The document discusses the origin and evolution of the solar system and the formation of elements. It describes how early scientists like Copernicus, Galileo and Kepler realized the sun was at the center of the solar system, rather than the Earth. It explains how the solar system formed from a rotating cloud of gas and dust 4.6 billion years ago. Key events included the solar nebula contracting and flattening into a disk, and planets forming from accretion of material in the disk. Nuclear fusion in stars produces lighter elements, while heavier elements are formed in supernova explosions when massive stars die.

1. Origin of earth
nmadhavan@jnu.ac.in

2. The Solar System

3. History of knowledge
• Nikolaus Copernicus (1473 – 1553), it was generally believed
that most celestial bodies of the universe revolved around the
earth.
http://en.wikipedia.org/wiki/Nicolaus_Copernicus

4. History of knowledge
• Galileo (1564 – 1642) with the invention of telescope, it was
proposed for the first the first time that the orbit of revolving
planets were around the sun.
http://en.wikipedia.org/wiki/Galileo_Galilei

5. History of knowledge
• Kepler (1571 – 1630) said the major planets revolve around
the sun were elliptical and the plane called ‘plane of ecliptic’
Diagram of the geocentric trajectory of Mars through
several periods of apparent retrograde motion.http://en.wikipedia.org/wiki/Johannes_Kepler

6. History of knowledge
• Newton’s (1643 – 1727) law of gravitation gave a distinct
physical and mathematical expression to the planetary motion
and their relative positions away from sun.
http://en.wikipedia.org/wiki/Isaac_Newton

7. Present knowledge
• The sun with its family of planets and their satellites,
asteroids, comets, meteors and all other objects revolving
around it under influence of its gravitational field, constitute
the solar system.
– dwarf planet is an object the size of a planet but that is neither a
planet nor a moon or other natural satellite.

8. Present knowledge on Pluto
• The planet Uranus was discovered in 1781, Neptune in 1846
and Pluto in 1930. Since 2008 and it was announced that
Pluto no more a planet in our solar system.
– Why Pluto is No Longer a Planet?
– http://www.universetoday.com/13573/why-pluto-is-no-longer-a-
planet/
http://www.feiteira.org/2012/08/why-pluto-is-no-longer-planet-picture.html

9. The planets
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
diameter
(km)
4,878 12,104 12,756 6,787 142,800 120,000 51,118 49,528
mass (Earth=1) 0 1 1 0 318 95 15 17
mean
distance
from Sun
(AU)
0 1 1 2 5 10 19 30
orbital
period (Earth
years)
0 1 1 2 12 29 84 165
mean
density
(water=1)
5 5 6 4 1 1 1 2
atmospheric
composition
none CO2
N2 +
O2
CO2 H2+He H2+He H2+He H2+He
http://www.windows.ucar.edu/tour/link=/space_missions/au.html

11. The stars
Many stars are several thousand times brighter than our sun while there are
others thousand times dimmer as well; thus very wide range of brightness
has been observed among the stars. Because of this they show different
colours, depending upon whether they are,
Red hot – 3500 ºC
Yellow hot – 6000 ºC
White hot – 11,000 ºC
Blue hot – 20,000 ºC
The luminosity of the stars depends upon their mass, varying with the cube of
the mass. If the star is 3 times more massive, it will be 27 times bright
One astronomical unit (AU) is equal to 150 million km, the distance of earth
from the sun

14. The Sun
• Spectral studies have revealed that the sun has
layered structure, consisting of three layers.
• The inner most called photosphere, has a
temperature range of about 4500-7000 ºC,
increasing towards its core. It is observable to the
naked eye.
• The outer layer of the sun, called the
chromospheres and the corona, are observable
only by using special devices.

15. Origin of the solar system
• The Solar System (including the Earth) formed from a large, rotating
cloud of interstellar dust and gas called the solar nebula.
• It was composed of hydrogen and helium produced in the Big Bang
at 13.7 Ga, as well as heavier elements ejected by supernovas.
• About 4.6 Ga, the solar nebula began to contract, possibly due to
the shock wave of a nearby supernova.
• Gigannum, usual symbol Ga, is a unit of time equal to 109 years.
Such a shock wave would have caused the nebula to gain angular
momentum. As the cloud began to accelerate its rotation, gravity
and inertia flattened it into a protoplanetary disk oriented
perpendicularly to its axis of rotation.

17. Stellar nucleosynthesis
1H + 1H = 2H (deuterium) + e
1H + 2H = 3He + n (neutron)
3He + 3He = 4He + 1H + 1H

18. Illustration of the proton–proton chain reaction sequence

19. Overview of the CNO-I cycle. The helium nucleus is released at the top-left step.

21. 4He + 4He+4He = 12C
12C+4He = 16O
16O+4He = 20Ne
12C+1H = 13N
13N = 13C + Positron
13C + 1H = 14N
14N + 1H = 15O
15O = 15N + Positron
15N + 1H = 16O
15N + 1H = 12C + 4He
20Ne + 4He = 24Mg
16O + 16O = 28Si +4He
16O + 16O = 32S + n
16O + 16O = 31P + 1H
32S + 32S = 56Fe + 4He + 1H

23. Supernova Explosions
• Most larger stars support nucleosynthesis kind of reactions within them
and attain a final stage of evolution with production of elements, up to the
mass number 56Fe. It becomes insufficient for elements with a greater
than mass number 56, since the binding energy beyond has a steeper
decline. The reactions required to produce heavier elements would
require extra energy to fuse the nuclides and thus cannot be exothermic.
They are endothermic and so tend to consume all the energy produced at
the oxygen burning stage, thereby slowing down considerably the process
of production of heavier elements.
• For greater amount of energy will be required to produce elements of still
higher mass numbers. This cannot take place in stars in their normal
process of evolution, unless they are very massive stars in which
temperatures of the order of 1010 ºC can be achieved. At this temperature,
nuclear fission of 56Fe forming the core regions of star takes place, leading
to consumption of excess energy.

27. references
• http://en.wikipedia.org/wiki/Solar_System
• Formation and evolution of the Solar System
http://en.wikipedia.org/wiki/Formation_and_evo
lution_of_the_solar_system
• Nucleosynthesis
http://en.wikipedia.org/wiki/Nucleosynthesis
• Abundance of the chemical elements
http://en.wikipedia.org/wiki/Abundance_of_the_
chemical_elements#cite_note-0
• Stellar evolution
http://en.wikipedia.org/wiki/Stellar_evolution