Galaxy is a system of millions or billions of stars held together by gravity. There are three main types of galaxies: irregular galaxies with an irregular shape resulting from galaxy collisions, elliptical galaxies with little structure or rotation, and spiral galaxies with a central hub and spiral arms promoting star formation. The Milky Way is a barred spiral galaxy containing our solar system. It is named for its hazy, milky appearance in the night sky. The Milky Way is part of a group of galaxies called the Local Group within the larger Virgo Supercluster.

1. GALAXY

2. What is Galaxy?
Galaxy is a system of millions or billions of stars, together with
gas and dust, held together by gravitational attraction.
 The word galaxy is derived from the Greek galaxias literally
"milky", a reference to the Milky Way.

4. These galaxies have an irregular
shape and are considered to be
the result of the collisions
galaxies. As a result, they
generally contain of a complex
mix of interstellar gas and dust,
young stars, and old stars.
Irregular

5. These galaxies have little to no
structure, rotation, or
interstellar matter. This results
in minimal tar formation and a
dominance of the long lived,
red stars. These ellipsoid-
shaped collection of stars are
the most common type of
galaxy.

6. These galaxies are disk-shaped
with either a round central hub
(unbarred) or a hub shaped
like a bar (barred). They rotate
with spiral arms that contain
interstellar dust and gas,
promoting star formation and
an abundance of young stars.

7. Milky Way Galaxy

8. What is Milky Way?
It is the name of the barred spiral galaxy in which our solar system is located. The
Earth orbits the Sun in the Solar System, and the Solar System is embedded within
this vast galaxy of stars. It is just one of hundreds of billions of galaxies in the
Universe, and ours is called the Milky Way because the disk of the galaxy appears to
be spanning the night sky like a hazy band of glowing white light.
In short, our galaxy was named because of the way the haze it casts in the night sky
resembled spilled milk. This name is also quite ancient. It is translation from the
Latin “Via Lactea“, which in turn was translated from the Greek for Galaxias,
referring to the pale band of light formed by stars in the galactic plane as seen from
Earth.

9. The Milky Way is part of a collection of galaxies called the Local Group.
The Milky Way is the galaxy that contains our Solar System. Its name "milky" is
derived from its appearance as a dim glowing band arching across the night sky
whose individual stars cannot be distinguished by the naked eye. T
The ancient Romans called our galaxy the Via Lactea, which literally means “The
Road of Milk.”
The Milky Way is the second-largest galaxy.
Notice that the total size of the Milky Way is about 50,000 light-years in radius,
with the Sun a little over halfway from the center.
The Milky Way contains between 100- 400 billion stars and at least 100 billion
planets

10. The Local Group

11. The Milky Way and the
Andromeda Galaxy are a
binary system of giant spiral
galaxies belonging to a
group of 50 closely bound
galaxies known as the Local
Group, itself being part of
the Virgo Supercluster.

12. The Virgo Supercluster
forms part of a greater
structure, called
Laniakea.

13.  The "Milky Way" can be seen as a
hazy band of white light some 30
degrees wide arcing across the sky.
 The area of the sky obscured by the
Milky Way is called the Zone of
Avoidance.

14.  The Milky Way consists of a bar-shaped core region
surrounded by a disk of gas, dust and stars. The gas,
dust and stars are organized in roughly logarithmic
spiral arm structures

16. The Milky Way began as one or several small over
densities in the mass distribution in the Universe
shortly after the Big Bang. Some of these over
densities were the seeds of globular clusters in
which the oldest remaining stars in what is now
the Milky Way formed.

17. Globular clusters are among the
oldest objects in the Milky Way,
which thus set a lower limit on the
age of the Milky Way. The ages of
individual stars in the Milky Way can
be estimated by measuring the
abundance of long-lived radioactive
elements such as thorium-232 and
uranium-238, then comparing the
results to estimates of their original
abundance, a technique called
nucleocosmochronology.
Age

18. Our Sun is located in the Orion Arm,
a region of space in between the two
major arms of the Milky Way, and
about 27,000 light years from the
galactic core. At the heart of the
Milky Way is a super-massive black
hole, just like all of the other
galaxies, known as Sagittarius A*.
This monster is more than 4 million
times the mass of the Sun and is
believed to have a diameter of 44
million kilometers.