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Home , Planetary mass, Small Solar System body

THE

‘The Solar System’ is the name given to the of which the is part. It comprises 8 , , , meteors, & dwarf planets which are all held together by the gravitational pull of a star, named either the or ‘Sol’.

Formation of the solar system:

The formation of the Solar System is estimated to have begun 4.6 billion years ago with the of a small part of a giant . Most of the collapsing collected in the centre, forming the Sun, while the rest flattened into a proto planetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.

The Planets:

The known planets in the solar system can be divided into two groups. The four planets closest to the sun: , , Earth & are called the ‘terrestrial planets’. The outer four planets are called the ‘gaseous giants’ or ‘Jovian planets’. The terrestrial & Jovian

18 planets are divided by a belt of asteroids between Mars & . was demoted to the status of ‘Dwarf ’ giving it home among similar sized objects & asteroids which make up the .

End of the solar system:

It is difficult to calculate exactly where our solar system ends. It ends at a point at which objects are no longer affected by the sun’s gravitational pull. The farthest reaches of the solar system are thought to be surrounded by a great halo: ; home to millions of nuclei & small icy rocks.

Voyager 1 & 2 are the farthest reaching man-made objects in the solar system. In 2004, Voyager 1 cleared the termination shock, the area where solar winds begin to slow down & increase in temperature as they come up against interstellar winds. Voyager probes will continue transmitting data for several more decades, but it would take thousands of years for them to reach the nearest star, Alpha Centauri.

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4.1 THE SUN:

In the grand scheme of the , the sun in just another middle aged star. Its stellar classification, G2, denoting its yellowish colouring & its surface temperature (5000°-6000° kelvin) is not extraordinary either; there are countless G2-type stars.

Fusion:

In the sun, nuclei collide with one another to form Helium atoms. In this process, called ‘fusion’, mass is transferred into energy, which is explained by Einstein’s famous equation: 퐸 = 푚푐2.

The period during which sun generates energy through fusion is called ‘Main sequence’. Our sun is estimated to be 5 billion years old & its main sequence will last another 5 billion years.

Solar Layers:

The of the sun is composed of several layers, mainly the photosphere, the chromosphere and the corona. It's in these outer layers that the sun's energy, which has bubbled up from the sun's interior layers, is detected as sunlight.

Sunspots:

These are minor regions where the temperature of the photosphere is cooler than its surroundings. Sunspots are the result of string localised magnetic field & follow a cycle of 11 years.

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4.2 MERCURY

Mercury is the smallest and closest to the Sun of the eight planets in the Solar System, with an orbital period of about 88 Earth days. Seen from Earth, it appears to move around its in about 116 days, which is much faster than any other planet. It has no known natural satellites. The planet is named after the Roman deity Mercury; the to the gods

Mercury has almost no atmosphere. Its surface is heavily cratered due to impacts from .

4.3 VENUS

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has no . It is named after the Roman goddess of love and beauty. After the , it is the brightest natural object in the night sky, bright enough to cast shadows. Venus is a and is sometimes called Earth's "sister planet" because of their similar size, gravity, and bulk composition.

It is the hottest planet in solar system. It rotates on its axis from east to west. Therefore, on Venus the sun rises in west & sets in east.

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4.4 EARTH

Earth, also known as Terra, is the third planet from the Sun, the densest planet in the solar system, the largest of the Solar System's for terrestrial planets, and the only celestial body to accommodate . It is home to millions of species, including billions of humans.

The Earth takes 365.26 days to orbit the sun & 23.93 hours revolve once around its axis which is tilted 23.5° to the planet’s orbit.

4.5 THE MOON

The Moon (Latin: Luna) is the Earth's only natural satellite. Although not the largest natural satellite in the Solar System, it is, among the satellites of major planets, the largest relative to the size of the object it and, after Jupiter's satellite , it is the second densest satellite among those whose densities are known.

The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters . It is the most luminous object in the sky after the Sun. It takes moon 27.3 days to revolve around earth.

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4.6 MARS

Mars is the fourth planet from the Sun and the second smallest planet in the solar system, after Mercury. Named after the Roman god of war, it is often described as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance.

Mars’s atmosphere is consists of 95% of carbon dioxide & remaining 5% of Argon & Nitrogen. Average surface temperature is 60° Celsius. Because of this water exist on mars in frozen & vapour form.

4.7 JUPITER

Jupiter is the fifth planet from the sun and the largest planet in the solar system. It is a with mass one thousandth of that of the sun but is two and a half times the mass of all the other planets in the Solar System combined.

Jupiter is primarily composed of hydrogen with a quarter of its mass being helium. There are also at least 79 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. , the largest of these moons, has a diameter greater than that of the planet Mercury.

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The Giant Red Spot is its most notable feature. It is a giant storm which flows anti-clockwise across in area of 24,000 km in length & 12,000 km in width.

4.8 - 82 Moon

Saturn is the sixth planet from the sun and the second largest planet in the Solar System, after Jupiter. It is named after the Roman god of agriculture. Saturn is gas giant with an average radius about nine times that of Earth. While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive.

One of the greatest fascinations of the solar system is the . They have often earned Saturn the title of the most attractive planet in solar system.

Titan, Saturn's largest and the Solar System's second largest moon larger than the planet Mercury and is the only moon in the Solar System to retain a substantial atmosphere.

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Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest in the Solar System. Uranus is similar in composition to , and both are of different chemical composition to the larger gas giants Jupiter and Saturn. For this reason, astronomers sometimes place them in a

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It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of −224.2 °C and has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane the uppermost layer of clouds. In contrast, the interior of Uranus is mainly composed of ices and rock.

4.10 NEPTUNE

Neptune is the eighth and farthest planet from the sun in Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Among the gaseous planets, Neptune is the densest. Neptune is 17 times the mass of Earth and is slightly more massive than its near- twin Uranus, which is 15 times the mass of Earth but not as dense. Neptune orbits the Sun at an average distance of 30.1 astronomical units. It is named after the Roman god of the sea.

Neptune's atmosphere is notable for its active and visible weather patterns. For example, at the time of the 1989 Voyager 2 , the planet's southern hemisphere possessed a Great Dark Spot comparable to the Great Red Spot on Jupiter.

4.11 PLUTO & THE KUIPER BELT

Discovered in 1930, Pluto was originally classified as the ninth planet from the Sun. Its status as a major planet fell into question following further study of it and the outer Solar System over the ensuing 75 years. Starting in 1977 with the discovery of the 2060

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Chiron, numerous icy objects similar to Pluto with eccentric orbits were found. The most notable of these was thes cattered disc object , discovered in 2005, which is 27% more massive than Pluto.

Pluto has five known moons: (the largest, with a diameter just over half that of Pluto), , , & . On July 14, 2015, the Pluto system is due to be visited by spacecraft for the first time. The probe will perform a flyby during which it will attempt to take detailed measurements and images of the plutoid and its moons.

KUIPER BELT:

Kuiper Belt is a region of the Solar System beyond the planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the belt, but it is far larger—20 times as wide and 20 to 200 times as massive. Like the , it consists mainly of small bodies, or remnants from the Solar System's formation. Although most asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia & water. The Kuiper belt is home to at least three dwarf planets: Pluto, , and . Some of the Solar System’s moons, such as Neptune's and Saturn's , are also believed to have originated in the region.

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4.12 MINOR BODIES IN SOLAR SYSTEM

4.12.1 ASTEROIDS

Asteroids are fragments of rock & metal which are greater than 50m in diameter. On New Year’s Day 1801, the Italian astronomer, Giuseppe Piazzi, discovered the first asteroid . Initially he thought it was a comet, but its orbit was too slow & uniform. Some scientists suggested it might be a planet between Mars & Jupiter. But in 1802, second asteroid was discovered, named Pallas. This 2nd find led William Herschel, the discoverer of Uranus, to offer a collective name ‘asteroids’, meaning ‘Star-like’.

Many of the asteroids in the solar system are located in a band between Mars & Jupiter called the ‘Asteroid Belt’. It is believed that the belt is failed planet- the chunks of rock & metal were unable to group together & form 5th terrestrial planet because of the strong gravitational pull of Jupiter.

4.12.2

Meteoroids can be found throughout the solar system. They are small fragments of rock & minerals, often the size of a grain of sand.

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Meteoroids are either the chipped away parts of grater bodies or are remnants from the creation of the solar system.

SHOOTING STAR

When meteoroids collide with the Earth they burn up in the upper atmosphere, creating a striking spectacle called Meteor.

METEOR SHOWERS

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4.12.3 COMETS

A comet is an icy that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or , and sometimes also a tail. These phenomena are due to the effects of solar radiation and the upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of loose collections of ice, dust, and small rocky particles. The coma and tail are much larger and, if sufficiently bright, may be seen from the Earth without the aid of a telescope. Comets have been observed and recorded since ancient times by many different cultures. Comets are known as the ‘dirty snowballs’.

Comets have a wide range of orbital periods, ranging from several years to several millions of years. Short-period comets originate in the Kuiper belt or its associated , which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside of the Kuiper belt to halfway to the next nearest star.

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