4. THE EARTH
The Earth is the third planet in the solar sytem.
It is the only planet which contains life as it contains oxygen.
It is also called the blue planet because most of the Earth’s surface is covered with water,
thta is 75% of water.
The Earth revolves around the Sun every 365.25 days, while rotating on a titled axis of 23.5
degree every 24 hours which causes day and night.
It follows an elleptical, or slightly egg-shaped orbit. Thus the distance between the Earth and
Sun varies, from a maximum of 152 million kilometres on July 4th to a mimimum of 147
kilometres on January 3rd. However, this variation has little effect on temperature on Earth.
The Earth has only 1 moon which itself isthe part of Earth, the moon revolves around the
Earth and completes it’s orbit in approximately in 30 days.
The Sun is the closest star to Earth.
The Sun is at the center of the solar system. Every planet in the solar system is revolving
around the sun
It is the Most important energy source for us as it gives heat and light.
It’s diameter is about 1.39 million killometers that is 109 times more than of Earth.
It is also made of hydrogen gas.
The Sun is moving through it’s life forms and research says thet rthe sun will one day become
a black hole or the present black hole will devour the sun.
If we didn’t have sun there would be winter all the time.
8. The Moon is an astronomical body that orbits the Earth as
its only permanent natural satellite.
It is the fifth-largest satellite in the Solar System, and the largest among planetary satellites
relative to the size of the planet that it orbits (its primary).
The Moon is, after Jupiter's satellite Io, the second-densest satellite in the Solar System
among those whose densities are known.
The Moon is thought to have formed about 4.51 billion years ago, not long after Earth.
The most widely accepted explanation is that the Moon formed from the debris left over
after a giant impact between Earth and a Mars-sized body called Theia.
New research of moon rocks, although not rejecting the Theia hypothesis, suggests that the
moon may be older than previously thought.
10. SOLAR SYSTEM
The Earth is the part of solar system.
This system consists of a group of planets and moons that orbit the Sun.
There are 8 planets in the solar system.
1. Mercury 2. Venus 3. Earth 4. Mars
5. Jupiter 6. Saturn 7. Uranus 8. Neptune
There is another planet called “Pluto”. It was first the ninth planet of solar system but because of
its irregular shape o0f orbit and its very small size. So thats why it is now called a “Dwarf Planet”.
These planets are seperated by an asteroid belt which is occupied by numerous irregularly
shaped bodies called “asteroids”.
The Solar System is divided into two parts that are “Inner Solar System” and “Outer Solar
System”. The inner solar system consists of first four planets, and outer solar system consists of
other planets of solar system. The inner and outer solar sytem is divided by the asteroid belt in
A Star is a celestial body which consist of a luminous spheroid of plasma held together by its
Many stars are visible to naked eye but some styars are very far away so we have have to see
thaem by stetscope. The closest star to Earth is Sun.
They are made up of Hydrogen and Helium gases, which are very common in our universe.
A star has 4 forms. Fisrst it is very bright with red colour. It is the first form of life of star. Then
it’s energy starts to grow and then it’s colour is changed to white. It is then called “A White
Dwarf”. It is very dense star. Then the core of the giant star collaspes. Then it is known as “A
neutron Star”. The neutron star is the smallest and the densest star. Then the star is changed
into a massive “Black hole”. It then starts to detroy planets and other stars and becomes
There are many stars which are bigger than the Sun and our Sun is also going through these
forms of life.
A “Galaxy” is a gravitationally bound system of stars, planets, interstellar gas, dust, and dark
The word galaxy is derived from Greek “galaxias” literally meaning “milky”.
There are many galxies in our universe which are bigger from our galaxy. The galaxy in which
we are living in is known as “The Milky Way Galaxy”.
16. The Milky Way is the galaxy that contains the Solar System, with the name describing the
galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars
that cannot be individually distinguished by the naked eye.
The Milky Way is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-
It is estimated to contain 100–400 billion stars and more than 100 billion planets.
The Solar System is located at a radius of 26,490 (± 100) light-years from the Galactic Center,
on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust.
The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate
from the bulge. The galactic center is an intense radio source known as Sagittarius A*,
assumed to be a supermassive black hole of 4.100 (± 0.034) million solar masses.
MILKY WAY GALAXY
18. The Virgo Stellar Stream Galaxy is located in the constellation of Virgo.
It is believed to be the remains of a dwarf spheroidal galaxy.
This galaxy is in process of merging with the Milky Way.
This stellar stream was discovered from photometric data from the Sloan Digital Sky Survey.
The Virgo Stellar Stream, also known as Virgo Over density, is the proposed name for a stellar
stream in the constellation of Virgo which was discovered in 2005.
The stream is thought to be the remains of a dwarf spheroidal galaxy that is in the process of
merging with the Milky Way. It is the largest galaxy visible from the Earth, in terms of
the area of the night sky covered.
VIRGO STELLAR STREAM
The Andromeda galaxy, also known as messier 31, M31, or NGC 224 and originally the
Andromeda nebula, is a spiral galaxy approximately 780 kilo parsecs from earth, and the
nearest major galaxy to the milky way.
The galaxy's name stems from the area of the earth's sky in which it appears, the
constellation of Andromeda.
The virial mass of the Andromeda galaxy is of the same order of magnitude as that of
the milky way, at a trillion solar masses (1012m☉).
The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought
that the Andromeda galaxy is more massive than the milky way by a margin of some 25% to
the Andromeda galaxy has a diameter of about 220,000 light-years, making it the largest
member of the local group at least in terms of extension, if not mass.
The Cartwheel Galaxy (also known as ESO 350-40 or PGC 2248) is a lenticular galaxy and ring
galaxy about 500 million light-years away in the constellation Sculptor.
It is an estimated 150,000 light-years diameter, and has a mass of about 2.9–4.8 × 109 solar
masses; its outer ring has a circular velocity of 217 km/s.
It was discovered by Fritz Zwicky in 1941.
Zwicky considered his discovery to be "one of the most complicated structures awaiting its
explanation on the basis of stellar dynamics."
An estimation of the galaxy's span resulted in a conclusion of 150,000 light years, which is
slightly larger than the Milky Way.
There are many types of “Clusters” in space.
1. Asteroid Clusters: An asteroid family where many asteroids share similar proper orbital
elements. If they do not share these similarities, they would have been different.
2. Galaxy Clusters: A galaxy structure that cosists of thousands of galaxies that are bond together
by gravity. They are the largest known gravitationally bound structures in the universe and were
believed to be the largest known structures in the universe untill the 1980sm, when
“superclusters” were discovered.
3. Globular Clusters: A globular cluster is a spherical collection of stars that orbit a galactic core,
like a setellite. Globular structures are very tightly bound by gravity which gives them the
4. Open Clusters: An open cluster is a group of few thousand stars that are formed by the
same giant molecular cloud and have roughly the sane age. They are very loosly bound by
the gravitational attraction.
5. Star Clusters: Star clusters are very large group of stars. It is made up of two star clusters
which can be distinguished that are globular clusters and open clusters by their properties.
A “Supercluster” is the largest known structure in the universe.
It is made up of many other clusters such as galaxy clusters.
The Milky Way Galaxy is the part of the “Local Group” galaxy group which in turn is part of
“Virgo Cluster”, which is in turn part of “Laniakea Supercluster”.
Scientists have discovered and observed almost 10 million superclusters.