SOLAR SYSTEM

 

SOLAR SYSTEM

Our solar system comprises of 1 Star (the Sun),  8 Planets and their Satellites, 5 Dwarf Planets and countless fragments left-over during condensation such as Asteroids, meteors, and comets etc. known as Small Solar System  bodies (SSSB).

 Origin of Solar System

Various theories have been given by different persons to explain the origin of Solar System.

Theory	Proposer	Time line
Gaseous Hypothesis	Emanuel Kant	1755 A.D
NEBULAR Hypothesis	Pierre Laplace	1796 A.D
Tidal Hypothesis	James Jeans & Harold Jeffrey	1919 A.D
Binary Star Hypothesis	H.N. Russel	1937 A.D

 

·         Astronomy: the study of stars or space.

·         Helioseismology: the scientific study of Sun.

·         Planetology: the study of Planets.

·         Selenography: the study of Moon.

The Sun

·         It is a medium size star in the  milky way Galaxy, of 4.5 billion years of age and has a total life of 10 billion years.

·         The radius of Sun is 109 time bigger than the radius of the Earth and weights about 2 x 10²⁷ tons(2 x 10³⁰ kg)

·         It contains 98% mass of the Solar System.

·         It takes 224 million years to complete one revolution around the galactic circle called a Cosmic Year.

·         Its glowing surface , which we can see by naked eye is called Photo Sphere.

·         Above the  photo sphere is the Chromo Sphere and beyond the Chromo Sphere is the CORONA which is visible during Solar Eclipses.

·         The surface temperature of Sun is around 5500 ⁰ C to 6000 ⁰C and it increases upto 15 million  ⁰C  in the core.

·         Super imposed on Suns white light are 100s of dark lines called Fraunhofer Lines. Each line indicates some elements present in the solar atmosphere.  

·         Diameter of sun is 13,91,980 km

·         Chemical composition : Hydrogen 70%, Helium 28% and other gases 2%

·         Gravitational pull is 28 times more than the gravitational pull of Earth.

·         Distance from earth is 14,95,98,900 km/ 150 million km.

·         Sun light takes 8 minutes 16.6 sec to reach earth.

Solar Flares

·         Sometimes streams of protons emitted from the solar surface travels for thousands of miles known as Solar Flares.

Solar Wind

·         A persistence stream  of protons and electrons is blowing out of the corona and sweeping over the whole solar system  is called as Solar Wind.

·         The earth’s magnetosphere bacts as a shield against the ever blowing solar wind and deflect it away from the earth.

·         Sometimes solar wind pierce the magnetic shield and enter the upper atmosphere and cause aroral display. In the arctic region they called as Aurora borealis and in Antarctic region they called as Aurora  Australis.

·         The surface of the sun changes continuously . Bright spots called Plages and dark spots called Sun spots.

·         Sunspots appear dark because they are cooler with temperature of about 1500⁰C.Sun Spot cycle have a periodicity of 11 years.

·         The energy of Sun comes from fusion of hydrogen in to helium.  

 

THE PLANETS

According to the 2006 redefinition of ‘Planet’ by the International Astronomical Union (IAU) states that , in the solar system , a planet is a celestial body that

·         Is capable of orbiting around  the Sun.

·         Has sufficient mass so that it assume a hydrostatic equilibrium  to have round shape.

·         Has capable of “cleared the neighbourhood” around its orbit.

A non-satellite body fulfilling the first two of these criteria is classified as a Dwarf planet, while a non-satellite body fulfilling only the first criterion is termed as a small solar system body(SSSB).

·         Accordind to the definition there are currently  8 planets and 5 dwarf planets in the Solar System.

·         The five Dwarf Planets are Pluto, Ceres, Eris, Makemake and Haumea.

·         The 8 Planets are Mercury, Venus, Earth, Mars(called inner and terrestrial planets) and Jupiter, Saturn, Uranus, Neptune(called outer, jovian planets or gas giants).

·         Planets according to size : Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars and Mercuruy.

 Mercury

·         Fastest revolutionary planet in the solar system with revolution period of 88 days.

·         Rotation : 58.65 days

·         Maximum diurnal range of temperature.

·         It has no atmosphere and no satellite.

Venus

·         Also called Earth’s Twin/ Earth’s Sister, because it is slightly smaller than earth(500 km less in diameter).

·         Popularly known as Evening Star and Morning Star. It is seen in the east in the morning and in the west in the evening.

·         It is the brightest planet in the solar system because of high albedo(70%).

·         Closest planet to Earth.

·         It is the hottest planet in the solar system due to the Green House Effect (90 to 95% Co₂) present in the atmosphere.

·         Rotates from east to west( clockwise ) unlike others.

·         It has slowest rotation (257 days) in solar system.

·         Almost equal rotation and revolution (224.7 days).

·         It has no satellite

Mars

·         Called as Red Planet due to presence of ferrous oxide in its surface.

·         Rotation: 24.6 hours(almost equal to earth)

·         Revolution;   687 days

·         It has a thin atmosphere comprising of nitrogen and argon.

·         The highest mountain named Nix Olympia which is three times higher than Mount Everest.

·         It has two satellites: Phobos and Deimos(smallest satellite in the solar system)

JUPITER

·         Largest of all planets having 71% mass of all planets and called as lord of heavens.

·         It gives off more energy than it receives from the sun, because of heat inside.

·         Its atmosphere contains hydrogen, helium, methane, ammonia etc.

·         A great red spot is detected on its surface. It represents a huge storm – a super hurricane , existing for 100s of years, without abating, probably powered by its internal heat.

·         It has fastest rotation time (9.8hrs) in the solar system.

·         Revolution :12 years

·         It has 79(67+12) satellites, of which Lo, Europa, Ganymede and Callisto are prominent and called as Galilean satellites.

·         Ganymede is the largest satellite of solar system.

Saturn

·         It is the second largest planet

·         It is the planet with maximum number of satellites(82=62+20)

·         It has least density of all( 30 times less dense than earth)

·         Rotation:10.3 hrs.

·         Revolution:29 years

·         It has 3 well defined rings. These are separate particles that move independently in circular orbits.

Uranus

·         Identified as a planet in 1781 by William Hershel

·         Seems to rotate from north to south as it is inclined at an angle of 98⁰ to its orbit.

·         Rotation:10.8 hours

·         Revolution:84years

·         Surrounded  by a system of 9 faint rings.

·         Called as green planet

·         It has 27 satellites of which Miranda and Ariel are prominent.

Neptune

·         Discovered by J.G. Galle in 1846

·         Rotation:15.7 day

·         Revolution:165 years

·         Has 5 faint rings

·         Have 13 satellites (Triton and Nereid)

Moon

·         Circumference:11,000 km

·         Diameter:3475 km

·         Gravitational pull: 1/6^th of Earth.

·         Its average distance from the earth is 3,85,000 km.

·         The maximum distance (4,06,000 km) of moon from earth is called Apogee and the minimum distance (3,64,000 km)is called Perigee.

·         It takes 27 days , 7 hours, 43 min and 11.47 sec to complete one revolution around the earth.

·         Rotates on its own axis in exactly the same time as it take to complete one revolution. This is why we see only one side of the moon.

·         The highest mountain on the moon are Liebnitz Mountains which are 10, 660 m high. They are situated at moons south pole

·         Moon has no satellite , no twilight, and no sound

·         Moonlight takes 1.3 second to reach earth surface.

·         It has low albedo(7%)

·         Neil Armstrong and Buzz Aldrin reached moon on July 20, 1969 on Apolo XI.( Landing spot is called sea of Tranquility)  

·         Ocean of Storms (Oceanus Procellarum) is a vast lunar mare on the western edge of the near side of the moon.

Kuiper Belt

• It is a region of the solar system that exist beyond the eight major planets extending from 30 AU to 50 AU from the sun. it is consists of various icy objects, which are ramnants from the solar system formation.
• Ultima Thule: it is officially known as 2014MU69, is a Kuiper Belt Icy object discovered by the Hubble Space Telescope in 2014. It became the farthest object ever visited by a space craft in 2019 as NASA’S New Horizons spacecraft fly past it.

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