August 20, 2013

Solar System and Planets for Civil Services

Solar system and planets Wiki. The solar system consists of the Sun and 8 planets revolving around it in different orbits.
Age:    About 5 Billion years
Distance:    149.8 Million Kms
Diameter:    1,38,400 Kms.
Photosphere temperature : 5,770 K
Core temperature:    150,000,000 K 
Absolute visual magnitude: 4.75
Rotation (as seen from the earth at the equator): 25.38 days
Rotation (near the poles): 33 days
  • The sun consists of 71% of Hydrogen, 26.5% Helium and 2.5% of other elements.
  • The rays of the Sun take about 8 minutes to reach the earth.
  • The Sun resides in one of the Milky Way's outer spiral arms, known as the Orion–Cygnus Arm or Local Spur.
  • Next closest star is the triple star system Alpha Centauri(A, B and C), which is about 4.4 light years away. 
  • The stars next closest to the Sun are the red dwarfs Barnard's Star (at 5.9 light years), Wolf 359 (7.8 light years), and Lalande 21185 (8.3 light years). The largest star within ten light years is Sirius.

 What is Galactic Year?
The Sun lies between 25,000 and 28,000 light years from the Galactic Centre, and its speed within the galaxy is about 220 kilometres per second (140 mi/s), so that it completes one revolution every 225–250 million years. This revolution is known as the Solar System's galactic year. 
Solar System and Planets for Civil Services
What are the conditions to be satisfied for planet-hood status? Why Pluto was removed from Planet list, which conditions it satisfied and where it failed?

1. A planet has to orbit the Sun. Pluto does that.
2. A planet needs enough gravity to pull itself into a sphere. Okay, spherical. Pluto’s is spherical.
3. A planet needs to have cleared out its orbit of other objects. Uh oh, Pluto hasn’t done that.
For example, planet Earth accounts for a million times the rest of the material in its orbit, while Pluto is just a fraction of the icy objects in its realm.

Comparison of planets based on size, radius, density, surface gravity:
(109 km3)
×1021 kg
(w/o gas)
The inner Solar System is the traditional name for the region comprising the terrestrial planets and asteroids. 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.

It is the planet nearest to the earth and smallest one in solar system.
Mercury has no natural satellites
Average distance to the Sun  :    57.6 Million Kms.
Diameter   :  4,849.6 Kms.
Period of revolution      :    88 days
Period of rotation          :    58 days 15 hrs 30 mts. 34sec.

(2)  VENUS
It is also known as the Morning Star or the Evening Star.
It is the brightest of all the planets. is close in size to Earth (0.815 Earth masses) and, like Earth, has a thick silicate mantle around an iron core, a substantial atmosphere, and evidence of internal geological activity.
 Venus has no natural satellites.
 It is the hottest planet, with surface temperatures over 400 °C (752°F), most likely due to the amount of greenhouse gases in the atmosphere
Diameter  :    12,032 Kms.
Period of revolution  :    225 days
Period of rotation   :    243 days 14mts.

(3)  EARTH
Surface Area                     :  510,100,500 Sq.Kms.
Polar radius                       :  6,357 Kms.
 Land Surface                    :  148,950,800 (29.08%)
Water Surface                   :  361,149,700 (70.92%)
Equatorial circumference  :  40,075 Kms.
Polar circumference          :  40,008 Kms
Equatorial radius              :  6,377 Kms.
Equatorial Diameter          :  1,22,756 Kms.
Polar Diameter                  :  12,714 Kms.
 Mean distance from the Sun  :  14,95,97,900 Kms.
Period of revolution   :  365 days 5 hours 48 mts. 45.51 Sec.
Period of rotation    :  23 hrs. 56 mts. 4.091 Sec.
Escape Velocity from the earth  :  11 Km per Sec. (minimum)

Some important Data about Earth:
                            The Earth is a sphere but it is not a perfect sphere. It is slightly flattened at the poles and bulges at the equator. The circumference of the earth is approximately 25,000 miles (40,000 Kms).It rotates on its axis once in every 24 hours, spinning from west to east. Besides spinning on its axis, it also moves round the Sun, called the revolution.
Its orbit round the Sun is oval or ecliptical. The time taken to complete one revolution is approximately 365¼  days or one year. For convenience, one year is taken  as  365  days  and  the  shortfall  of  ¼  day  each year  is  made  good in the Leap Year which consists of 366 days. The Earth’s axis inclined to the plane of its orbit at an angle of 66½ position in the course of its revolution about the Sun, and to the inclination of its axis. The Equator is an imaginary line drawn round the Earth midway between the Poles. There are two other lines, namely, Tropic of Cancer (23½ N) and the Tropic of Capricon (23½ S). The word tropic means, ‘turning place’. The inclination of the Earth’s axis together with its revolution round the Sun is the cause of the varying length of day and night in different parts of the world. On March 21 (Vernal Equinox) and September 23 (Autumnal Equinox) the Sun is over- head at the Equator. On these dates, except at the Poles,
 (a) days and nights are equal all over the world; and
(b) the Sun rises exactly due east and set exactly due west at all places on the Earth’s surface.
 At the Equator itself days and nights are equal throughout the year.
Between March 21 and September 23, when the North Pole is tilted towards the Sun, the days are longer than the nights throughout the Northern Hemisphere and there is continuous daylight at the North Pole. Similar conditions are experienced in the Southern Hemisphere and the South Pole between September 25 and March 21.

(4)  MARS
Diameter   :    6,755.2 Kms. is smaller than Earth and Venus (0.107 Earth masses).
Its surface, peppered with vast volcanoes such as Olympus Mons and rift valleys such as Valles Marineris.
Its red colour comes from iron oxide (rust) in its soil.
Mars has two tiny natural satellites (Deimos and Phobos) thought to be captured asteroids
Distance from the Sun   :    225.6 Million Kms.
Period of revolution      :    687 days
Period of rotation          :    24 hrs 37 mts. 22.663 sec.

Outer planets of Solar System:
he four outer planets, or gas giants (sometimes called Jovian planets), collectively make up 99% of the mass known to orbit the Sun

(5)  JUPITER   :    This is the largest planet in the solar system.
Diameter     :    141,968 Kms.
Distance from the Sun   :    772.8 Million Kms.
Period of revolution      :    11.9 years
Period of rotation          :    9 hrs 50 mts. 30 sec.
It is composed largely of hydrogen and helium. Jupiter's strong internal heat creates a number of semi-permanent features in its atmosphere, such as cloud bands and the Great Red Spot.
Jupiter has 67 known satellites.
The four largest, Ganymede, Callisto, Io, and Europa.
Ganymede, the largest satellite in the Solar System.

Topics To Be Read
 (6)  SATURN    :    It was discovered by Galileo.
Diameter :     119,296 Kms.
Distance from the Sun   :    1,417.6 Million Kms.
Period of revolution      :    29.5 years
Period of rotation          :    10 hrs 14 mts.
least dense planet in the Solar System.
Saturn has 62 confirmed satellites; two important moons are Titan and Enceladus.
Titan, the second-largest moon in the Solar System.

Diameter     :    52,096 Kms.
 Distance from the Sun   :    2,852.8 Million Kms.
 Period of revolution      :    84 years
Period of rotation          :    16 hrs 10 mts.
its axial tilt is over ninety degrees to the ecliptic.
Uranus has 27 known satellites, the largest ones being Titania, Oberon, Umbriel, Ariel, and Miranda.

Diameter                        :    49,000 Kms.
Distance from the Sun   :    4,497 Million Kms.
Period of revolution      :    165 years
Period of rotation          :    18 hrs 26 mts.
Neptune has 14 known satellites. The largest, Triton, is geologically active, with geysers of liquid nitrogen

(9)  PLUTO :   It's not a planet anymore. But it is the coldest and smallest of all planets. It is also the most distant one(while it was planet)
Diameter  :    3,040 Kms.
Distance from the Sun   :    5,865.6 Million Kms.
Period of revolution      :    248 years
Period of rotation          :    6 days 9 hrs and 18 mts.

MOON   :  Monn is a dead planet.  Moon is earth's satellite. Its period of rotation and Period of Revolution are the same. i.e.29.5  days. 
Solar System and Planets for Civil Services
Some other Important Points:
  • The asteroid belt occupies the orbit between Mars and Jupiter
  • Ceres (2.77 AU) is the largest asteroid, a protoplanet, and a dwarf planet
  • Uranus and Neptune are called Ice Giants.
  • Saturn's ring system is easily observed from Earth.
  • Eris (68 AU average) is the largest known scattered disc object, and caused a debate about what constitutes a planet.
Solar System and Planets for Civil Services
What is 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. The Kuiper Belt is a disc-shaped region of icy objects beyond the orbit of Neptune -- billions of kilometers from our sun. The makeup of Kuiper Belt Objects is similar to the composition of comets – a mixture of frozen water, ammonia and various hydrocarbons, such as methane.

What are Centaurs?
The centaurs are icy comet-like bodies with a semi-major axis greater than Jupiter's (5.5 AU) and less than Neptune's (30 AU). The first centaur discovered, 2060 Chiron, has also been classified as comet (95P) because it develops a coma just as comets do when they approach the Sun.

What is comet, how is it different from Asteroid?
Comets have eccentric orbits so their distance from the Sun varies considerably. The nucleus of a comet is composed of volatile material. When a comet is far from the sun, this material usually stays pristine but when the comet comes closer to the sun, solar radiation and solar winds cause it to lose some volatile compounds from its surface. This gives it a coma i.e. a nebulous appearance and a thin, transient atmosphere, which differentiates it from asteroids.

What’s the difference between a comet, asteroid, meteoroid, meteor & meteorite?
Comet: A comet is a relatively small solar system body that orbits the Sun. When a comet enters the inner Solar System, its proximity to the Sun causes its icy surface to sublimate and ionise, creating a coma: a long tail of gas and dust often visible to the naked eye.

Asteroid: Asteroids are small solar system bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds. Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do.

Meteoroid: A meteoroid is a small rock or particle of debris in our solar system. They range in size from dust to around 10 metres in diameter (larger objects are usually referred to as asteroids).

Meteor: A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor. If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor.

Meteorite: A meteoroid that survives falling through the Earth’s atmosphere and colliding with the Earth’s surface is known as a meteorite.

What is Heliopause?
The region surrounding the solar system at which pressure from the outgoing solar wind equals the pressure from the interstellar medium (made up mostly of hydrogen and helium), and the solar wind can penetrate no further. It is considered to be the outer boundary of our solar system


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