1. Astronomy – The Original Science

2. Lets talk about calendars….

3. Ancient Calendars Based on observations of the sky
Ancient Mayans – used the cycles of the sun, moon and Venus
Ancient Chinese – used the moon’s phases and positions in the sky
Ancient Egyptians – used the sun
Ancient Hebrews – used the moon and sun

4. Getting closer to our Modern Calendar
Early Roman calendar
Had 365 days in a year
Had 7 days in a week
Eventually the seasons began to shift

5. Getting closer to our Modern Calendar
Julian calendar
Had days in a year
Added an extra day every 4 years (Leap year)
Gregorian calendar
Had days in a year
Dropped 10 days from the year 1582
Restricted leap years to years divisible by 4 but not 100
Scientists calculate this calendar will be accurate for 3,000 years

6. The Beginnings of Astronomy
Recorded astronomical observations date back to 6,000 to 7,000 years ago
Stonehenge is probably one such place
Built between 3000 B.C. and 1500 B.C.

7. Early Astronomers Ptolemy
In 140 A.D. he theorized the Earth was the center of the solar system and all celestial bodies revolved around it Geocentric

9. Early Astronomers Copernicus
In 1543 created a new theory about the movement of celestial objects
He theorized the sun is the center of the solar system not the Earth Heliocentric

10. Early Astronomers

11. Early Astronomers Brahe Disputed Copernicus’ theory
Believed the Earth was the center, and the solar system revolved around the Earth

13. Early Astronomers Kepler
Sided with Copernicus, but discovered the orbits of the planets are elliptical not circular

14. Early Astronomers Galileo
In 1609, he became the first person to use a telescope to observe celestial bodies
Contributions
4 moons of Jupiter
Craters/mountains on the moon
Sunspots on the sun
Phases of Venus
Showed planets as more than dots of light but actual physical bodies like the earth

18. Early Astronomers Sir Isaac Newton
Explained why planets orbit the sun and moons orbit planets Gravity

19. Mapping the Stars
Constellations - sections of the sky that have recognizable star patterns.
Different cultures had different names
There are a total of 88 constellations
The constellations change from season to season

21. Common Constellations

22. Aries

23. Cancer

24. Aquarius

25. Finding stars in the Night Sky
Concepts that describe the location of a celestial object
Altitude – the angle between the object and the horizon
Zenith – an imaginary point directly over the observer……. Always 90 degrees
Horizon – the line where the sky and Earth appear to meet …….. Always 0 degrees

27. Astrolabe

29. Sextant

30. Describing a Star's Position
Celestial equator – an imaginary circle created by extending the Earth's equatorinto space.
Right Ascention – hours eastward from the vernal equinox.
Declination – defrees north and south of the celestialequator.
Ecliptic- the apparent path the sun takes across the sky

31. Circumpolar Stars
Circumpolar stars – stars that can be seen any time of the year and at any time of night.
* found near the north and south pole areas
Animation

32. Telescopes and the Electromagnetic Spectrum Section 3

33. Optical Astronomy Optical telescope
Collects visible light for closer observation
2 lenses
Objective lens: collects light and forms an image at the back of the telescope
Eyepiece: magnifies the images from the objective lens

34. Without an optical telescope you can see about 6,000 stars
With an optical telescope you can see millions of stars

36. Refracting Telescopes
Use a set of lenses
Curved objective lens bends light and focuses it to the eyepiece
Eyepiece lens magnifies the image
Disadvantage: if the curved lens is too large the glass will sag and distort the image
Disadvantage: imperfections in glass can distort image

38. Reflecting Telescopes
Use curved mirrors
Large curved mirror reflects light to a focal point
The focal point reflects light to the eyepiece
Advantages:
Mirrors can be made very large
Mirrors are polished on one side to prevent flaws from glass
Mirrors reflect light of all colors to the same place

39. Optical Telescopes Continued

40. Hubble Telescope

41. What do you think would be an advantage to having a telescope in space compared to one on Earth?

44. Electromagnetic Spectrum
Made of all the wavelengths of electromagnetic radiation
Visible light is only a small portion
Earth’s atmosphere allows these in….
Infrared, visible light, some ultraviolet, and radio
Earth’s atmosphere blocks….
Gamma, X rays, some ultraviolet
Astronomers can detect….
Visible light, infrared, and radio waves

46. Non Optical Telescopes
Radio telescope -n telescope designed to listen for radio waves (sound) coming from space.
X-ray Telescope – designed ton detect x rays that are coming from space. This telescope can only be used in space because the Earth's atmosphere blocks all x rays.
Infrared Telescope – a telescope that uses infrared light to detect celestial bodies.

47. Radio Telescope

48. VLA (Very Large Array)