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

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• 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

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

SC001 Equatorial Region

• Using Equatorial (RA-dec) System

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

Polar Region

• Circumpolar region• North version• South version

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