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THE SOLAR SYSTEM
1. Eight major planets,
2. one dwarf planet (Pluto),
3. satellites and countless minor planets
4. asteroids,
5. meteors, and
6. comets orbit the Sun to form the solar system.

Located in Orion arm of Milky Way galaxy

formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud.

The vast majority of the system's mass is in the Sun, with most of the remaining mass contained
in Jupiter.

The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets
(mostly made of denser materials unlike outer gaseous plantes), are primarily composed of rock
and metal.

The four outer planets, called the gas giants, are substantially more massive than the terrestrials.

The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two
outermost planets, Uranus and Neptune, are composed largely of substances with relatively high
melting points (compared with hydrogen and helium), called ices, such as water, ammonia and
methane, and are often referred to separately as "ice giants".

The asteroid belt, which lies between Mars and Jupiter, mostly contains objects composed, like
the terrestrial planets, of rock and metal.

Beyond Neptune's orbit lie the Kuiper belt and scattered disc, linked populations of trans-Neptunian
objects composed mostly of ices. Within these populations are several dozen to more than ten
thousand objects that may be large enough to have been rounded by their own gravity. Such
objects are referred to as dwarf planets. Identified dwarf planets include the
and
the trans-Neptunian objects

Each of the outer planets is encircled by planetary rings of dust and other small objects.

Bodies close to the Sun (the terrestrial planets) were formed from rocks and metals that crystallized
at high temperature, while the outer planets were formed from elements that form solids (condense)
at low temperatures.
Origin of Solar System

The solar system was probably formed by the gravitational collapse of a huge cloud of gas and
dust.

The reason for differences in planetary composition appears to be related to distance from the Sun.
Discovery and exploration

Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric system (Sun
at the centre). [Geocentric: Earth at the centre]

His 17th-century successors, Galileo Galilei, Johannes Kepler and Isaac Newton, developed an
understanding of physics that led to the gradual acceptance of the idea that Earth moves around the
Sun and that the planets are governed by the same physical laws that governed Earth.
Structure and composition

The principal component of the Solar System is the Sun, a G2 main-sequence star that contains
99.86% of the system's known mass and dominates it gravitationally

The Sun's four largest orbiting bodies, the gas giants, account for 99% of the remaining mass, with
Jupiter and Saturn together comprising more than 90%

Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic.
The planets are very close to the ecliptic, whereas comets and Kuiper belt objects are frequently at
significantly greater angles to it

Sun is rotating (counter-clockwise, as viewed from a long way above Earth's north pole).

Kepler's laws of planetary motion describe the orbits of objects about the Sun. Following Kepler's
laws, each object travels along an ellipse with the Sun at one focus.

A body's closest approach to the Sun is called its perihelion, whereas its most distant point from the
Sun is called its aphelion.

The orbits of the planets are nearly circular, but many comets, asteroids, and Kuiper belt objects
follow highly elliptical orbits

All planets have almost circular orbits that lie within a nearly flat disc called the ecliptic plane (The
plane of the Earth's orbit around the Sun. The ecliptic plane is used as the primary reference plane
when describing the position of bodies in the solar system).

Although the Sun dominates the system by mass, it accounts for only about 2% of the angular
momentum due to the differential rotation within the gaseous Sun.

The planets, dominated by Jupiter, account for most of the rest of the angular momentum due to the
combination of their mass, orbit, and distance from the Sun, with a possibly significant contribution
from comets.

The Sun, which comprises nearly all the matter in the Solar System, is composed of roughly 98%
hydrogen and helium (Same as that of Jupiter and Saturn). Jupiter and Saturn, which comprise
nearly all the remaining matter, possess atmospheres composed of roughly 99% of these elements.

Those objects closer to the Sun, which are more affected by heat and light pressure, are composed
of elements with high melting points.

Objects farther from the Sun are composed largely of materials with lower melting points
Sun

The Sun was formed when a swirling cloud of dust and gas contracted, pulling the matter into its
centre.

When the temperature at the centre rose to 1,000,000°C, nuclear fusion — the fusing of
hydrogen into helium, creating energy—occurred, releasing a constant stream of heat and light.




Age  4.6 billion years
Diameter  13,91,785km = 1.3 million kms
Temperature  6000 C on surface and 16 million C in core
Density  1.41 times that of water
[Density of water = 999.97 kg/m³; Density of Iron = 7870 kg/m³]Iron is (7870/999.97) = 7.87
times denser than water



Period of rotation  25days 9hrs
Speed of rotation  7179.73 km/hr (Earth’s rotational velocity  1675Km/hr)
Its large mass (3,32,900 Earth masses) produces temperatures and densities in its core high
enough to sustain nuclear fusion, which releases enormous amounts of energy, mostly radiated into
space as electromagnetic radiation, peaking in the 400–700 nm band of visible light.

The Sun is a type G2 main-sequence star. Compared to the majority of stars in the Milky Way, the
Sun is rather large and bright.

Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs, are common,
making up 85% of the stars in the galaxy
Photosphere

The photosphere is the bright outer layer of the Sun that emits most of the radiation, particularly
visible light.

The photosphere is an extremely uneven surface.

The effective temperature on the outer side of the photosphere is 6000°K (11,000°F).
Chromosphere

Just above the photosphere is the chromosphere. It is relatively a thin layer of burning gases.
Sunspot

A dark patch on the surface of the Sun is known as sunspot.

Sunspots appear as dark areas because they are about 1500° cooler than the surrounding
chromospheres.

The individual sunspot has a lifetime ranging from a few days to a few months.

Each spot has a black centre or umbra, and a lighter region or penumbra, surrounding it.

It has been suggested that the Sun is 1% cooler when it has no spot, and that this variation in solar
radiation might affect the climates of the Earth.
Solar Wind

The solar wind is a stream of energized, charged particles, primarily electrons and protons,
flowing outward from the Sun, through the solar system at speeds as high as 900 km/s and at a
temperature of 1 million degrees (Celsius). It is made of plasma.
Effect on the Solar System

As the solar wind approaches a planet that has a well-developed magnetic field (such as Earth,
Jupiter and Saturn), the particles are deflected

This region, known as the magnetosphere, causes the particles to travel around the planet rather
than bombarding the atmosphere or surface.

The magnetosphere is roughly shaped like a hemisphere on the side facing the Sun, then is drawn
out in a long trail on the opposite side.

The boundary of this region is called the magnetopause, and some of the particles are able to
penetrate the magnetosphere through this region by partial reconnection of the magnetic field lines.

The solar wind is responsible for the overall shape of Earth's magnetosphere

Moreover, planets with a weak or non-existent magnetosphere are subject to atmospheric
stripping by the solar wind.

Venus, the nearest and most similar planet to Earth in the Solar System, has an atmosphere 100
times denser than our own, with little or no geo-magnetic field.
Plasma

one of the four fundamental states of matter, the others being solid, liquid, and gas.

Plasma is simply ionized gas [convert (an atom, molecule, or substance) into an ion or ions, typically by
removing one or more electrons]

Much of the understanding of plasmas has come from the pursuit of controlled nuclear fusion and
fusion power, for which plasma physics provides the scientific basis

lightning and electric sparks are everyday examples of phenomena made from plasma. Neon lights
could more accurately be called "plasma lights", because the light comes from the plasma inside of
them.
Aurora

An aurora is a natural light display in the sky, predominantly seen in the high latitude (Arctic and
Antarctic) regions.

Auroras are caused by charged particles, mainly electrons and protons, entering the atmosphere
from above causing ionisation and excitation of atmospheric constituents, and consequent optical
emissions.
Planet

A celestial body moving in an elliptical orbit round a star, the Earth is known as planet. Planets are
generally divided into:
(i)
the Inner Planets (Mercury, Venus, Earth and Mars), and
(ii)
the Outer Planets (Jupiter, Saturn, Uranus, Neptune, and Pluto-dwarf planet).
Inner Planets

The inner Solar System is the traditional name for the region comprising the terrestrial planets and
asteroids

Composed mainly of silicates and metals

The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring
systems.

They are composed largely of refractory minerals, such as the silicates, which form their crusts and
mantles, and metals, such as iron and nickel, which form their cores.

Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to
generate weather; all have impact craters and tectonic surface features, such as rift valleys and
volcanoes.

The term inner planet should not be confused with inferior planet, which designates those planets
that are closer to the Sun than Earth is (i.e. Mercury and Venus).
Mercury

Surface gravity: 1kg = 0.38 kg

Mercury is similar to the Moon with a surface dominated by craters and a younger area of dark
plains presumably made from floods of lava.
Venus

Surface gravity: 1kg = 0.88 kg

Venus is often considered to be the Earth's twin, but the two planets are not identical.

Venus has high plateaus, folded mountain belts, numerous volcanoes, and relatively smooth
volcanic plains.

The surface of Venus is totally obscured by a thick atmosphere composed mostly of carbon dioxide,
with clouds of sulfuric acid.

It is much drier than Earth, and its atmosphere is ninety times as dense.
Earth

Surface gravity: 1 kg =1 kg

The Earth is shaped like a ball, but it is not perfectly round. The force of the Earth's rotation
makes the world bulge very slightly at the equator and go a little flat at the North and the South
poles. So the Earth is actually a flattened sphere, or a 'geoid'.

It is large enough to develop and retain an atmosphere and a hydrosphere.

The Pacific Ocean contains the deepest places on the Earth's surface-the ocean trenches. The
very deepest is the Challenger Deep in the Mariana Trench which plunges 11022 m into the
Earth's crust.
The Earth's Atmosphere

During the early stages of the Earth's formation, ash, lava, carbon and water vapour were
discharged onto the surface of the planet by constant volcanic eruptions.

The water formed the oceans, while carbon dioxide entered the atmosphere or was dissolved in
the oceans.

Clouds, formed of water droplets, reflected some of the Sun's radiation back into space. The
Earth's temperature stabilised and early life forms began to merge, converting carbon dioxide
into life-giving oxygen.
Mars

Surface gravity: 1 kg = 0.38 kg

surface has been dynamic. Almost every geologic feature is gigantic. Three huge volcanoes, one
more than 28 km high exists at Mars.

Wind action is also an important process: volcanoes, canyons, and landslides.

There is evidence not only of stream action, but of catastrophic flooding

Wind action is also an important process on Mars.

In addition polar regions are covered with alternating layers of ice and wind blown sediment.

It possesses an atmosphere of mostly carbon dioxide

Its surface, peppered with vast volcanoes, such as Olympus Mons, and rift valleys, such as
Valles Marineris, shows geological activity that may have persisted until as recently as 2 million
years ago. [A rift valley is a linear-shaped lowland between several highlands or mountain ranges
created by the action of a geologic rift or fault]

Its red colour comes from iron oxide (rust) in its soil

Mars has two tiny natural satellites (
and
) thought to be captured asteroids.
Asteroid belt

Millions of objects, remnants of planetary formation, circle the Sun in a zone lying between Mars
and Jupiter. They are known as asteroids. Fragments of asteroids break off to form meteoroids,
which can reach the Earth's surface.

Asteroids are small Solar System bodies composed mainly of refractory rocky and metallic
minerals, with some ice

The asteroid belt occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU from the
Sun.

It is thought to be remnants from the Solar System's formation that failed to coalesce because of
the gravitational interference of Jupiter

Asteroids range in size from hundreds of kilometres across to microscopic. All asteroids except the
largest, Ceres, are classified as small Solar System bodies
Ceres

Ceres (2.77 AU) is the largest asteroid, a protoplanet, and a dwarf planet.

It has a diameter of slightly under 1,000 km, and a mass large enough for its own gravity to pull it
into a spherical shape
Outer Planets

Outer Planets are Jupiter, Saturn, Uranus, Neptune and the dwarf planet - Pluto.

Planetary bodies in the outer solar system were formed mostly of the lighter elements: hydrogen,
helium, and oxygen.

Hence, the satellites of the giant planets are composed mostly of ice, not of rock, like the inner
planets.

The four outer planets, or gas giants (sometimes called Jovian planets), collectively make up 99%
of the mass known to orbit the Sun. J

upiter and Saturn are each many tens of times the mass of Earth and consist overwhelmingly of
hydrogen and helium;

Uranus and Neptune are far less massive (<20 Earth masses) and possess more ices in their makeup.
For these reasons, some astronomers suggest they belong in their own category, "ice giants".

All four gas giants have rings, although only Saturn's ring system is easily observed from Earth. The
term superior planet designates planets outside Earth's orbit and thus includes both the outer
planets and Mars.
Jupiter

Surface gravity: 1 kg = 2.53 kg

It is composed mostly of gas and liquid swirling in complex patterns.

Jupiter has no solid surface and hence no record of a geologic history.

Its moons are, however, solid planetary bodies that contain geologic wonders.

Jupiter's four large moons (Io, Europa, Ganymede, and Callisto), called the Galilean satellites
because they were discovered by Galileo in 1610
Saturn

1 kg = 1.07 kg

mostly of hydrogen, and helium

Saturn's rings for long have been considered as its most dramatic feature.

The rings are probably made up of billions of particles of ice and ice-covered rocks, ranging from a
few micrometers to a metre or more in diameter.

Titan, the second-largest moon in the Solar System, is larger than Mercury and the only satellite in
the Solar System with a substantial atmosphere. (Our Moon is the fifth largest natural
satellite.
, a moon of Jupiter, is the largest in this solar system. At 5,268 km at the
equator, it is larger than Mercury, the dwarf planet Pluto, and three times larger than the Moon
orbiting Earth.)
Uranus

1 kg = 0.92 kg

no solid surface

enveloped by a thick atmosphere of hydrogen and helium.

In contrast to all other planets in the solar system, it is tipped and spun on its sides, that is its axis
of rotation lies nearly the plane of its orbit.
Neptune

1 kg = 1.18 kg

Uranus and Neptune are called the twins of the outer solar system.

Surrounded by thick atmosphere of hydrogen, helium and methane.
Pluto and Charon

1 kg = 0.30 kg

The dwarf planet Pluto (39 AU average) is the largest known object in the Kuiper belt.

When discovered in 1930, it was considered to be the ninth planet; this changed in 2006 with the
adoption of a formal definition of planet.

Pluto was moved into the list of Dwarf Planets along with Ceres and Eris.

Charon, Pluto's largest moon
Kuiper belt

The Kuiper belt is a great ring of debris similar to the asteroid belt, but consisting mainly of objects
composed primarily of ice

It extends between 30 and 50 AU from the Sun.
Comets

A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins
to outgas, displaying a visible atmosphere or coma, and sometimes also a tail.

These phenomena are due to the effects of solar radiation and the solar wind upon the nucleus of
the comet.

Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond
the orbit of Neptune.

Comets, composed of ice and dust, originated outside our solar system. Their elliptical orbit brings
them close to the Sun and into the inner Solar System.

Comets are among the most spectacular and unpredictable bodies in the solar system.

they are made of frozen gases (water, ammonia, methane and carbon dioxide) which hold together
small pieces of rocky and metallic minerals

One of the larger comets is the Halley's Comet. The orbit of Halley's Comet brings it close to the
Earth every 76 years. It last visited in 1986.
Meteorite

Any solid debris origination from asteroids or comets or from outer space that fall to the Earth, the
Moon, or another planet in the solar system.

Meteor is a body of matter travelling at a great speed through space which becomes luminous when
enters into the atmosphere (mesosphere) at about 200 km above the Earth's surface, because it is
heated by friction. Generally, this latter process dissipates the material into meteoric dust. A meteor
is popularly termed a 'shooting star' or 'falling star'.

Largest Meteor Crater: A meteor crater in Arizona (USA) is 4,200 ft (1,300 m) deep is the largest
meteor crater in the world. It was formed over 10,000 years ago.
Planets
in
the
ascending
order of proximity to sun
Diameter
in
kms;
relative to Earth
Diameter
Distance from Sun; Distance in
Astonomical Units(AU)
1 AU = Distance between Sun and
Earth = 149.6 milliom kms
Mercury
4,878
= 0.38
57.9 mkm
= 0.38
Venus
12,104
= 0.96
108.2 mkm
= 0.72
Earth
12,576.3 = 1
149.6 mkm
=1
Mars
6,794
= 0.54
227.9 mkm
= 1.52
Jupiter
143,884
= 11.44
778.4 mkm
= 5.22
Saturn
120,536
= 9.58
1.426 mkm
= 9.57
Uranus
51,118
=4
2.87 mkm
= 19.26
Neptune
50,538
=4
4.498 mkm
= 30.18
Relative size of Planets
The Sun compared to the planets
Planets in the ascending
Temeperature in °C
order of proximity to sun
Mercury
+427
Venus
+480
Earth
+22
Mars
-23
Jupiter
-150
Saturn
-180
Uranus
-214
Neptune
-220
Planets in the ascending
Period of Rotation
Period of Revolution
Mercury
58 days
87 days
Venus
243 days
224 days
Earth
23:56 hrs
365d, 5:48
Mars
1.05 days
687 days
Jupiter
9 hrs
11.86 years
Saturn
10 hrs
29.46 years
Uranus
17 hrs
84.01 years
order of proximity to sun
Neptune
16 hrs
Planets in the ascending
Density relative to water
order of proximity to sun
(Taking, density of water = 1)
Mercury
5.43
Venus
5.24
Earth
5.51
Mars
3.94
Jupiter
1.33
Saturn
0.70
Uranus
1.3
Neptune
1.76
Planets
No of Known Moons
Mercury
0
Venus
0
Earth
1
Mars
2
Jupiter
61
Saturn
31
Uranus
21
Neptune
11
Planets
Rank accorging to size
Mercury
8
Venus
6
Earth
5
Mars
7
Jupiter
1
164.8 years
Saturn
2
Uranus
3
Neptune
4
Planet
Inclination angle to Ecliptic
Orbital Velocity in km/s
Mercury
7°
47
Venus
3°
35
Earth
23°
29
Mars
1°
24
Jupiter
1°
13
Staurn
2°
9
Uranus
0°
6
Neptune
1°
5
17°
4
Pluto
(Dwarf
planet)
Heliocentrism vs Geocentric

astronomical model in which the Earth and planets revolve around a relatively stationary Sun at the
center of the Solar System.
Kepler's laws of planetary motion
1. The orbit of a planet is an ellipse with the Sun at one of the two foci.
2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
3. The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its
orbit.

almost the same size,

have about the same mass (they weigh about the same), and

have a very similar composition (are made of the same material).

They are also neighboring planets.

Venus has an atmosphere that is about 100 times thicker than Earth's and has surface temperatures
that are extremely hot.

Venus does not have life or water oceans like Earth does.

Venus also rotates backwards compared to Earth and the other planets.

53% the diameter of Earth

10% the mass of Earth

surface gravity on Mars is only 38% the gravity on Earth

A day on Mars lasts 1.03 Earth days

axial tilt on Mars is 25.19 degrees. Very close to Earth’s 23.5 degree tilt

a year on Mars lasts about twice as long as an Earth year, the seasons are twice as long.

The atmosphere of Mars is less than 1% the thickness of Earth’s atmosphere. Furthermore, it’s made
up of 95% carbon dioxide
The moon
Its diametre is only one-quarter that of the earth.
It is about 3, 84,400 km away from us.
The moon moves around the earth in about
It takes exactly the same time to complete
one spin. As a result, only one side of the moon is visible to us on the earth.
Neil armstrong was the first man to step on the surface of the moon on 29 july 1969.