Astrophysics Part 1 2012


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IBO Diploma Physics Option E

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Astrophysics Part 1 2012

  2. 2. The Solar SystemYou need to know the names of the planets
  3. 3. Planets orbit in ellipses An ellipse is a “flattened circle” with two foci about which the planet orbits. Planet SUN X Foci Moons orbit the planets in much the same way.
  4. 4. The Sun  Mass: 1.99 x 1030 kg  Radius:6.96 x 108 m  Surface temperature: 5800 K
  5. 5. Planets DataPlanet Picture Distance to the Sun Diameter(km) Orbital period Orbital Surface day Density Satellites (km) around its period temp (ºC) (water=1) axisMercury 58 million 4 878 km 59 days 88 days 167 5,43 0Venus 108 million 12 104 km -243 days 225 days 464 5,24 0 Earth 149,6 million 12 756 km 23, 93 h 365,2 days 15 5,52 1 Mars 228 million 6 794 km 24h 37min 687 days -65 3,04 2Jupiter 778 million 142 800 km 9h 50min 30s 12 years -110 1,32 +63Saturn 1 427 million 120 000 km 10h 14min 29,5 years -140 0,69 +56Uranus 2 870 million 51 800 km 16h 18min 84 years -195 1,27 27Neptune 4 497 million 49 500 km 15h 48min 164 years -200 1,77 13 Pluto 5 900 million 2 400 km 6 days 248 years -225 2 1
  6. 6. Compare The diameter of the Earth and  A) Mars  B) Saturn The distance to the Sun of Jupiter and  A) Venus  B) Uranus
  7. 7. Mercury and Venus
  8. 8. Earth and Moon Mariner 10
  9. 9. Earth and Moon
  10. 10. MarsSpirit Rover: Mars’ West Valley
  11. 11. Mars
  12. 12. MarsViking: Martian Face ESA’s Mars Express: Cydonia Region
  13. 13. Asteroid Belt Ceres (480km): it was the first asteroid to be seen. Now it’s a dwarf planet. Mathilde (52km) Eros (13x13x33km)
  14. 14. How far is the asteroid belt? It is 2 – 3.5 AU An AU is the astronomical unit, the mean distance from the Earth to the Sun Distance = 2 * 1.496 x 108 km = 293200000000 m from the sun
  15. 15. JupiterJupiter and its moons: Io, Approximate size comparison ofEuropa, Ganymede and Earth and JupiterCallisto
  16. 16. SaturnA rough comparison of the sizesof Saturn and Earth
  17. 17. Uranus Size comparison of Earth and Uranus
  18. 18. NeptuneSize comparison of Neptune andEarth.
  19. 19. Planets & Stars Scale of Planets & Stars
  20. 20. Comets COMETS are frozen balls of ice and dust that can resemble a “dirty snowball”. They orbit the Sun is highly elliptical orbits. Their orbital periods can range from a few years to several thousand years. Halleys Comet is famous due to the fact that everyone has a chance to see it in their lifetime (Orbital Period of 77 years).
  21. 21. Planet Orbits Solar System Simulation TOK Why were ancient civilisations so interested in the motion of the planets?
  22. 22. Comet’s orbit Earth’s OrbitComet Sun
  23. 23. Lightyear Light Year (ly) – is the distance that light travels in one year.  One light year equals 9.46 x 1015 metres. c = distance/time 300000000 = distance/365x24x60x60
  24. 24. Lightyear The distance across our galaxy, The Milky Way is 80 000 light years. Our nearest neighbouring galaxy, The Andromeda galaxy, is 2.2 million light years away.
  25. 25.  The furthest galaxies that can be detected with the Hubble Telescope are over 10 billion light years away!!! This marks the edge of the detectable Universe. It is a big place!
  26. 26. Stellar cluster A number of stars that are held together in a group by a gravitational attraction. They were created at about the same time There may be many thousands of stars in a group.
  27. 27. Galaxies A galaxy is a collection of a very large number of starsmutually attracting each other through the gravitational forceand staying together. The number of stars varies between afew million and hundreds of billions. There approximately100 billion galaxies in the observable universe. There are three types of galaxies: - Spiral (Milky Way) - Elliptical (M49) - Irregular (Magellanic Clouds)
  28. 28. Spiral Galaxies Spiral galaxies consist of a rotating disk of stars andinterstellar medium, along with a central bulge ofgenerally older stars. Extending outward from thebulge are relatively bright arms. Milky Way
  29. 29. Spiral GalaxiesAndromeda
  30. 30. Spiral Galaxies Sombrero Galaxy
  31. 31. Elliptical Galaxies M49 ESO 325-G004Elliptical cross-section and no spiral arms.They range in shape from nearly spherical to highly flattenedellipsoids and in size from hundreds of millions to over onetrillion stars.In the outer regions, many stars are grouped into globularclusters.
  32. 32. Irregular Galaxies• Irregular galaxies have no specific structure. The Large and Small Magellanic Clouds, the nearest galaxies, are an example of irregular galaxies. Small Magellanic Cloud Hoags Object, a ring galaxy.
  33. 33. Constellations A group of stars in a recognizable pattern thatappear to be near each other in space.Orion
  34. 34. Polaris
  35. 35. NebulaeNebula is an interstellar cloud of dust, hydrogen gas andplasma. It is the first stage of a stars cycle but it can also referto the remains of a dying star (planetary nebula).Originally nebula was a general name for any extendedastronomical object, including galaxies beyond the Milky Way(some examples of the older usage survive; for example, theAndromeda Galaxy was referred to as the Andromeda Nebulabefore galaxies were discovered by Edwin Hubble).Nebulae often form star-forming regions, such as in the EagleNebula.
  36. 36. NebulaeEagle Nebula and the Cone nebula: star-forming regions
  37. 37. Cat’s Eye NebulaPlanetary nebulae are nebulae that form from the gaseousshells that are ejected from low-mass giant stars when theytransform into white dwarfs.
  38. 38. Eskimo nebula
  39. 39. SupernovasEta Carinae Crab Nebula
  40. 40. Apparent Motion of Night Sky At night the star field appears to “rise in the east and set in the west”. The Sun and the Moon also follow a similar path across the sky. Early astronomers felt that the Earth was the centre of the Universe and all stars, planets, the Moon and the Sun orbited the Earth. This was called the Geocentric Solar System.
  41. 41. Southern sky
  42. 42. Apparent Motion of Night Sky The Earth was at the centre and did not move. Everything else revolved around the Earth. Sun, Planets, Stars, Moons, Comets Earth Geocentric Solar System
  43. 43. Apparent Motion of Night Sky Several problems arose in the 1600’s in regards to this model of the universe. One was the apparent “wandering” of the planets, what is now called retrograde motion. Planets sometimes “drift” back towards the eastern horizon over the course of a few nights.
  44. 44. Apparent Motion of Night Sky Eventually Copernicus (1600’s) put forward a new theory that had the Sun as the centre of our Solar System. This was called the Heliocentric Solar System. The 9 planets orbit the Sun. The Asteroid Belt orbits the Sun between Mars and Jupiter. Comets also orbit the Sun. The moons orbit the planets.
  45. 45. Apparent Motion of Night Sky It is the Earth ROTATING (spinning) once every 24 hours that gives the impression that the Sun, the Moon, the planets and the entire star field are moving from east to west. The Earth rotates from WEST to EAST. This is why we call it “apparent motion”.
  46. 46. Apparent Motion of Night Sky There is also a shift in the star pattern of the night sky over the course of a year. The Earth REVOLVES around the sun once every 365 days. We will see a different background of stars on the Celestial Sphere during each season.  Orion is a constellation that is prominent in the winter sky. It is not visible in the summer.