Astronomy 1 - September 14, 1998 Lecture

  1. Astronomical Units and Sizes
  2. Scientific Notation and Mathematics
  3. Angular Measurements
  4. Rotation and Revolution of the Earth
  5. Earth Coordinates (aside - Global Positioning Systems)
  6. Celestial Coordinates, Stars and Constellations

READ: Chaisson and McMillan - Chapter 1 (including More Precisely 1-1, 1-2)
Read or be aware of information in Appendices 1, 2, 3 
NOTICES
 	Halifax Centre of the Royal Astronomical Society of Canada
	N.S. Museum on Summer Street (Open to the Public)
	8 pm Friday, September 18, 1998
	Speaker: Dr. David Turner, Astronomer, St.Mary's University
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EQUIPMENT AND VISUAL AIDES
-- Transparencies: (Kaler, Chaisson, and my set)
			Horizon Coordinates 
          			Celestial Coordinates
          			Star Chart showing Equator/ecliptic
				Atlases of Constellations
				Precession of Coordinates
-- Earth Centred Universe (on AXE x:\public\apps\ecu\ecu.exe)
-- Ball with rotation Axis
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LECTURE 
	
	-- Units of Measurement/ light year, AU, time, Mass
			DISTANCE
		Earth R = 6371 km (average)
 		Sun = 700,000 km
		Astronomical Unit = 149,600,000 km (radius of Earth orbit around Sun)
			TIME
		Year = 365.25 days x 24 hr/day x 3600 sec/hr = 31,600,000 seconds
		Age of the Universe = 10,000,000,000 years = 1010 years 
				= 10 Billion years
			SPEED
		Equatorial Speed of Earth = 2 x 3.1416 x 6371 km /24 hr = 961 km/hr
		Satellite in Low Earth Orbit (period = 90 minutes) 
			speed = (2 x 3.1416 x 6371 km) / (1.5 hr) = 15,400 km/hr = 4.27 km/s
		Orbit Speed of Earth = 2 x 3.1416 x 149,600,000/(31,600,000) = 29.8 km/s
		Speed of Light = c = 299,792 km/s (use 300,000 in most cases)
 			DISTANCE
		Light Year  (approximately stellar separations)
			ly = 300,000 km/s x 31,600,000 s/year = 9.47 x 1012 km
				(note: approximately 1013 km) 
				= 9.47 x 1012 km/149,600,000 km/AU = 63,300 AU
		Size of Galaxy = 100,000 ly
		Size of Clusters of Galaxies ~ 10,000,000 
		Separation of Clusters of Galaxies ~ 30,000,000 ly
		Size of Universe = 10,000,000,000 ly 
			= 1010 ly x 63,300 ly/AU = 6 x 1014AU
	-- Scientific Notation Mathematics
		POWERS
		1/10n = 10-n
		10n x 10m = 10m+n
		10n/10m = 10n-m	
		(a x 10n)x(b x 10m) = (a x b) x 10n+m	
		(a x 10n)/(b x 10m) = (a/b) x 10n-m
		LOGARITHM
		loga(an) = n		(named: log base a) 
		e = 2.718		(basis for 'natural' logarithm)
		loge(A) = ln(A)
		log10(a x 10n) = log10(a) + n
		log(an) = n log(a)
		ln(an) + ln(am) = n ln(a) + m ln(a) = (n+m)ln(a) = ln(an+m) 
		ln(a) + ln(b) = ln(a x b)
	-- Angles (degrees, minutes, seconds, radians)
			Circular Measure - the radian
          		Skinny Triangle Approximation
				angle (radian) = (linear size)/distance
			Approximation good up to 10 degrees (1% error at 10 degrees)
          		Example 1: Small Angles (15 cm diameter head lamp of car at 1 km)
				15 cm at 1000 m: angle = 0.15m/1000m = 0.00015 radians
				1 radian = 57.3 degrees = 57.3 x 60 'arc/deg = 3438 'arc
					= 57.3 x 3600 "arc/deg = 206,300 "arc
				headlight = 0.00015 radian x 3438 'arc/radian = 0.52 'arc
				Compare: Moon, Sun = 30 'arc diameter
				Eye resolving power = 1'arc
			Example 2: 	Star size: dia = 106km
					Distance = 10 ly ~ 1014 km
				star angular size = 106/1014 = 10-8 radians
					= 206,300 "arc/radian x 10-8 radians = 0.002 "arc
				Compare Resolution of 
					Standard Large Earth-based Telescope = 0.5 "arc
					Hubble Space Telescope = 0.01 "arc
					
          -- Estimation of angles in the sky(HAND METHOD)
        		Open Hand = 20
          		Fist = 9
          		Pointer Finger Joints = 6, 4, 3 degrees
          		Examples: (use ECU to show these) 	
				Big Dipper (top of bowl) to Polaris = 28 deg
					(Bowl Edge = 5 deg)
	  -- Earth Coordinates System (Latitude and Longitude)
			Rotation Period (24 hours Solar) and Direction (West to East)
			Rotation Axis Tilt (relative to Orbital Plane of Earth) = 23.5o
			(Equatorial plane tilted 23.5o to Orbit Plane)
				-Seasonal Change
				-Precession of Axis of Rotation due to Moon and Earth
					pull on equatorial bulges
          		Terms:	meridian
        (overhead)- see 'More Precisely 1-2
          		Celestial Equator, Ecliptic
				Path of Sun through the Stars = Ecliptic
				Earth equator projected on Celestial Sphere = Celestial Equator
				Sun 	March 21 - on equator (moving north)
					June 21 - maximun north of equator
					Sept 22 - on equator (moving south)
					Dec 21 - maximum south of equator
          		Vernal Equinox and zero hours Right Ascension
          		Equator and Declination	
          		Example: Star's RA/dec from transparency
          			 locate star using RA/dec 
			[examples with ECU - eg.]


          NEXT TIME - Celestial Star Globe
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