Galaxy and Star

1. GALAXY and STAR

2. GALAXY

3. What is Galaxy ?
 A galaxy is a gravitationally bound system of stars,
interstellar gas, dust, and dark matter.

4. Types of Galaxy
 There are three main types of galaxies:
 Elliptical
 Spiral and
 Irregular

5. Elliptical Galaxy
 Elliptical galaxies are shaped like a
spheriod, or elongated sphere. In the sky,
where we can only see two of their three
dimensions, these galaxies look like
elliptical, or oval, shaped disks
 Elliptical galaxies have no particular axis
of rotation

6. Spiral Galaxy
 Spiral galaxies have three main
components: a bulge, disk, and halo.
 The bulge is a spherical structure found
in the center of the galaxy. This feature
mostly contains older stars.
 The disk is made up of dust, gas, and
younger stars.
 The halo contains old clusters of stars,
known as globular clusters.

7. Irregular Galaxy
Irregular galaxies have no regular or
symmetrical structure.
Having a lot of gas and dust means
that these galaxies have a lot of star
formation going on within them. This
can make them very bright.
The Large Magellanic Clouds are
examples of irregular galaxies.

8. Milky Way Galaxy
 The Milky Way is a barred spiral galaxy.
 Milky Way is the galaxy that contains our Solar
System
 The Milky Way is estimated to contain 100–400
billion stars. There are probably at least 100
billion planets in the Milky Way .
 The Milky Way consists of a bar-shaped core
region surrounded by a disk of gas, dust and
stars.

9. Whirlpool Galaxy
The Whirlpool Galaxy, also known
as Messier 51a, M51a, and NGC 5194.
 It was the first galaxy to be classified
as a spiral galaxy.
Its mass is estimated to be 160 billion
solar masses.
 Overall the galaxy is about 35% the
size of the Milky Way.

10. STAR

11. What is Star ?
 A star is a luminous ball of gas, mostly hydrogen and helium, held together by
its own gravity.
 The nearest star to Earth is the Sun.

12. Different Types 0f Stars ?
Protostar
T Tauri Star
Main Sequence Star
Red Giant Star
White Dwarf Star
Red Dwarf Star
Neutron Star
Supergiant Star

13. Protostar
A protostar is a very young star.
 Protostar is a collection of gas that has
collapsed down from a giant molecular
cloud.

14. T Tauri Star
A very young, lightweight star, less than
10 million years old.
T Tauri stars don’t have enough pressure
and temperature at their cores to
generate nuclear fusion.

15. Main Sequence Star
The majority of all stars in our galaxy,
and even the Universe, are main
sequence stars.
Our Sun is a main sequence star.
 Main sequence stars can vary in size,
mass and brightness.

16. Red Giant Star
 A red giant is a luminous giant star of low or
intermediate mass in a late phase of stellar
evolution.
They have radii tens to hundreds of times
larger than that of the Sun.

17. White Dwarf Star
 When a star has completely run out of
hydrogen fuel it becomes a white dwarf
star.
 A white dwarf shines because it was a hot
star once, but there’s no fusion reactions
happening any more.

18. Red Dwarf Star
 A red dwarf is a small and relatively cool
star.
Red dwarfs are very-low-mass stars. As a
result, they have relatively low pressures, a
low fusion rate, and hence, a low
temperature.
Red dwarf stars are able to keep the
hydrogen fuel mixing into their core.

19. Neutron Star
Neutron stars are the smallest and densest stars
known to exist.
Neutron stars are created when giant stars die
in supernovas and their cores collapse.
At present, there are about 2000 known
neutron stars in the Milky Way and the
Magellanic clouds.

20. Supergiant Star
 The largest stars in the Universe are
supergiant stars.
 They can be thousands of times bigger
than our Sun and have a mass up to 100
times greater.
Direct image of the star “ UY Scuti ” , a red
supergiant which is one of the largest known
stars.

21. THE END