Our Solar System

The solar system consists of the Sun, the eight planets and their satellites and various other smaller heavenly bodies such as asteroids, comets and meteors.
The Sun
➤ The sun is a star. It is the star around which the earth and other planets revolve.
➤ It is the nearest star to the earth. It is at a distance of 150×106 kilometres from the earth.
➤ Light travelling at a speed of 300,000 km. per second, takes about 8 minutes to reach us from the Sun.
➤ The next nearest star to earth is “Alpha Centuari”.
➤ The Sun is mainly composed of hydrogen. The glowing surface of the Sun which we see is called ‘Photosphere’.
➤ Above the photospheres is the red cloud ‘Chromosphere’. Beyond the chromospheres is the ‘Corona’, which is visible during eclipses.
➤ The temperature of the photospheres is about 6000°C, that of the chromosphere about 32400°C, and that of the corona about 2,700,000°C.
➤ The core of the Sun has a temperature about 15 million degrees C.
➤ The dark lines in the corona are called ‘Fraunhofer lines’. The emission of hydrogen in all directions is called ‘Prominences’.
➤ Sometimes they roll out of the atmosphere to be seen as ‘Solar flares’.
➤ The outward stream of protons flowing out from the corona are called ‘Solar winds’, which is made up of plasma.
➤ The earth’s Magnetosphere or Van Allen belts, as they were earlier called, acts as a shield and deflects the Solar winds.
➤ ‘Sun spots’ are dark patches notched on the surface of the Sun. They appear dark because they are cooler i.e. they have a temperature of about 1500°C.

The Moon

➤ The Moon’s diameter is onefourth of Earth diameter.
➤ Circumference: 11000 km. approximately.
➤ Gravitational Pull in 1/6th of the Earth.
➤ Its orbit around the earth in elliptical orbit.
➤ Distance between the Earth and the Moon is 3,82500 km. approx. (According to NASA)
➤ The distance varies because it revolves around the Earth is an elliptical orbit.
➤ At Perigee the point at which the moon is closest to the Earth, the distance is approximately 3,60000 km.
➤ At Epogee the point at which the moon is farthest to the earth, the distance is approximately 4,05,000 km. (According to NASA).
➤ The Moon is 1/4th size of the Earth.
➤ The Moon take 27 day, 7 hrs, 43 min. and 11.47 sec. to complete one revolution around the Earth.
➤ The Moon in the only satellite of the Earth.
➤ The Moon rotates on its axis in exactly the same time as that of its revolution. That’s why we see only one part of the moon.
➤ We can see only 59% of its surface.
➤ There is no atmosphere on the moon.
➤ The moon has no light of its own. It reflects sun light.
➤ The reflected light by the moon reaches on the Earth in 1.3 seconds.
➤ It has a low albedo.
➤ It reflects only 7% and the rest is absorbed by venus.
➤ Neil Armstrong and Aldrin reached the moon on 21, July 1969. Through Apollo × 1.
➤ Landing spot is called ‘sea of tranquility’
➤ The black spot on the moon is called ‘sea of tranquility.’

The Earth

➤ It is our planet.
➤ As per order in distance from the sun. It is at third position.
➤ It is at 5th position according to size.
➤ It takes 365 days and 6 hrs. for one rotation around the sun.
➤ It is similiar to venus in shape and size.
➤ It is the only planet where life exists.
➤ It is also called ‘Blue Planet’.
➤ It is the densest of all Planet.
➤ Perihelian is the nearest position of the Earth to the Sun.
➤ The Earth reaches its perihelion on January 3 every year at a distance of about 147 million km.
➤ Aphelian is the farthest position of the Earth from the Sun.
➤ The Earth reaches its aphelian on july 4, when the earth is at a distance of 152 million km.
➤ It is also called ‘Green Planet’ because of ecology.
➤ Venus is the nearest planet to the Earth.
➤ The Earth revolves around the sun at a speed of 29.8 km/second. Eclipse
➤ An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer.

Solar Eclipse

➤ As observed from the Earth, a solar eclipse occurs when the Moon passes in front of the Sun.
➤ The type of solar eclipse event depends on the distance of the Moon from the Earth during the event.
➤ A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon’s shadow.
➤ When the umbra does not reach the surface of the Earth, the Sun is only partially occulted, resulting in an annular eclipse.
➤ Partial solar eclipses occur when the viewer is inside the penumbra.
➤ When observed at points in space other than from the Earth’s surface, the Sun can be eclipsed by bodies other than the Moon.
➤ Two examples are when the crew of Apollo 12 observed the Earth to eclipse the Sun in 1969 and when the Cassini probe observed Saturn to eclipse the Sun in 2006.

Lunar Eclipse

➤ Lunar eclipses occur when the Moon passes through the Earth’s shadow.
➤ Since this occurs only when the Moon is on the far side of the Earth from the Sun, lunar eclipses only occur when there is a full moon.
➤ There are three types of lunar eclipses:
● Penumbral, when the Moon crosses only the Earth’s penumbra;
● Partial, when the Moon crosses partially into the Earth’s umbra;
● Total, when the Moon crosses entirely into the Earth’s umbra.

Planets
➤ Planets are solid heavenly bodies which revolve around the Sun in closed elliptical paths.
➤ A Planet is made up of rock and metal.
➤ The Planets move around the Sun from west to east.
➤ There are eight major Planets including earth.
The Eight Planets are –
(1) Mercury (Budha)
(2) Venus (Shukra)
(3) Earth (Prithvi)
(4) Mars (Mangal)
(5) Jupiter (Brihaspati)
(6) Saturn (Shani)
(7) Uranus (Indra)
(8) Neptune (Varun)

Pluto (Yama) is not a planet now, Pluto is considered as Dwarf planet.
Pluto was discovered by Clyde Tombaugh in 1930. The redefinition of planet by the International Astronomical Union (IAU) on August 24, 2006 states that, in the Solar System, a planet is a celestial body that
➤ orbit around the Sun.
➤ has sufficient mass so that it assumes a hydrostatic equlibrium (nearly round) shape.
➤ has cleared the neighbourhood around its orbit.
➤ A non-satellite body fulfilling the first two rule is classified as a Dwarf planet. So, Pluto is considered as Dwarf planet.
➤ A non-satellite body fulfilling the first rule is termed as Small Solar System Body (SSSB).
➤ According to the definition, there are currently eight planets and five Dwarf planets known in the Solar System. The 5 Dwarf planets are Pluto, Ceres, Eris, Makemake and Haumea.
➤ Pluto has been given the number 134340. Asteroids: Asteroids are very small planets of rock and metal which revolve around the Sun mainly between the orbits of Mars and Jupiter.

Comets.

A comet is a collection of gas and dust which appears as a bright ball of light in the sky with a long glowing tail.

Meteors.

Meteors are the heavenly bodies from the sky which are seen as a bright streak of light in the sky. The meteors are also called as shooting stars.

Meteorite.

A meteor which does not burn completely on entering the earth’s atmosphere and lands on earth surface is known as Meteorite.