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The Solar System

The Solar System. Figure Courtesy NASA/JPL-Caltech. The Sun. Luminosity 3.9 x 10 26 W Mass 1.99 x 10 30 Kg Radius 6.96 x 10 8 m Temperature 5800 K Distance 1.50 x 10 11 m (1 AU) AU = Astronomical unit. Sun and the planets. Mass distribution.

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The Solar System

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  1. The Solar System Figure Courtesy NASA/JPL-Caltech

  2. The Sun Luminosity 3.9 x 1026 W Mass 1.99 x 1030 Kg Radius 6.96 x 108 m Temperature 5800 K Distance 1.50 x 1011 m (1 AU) AU = Astronomical unit

  3. Sun and the planets Mass distribution Major portion of angular momentum in planets

  4. The Eight Planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune Pluto? • Elliptical orbits with Sun at one focus • Orbits nearly circular – Mercury maximum eccentricity • Orbits nearly coplanar – Mercury inclined at 7 degrees • Other than Mercury and Venus, all are known to have • Planetary satellites

  5. Orbit Parameters (J2000)

  6. Physical Parameters

  7. Physical Parameters

  8. Inner Planets 10 January 2010 Revolve conter-clockwise Looking down at Earth’s N-pole Terrestrial Planets composed of rock and metals relatively high densities slow rotation solid surfaces no rings and few satellites Small Mass Solar System Livehttp://www.fourmilab.ch/cgi-bin/SolarPortion of orbit in blue is above the plane of the ecliptic; in green is below the plane of the ecliptic. Orbits to scale not planet sizes

  9. Outer Planets Four Giant Planets - low densities, rapid rotation, rings and lots of satellites, strong magnetic filed Jupiter and Saturn largest and second largest Mainly Hydrogen and Helium Gas Giants Neptune and Uranus Mainly ice (fluid)– water, rocks – silicate and metal condensates ammonia and methane Ice Giants

  10. Rotation Venus and Uranus Retrograde rotation Rest Direct Rotation Courtesy: http://cseligman.com/text/sky/rotationvsday.htm Angle relative to orbital axis

  11. Origin of the Solar System Coplanar orbits – ecliptic plane Rotation axis of nearly all planets and Sun normal to ecliptic Alignment of angular momentum suggests that the Solar System formed by the fragmentation of a spinning disk made of gas and dust 4.5 billion years ago

  12. Nebular Hypothesis Cloud (nebula) of gas and dust collapses under its own gravity, possibly triggered by an external disturbance eg. Supernova blast wave Figure courtesy http://www.nineplanets.org/by Bill Arnett

  13. Spinning DIsk Conservation of angular momentum Nebula forms a disk Figure courtesy http://www.nineplanets.org/by Bill Arnett

  14. Protosun and protoplanets Figure courtesy http://www.nineplanets.org/by Bill Arnett

  15. Inner Solar System (Revisited) 1 January 2010 Asteroids (Yellow dots), Comets (sunward-pointing wedges). Vernal Equinox to right along +x axis of right figure

  16. Outer Solar System (Revisited) Positions of asteroids and comets with semi-major axis (a) greater than 5 AU (orbital periods greater than ~11 years) on 2010 January 1. The orbits and positions of Earth, Jupiter, Saturn, Uranus, Neptune, Pluto, and comets Halley and Hale-Bopp are also shown.

  17. Distant Solar System Objects with semi-major axes (a) greater than 6 AU (orbital periods greater than ~15 years) on 2010 January 1. Jupiter, Saturn, Uranus, Neptune, Pluto, Eriss, Sedna, and comets Halley and Hale-Bopp are shown. The brighter color is used for the portion of the orbit above the ecliptic plane. Trans-Neptunian objects larger than about 700 km in diameter are shown as white diamonds,

  18. Distant Solar System

  19. Pluto is no longer a planet • IAU resolution in 2006 • A planet is a celestial body that: a. is in orbit about the sun b. has sufficient mass for its self-gravity to overcomeits rigid body forces so that it assumes a hydrostaticequilibrium (nearly round) shape, c. has cleared the neighbourhood around its orbit.

  20. Pluto is a dwarf planet (2) A dwarf planet is a celestial body that a. is in orbit about the sun b. has sufficient mass for its self-gravity to overcome its rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and c. has not cleared the neighbourhood around its orbit, and d. is not a satellite (3) All other objects, except satellites, orbiting the sun shall be referred to collectively as Small Solar-System Bodies.

  21. Dwarf Planets Pluto is a “dwarf planet” by the above definition and isrecognized as the prototype of a new category of trans-Neptunian objects. Designated Dwarf Planets 1 Ceres, 134340 Pluto, and 136199 Eris

  22. Asteroids • Small rocky bodies • Those observed range in diameter from 948 km (1Ceres) to a few meters. • Primarily in orbit between Jupiter and Mars (i.e. main-belt). • Near-Earth asteroids (NEAs) are a subsetof asteroids whose orbits approach and/or cross the Earth's orbit.

  23. Asteroids • Includes Trojans - bodies captured in Jupiter's 4th and 5th Lagrange points • Centaurs - bodies in orbit between Jupiter and Neptune • Trans-Neptunian objects - orbiting beyond Neptune • Minor Planets

  24. Lagrange Points Two masses in nearly circular orbit Test particle has equilibriun points L1, L2, L3 Unstable L4, L5 stable

  25. Comets • Small icy bodies (water and dust) • Few km (~1 km) in extent • Formed in Outer Solar System – Cold • Orbits are disturbed by massive planets • Approach the Sun (few AU) • Vapourised • Atmosphere – upto few hundred thousands of km

  26. Comets • Reflected light • Atmosphere glows – fluorescence • Tail pointing away from Sun • Gas – pushed by Solar wind • Dust – radiation pressure

  27. Comet Halley 76 year period – small changes e 0.967142908462304 a 17.8341442925537 AU

  28. Comet Halley

  29. Hale Bopp Hale-Bopp 1997 Time period 2520 yr

  30. Comets • Short period < 200 yrs lie in ecliptic • Possibly originate in trans-Neptune region • Disturbed by outer planets • Orbit often in ecliptic • Long period > 200 to millions of years • Orbit generally not in ecliptic • Possibly scattered from between Uranus and Neptune to Oort Cloud

  31. Oort Cloud • Comets – not from interstellar space • Apohelion around 50,000 AU • No preferred direction • Comets reside in a cloud at peripheryy of Solar Susyem • Maybe as many as a trillion • Come into Solar System due to disturbance- long period Comets

  32. Trans-Neptunian Objects Several Scientists have proposes the existence of small objects in the Solar System beyond Neptune’s orbit – source of Short Period Comets Leonard (1930), Edgeworth (1945), Kuiper (1951) KuiperBelt between 30 to 50 Au from Sun Short period Comets – scattered disk Beyond Kuiper belt

  33. Edgeworth-Kuiper belt • First EKBO 1992 (Jewitt and Luu) • Around 1000 EKBOs known • ~70,000 predicted larger than 100 km • Ice – frozen volatides (methane, ammonia and water) • Temperature ~50 K • Pluto, Makemake, Humea dwarf planets • Pluto largest EKBO

  34. Scattered DIsk

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