The solar system is a gravitationally bound system consisting of the Sun and various celestial bodies that orbit it, including eight planets, dwarf planets, asteroids, and comets. It formed approximately 4.6 billion years ago from the gravitational collapse of a molecular cloud, with the Sun containing nearly all of the system's mass. The document details the composition, structure, and exploration of the solar system, highlighting the characteristics of both inner and outer planets, as well as the Oort cloud and its boundaries.

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The Solar System is the gravitationally boundplanetary
system ofthe Sunand the objects that orbitit.
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2. Solar
System
Definition
TheSolar System is the gravitationally bound planetarysystem oftheSun and the
objects that orbit it, either directly or indirectly. Of theobjects that orbit theSun
directly, thelargest aretheeight planets,with theremainder beingsmaller objects,
such as thefive dwarfplanets and small Solar System bodies.

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Evolution of the
Solar System
The formation and evolution of the Solar System began 4.6 billion years ago
with the gravitational collapse of a small part of a giant molecular cloud.
Most of the collapsing mass collected in the centre, forming the Sun, while the
rest flattened into a protoplanetary disk of loose dust, out of which
the planets, moons, asteroids, and other Solar System bodies formed

4. Discovery and Exploration
For thousands of years, people had noneed for a name for the "Solar System". They thought
the Earth stayed still at the center of everything (geocentrism). Althoughthe Greek
philosopher Aristarchus ofSamos suggested that there was a special order in the
sky, Nicolaus Copernicus was the first to develop a mathematical system that described
what we now call the "solar system". This was called a new "system of the world“

5. 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 gravitation. The Sun's four largest orbiting bodies, the giant
planets, account for 99% of the remaining mass, with Jupiter and Saturn
together comprising more than 90%. The remaining objects of the Solar
System including the four terrestrial planets, the dwarf planets,
moons, asteroids, and comets) together comprise less than 0.002% of
the Solar System's total mass.
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6. The Sun
At thecenter oftheSolar System is theSun. It is a star, likethe billions ofother stars in thesky.TheSun is important to us
becauseit gives us heat and energy that allows life
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7. Inner Planets
The first four planets closest to the Sun are called the inner planets. They are small
and dense terrestrial planets, with solid surfaces. They are made up of mostly rock
and metal with a distinct internal structure and a similar size
Mercury
Venus
Earth
Mars
Asteroid belt
Ceres
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8. Mercury
Mercury (0.4 AU from the Sun) is the closest planet to the Sun and the smallest planet in
the Solar System (0.055 M⊕). Mercury has no natural satellites; besides impact craters,
its only known geological features are lobed ridges or rupes that were probably
produced by a period of contraction early in its history.
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9. Venus
Venus (0.7 AUfrom theSun) is closein size to Earth (0.815 M⊕) and,like Earth, has a thick silicate mantlearound an iron
core, a substantial atmosphere,and evidenceofinternal geological activity. It is much tdrier han Earth, and its atmosphere
is ninety times as dense

10. Earth
Earth (1 AU from theSun) is thelargest and densest oftheinner planets,the
only oneknown to havecurrent geological activity,and theonly placewhere
life is known to exist. Its liquid hydrosphereis uniqueamongtheterrestrial
planets,and it is theonly planet whereplatetectonics has been observed

11. Mars
Mars (1.5 AU from theSun)is smaller than Earth and Venus (0.107 M⊕). It has an atmosphereofmostly carbon
dioxide with a surfacepressureof6.1 millibars (roughly 0.6% ofthat ofEarth). Its surface, peppered with vast
volcanoes,such as Olympus Mons,and rift valleys,such asValles Marineris, shows geological activity that
may havepersisted until as recently as 2million years ago.
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12. Asteroid Belt
Asteroids except for the largest, Ceres, are classified as small Solar System bodies and are
composed mainly of rocky and metallicminerals, with some ice. They range from a few
metres to hundreds of kilometres in size. Asteroids smaller than one meter are usually
called meteoroids and micrometeoroids (grain-sized)
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13. Ceres (2.77 AU) is the largest asteroid, a protoplanet,
and a dwarf planet. Its mass is large enough for its
own gravity to pull it into a spherical shape Ceres was
considered a planet when it was discovered in 1801,
and was reclassified to asteroid in the 1850s as further
observations revealed additional asteroids. It was
classified as a dwarf planet in 2006 when the
definition of a planet was created.
Ceres
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14. Neptune
Uranus
Saturn
Jupiter
Outer Planets
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15. Jupiter
Jupiter (5.2 AU), at 318 M⊕, is 2.5 times the mass of all the
other planets put together. It is composed largely of
hydrogen and helium. Jupiter's strong internal heat creates
semi-permanent features in its atmosphere, such as cloud
bands and the Great Red Spot.
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16. Saturn
Saturn (9.5 AU), distinguished by its extensivering system,has several similarities to
Jupiter, such as its atmosphericcomposition and magnetosphere.AlthoughSaturn has
60% of Jupiter's volume,it is less than athird as massive, at 95 M⊕. Saturn is theonly
planet oftheSolar System that is less densethan water.

17. Uranus
Uranus (19.2 AU), at 14 M⊕, is the lightest of the outer planets. Uniquely among the planets, it
orbits the Sun on its side; its axial tilt is over ninety degrees to the ecliptic. It has a much colder
core than the other giant planets and radiates very little heat into space.

18. Neptune
Neptune (30.1 AU), thoughslightly smaller than
Uranus, is more massive (17 M⊕) and hence
more dense. It radiates more internal heat, but not
as much as Jupiter or Saturn. Neptune has 14
known satellites. The largest, Triton, is geologically
active, with geysers of liquid nitrogen. Triton is the
only large satellite with a retrograde orbit.

19. It’s Time
To
Break

20. Dwarf Planets
Pluto had been called a planet since it was discovered in 1930, but in
2006 astronomers meeting at the International Astronomical Union
decided on the definition ofa planet, and Plutodid not fit. Instead
they defined a new category of dwarf planet, into which Plutodid fit,
along with some others.
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21. TheseSmallPlanetsAre
SometimesCalledPlutinos
Eris
Haumea
Cares
Pluto
Makemake

22. Trans – Neptunian Region
Beyond theorbit ofNeptunelies theareaof the
"trans-Neptunian region",with thedoughnut-
shaped Kuiper belt, homeofPluto and several
other dwarfplanets,and an overlappingdiscof
scattered objects, which is tilted toward the
planeoftheSolar System and reaches much
further out than theKuiper belt.
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23. Farthest
Regions
The point at which the Solar System ends and interstellar
space begins is not precisely defined because its outer
boundaries are shaped by two separate forces: the solar
wind and the Sun's gravity. It is thought to extend up to a
thousand times farther and contain the Oort Cloud
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24. Oort Cloud
The Oort cloud is a hypothetical spherical cloud of upto a
trillion icy objects that is thought to be the source for all
long-period comets and to surround the Solar System at
roughly 50,000 AU (around 1 light year (ly)), and possiblyto
as far as 100,000 AU (1.87 ly). It is thought to be composed
of comets that were ejected from the inner Solar System by
gravitational interactions with the outer planets
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25. Boundaries
Much of the Solar System is still unknown. The Sun's gravitational field is estimated to dominate the gravitational forces
of surrounding stars out to about twolight years (125,000 AU). Lower estimates for the radius of the Oort cloud, by contrast, do
not place it farther than 50,000 AU. Despite discoveries such as Sedna, the region between the Kuiper belt and the Oort cloud,
an area tens of thousands ofAU in radius, is still virtually un-mapped. There are also ongoing studies of the regionbetween
Mercury and the Sun. Objects may yet be discovered in the Solar System's uncharted regions.
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26. Galactic Context
The Solar System is located in the Milky Way, a barred
spiral galaxy with a diameter of about 100,000 light-years
containing about 100 billion stars. The Sun resides in one
of the Milky Way's outer spiral arms, known as the Orion–
Cygnus Arm or Local Spur. The Sun lies between 25,000
and 28,000 light-years from the Galactic Centre, and its
speed within the Milky Way is about 220 km/s, so that it
completes one revolution every 225–250 million years. This
revolution is known as the Solar System's galacticyear.
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27. Therefore,theSun passes through arms only rarely.Becausespiral arms arehometo afar larger
concentration ofsupernovae,gravitational instabilities,and radiation that could disrupt theSolar
System, this has given Earth longperiods ofstability for life to evolve
Galactic Context

28. Exploration
Before the telescope, people explored the sky with their eyes. They saw how the planets seemed to "wander" through the sky. They learned to
predict where the Sun, the moon, and planets would be in the sky. They built some observatories - places for watching the sky. They observed the
Sun and stars to tell the time of year
elescopes were first made in the early 17th century and have vastly improved since. Astronomers saw that planets are not like stars. They are
worlds, like the Earth. They could see that some planets have moons. They began to think about what these worlds were like. At first, some
thought that the other planets and moons had life. Eventual progress sent spacecraft into space, and found that there life on the Moon or on Mars.

29. Exploration
Twelve Astronauts walked on the Moon about 35 years ago. They brought rocks
and dirt back to Earth. Spacecraft flew by Venus, Mars, and the outer planets. The
pictures they took showed us a lot of what we know about these worlds. Robots
landed on Mars in 1971, 1976, and 1997. They took thousands of pictures of the
planets. Two robots, "Spirit" and "Opportunity" (on February 13, 2019, NASA
officials declared that the Opportunity mission was complete, after the
spacecraft ailed to respond to repeated signals sent since August 2018).

30. Thanks
For
Watching
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