Essay, Paragraph or Speech on “Our Universe” Complete Essay, Speech for Class 10, Class 12 and Graduation and other classes.

Our Universe

The Universe consist of innumerable stars, galaxies, nebulae and other celestial bodies.

Galaxy—A galaxy is a huge congregation of millions of stars held together by its own gravitational field. Based on structure they are classified into three types—Spiral galaxies, Elliptical Galaxies and Irregular galaxies.

Spiral Galaxies

There is a greater concentration of old stars in the centre, whereas younger stars are concentrated in the arms.

Elliptical Galaxies

Elliptical galaxies constitute about 2/3 of all galaxies consisting of old stars

Irregular Galaxies

Irregular galaxies comprise of 1/10 of all galaxies consisting of only young stars.

Milky Way (which is our galaxy) and Andromeda are spiral galaxies. The large Megellanic Cloud and the Small Magallanic Cloud are the two nearest galaxies to our galaxy Milkyway.

Local Group—Local group is the group/cluster of 23 galaxies of which Andromeda and the Milky Way are the largest.

Nebulae—Nebulae is steller system of luminous bodies made up of gas and dust particles. Orion Nebulae exists in our Milky Way galaxy.

Constellations—Constellations are the clusters of stars which are organised into distinct shapes and figures and named accordingly. Hydra is the largest constellations in the Universe.

Asteroids—Asteroids are the series of planets or fragments of planets. They lie between the orbits of Jupiter and Mars and number nearly about 40000 to 45000. Ceres is the largest Asteroid in the Universe. Its length is nearly about 1000 km. Asteroids move around the sun in the same ways as the planets do.

Comets—Comets are the huge clouds of frozen gases existing in the outer cold fringes of the solar system. A comet has three parts viz., Centre Coma and Tail. A comet has an eccentric orbit and definite periodicity, for example Halleys Comet appears after every 76 years. The central part of a comet consists of dust and particles; when it gets closer to the sun, the tail originates but is away from the sun.

Meteor—Meteors are the scattered remains of comets lying in the interplanetary space. When they come in contact with Earth’s atmosphere. They start burning due to friction. The meteors which are burnt to ash completely are known as Meteors or shooting stars. Thus Meteors are also called shooting stars.

Meteorites—When the scattered remains of comets lying in the interplanetary space do not get burnt completely after coming into contact with Earth’s atmosphere. They are called meteorites. They strike the earth in the form of rock; for example the Allan Hills 84001 meteorite which threw light on the possibility of life on Mars when it struck the Earth in the form of rock.

Quasars—Quasars are the matters in the Univers which appear small but emit more energy than the stars in the Milky Way.

The Sun and Nine Planets—The solar system which consist of the sun, nine planets and their satellites constitute a very small part of the galaxy—Milky way. The planets in Solar System are divided into types viz., inner or terrestrial planets having higher densities such as Earth, Mars, Venus and Mercury and outer planets having lighter densities such as Jupiter, Saturn, Uranus, Neptune and Pluto. Of all inner or terrestrial planets the earth is the largest. The outer planets (i.e. Jupiter, Saturn) being big are also called Giant Planets.

The Sun—The sun is mainly composed of hydrogen, its surface (visible) is known as photophere above the ptotosphere, the red coloured chromosphere lies and beyond chromosphere is the portion called corona. The temperature of pholosphere is 6000°C and that of chromosphere is 32400°C. The temperature of corona is 2700000°C. Sun spots are the dark patches on the surface of the sun. Fraunhofer are dark line on the corona. Solar winds are outward flowing stream of protons from corona. It is van Allen belt which shield us from solar winds by deflecting solar winds. Sun takes 250 million years to take a complete revolution around its centre known as cosmic year.

Planets : At a Glance

Planets                                             Characteristic Features                          Number of Satellites

1. Mercury No Atmosphere has Rocks, many No satellite craters Temp 170°C to 400°C

2. Venus (brightest hottest) Atmosphere is mostly carbon No satellites dioxide, vast plains and high mountains,  temp-500°C.

3. Earth (Blue Planet) Atmosphere mostly is nitrogen and Oxygen, 1 satellite (moon) Surface covered with water. Temp-15°C.

4. Mars (Red Planet) Thin Atmosphere with Carbon 2 Satellites Phobos & Deimos dioxide and nitrogen. There are polar ice caps and dry river beds on surface. Temp-100°C to 30°C.

5. Jupiter Atmosphere mostly hydrogen and helium. No solid surface, Temp-125°.                 16 satellites 4 largest satellites & Europa Garymede Callists

6. Saturn Atmosphere mostly hydrogen and 18 satellites, only Titan helium. No solid surface. visible. Av. Temp. 180°.     

7. Uranus Atmosphere mostly hydrogen 1 satellite and helium. No solid surface. Temp —225°C.

8. Neptune Atmosphere mostly hydrogen. 18 satellites No solid surface. Temp —220°C.

9. Pluto Atmosphere mostly methne; surface 8 satellites is solid. Temp is —23°C.

Earth at A Glance

1. Estimated Age 4600 million years
2. Mean Distance to the Sun 14,95,03,923 km.
3. Mean Distance to the Moon 381597.5 km.
4. Polar Diameter 12713.8 km.
5. Mean Diameter 12735.3 km.
6. Equatorial Circumference 40,075 km.
7. Mass (in metric tons) 597, 90,00,00,0000000000000
8. Period of Revolution 365 day 5 hrs. 48 min. and 46 seconds
9. Speed of Revolution 10716 km./hour
10. Perod of Rotation 23 hours, 56 minutes.
11. Speed of Rotation 1610 km./hr.
12. Total Area 510066000 sq. km.
13. Land Area 14,84,29000 (29.1%)
14. Water Area 361637000 sq. km. (70.9%)
15. Volume 10,83,230 x 106 Cubic km.
16. Population 6 billion

Equator—Equator is an imaginary line around the earth at an equal distance from the North and South Poles.

Equinox—One of the two time in the year (around 20 March and 22 September) when the sun is above the equator.

Meridian—One of the lines that is drawn from the North pole to the South pole on a map of the world. All meridians are halves of great circle and contain 180 of arc. They are spaced farthest at equator and converg to a common points at poles.

Latitude—The distance of place north or south of the equator measured in degree.

Longitude—The distance of a place east or west of the Greenwich Meridian (which crosses London, England).

Rotation—The spining movement of the earth from west to east on its axis in 24 hours is called rotation of earth.

Revolution—The movement of earth around the sun in a fixed elliptical orbit or path is called revolution. It is completed within 365 1/4 day.

Great Circle—Any hypothetical circle on earth’s surface the plane of which passes through earth’s centre dividing it into two equal halves : northern hemisphere and southern hemisphere.

Small Circle—Any imaginary or hypothetical circle made by a plane passing through the centre. Tropic of capricorn (23° 3°S) and Tropic of Cancer (23° 30N) are small circle.

Solastice—One of the dates in year (21 or 22 June in summer on the Tropic of Cancer and December 21 or 22 in winter on tropic of Capricorn) on which the sun reaches its greatest height north or south of the equator and is directly overhead along one of the tropics.

International Date Line—The 180th meridian is the International date line