OUR UNIVERSE and SOLAR SYSTEM
Origin:
The universe’s beginnings are explained by the big bang theory. This theory states that 15 billion years ago, cosmic stuff was compressed, and that primordial matter began to expand blast.
Ultimately, the incredibly dense ball fractured into stars, which broke into planets, and then broke again into galaxies.
including the planet Earth. Conventional units of measurement are inappropriate for measuring distances in outer space since it is infinite.
Hence new units as follows are used:
Light Year: Distance covered by light in one year in vacuum at a speed of 3×10 m/s. One light year is equal to 9.46 x 1012 kilometers.
• Astronomical Unit: The Mean distance between the Sun and the Earth (1.49 x 108 km). One light year is equal to 60,000 AU
• Cosmic Year: Sun’s period of revolution around the galactic centre (250 million years). Also called as ‘galactic year’
Parsec: Distance at which the mean radius of the Earth’s orbit subtends an angle of one
second of an arc. It is equal to 3.26 light years.
Galaxies:
These are huge congregation of stars that hold together by force of gravity e.g. the Milky Way. Andromeda galaxy, large and small magellanic cloud, Ursa Minor system, sculptor system, etc. Milky Way or Akashganga is our home galaxy. Our solar system is located in this galaxy.
Stars:
98% of the substance in a galaxy is made up by stars, which are self-luminous bodies. Certain stars in the universe appear little, but they release more energy than the Milky Way’s other stars combined. ‘Quasars’ are the term for these stars. when a star is being formed by the compression of the dense galactic center. ‘Proto-star’ is the term used to describe this phase of star formation.
As a result of the high temperature, light and heat are released when hydrogen changes to helium. Consequently, a star forms. The outer portions of a star swell and turn red when the star’s hydrogen is exhausted. ‘Red Giant’ is the term for this stage of a star. In five billion years, our sun will become a “Red Giant.”
Constellations:
In the sky at night there are various patterns formed by different groups of stars. These are called constellations
Solar System
The sun along with its eight planeta, asteroids and comets comprise the ‘solar system”. The planets are divided into inner or terrestrial planets which have higher densities eg. Mercury. Venus, Earth and Mars and outer planets which have lower densities eg. Jupiter, Saturn, Uranus and Neptune.
The Sun
The sun is in the center of the solar system. It is made up of extremely hot gases particularly hydrogen.
The sun is 109 times bigger than the earth and weighs 2 x 1027 tonnes. The sun is about 150 million km away from the earth. The light from the sun reaches earth in about 8 minutes.
The term “photosphere” refers to the sun’s luminous surface. The “Chromosphere” is crimson and located above the “Photosphere.” ‘Corona’ is the region visible during eclipses, situated beyond the Chromosphere. About 6000°C is the temperature of the photosphere, 32400°C is the temperature of the chromosphere, and 2,700,000°C is the temperature of the corona.
At roughly 15 million degrees Kelvin, the sun’s core is extremely hot. However, even though it is our nearest star, we do not feel its immense heat as much because it is far away.
A single rotation around its center takes 250 million years to complete. ‘Cosmic year’ is the term given to this period.
Spots on the sun’s surface are dark areas with a notch in them. Since they are colder, or have a lower temperature, they seem darker.
The Moon
The moon is the only satellite of the earth.
Its size is approximately one-fourth that of the earth. It has a diameter of 3475 km
Its orbit is elliptical. The maximum distance (apogee) of the moon from the earth is 406,000 km and the minimum distance (perigee) is 364,000 km.
The moon moves around the earth in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the moon is visible to us on the earth.
The bright parts of the moon are mountains whereas the dark patches are low-lying plains.
Asteroids:
Asteroids are a group of microscopic planets or pieces of planets situated in the orbits of Jupiter and Mars. There are roughly 45,000 of them. The greatest distance is ‘Ceres,’ stretching roughly 1000 miles in length. They follow the same path as the planets around the sun.
Meteors and Meteorites:
In the solar system’s interplanetary space, comet remnants can be found interspersed among meteors. Friction between them and the earth’s atmosphere causes them to burn.
Those that totally burn up into ash are called as “shooting stars” or meteors.
‘Meteorites’ are those which strike the earth as rocks after they partially burn.
Planetary System:
>There are eight planets in our solar system. They are:
>Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
>Earlier, Pluto was considered as a planet,But recently it has lost this status.
>All the eight planets of the solar system move around the sun in fixed paths.
These paths are elongated. They are called orbits. A new planet 2003 UB 313 has been discovered recently in our solar system. It is bigger than Pluto and farthest from the Sun.
A. MERCURY (Budh)
1. Mercury is the smallest and the nearest planet to the Sun.
2. It takes only about 88 days to complete one round along its orbit.
3. It has no atmosphere and no satellite. 4. Its days are scorching hot and nights are frigid.
B. VENUS (Shukra)
1. Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
2. It is also called the ‘morning’ or ‘evening star’ although it is not a star
3. It is probably the hottest planet because its atmosphere contains 90-95% of carbon dioxide. The day and night temperatures are almost the same.
4. The atmospheric pressure is 100 times that of the earth.
5. It rotates from East to West and having no satellites of its own.
C. The EARTH (Prithvi)
1. The earth is the third nearest planet to the Sun.
2. In size, it is the fifth largest planet.
3. It is slightly flattened at the poles. That is why its shape is described as a Geoid.
4. From the outer space, the earth appears blue because its twothirds surface is covered by water It is, therefore, called a blue planet.
D. MARS (Mangal)
1 Mars is the fourth planet from the Sun and is the second smallest planet in the solar system.
2. Mars has the largest dust storms in the solar system which can last for months and cover the entire planet.
3. Mars is a rocky body about half the size of earth.
4. Mars is home to the tallest mountain in the solar system named Olympus Mons, a shield volcano which is 21 km high and 600 km in diameter.
5. Mars appears slightly reddish so it is also called red planet. Mars has two small natural satellites named Phobos and Deimos.
E. JUPITER (Brihaspati)
1. The planet Jupiter is the fifth planet out from the Sun, and is two and a half times more massive than all the other planets in the solar system combined.
2. It is made primarily of gases and is therefore known as a gas giant.
3. It is the largest planet of the solar system (about 1300 earth can be placed inside the Jupiter).
4. Mass of Jupiter is about 318 times that of our earth.
5. It has a large number of satellites amongst which four are visible from a telescope easily,
6. It has a faint ring around it.
7. It has 16 satellites like Ganymede, Aayo, Europa, Callisto etc.
F. SATURN (SHANI)
1. It is the second largest planet of the solar system.
2. It has a celebrated rings composed of thousands of rippling, spiraling bands of icy rock and dust just 200 feet thick and 270,000 km in diameter.
3. It has 21 known satellites. Among them Titan, Phobe, Tethys and Mimas are important.
4. Its moon, Titan has nitrogen atmosphere and hydrocarbons, the necessity of life but no life exists.
G. URANUS
1. It is the only planet that lies on its side. Hence, one pole or the other faces the sun as it orbits.
2. It is one of the coldest planets because of having an average temperature of -223°C.
3. Its atmosphere is made of mainly hydrogen. The landscape is barren and there is frozen methane cloud.
4. There are 9 dark compact rings around the planet and a corkscrew shaped magnetic field.
5. It has 15 satellites; prominent ones are Aerial, Ambrial, Titania, Miranda etc.
6. It rotates north to south.
H. Neptune
1. It is the most distant planet from the sun.
2. There are five rings of Neptune. The outer ring seems to be studded with icy moonlets while the
inner ring appears narrow and nearly solid.
3. It has 8 satellites like Titron, Merid, N-1, N-2, N-3 etc.
4. Its atmosphere mostly contains hydrocarbon compounds. The atmosphere appear blue, with quickly changing white icy methane clouds often suspended high above an apparent surface.
PLUTO(from planet to plutoid)
1. Pluto, demoted from planet status in 2006, got a consolation prize – it and other dwarf planets like it will be called plutoids.
2.Plutoids are celestial bodies in orbit around the Sun at a distance greater than that of Neptune that have sufficient mass for their hydrostatic equilibrium (nearspherical) shape.
3. The two known plutoids are Pluto and Eris.
4. It is expected that more plutoids will be named as science progresses and new discoveries are made.
