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Observational Astronomy

Delve into the realm of observational astronomy from space with Hubble Space Telescope, uncovering nebulae, spiral galaxies, and the vast Universe's mysteries. Explore cosmic epochs, the Milky Way, stellar distances, and the intricacies of measuring celestial objects. Learn about parallax, distance scales, geocentric vs. heliocentric models, and celestial navigational basics. Understand the celestial sphere, equinoxes, and coordinate systems in the sky, connecting Earth's movements with celestial bodies.

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Observational Astronomy

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  1. Observational Astronomy

  2. Astronomy from spaceHubble Space Telescope

  3. Atomic Energy Theory of Relativity

  4. Nebulae – stellar nurseries

  5. Spiral Galaxy and Nucleus

  6. Hubble Deep Field: 10,000 Galaxies

  7. Universe: Past and Present

  8. Cosmic Epochs and Evolution

  9. Relative Sizes in astronomyFrom very small to very large(meters)

  10. Some Essential Numerical Figures • Radius of the Earth = 6500 Km • Speed of light – 300,000 Km/sec • Astronomical distances are so large that we use the speed of light to measure them • Mean Earth-Sun Distance – 150 million Km = 1 Astronomical Unit (AU) = 8.3 Light Minutes • 1 Light Year (Ly) = 9.5 trillion Km = 63,240 AU • Parsec = 3.26 Lys (parallax angle unit)

  11. The Milky Way100,000 Lys Across

  12. Stellar Constellations Connect bright stars to discern some shape

  13. Ancient Figures and Constellations

  14. The Orion Constellation

  15. The North Star (Polaris)

  16. The Summer Triangle

  17. Winter Triangle of Bright Stars

  18. The Distance Scale http://htwins.net/scale2/

  19. LINEAR AND ANGULAR SIZE OF OBJECTS •  angle subtended by the object at the observer; the farther the object, smaller the a

  20. Angular size of moon = 30’ 1 Degree = 60’ (minutes) = 60 x 60 = 3,600 ‘’ (seconds) What is the angular size of the Sun? How large does the Sun appear ?

  21. Angular ‘distance’ between stars While angular distance can be measured by observations, actual distances are difficult to measure (What do we need?)

  22. Orbital and angular motion of the Earth The Earth moves one degree in its orbit around the Sun each day. Why?

  23. Parallax: Measurement of Distance Apparent movement due to viewing position No actual motion of the viewed object Difference in angle between line of sight from the Earth and from the Sun (half the diameter or the radius of the Earth’s orbit, 1AU) Since the parallax of stars is very small, it is measured in parsec (parallax second) distance d= 1/p OR p = 1/d 1 parsec = 3.26 LY = 206,265 AU

  24. Distance Measure in Astronomy:The Parallax Method Parallax is the change in angle due to motion Circle = 360o (degrees) 1 degree = 60’ (minutes) 1 minute’ = 60” (arcseconds) 1 AU 90 Measure of distances in angles: The distance d of an object that makes an angle of 1” as the Earth moves to opposite sides of the Sun d d a a d (pc) = 1 / a 1 parsec (pc) = 3.26 Light Years (Ly) Object at a distance of 1 pc

  25. Stellar and Astronomical Distances • 1 parsec (pc) = 3.26 LY = 205,000 AU • The stars are very far away • Nearest Star Alpha Centauri  4.3 LY, more than 1 pc ! The parallax angle a is less than one arcsecond (“) • That’s why the Greeks could not see the stars move • Galaxies have been seen up to more than 10 billion Lys away

  26. Night Sky ExposureGeocentric or Heliocentric ?

  27. Earth’s rotation and the Sky

  28. Daily Rotation of the Earth and Stars

  29. Annual Revolution of the Earth around the Sun and position of stars

  30. Location of Heavenly Objects • How do you locate places on the Earth? • Latitude and Longitude • Latitude: angle measured from the Equator (0o), up or down, N-S • Longitude: angle measured from the Prime Meridian, E-W, 0o – 180o • How would you find location in mid-ocean ? • First rule of navigation: Lookup angle of Polaris  Latitude • How do you find the longitude? Clock ?

  31. Celestial Map and Celestial Coordinates Analogous to Latitude and Longitude on The Earth – Measured in Degrees Celestial Poles And Equator – Extension of the Earth’s poles And equator Celestial Equator is the extension of the Earth’s Equator up to the CS

  32. Ecliptic and the Celestial Equator Ecliptic is the apparent Path of the Sun on the Celestial Sphere Autumn Equinox Summer Solstice The Ecliptic and the Celestial Equator Intersect at Vernal (Spring) and Autumn Equinoxes At an angle of 23.5o to each other Vernal Equinox Winter Solstice

  33. THE CELESTIAL SPHERE:Coordinates and Map of Objects in the Sky Star Declination d: “celestial latitude” Right Ascension a: “celestial longitude” Star at(a,d) “celestial coordinates” Vernal Equinox: Position of Sun In the Sky on the first day of spring; Day = Night a = 0

  34. Apparent Rotation of Celestial Sphere

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