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
SphericalCoordinate
System
GeographicLatitude -Longitude
HorizonAlt-AZ
Local EquatorialHA – Dec
Equatorial RA-Dec
Ecliptic Longitude-Latitude
Galactic Longitude-Latitude
Earth vs. SkyBased System
Earth Earth - Local Earth – Local Sky Sky Sky
Great Circle ofFundamental Plane( x-y plane)
Equator
Astronomical Horizon
Celestial Equator Celestial Equator Ecliptic Galactic Plane
Polar Axis (z axis)
North and SouthEarth Poles
Zenith, Nadir North and SouthCelestial Poles
North and SouthCelestial Poles
North and South Ecliptic Poles
North and South Galactic Poles
Latitude-LikeCoordinatesN is + 90S is – 90
Latitude (L, lat) 0 to 90N 0 to 90S
Altitude (Alt)Latitude of
Observer 0 to + 90
Declination (Dec) 0 to +90 (N) 0 to – 90 (S)
Declination (Dec) 0 to + 90 (N) 0 to – 90 (S)
Ecliptic Latitude (Lat) 0 to +90 (N) 0 to – 90 (S)
Galactic Latitude (B)
0 to +90 (N) 0 to – 90 (S)
Longitude-Like
Coordinates 360
Longitude (long)0 to 180 E and 0 to 180 W
Azimuth (AZ)N=0, E=90S=180, W=270Clockwise - 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 360Counterclockwise-
RH (W to E)
Ecliptic Longitude(Lon)
0 to 360Counterclockwise-
RH (W to E)
Galactic Longitude(L)
0 to 360Counterclockwise-RH (W to E)
Longitude (Zero Point)
Prime Meridian North Point ofHorizon
CelestialMeridian Zero-PointAffixed to Earth
Vernal Equinox Zero-Point Affixed
to Sky
Vernal Equinox Galactic Center
Physical Basis Circumferenceof the Earth
Direction ofGravity
Earth’s Rotation Earth’s Rotation Earth’s OrbitalMotion
Galactic Plane
Used For: DeterminingGeographicLocation
PersonalObservation and Some telescopes
Setting ofTelescopesTo Track Objects
CatalogingPositions and to DetermineLocations
Solar SystemStructure
Milky Way and Other Galactic Structures
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 34th 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
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• 0h = 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. ds9 and Visual Observatory
3. Chandra Sky Map
Science Olympiad
Related to 1.Elementary Science Olympiad events in
Starry, Starry Night and Map Reading2.Reach for the Stars and Road Scholar for
Division B 3.Astronomy and Remote Sensing for
Division C4.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, ds9,
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
Map Projections
• Attempts to represent sphere on flat map
• Always some distortion
• Types to emphasize specific regions of sphere
Whole Sky (Aitoff) Projection
• Whole sky projection is popular with astronomers• Projections for Equatorial, Ecliptic, or Galactic Systems
Mercator - Equatorial Region
• Shows the regions near the equator
• Less distortion when put on a flat surface
• Regions north and south of equator
SCOO1 - Declination
• Declination (latitude-like) from +60 deg above to -60 deg below celestial equator.
• Degrees, minutes, and seconds of arc
SC001 – Right Ascension
• Right Ascension (longitude-like) from 0-24 hrs.• Hours, minutes, seconds• Hour circles “meridians” of Right Ascension
SC002 - Declination
• North Version• 30 – 90 deg
declination• Parallels of
declination• Equatorial region not
visible
SC002 – Right Ascension
• North polar version • RA = 0 to 24 hours• Hour circles or
“meridians” • Note the chart
symbols for objects and magnitude
Coordinates
EquatorialJ2000
EquatorialB1950 Galactic Ecliptic
RA Dec RA Dec L B Lon Lat
02h31’ 49.08 “ 89o15 ’50.8 “ 01h 48 ’56.79 “ 89o 01’43.4 “ 123o16’ 50.0 “ 26o27 ’41.0 “ 88o34’03.3 “ 66o06’05.3 “
37.954516o 89.264109o 27.236644o 89.028733o 123.280542o 26.461395o 88.567594o 66.101463o
• Longitude-like coordinate listed first• Latitude-like coordinate listed second• Equatorial coordinates will reflect epoch – B1950
or J2000
Polaris
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