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Astronomy and Solar System

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Our Solar System

The Sun, the nine known planets, their 31 known satellites, a great number of asteroids, and some other bodies like comets and meteors constitute the solar system.

Sun

The incandescent, approximately spherical heavenly body around which the planets rotate, is known as the Sun. It is one of some 1.00,00,00,00,000 stars which constitute our galaxy, its mean distance from the earth is approximately 9,29,00,000 miles, diameter about 864,000 miles, mass 2×10^27 tons and its average density 1.4 grams per cc.

Sun’s Temperature

The outer surface of the Sun, called photosphere, has a temperature of about 6000 C and its interior temperature is about 13,000,000 C. Such a high temperature inside the sun give rise to thermonuclear reactions in which Hydrogen is converted into Helium.The heat produced in this reactions makes up the loss of heat by Sun`s radiation, thereby keeping the sun’s temperature constant and high.

Sunspots

These are the region on the Sun`s photosphere visible are irregular dark patches scattered on either side of sun’s equator, emitting strong magnetic field which disturbs wireless communication and produces magnetic storms on the earth.

Production of holes

A luminous ring sometimes observed around the sun or Moon called halo is caused by the reflection of light by ice crystals present in the atmosphere.

Planets

The bodies revolving around the sun are called planets.These are not self-luminous but shines by radiating the light received from the sun.The orbits of all planets are elliptical.Their sizes, speeds, and distances from the sun vary.

Names of planets

There are nine planets so far known. In order of their nearness to the sun, they are (i) Mercury, (ii)Venus (iii)Earth (iv)Mars (v)Jupiter (vi)Saturn (vii)Uranus (viii) Neptune (ix)Pluto.

Farthest and Nearest planets

Pluto is the planet farthest from the sun while mercury is the planet nearest to the sun.

Largest and smallest planets

Jupiter with its diameter of about 85,750 miles (about eleven times of earth’s diameter) is the largest known planet of the solar system. Mercury with a diameter of about 3,030 miles is the smallest known planet.

Brightest planet

Venus appearing as a brilliant crescent is the brightest known planet.

Heaviest planet

Jupiter is the heaviest planet (314.5 times heavier than the earth).

Planets with the largest number of satellites

Jupiter has the maximum number of satellites (69).
Must Read:

The Solar System

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The Solar System formed billion years ago from the gravitational collapse of a region within a large molecular cloud. This initial cloud was likely several light-years across and probably birthed several stars. As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars. As the region that would become the Solar System.

Our solar system consists of an average star we call the Sun, the planets Mercury,   Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It includes the satellites of the planets; numerous comets, asteroids, and meteoroids; and the interplanetary medium.

Ancient astronomers observed points of light that appeared to move among the stars. They called these objects “planets,” meaning wanderers, and named them after Roman deities—Jupiter, king of the gods; Mars, the god of war; Mercury, messenger of the gods; Venus, the goddess of love and beauty, and Saturn, father of Jupiter and god of agriculture. The stargazers also observed comets with sparkling tails, and meteors or shooting stars apparently falling from the sky.

The four planets closest to the sun—Mercury, Venus, Earth, and Mars—are called the terrestrial planets because they have solid rocky surfaces. Jupiter, Saturn, Uranus, and Neptune are known as the Jovian (Jupiter-like) planets, because they are all gigantic compared with Earth, and they have a gaseous nature like Jupiter’s. The Jovian planets are also referred to as the gas giants, although some or all of them might have small solid cores.

Read Also: Solar System: Some Important Facts

Nearly every planet—and some of the moons—has an atmosphere. Earth’s atmosphere is primarily nitrogen and oxygen. Venus has a thick atmosphere of carbon dioxide, with traces of poisonous gases such as sulfur dioxide. Mars’s carbon dioxide atmosphere is extremely thin. Jupiter, Saturn, Uranus, and Neptune are primarily hydrogen and helium.

The Sun is the richest source of electromagnetic energy (mostly in the form of heat and light) in the solar system. The Sun’s nearest known stellar neighbour is a red dwarf star called Proxima Centauri, at a distance of 4.3 light years away. The whole solar system, together with the local stars visible on a clear night, orbits the center of our home galaxy, a spiral disk of 200 billion stars we call the Milky Way.

The Milky Way has two small galaxies orbiting it nearby, which are visible from the southern hemisphere. They are called the Large Magellanic Cloud and the Small Magellanic Cloud. The nearest large galaxy is the Andromeda Galaxy. It is a spiral galaxy like the Milky Way but is 4 times as massive and is 2 million light years away. Our galaxy, one of the billions of galaxies known, is travelling through intergalactic space.

Mercury

  • Mercury is the closest and second smallest in the Solar System.
  • Mercury is the second densest planet after Earth.
  • The only visit to Mercury was a flyby made by the Mariner 10 spacecraft in 1974.
  • Mercury speeds around the sun every 88 days, traveling through space at nearly 50 km (31 miles) per second
  • Galileo first observed Mercury during the 17th century.

Venus

  • Venus is the second closest and sixth largest planet in the Solar System
  • The orbital speed of Venus is 35 km per second.
  • Venus is the hottest planet in the Solar System.
  • Venus appears to be the brightest planet in the sky.
  • It takes 244.7 days for Venus to rotate on its axis.
  • The first robotic space probe mission to Venus and the first to any planet began on 12 February 1961, with the launch of the Venera 1 probe

Must Read: ‘Super-Jupiter’ Discovery Dwarfs Solar System’s Largest Planet

Earth

  • Earth formed approximately 4.54 billion years ago, and life appeared on its surface within one billion years.
  • The Earth is the densest planet in the Solar System.
  • Earth is the fifth largest planet in the Solar System.
  • The Diameter of the Earth is 12,756 km (7,926 miles)
  • The earth’s orbital speed is 29.8 km per second.
  • Earth atmosphere consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other ingredients.
  • Earth rotates about its own axis 366.26 times, creating 365.26 solar days

Mars

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System.

  • Iron oxide prevalent on its surface gives it a reddish appearance, often described as “ Red Planet”
  • A Mars year is equal to 686.98 Earth Days
  • A day on Mars is equal to 24.6 Earth Hours
  • Like Earth, Mars experiences seasons because of the tilt of its rotational axis
  • Asaph Hall discovered both of Mars’ moons, Phobos, and Deimos, in August 1877.
  • Mariner 4 – first successful flyby mission to Mars. Launched on November 28, 1964, and arrived at Mars on July 14, 1965.
  • Viking 1 – Successful orbit and landing on the surface of Mars. Launched August 20, 1975, and arrived on Mars July 20, 1976.

Jupitar

Jupiter, the largest planet in our solar system, is 318 times larger than Earth.

  • The orbital speed of Jupiter is 13.1 km/sec
  • A year on Jupiter is equal to 11.9 Earth Years
  • Jupiter has 67 natural satellites. 105 Of these, 51 are less than 10 kilometres in diameter and have only been discovered since 1975.
  • Galileo Galilei had discovered Jupiter’s four largest moons, now called Io, Europa, Ganymede, and Callisto. These four moons are known today as the Galilean satellites.
  • In 1610, Galileo Galilei makes the first detailed observations of Jupiter.
  • Jupiter’s moon Ganymede is the biggest satellite in solar system
  • Jupiter has rings, the third planet discovered to have a ring system in our Solar System.
  • Jupiter’s rings are identified as  Halo ring, Main ring, Amalthea gossamer ring, and Thebe gossamer ring.
  • Jupiter’s rings were discovered by Voyager 1 in 1979.

Saturn

Saturn is the sixth planet from the Sun and the second largest.

  • Saturn has 62 known moons, fifty-three have been named. Most of them are small in size.
  • Names of some of Saturn’s moons: the largest is Titan, discovered in 1655; Tethys, Dione, Rhea, & Iapetus, discovered from 1671 to 1672; Mimas & Enceladus, discovered in 1789; and Hyperion, discovered in 1848.
  • A year on Saturn is equal to 29.5 Earth Years
  • Pioneer 11 is the first spacecraft to reach Saturn, in 1979
  • Saturn has a prominent ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust.

Uranus

The orbital speed of Uranus is 6.6 km/sec

  • Uranus takes 84 Earth years to complete one orbit.
  • Uranus is the third largest planet in the Solar System.
  • Voyager 2, the only spacecraft to visit Uranus,
  • A day on Uranus is equal to a little more than 17 hours on Earth.
  • Uranus has 27 known moons, named for characters from the works of William Shakespeare or Alexander Pope
  • Uranus was discovered by Sir William Herschel in 1781

Don’t Miss: Satellites and Asteroids

Neptune

Neptune is the fourth largest planet and the coolest planet in the Solar System.

  • Neptune was the first planet located through mathematical predictions rather than through regular observations of the sky.
  • Neptune was discovered by Urbain Le Verrier, John Couch Adams, and Johann Galle on September 23, 1846.
  • The only spacecraft ever to visit Neptune was Voyager 2 in 1989.
  • The magnetic field of Neptune is about 27 times more powerful than that of Earth.
  • One Neptune year is equal to 164.83 Earth Years
  • Neptune has six known rings.
  • In 2011, Neptune completes its first 165-year orbit of the sun since its discovery in 1846.
  • Neptune has 13 moons, the largest of which is named Triton. The other moons are Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Nereid, Halimede, Sao, Laomedeia, Neso, and Psamathe.

Pluto

Pluto is the smallest planet in the Solar System, now consider as dwarf planet

  • Pluto is colder than Neptune.
  • Pluto’s journey around the Sun takes 248 Earth years.
  • Pluto is the second most contrast body in the Solar System
  • Pluto has not yet been visited by a spacecraft.
  • Pluto has a satellite, Charon, which was discovered (in 1978). The distance between them is 19,640 km (12,200 miles). The other 3 are Nix, Hydra, and newly discovered S/2011 P 1 on July of 2011.
  • Pluto rotation (a Pluto day) takes 6.4 Earth days, meaning that it has the second slowest rotation in the Solar System after Venus
  • Pluto was discovered by Tombaugh in 1930

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10 Countries with Space presence

Movements of Earth

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Syskool
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earth movements

There are three basic movements of the Earth has three basic movements: (i) Galactic movement, (ii) Rotation, and (iii) Revolution.

Galactic Movement

This is the movement of the Earth with the sun and the rest of the solar system in an orbit around the center of the Milky Way Galaxy. This movement has the little effect in changing the environment of the Earth.

Must Read: All About Earth

Rotation of the Earth

The Earth rotates (spins) around its axis. The axis is an imaginary line passing through the center of the Earth. Its two ends on the surface are called NORTH and SOUTH POLES. The Earth completes a rotation in 24 hours (23 hours, 56 minutes and 4 seconds to the exact).
The Earth rotates in an eastward direction opposite to the apparent movement of the sun, moon and stars across the sky. Looking down on a globe from above the North Pole, the direction of rotation is counter-clockwise (anti-clockwise direction). This eastward direction of rotation not only defines the movements of the zone of daylight on the Earth’s surface but also helps define the circulatory movements of the atmosphere and oceans.

The velocity of rotation of the Earth varies depending on the distance of a given place from the EQUATOR (the imaginary circle around the Earth halfway between the two poles). The rotational velocity at the poles is nearly zero. The greatest velocity of rotation is found at the Equator where the distance traveled by a point in 24 hours is largest, the velocity is about 1700 km per hour. At 60 degree parallel, it is half of what it is at the Equator (850 km per hour).

Rotation accounts for our alternating days and rights. While one-half of the Earth receives the light and energy of solar radiation, the other half would have been in darkness.

We are unaware of the speed of rotation, however, because—
(i) the rate is constant for each place on the Earth’s surface;
(ii) the atmosphere rotates with the Earth:
(Hi) there are no nearly objects, either stationary or moving at a different rate with respect to the Earth, to which we can relate the Earth’s movements.

Thus, without references, we are unable to perceive the speed of rotation. The line around the Earth separating the light and dark halves is known as the CIRCLE OF ILLUMINATION.

Also, Read: The Earth and the Moon

Revolution of the Earth

Earth also revolves around the sun in an elliptical, almost circular, orbit at an average distance from the sun of about 149,000,000 km. This motion is called REVOLUTION. The path in which the Earth describes its motion is called ORBIT. Because of the elliptical shape of the orbit, the distance varies from time to time. About January 3 the Earth is closest to the Sun and is said to be at PERIHELION (from Greek: ‘peri’ = close to; ‘helios’ = sun); its distance then from the sun is approximately 147 million km.

Around July 4 the Earth is about 152 million km from the sun. It is then that the Earth has reached its furthest point from the sun and is said to be at APHELION (Greek: ‘ap’ = away; ‘helios’ = sun). Five million km is insignificant in space and these varying distances from the Earth to the Sun do not materially affect the receipt of energy or Earth.

Speed of Revolution

The mean speed of the Earth is its orbit is 107,000 km per hour. The speed comes to 29-72 km per second. The bullet from a gun travels with a speed of 9 km per second.

The Period of Revolution

The period of time the Earth takes to make one revolution around the Sun determines the length of one year. Earth takes to complete one revolution of the Sun in 365 days & 6 hours. Because the Earth makes 365 degrees rotations on its axis during the time it takes to complete one revolution of the Sun, a year is said to have 365 days. Because of the difficulty of dealing with a fraction of a day, it has been decided that a year would have 365 days and that in every fourth year, called LEAP YEAR, an extra day would be added in February.

Plane of Ecliptic, Inclination, and Parallelism

The Earth in its orbit around the sun moves in a constant place. This plane is called the PLANE OF THE ECLIPTIC. The plane of the Earth’s 1° equator makes an angle of 23° with the plane of the ecliptic. Thus, the imaginary Earth axis, being perpendicular to the equator, has a constant ANGLE OF INCLINATION, 1° as it is called, of 66° with the plane of the ecliptic.

In addition to a constant angle of inclination, the Earth’s axis maintains another characteristic called PARALLELISM. As the Earth revolves around the Sun, the Earth’s axis remains parallel to its former position. That is, at every position in the Earth’s orbit the axis remains pointed towards the same spot in the sky. For the North Pole that spot is close to the star we call the NORTH STAR or POLARIS. Thus, the Earth’s axis is fixed with respect to the stars outside our solar system, but not with respect to the Sun.

Have a look at:

Geothermal Energy

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Syskool
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When we use heat from the Earth to generate energy it’s called geothermal energy. The name geothermal is a combination of the word “geo”, which means earth, and “thermal”, which means heat.

History of Geothermal Energy

The Ancient Romans took the concept a step further and used hot springs as a way to heat flooring and public baths. The first use of geothermal energy for electricity was in 1904 when the geothermal electric generator was invented. A few years later, in 1911, the first geothermal electric plant was built. In the 1940s, the heat pump began to be used for heating buildings, but it didn’t become popular until the 1970s oil crisis.
Must Read: Renewable energy

Uses of Geothermal Energy

There are three main ways that we harness and use geothermal energy:

  • Geothermal heat pumps – Geothermal heat pumps take advantage of this constant temperature to heat or cool water. By moving water through the Earth it can be heated in the winter or cooled in the summer. This water can then be used by a heat exchanger to heat or cool the air in a home. This can be a very efficient and inexpensive way to heat or cool buildings.
  • Direct use – Another way to take advantage of the Earth’s heat is to directly use hot water from hot springs. This water can be used with heat exchangers to heat up homes and buildings. It also can be used to heat pools.
  • Generating electricity – Finally, geothermal energy can be used by power plants to create electricity. Power plants take advantage of extremely hot water that is between one and two miles deep in the Earth. Some power plants pipe the steam directly up to the generator. They are called dry steam power plants. Other power plants, called flash steam plants, use high pressure from deep in the Earth to create steam to drive the generator.

Probably the main disadvantage to geothermal energy is the cost. It can be very expensive to build a geothermal plant. Building a plant can also be risky for a power company as the steam can potentially run out at a given site. The main environmental disadvantage is the possibility of releasing toxic gasses when the well is drilled into the ground.

Also Read: Renewable Energy (RE): Promoting ‘Make in India’

Facts about Geothermal Energy

  • The majority of geothermal electric plants in the United States are found in the western portion of the country. California is the number one producer, followed by Nevada, Utah, Hawaii, and Idaho.
  • The United States is the largest producer of geothermal electricity.
  • In 2011, the Philippines generated around 16% of their total electricity using geothermal electric plants. Iceland produced 26% of their total electricity using geothermal energy.
  • It is possible for geothermal electric plants to cause earthquakes.
  • The best place to find geothermal resources is along plate boundaries. This is also where you find the most volcanoes and get the most earthquakes.

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Important International Lines

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Syskool
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Important International Lines
Important International Lines
  • Durand Line: Between Pakistan and Afghanistan, demarcated by Sir Mortimer Durand in 1896.
  • Hindenberg Line: The line to which the Germans retreated in 1917 during the First World War, defines the boundary between Germany and Poland.
  • Line of Control: It divides Kashmir between India and Pakistan.
  • Maginot Line: Boundary between France and Germany.
  • Mannerheim Line: Drawn by General Mannerheim; fortification on the Russia and Finland border.
  • McMahon Line: The boundary between India and China as demarcated by Sir Henry McMahon in 1914.
  • Oder Niesse Line: Boundary between Germany and Poland.
  • Radcliffe Line: Drawn by Sir Cyril Radcliffe in 1947 as demarcation between India and Pakistan.
  • Seigfrid Line: Line of fortification drawn by Germany on its border with France.
  • 17th Parallel: Boundary between North Vietnam and South Vietnam before two were united.
  • 24th Parallel: Line which Pakistan claims for demarcation between India and Pakistan. This, however, is not recognized by India
  • 26th Parallel south: It is a circle of latitude which crosses through Africa, Australia and South America.
  • 30th Parallel north: It is a line of latitude that stands one-third of the way between the equator and the North Pole.
  • 33rd Parallel north: It is a circle of latitude which cuts through the southern United States, parts of North Africa, parts of the Middle East, and China.
  • 35th Parallel north: Boundary between the State of North Carolina and the State of Georgia and the boundary between the State of Tennessee arid the State of Georgia, the State of Albama, and the State of Mississippi.
  • 36th Parallel: Forms the southermost boundary of the State of Missouri with the State of Arkansas.
  • 37th Parallel north: It formed the southern boundary of the historic and extralegal Territory of Jefferson.
  • 38th Parallel: Is the parallel of latitude which separates North Korea and South Korea.
  • 39th Parallel north: Is an imaginary circle of latitude that is 39 degrees north of Earth’s equatorial plane.
  • 40th Parallel north: Formed the original northern boundary of the British Colony of Maryland.
  • 41st Parallel north: Forms the northern boundary of the State of Colorado with Nebraska and Wyoming and the southern boundary of the State of Wyoming with Colorado and Utah.
  • 42nd Parallel north: Forms most of the New York – Pennsylvania Border.
  • 43rd Parallel north: Forms most of the boundary between the State of Nebraska and the State of South Dakota and also formed the northern border of the historic and extralegal Territory of Jefferson.
  • Parallel 44o north: It is an imaginary circle of latitude that is 44 degrees north of the Earth’s equatorial plane.
  • 45th Parallel north: It is often the halfway point between the Equator and the North Pole.
  • The 45th parallel: It makes up most of the boundary between Montana and Wyoming.
  • 49th Parallel: It is the boundary between USA and Canada.
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