The Universe | SEE Notes

Table of Contents

The Universe | SEE Notes

Universe: The huge space which contains everything that exists is called the Universe. The earth, the sun, the moon, planet, stars, atmosphere, etc. Whatever we see are in the universe. The breadth of the universe is about 10⁵ light-years.

Solar system: The family of the sun including all planets, satellites, asteroids, meteoroids, comet, etc is called solar system.

Light Year: The distance that the light travels in one year through a vacuum or air is called a light year. Its value is 9.46 x 105m. It is used to the celestial distance.

AU (Astronomical unit): The distance between the earth and the sun i.e about 15 x 10⁷ Km is considered as one AU. The diameter of the solar system is 78.1 AU.

Planets: Planets are the non-luminous heavenly bodies which revolve around the sun in elliptical orbits. Example: The earth, The Jupiter, etc.

Satellite: A Satellite is a small body which revolves around a planet due to the effect of gravitational force. Example: The moon is the natural satellite of the earth.

Comet: Comets are heavenly bodies revolving around the sun in very long elliptical orbits. They are collection of gasses, dusts, ice, etc. Example: Helley’s comet.

Meteor: A meteor is a piece of rock in outer space that travels very fast and burns with bright light as it enters the earth’s atmosphere. It is also called shooting star or falling star.

Meteorite: Meteorite is the meteor in the space which hits the earth’s surface. Its types are:
a. Stony Meteroite
b. Irony Meterotie

Stars: The stars are self-luminous and twinkling large sphere of gases (mainly hydrogen) in the sky. Example: The sun, Polar star, Capella, etc.

Constellation: The closer group of stars which appear in the form of recognizable shape and pattern (like lion, ox, Fish, Virgo, etc) is called Constellation.

Galaxy: Galaxy is an extremly large mass of stars dust particles and gaseous matter. Example: Milkey way galaxy and Andromeda galaxy, etc.

Black hole: Black hole is a lightles or black area in the space what nothing, not even light can escape from it due to its extremely large gravitational pull. It is formed by the indefinite contraction of heavy and large neutron stars under the action of their own gravity.

Protostar: The pre-star stage formed due to the combination of the nucleus of hydrogen or gaseous or called a protostar.

Nova: The extremely expanded star formed due to decrements of hydrogen content in star having mass unto the sun is called Nova.

Supernova: Supernova is formed due to the sharp decrement of Hydrogen in the core of star having more mass than solar mass.

Coma: The solid central mass around which a gaseous atmosphere of mixture of dust particles and ice exists is called coma. The coma is also called head or nucleous of comet.

Types of Galaxy:
a. Spiral galaxy: Milkyway, Andromeda, etc.
b. Elliptical galaxy: Fornax, Sculptor, etc.
c. Irregular galaxy: IC1613, NGC6822, etc.

Comet and Asteroid:

Comet	Asteroid
It contains frozen ice.	It is stony mass containing dust.
It vaporizes when approaches near the sun.	It doesn’t vaporize.

Galaxy and Constellation:

Galaxy	Constellation
An Extremely large group of stars and the gaseous matter is called a galaxy.	The group of star that has definite shape is called constellation.
It occupies a large space.	It occupies less space.
They are not limited in number	They are limited in number
Example: Milky Way, Andromeda, etc.	Example: Virgo, Leo, Ursa Major, Ursa minor, etc.

Cosmic year: The total time taken by the sun the complete one revolution around its galactic center is called Cosmic year.
1 Cosmic year- 2.5×10⁸ light year.

Galactic center: The center of Milkyway (Or Galaxy) around which solar system revolves is called the Galactic center.
Diagram:

Proxima Century: It is a star present in Galaxy.

Inner Planet and outerplanet:

a. The mercury, venus, and Earth and Mars are called innear planets. The planets between sun and asteroid belt are called inner planets.

b. Outer plant: The planets between asteroid belt to Neptune (Jupiter, Saturn, Uranus and Neptune) are called Outer planets.

Asteroid belt: The group of asteroids between orbit of Mars and Jupiter is called Asteroid belt.

Planets with their names

The planets with ring of dusts, cloud: The Saturn
The green planet: The earth
The red planet: Mars
The small planet: Mercury
The brightest planet: Venus
The planet without moon: Mercury, Venus
The planet with Maximum number of Moon (Satellites): Saturn
The planet with a minimum number of satellites (moon): Earth

Planets and their Satellites name

Planets	Satellites name
Earth	Moon
Mars	Phobos, Deimos
Juipter	Europe, Callisto, Ganymede, etc.
Saturn	Titan
Uranus	Miranda, Ariel
Neptune	Triton, Nereid

Important Answer Question

What is the universe? which units are used to measure the distance between heavenly bodies of the universe?
Ans: The huge space which contains everything that exists is called the Universe. Light year units are used to measure the distance between heavenly bodies of the universe.
Which planet is known as the Red planet? Why?
Ans: Mars is known as the red planet because it is very rich in limonite (iron ore) which is red in colour and it is rich in dust also.
Why is Saturn known as ring planet, Why?
Ans: Around Saturn, there is the presence of three spherical shaped rings. So it is known as ring planet.
Comet is seen in an interval of many years, why?
Ans: Comet revolve around the sun in the spherical axis which is very much longer, so it takes many years to revolve around the sun. Thus, Comet is seen in an interval of many years.
Why is the tail of comet directed opposite to the sun, why?
Ans: Due to the solar wind, the tail of a comet is directed opposite to the sun.
Why is life impossible in Venus?
Ans: The temperature of the venus is very high so there is no possibility of life through there is the presence of water, oxygen and carbon dioxide.
What is meant by Zodiac?
Ans: 12 of the 88 constellations lie in the revolving path of the sun known as zodiacs.