International Astronomical Union / Office of Astronomy for Development

1. International Astronomical Union / Office of Astronomy for Development www.astro4dev.org Kevin Govender – kg@astro4dev.org J.-C. Mauduit – jcm@astro4dev.org OAD IAU: International Astronomical Union NRF: National Research Foundation

2. From planets to superclusters of galaxies The different scales of the Universe Dr. Jean-Christophe Mauduit IAU Office of Astronomy for Development National Research Foundation

3. From the Solar system to the Milky Way…

6. The blue planet: Earth Radius ~ 6 378 km Atmosphere< 600 km Troposphere < 15 km

7. From the Earth to the Moon Earth-Moon distance: 384 401 km 30 Earth planets one after the other ~ 2 months of high speed train Apollo missions : less than 2 days (Speed of ~ 8000 km/h to ~ 40 000 km/h)

8. Space shuttle take-off

10. The crescent Earth from the Moon

11. You are here ! As imaged from the red planet, Mars

12. Our star, the Sun Characteristics: Radius~ 695,000 km Mass = 1.9891×1030 kg Volume = 1.41×1018 km³ Luminosity = 3.827×1026 W Comparison to Earth: 109 × Earth 332 950 × Earth 1 300 000 × Earth 9.15 × 1016 tons of TNT / s

13. Sun 0 109 Mercury 0,39 0,38 Venus 0,72 0,95 Earth 1,0 1,00 Mars 1,5 0,53 Jupiter 5,2 11 Saturn 9,5 9 Uranus 19,2 4 Neptune 30,1 4 Pluto 39,5 0,18 Distances in the Solar system The astronomical unit (A.U.) is the Earth-Sun distance : 1 A.U. = 149 597 871 km Distance Mass Voyager, The furthest probe sent by humans is at 12,5 billion kilometres of the Earth, hence 82 A.U. of us…

21. The Solar system, as seen from the Voyager probe Credits : Sonde Voyager

22. Average planet distances to the Sun Light-minutes Astronomical Units The speed of light c ~ 300 000 km/s The Sun is at ~ 8 light-minutes The Voyager probe is at ~ 12 light-hours 1 Light-year = 63240 Astronomical Units = 9,46 x 1012 km

23. The stars in the sky are similar to our Sun But so far away that we see them as points of light

24. Proxima Centaurus, The closest star from our Sun • Located at 4.22 Light-year from the Sun. • Its light takes about 4 years to reach us

25. Stars sometimes form clusters D (Sun– M3) ~ 34 000 light years Messier 3 (M3) Star cluster

27. After Before The Milky Way The city sky

29. A little geography of our Milky Way

30. Two satellite galaxies of the Milky Way The Milky Way, as seen from the inside Magellanic clouds Galactic bulb Spiral arms

31. The extragalactic domain

32. M75 M32 M101 The extragalactic « nebulae » Star clusters belong to our Galaxy But these other diffuse objects are galaxies

33. Voie Lactée ~ 160 000 l.y. ~ 2.5 million l.y.. ~ 200 000 l.y.

34. Our greatest neighbor, the “Andromeda” galaxy r ~ 50000 l.y. D (Milky Way – M31) ~ 2.5 million l.y.

35. 1 Million Light Years Our Galaxy M31 fait partie du groupe “Local ”de galaxies …

36. From Earth… To the Local Group of galaxies

37. M74 : 30 million l.y.

38. Sombrero : 40 million l.y.

41. 500 000 l.y. A compact group Hickson compact group 79

42. 10 million l.y. Virgo cluster At ~ 60 Million Light Years

43. The large-scale structure of the Universe

45. 10 million l.y. Abell cluster 1689

46. How many galaxies on this image? ! Hubble Ultra-Deep Field

47. 2D view of galaxies in the sky as observed in infrared From the Perseus cluster… … to the large-scale structure of the Universe

48. ~ 1 Billion l.y. Large galaxy surveys generally focus on small portions of the sky

49. The local group of galaxies within the local supercluster 3D Diagram Scale: 100 Million l.y. ~ 260 Millions l.y. ~ 163 million l.y.

50. The most distant galaxies ever observed ~ 11 Billion years