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 x 108 m
Temperature K
Distance x 1011 m (1 AU)
AU = Astronomical unit

3. Sun and the planets Mass distribution
99.85 %
Sun
0.135 %
Planets
0.015 %
Comets, Kulper Belt Objects, Planetary Satellites, Minor Planets, Meteorids, Interplanetary Medium
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) Planet Semi-major axis (au) Eccentricity e
Inclination
Mercury
Venus
EM Binary
Mars
Jupiter
Saturn
Uranus
Neptune

6. Physical Parameters 25362 86.8103 Planet Mean Radius (km)
Mass (x kg)
Mercury
2439.7 
Venus 
6051.8
Earth
Mars
Jupiter  
69911
Saturn
58232
Uranus   
25362
Neptune
24622

7. Physical Parameters 0.44401 -0.71833 0.6713 Planet
Sidereal Orbit Period (y)
Sidereal Rotation Period (d)
Mercury
Venus    
Earth
Mars
Jupiter  
Saturn
Uranus   
Neptune
0.6713

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 Live Portion 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:
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 by Bill Arnett

13. Spinning DIsk Conservation of angular momentum Nebula forms a disk
Figure courtesy by Bill Arnett

14. Protosun and protoplanets
Figure courtesy 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, Pluto, and 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 subset of asteroids whose orbits approach and/or cross the Earth's orbit.

24. 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

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

26. 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 or less)
Vapourised
Atmosphere – upto few hundred thousands of km

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

28. Comet Halley 76 year period – small changes
e a AU

29. Comet Halley

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

31. Comets Short period < 200 yrs (eg. Comet Halley)
Orbit often in ecliptic
Period often 5 – 7 yr - frequent passes close to Sun – vaporized
Long period > 200 yrs to millions of years
Example Hale-Bopp
Orbit generally not in ecliptic

32. Long Period Comets In bound orbits around Sun
Apohelion around 50,000 AU
No preferred direction
Where do these come from?
not from interstellar space

33. Oort Cloud Oort proposed
A clound of objects at peripheryy of Solar Susyem
50,000 AU to 150,000 AU
Maybe as many as a trillion objects
Come into Solar System due to disturbance from passing star or Galaxy disk
long period Comets

34. SOURCE OF OORT CLOUD? Asteroids in orbit between Uranus and Neptune
Disturbed by massive planets
Scattered to Outer parts of Solar System
form the Oort Cloud

35. Short Period Comets

36. Trans-Neptunian Objects
Several Scientists have proposed existence of small objects in the Solar System beyond Neptune’s orbit
Disturbance from passing planet
Orbit changed towards interior of Solar System
source of Short Period Comets L

37. Trans-Neptunian Objects
Leonard (1930), Edgeworth (1945),
Kuiper (1951)
Edgeworth-Kuiper Belt or
KuiperBelt
between 30 to 50 Au from Sun

38. 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

40. Kuiper Belt possibly not the source of Short Period Comets Scattered Disk – beyond 50 AU

42. Mass of Solar System Estimated that Kuiper Belt contains
108 to objects of size greater than 1 km
Oort cloud contains
1012 to objects of size greater than 1 km
Total Mass Estimates Vary
Mass in outer parts may excedd planets

43. Sun and the planets Mass distribution
99.85 %
Sun
0.135 %
Planets
0.015 %
Comets, Kulper Belt Objects, Planetary Satellites, Minor Planets, Meteorids, Interplanetary Medium
Major portion of angular momentum in planets

44. Much remains to be explored in the Solar System