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Astronomy (100)
ASTA01H3 (100)
Lowman (10)
Lecture 2

lecture 2-3


Department
Astronomy
Course Code
ASTA01H3
Professor
Lowman
Lecture
2

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Lecture 2:
If Sun was a basketball = Moon is ball point = Earth is 4 time larger than ball
point
1 Sun radius = 100 Earth radius
Universe: The totality of all space, time, matter and energy, dark matter,
dark energy
1 Light Year = 10 trillion km or 1013km
It takes 8 18 seconds minutes from light to travel from the sun to the Erath
This galaxy is 100 000 light years across
This galaxy is called a spiral arm galaxy
Stars we can see with the naked eye are all members of the milky way galaxy
Polaris star is due North
Stars that appear close to the sky may not be close in space
1o = 60’ = 3600’’ 1296000’’=360o
Moon & Sun have angular diameter of 0.5 degrees
Declination: degrees north or south of celestial equator
Right ascension: Hours, minutes and seconds eastward from vernal equinox.
Celestial equator ,pole= earth equator, pole
Right ascension is time dependent. The position of vernal equinox drifts each
year due to precession of the pole
Lecture 3:
Total Eclipse: Sun is completely covered by the moon
Annular eclipses occur when the Moon is further from the Earth
Motion of the Moon and Length of a Month
oSidereal Month: Measure of the rotation of the Moon to sidereal day
(meaning 360 rotation relative to a fixed point i.e. star)
o1 Sidereal Month takes 27.3 days
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