1. INTRODUCTION TO ASTRONOMY
Astronomy: is a science that studies everything outside Earth’s atmosphere such as planets, stars, asteroids, galaxies, and the properties and relationships of those celestial bodies.
Brief intro

2. Astrology – the study of the movements and relative positions of celestial bodies interpreted as having an influence on human affairs and the natural world.

3. ASTROPHYSICS - the branch of astronomy concerned with the physical nature of stars and other celestial bodies, and the application of the laws and theories of physics to the interpretation of astronomical observations
INTRO

4. Universe: the totality of all space, time, matter, and energy
Expansive ---Massive----Large
Universe -----Galaxy -----Solar system
How Big

5. Milky Way is a Spiral Galaxy can Expand for 100,000 LY across What does this mean? Light Year = distance traveled by light in one year. One LY = about 9 trillion KM Rate: 300,000 KM/sec Sun’s light takes 8.3min to reach us Sun is 93 million miles away Video 2: light year explained

7. 10 trillion kilometers 103 = 1,000 thousand 106 = 1,000,000 million
109 = 1,000,000,000 billion
1012 = 1,000,000,000,000 trillion
If you were to count out 1,000 at a rate of 1number per second it would take 16min
1 million would take 2 weeks (16hrs per day)
1 billion = 50 years
Video 2: How big is the universe

8. How “big” is the Earth?
TINY?

9. Celestial Sphere
Celestial sphere – imaginary sphere surrounding Earth to which objects in the sky
were once considered attached
animation of sphere

10. Constellations appear to move across sky from east to west (88 constellations)
Polaris – North Star
Axis for which the celestial sphere rotates
Video 3 Constellations

12. Constellations today???

15. Zodiac - 12 constellations which the sun passes as it moves along ecliptic –
that is, the constellations we would see looking in the direction of the sun if they weren’t overwhelmed by the sun’s light

16. Celestial coordinates
Latitude= declination – degrees N and S of celestial equator (o)
Longitude= right ascension – measured in angular units called hours, minutes, and seconds starting point is the sun

18. Video 4
The Universe - beyond the Big Bang - 85 min
Beyond

19. Earth’s Orbital Motion
Time is measured by the Sun
Sunrise to sunset = 24 hour solar day
Diurnal motion - apparent daily progress of sun and stars across sky
diurnal motion

20. Sidereal day – day measured by stars, celestial sphere shifts daily causing day measured by stars different from
a day measured by
earth’s rotation
solar vs sidereal

21. Reason for difference between days
Earth moves with two motions simultaneously – Rotation & Revolution
Rotates on its central axis while at the same time revolves around sun
Noon on one day is
slightly later at noon
the next day

22. Seasonal changes Earth revolves 1 degree per day.
Every few months we see different group of stars and constellations.
Ecliptic – apparent motion of the sun the sky traces out on a celestial sphere

23. Solstices
Northern Hemisphere’s summer: Earth’s axis is pointed toward the sun

24. June 21- Summer Solstice, longest day of the year

25. Northern Hemisphere Winter: Earth’s axis is pointed away from sun

26. Winter Solstice
December 21 - Shortest day in Northern Hemisphere

27. Equinoxes
Autumnal and Vernal Equinox for Northern hemisphere occur when north axis is not pointed away or toward the sun

28. Reason for Seasons Revolution Parallelism 23.5 degree Earth’s tilt
Bill Season

29. Earth’s Long Term orbital changes
Sidereal year – time required for Earth to complete exactly one orbit around the Sun, relative to the stars
One Sidereal Year = solar days long
20 minutes longer than tropical year
Tropical year – interval of time from one vernal equinox to next = solar days

30. Difference between tropical and sidereal year
Precession – earth's axis changed direction over time caused by gravitational pull of moon and sun.
Precession

31. introduction to pltomey and others