OUR UNIVERSE

IMPORTANT TERMS

Core                            – The innermost layer of the Earth.

Mantle                         – The middle layer of the Earth.

Crust                           – The outermost layer of Earth.

Corona                        – The layer of air around the Sun.

Solar Eclipse                – When Sun, Moon and Earth come in a straight line and Moon casts a shadow on Earth.

Lunar Eclipse               – When Sun, Moon and Earth come in a straight line and Earth casts a shadow on Moon.

Total Solar Eclipse        – When Sun, Moon and the Earth come in a straight line and Sun is completely hidden by the Moon.

Partial Solar Eclipse      – When Sun, Moon and the Earth come in a straight line and Sun is partially hidden by the Moon.

Total Lunar Eclipse       – When Sun, Moon and the Earth come in a straight line and Moon is completely hidden by the Earth.

Partial Lunar Eclipse     – When Sun, Moon and the Earth come in a straight line and Moon is partially hidden by the Earth.

Solar System               – The Sun and the celestial bodies that revolve around it forms the Solar System.

Satellite                       – A celestial body that orbits the planet in the solar system.

Artificial Satellite           – Man made satellite sent to space for weather forecasts, navigation, and communication etc.

SOLAR SYSTEM

Our solar system consists of Sun, planets, their moons, comets, asteroids etc.

 

In order of increasing distances from the Sun, the eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto is no longer considered a planet since 2006 and it has been put in the category of Dwarf planets.

 

SUN

Sun is a big ball of hot burning gases.It is made up of hydrogen and helium. Hydrogen keeps changing to helium and this process emits lot of heat and light.

Sun is a star and centre of the solar system. It is at a distance of 150 million kilometer away from Earth. The temperature at the centre of the Sun is 15 billion degree Celsius.  It has a diameter of about 1,392,000 Km.

EARTH

Our earth is the only planet which sustains life. Two-third of the Earth’s surface is covered with water. It has water, air and soil.

There is a blanket of air around the earth called as atmosphere. The atmosphere contains Ozone layer that protects us from harmful Ultra violet rays.

Internal structure of the earth

Our planet Earth is made up of three layers:--

Crust

Mantle

Core

It is the outermost layer.

It is the middle layer.

It is the inner most layer and contains two part i.e. outer core and inner core

It thickness varies from 5

Km under the ocean floor to 70 Km under the continents.

It is about 2,900 Km thick.

The outer core has a thickness of 2,300 Km.

The inner core has a thickness of 1,200 Km.

It is made up of Rocks.

It is made up of iron and magnesium, the upper part is made up of solid rock and the lower part is made up of molten rock.

The outer core is made up of iron and nickel in molten state and the inner core is made up entirely of iron.

 

MOON

Moon is a natural satellite of the earth. It is at a distance of 384,400 Kilometer from Earth. It does not have its own light, it reflects the Sun’s light to us. The surface of Moon is covered with craters, mountains, valleys.

Moon does not have air, water or atmosphere, due to which sound cannot be heard on Moon. Since Moon does not have an atmosphere, it cannot filter the heat of the Sun. So, it becomes quite hot during the day (100 degree Celsius) and freezing cold at night (-150 degree Celsius).

Moon is about one-fourth in mass to earth. Its gravity is about one-sixth to that of Earth. So, if you weight yourself on Moon it is about one-sixth to that of the earth.

 

 

Phases of moon

The moon appears to change its shape almost daily. These illusionary shapes of the moon are called the phases of the Moon.

Day 1 – When the side of the Moon facing the Earth reflects no sunlight, we cannot see the Moon and it is called New Moon.

Day 3 – When a small portion of the Moon can be seen, it is called as Crescent Moon.

Day 7 – When half of the Moon can be seen, it is called Half Moon.

Day 10 –When we see three-quarters of the Moon, it is called Gibbous Moon.

Day 14 –When the entire side of the moon facing the Earth gets sunlight, we can see the full Moon.

The phases of the moon move in the reverse order after reaching Full Moon.

The time between two full Moons is approximately 29.53 days on an average and is called as Synodic Month. The time Moon takes to have a orbit around the earth with respect to fixed stars is about 27.32 days and is called a sidereal month. The second Full Moon of the month is called Blue Moon.

Moon Landings

The first manned spacecraft to land on the moon was Apollo11. It was carried by the rocket Saturn-5. It was commanded by Commander Michael Collins and carried Neil Armstrong and Edwin Aldrin and to Moon on 21 July 1969.Neil Armstrong became the first man to land on Moon.

Chandrayaan-1 was the India’s first space craft sent to moon. It was launched on 22 October 2008 from ISRO.

Artificial Satellites

There are different types of satellites each designed for a special purpose.

Communication Satellites send signals for T.V and Radio programs and telephone calls.

Navigation Satellites helps ships and aircrafts find their way.

Astronomy Satellites carry telescopes into space.

Weather satellites help in weather forecasting.

Aryabhatta was India’s first artificial satellite launched in 1975.

 

Characteristics of the Planets of Solar System

Planets (in order of distance from Sun)

No. of Moons

Time  of       Revolution

Other Characteristics

Mercury

No Moon

88 Days

Smallest Planet

 

Venus

No Moon

224 Days

Hottest and Brightest Planet

Earth

1 Moon

365 Days

Only planet where life exists.

About 70% of the surface is covered with water.

Mars

2 Moons

687 Days

Contains lot of rusted iron, which makes it look red and known as the Red planet.

Jupiter

 

63 Moons

12 Years

Largest Planet

Saturn

60 Moons

30 Years

Second largest Planet.

Contains rings around it.

Uranus

27 Moons

84 Years

Contains many gases such as Hydrogen, Helium and Methane.

Neptune

13 Moons

165 years

Appears blue in colour due to the presence of Methane gas.

 

INTRESTING FACTS

Pluto is smaller than the U.S.A

The hottest planet Venus is actually not the closest to the Sun. It is planet Mercury which is closest to the Sun but not the hottest.

There are five dwarf planets in our Solar System. They are Pluto, Ceres, Eris, Makemake, Haumea.

One day on Mercury is equal to 58 Earth Days.

One seasons on Uranus last for about 20 Earth Years.