ecliptic is fundamental plane • Axis of rotation • North Ecliptic Pole • South Ecliptic Pole • Planets have similar paths around sun

Ecliptic System & Planets • Used to study solar system • Except for Pluto at 17 degrees • Orbital Inclination within 7 degrees of Ecliptic Planet Orbital Inclination Mercury 7. 00° Venus 3. 39° Earth 0. 00° Mars 1. 85° Jupiter 1. 31° Saturn 2. 49° Uranus 0. 77° Neptune 1. 77° Pluto 17. 15°

Zodiac Constellations • As earth revolves, sky appearance changes. • Constellations around ecliptic called Zodiac

Galactic System • Study Milky Way and beyond • Plane of Galaxy • Inclined about 63 deg to Celestial Equator

Galactic System • Fundamental plane = plane of Milky Way • Galactic Equator • North Galactic Pole • South Galactic Pole • Center of Galaxy

Galactic Coordinates • • Galactic Latitude NGP = 90 deg SGP = -90 deg Galactic Longitude Counterclockwise 0 to 360 deg 0 = center of our galaxy

Coordinate Curriculum K-13 • • • Elementary Activities Middle School – Junior High Activities Senior High Activities Aligned to National Standards Involve science, geography, math, language arts, art, problem-solving • Introductory, skill-development, and assessment activities

Chandra Related to 1. Chandra Classroom-ready activities as Stellar Evolution, Variable Stars, Electromagnetic Spectrum, Imaging for Junior and Senior High 2. ds 9 and Visual Observatory 3. Chandra Sky Map

Science Olympiad Related to 1. Elementary Science Olympiad events in Starry, Starry Night and Map Reading 2. Reach for the Stars and Road Scholar for Division B 3. Astronomy and Remote Sensing for Division C 4. Trial events as Global Positioning Systems

Tools of Astronomy • 3 -d models, globes, grids, star maps, charts, graphs, quadrant, astrolabe, cross-staff, pinhole protractor, parallax, hand angles • binoculars, telescope, star lab, planetarium • Computer technology as Chandra Sky Map, ds 9, Remote Sensing, GPS, Sky Map programs • Coordinates, measurements, angles, relative positions, times, navigation

Sample Activity • Chandra’s Stellar Evolution poster recently in the Science Teacher magazine • Map projections • Coordinate grids • Problem-solving

Chandra’s Stellar Evolution Poster

Map Projections • Attempts to represent sphere on flat map • Always some distortion • Types to emphasize specific regions of sphere

Sky Maps

Whole Sky (Aitoff) Projection • Whole sky projection is popular with astronomers • Projections for Equatorial, Ecliptic, or Galactic Systems

Different Reference Planes

Mercator - Equatorial Region • Shows the regions near the equator • Less distortion when put on a flat surface • Regions north and south of equator

SC 001 Equatorial Region • Using Equatorial (RA-dec) System

SCOO 1 - Declination • Declination (latitude-like) from +60 deg above to -60 deg below celestial equator. • Degrees, minutes, and seconds of arc

SC 001 – Right Ascension • Right Ascension (longitude-like) from 0 -24 hrs. • Hours, minutes, seconds • Hour circles “meridians” of Right Ascension

Polar Region • Circumpolar region • North version • South version

SC 002 - Declination • North Version • 30 – 90 deg declination • Parallels of declination • Equatorial region not visible

SC 002 – Right Ascension • North polar version • RA = 0 to 24 hours • Hour circles or “meridians” • Note the chart symbols for objects and magnitude

Coordinates Polaris Equatorial J 2000 B 1950 RA Dec Galactic L Ecliptic B Lon Lat 02 h 31’ 49. 08 89 o 15 ’ 50. 8 “ “ 01 h 48 ’ 56. 79 “ 89 o 01’ 43. 4 123 o 16’ 50. 0 26 o 27 ’ 41. 0 88 o 34’ 03. 3 “ “ 66 o 06’ 05. 3 37. 954516 o 27. 236644 o 89. 028733 o 66. 101463 o 89. 264109 o 123. 280542 o 26. 461395 o 88. 567594 o “ • Longitude-like coordinate listed first • Latitude-like coordinate listed second • Equatorial coordinates will reflect epoch – B 1950 or J 2000