This slide share helps to know more about space science and terms related to stars and galaxies.

1. Space Science
(A) Stars and Galaxies
Astronomy : It is the branch of
science deals with study of
celestial objects, space and
universe
Star:1) It is a massive self
luminous celestial object
2)It contain lot of gaseous matter
held together by gravity.
3) It emits radiation through
nuclear reactions
Eg: Sun , Sirius, Polaris , Arcturus
* Star nearest to earth is ------>
Sun
(Distance = 1.5 X 108 Km )

2. ● Stellar evolution is the process involved in the
entire life cycle of Stars from birth to death
Stellar evolution

3. How a star is Born :(Sun like Star )
Step 1: Protostar :
● Huge gaseous
hydrogen contracts
under its own gravity
● Density and
temperature increases
at center
● Formation of spherical
structure at centre
● This is called protostar

4. Step II : Steady state
● Hydrogen nuclei fuse to form Helium nuclei
● Temperature increases and lot of energy is released
● Due to enormous release of energy matter is expanded
away from center
● Force of gravity tries to contract matter but radiation
pressure tends to expand matter
● Two opposing forces balance each other
● Now star attains steady state.

5. ● Red Giant is the stage in the life cycle of
star when core consists of helium and
star become huge in size due to
expansion and hence become red in
colour
● Eg: Betelgeuse – a star in the
constellation Orion , is a red Giant
How is Red Giant Formed?
● Helium core began to contract under
gravity
● Hydrogen fuel at core get exhausted and
fusion stops in core
● There is increase in temperature
● Hydrogen left in peripheral region start
fusion reaction causing outer layer to
expand
● Star become gigantic in size
● This cools the star and its colour
changes to red
Step III: Red Giant Star

6. Planetary Nebula
● The shell of glowing
gaseous matter surrouding
an evolved star from which
it is ejected into space due
to outward pull of radiation
is called planetary nebula
● Sun like stars usually shed
their outer shell towards
the end of their red giant
stage
● The material ejected fro
the star has similarity with
that of planet and hence
the name

7. Chandrashekar’s Limit
● What happens to a star after
Red giant Stage depends on
its initial mass
● Here the critical value is
about 1.4 times the solar
mass .
● This value is known as
chandrashekar’s limit
● Star with mass lower than
chandrashekar’s limit will end
up as ------> White dwarf
● Star with mass higher than
chandrashekar’s limit will
Undergo a ------>
Supernova explosion

9. Step IV : White Dwarf
(Mass less than 1.4 Chandrashekhar’s Limit)
● A helium star that is dense , small and bright is called white dwarf.
● Star of mass less than 1.4 times the solar mass evolve into white dwarf stage
How is White dwarf formed?
● As the core of red giant contracts temperature reaches 108 Kelvin
● Helium fuses to form Carbon
● Once entire Helium fuses into carbon the core cannot contract
● Outer envelope get detached and thrown into space
● Star collapse under the gravity
● Due to increase in temperature Star shines and now called White Dwarf

10. Step V : Black Dwarf
● After White dwarf stage
nuclear reaction inside
the star stops
● Internal energy is lost
● NO light is emitted
● Star become Black
dwarf that is the death
of star

11. Death of Sun like Star

12. Stages of stellar Evolution
Sun like Star 5 times as sun 30 times as sun
1. Protostar 1. Protostar 1. Protostar
2.Steady State 2.Steady State 2.Steady State
3.Red Giant 3.Red Giant 3.Red Giant
4.White Dwarf 4. Supernova 4. Supernova
5.Black DWarf 5.Neutron Star 5.Black Hole

14. Supernova
● After red giant if the mass of star is about 5
times that of sun then supernova explosion
takes place
●
Helium formed in the core continue to
contract under gravity.
● Due to increase in the temperature helium
fuses into Carbon -----this followed by
fusion of carbon into Oxygen
● The process continues and ther is formation
of heavier elements such as Magnesium
and silicon core which lie one inside other
● Huge amount of energy is produced
●
This result in increase in temperature and
pressure
● Star explode with brilliant flash
● Matter is thrown into the space with high
speed
● This is called supernova

15. ● After Supernova a
sphere of neutron
remains at center and is
called neutron star.
● It is highly dense object.
● It collapse under the
influence of its own
gravity
● It is a star composing
mainly of packed
neutrons
● It is the super dense
remnant of supernova
Neutron Star

16. Black Hole
● Black hole takes place if
the mass of star is 30
times that of the mass of
sun
● Black hole are formed from
a massive neutron star that
go on contracting infinitely
under the influence of their
own gravity
● Black hole are so massive
and dense that even light
cannot escape from them.

17. Properties of Black hole cannot be
determined
● Nothing comes out of
black hole
● No information in the
form of light or radio
waves comes from a
black hole.
● This is why it is not
possible to determine
temperature , pressure
or chemical composition
of a black hole.

18. Special stars
Pulsar : a spinning
neutron star that emmits
radio wave is called
Pulsar.
Quasar :
● It is massive and remote
celestial object
● Emits large amount of
energy
● It has Star – like image in
telescope
● Quasar is the short form
of Quasi Stellar Sources

19. ● The Stars differ in their temperature.
● The different colour of the star are due to
difference in their temperature
Star Name Colour Surface temperature
Betelgeuse ( Red
Star in the night
Sky)
Red 2500 – 3500 K
Arcturus Orange yellow 3500 – 5000 K
Sun Yellow 5000 – 6000 K
Sirius ( Brighest
star in the sky )
Yellowish white 6000 – 10000 K
Rigel Bluish White 10000 - 50000 K
Why do star differ in their Colour

20. Betelgeuse ( Red Star in the night Sky) Arcturus
Sun Sirius
( Brighest star in the sky ) Rigel

21. Galaxy
A group of star containing thousand
of million of stars along with gas
and dust held together by the force
of gravity orbiting about a common
center is called Galaxy.
Milky way: ( Spiral Galaxy)
● It is the galaxy which includes the
sun and solar system.
● The diameter of galaxy is about
1,00,000 light years
● It looks like Flat Disc with a central
bulge and thickness tapers towards
edge
● Sun is located in the galaxy about
28,000 light years from the center

22. Different types of Galaxies
1.Elliptical Galaxies :
● These are most common
type of galaxies in the
universe
● They contain quite dim
stars
● It is difficult to see the
stars of galaxy

23. Spiral galaxy
● They have spiral
shape .
● They contain very
bright and newly
formed stars.
● Our galaxy milky way
is a spiral galaxy

24. Irregular Galaxy
● These galaxies do not
have shape
● These galaxies are
normally small and faint
● Hence more difficult to
detect

25. Cosmology
● The study of the universe as a whole, including
theories about its origin , evolution, structure
and future is called Cosmology
● The most accepted theory about origin of
universe is ------ Big Bang Theory

26. Big Bang Theory
● Big bang theory was put forward by
Edwin Hubble.
● According to this theory the matter
in the universe was in the form of
fiery region forming a huge dens
primordial mass known as
primordial fire ball
● It had high density and temperature
● Due to increase in the pressure and
temperature it was exploded about
15-20 billions years ago
● This explosion is called big bang
● This explosion threw matter and
radiation in space with high speed
● This caused universe to expand
● As the matter and radiation cooled ,
stars and galaxies were formed

27. Red Shift● Long observation of the spectra of
galaxies reveals a gradual shift of the
spectral lines towards longer
wavelength. This shift is known as ‘RED
SHIFT’ of galaxies.
● Edwin Hubble and his co-workers
studied the red shift of various
galaxies .
● They discovered that red shift of galaxy
is proportional to its distance from us.

28. Hubbles Law
“ The velocity of recession of a
celestial body is proportional to its
distance from observer’’

29. ➢ The star nearest to earth is _____
➢ The sun is currently in ______stage
➢ The nuclear fuel that is currently used up in the sun is _______
➢ The colour of Betelgeuse is_____
the densest celestial object in the universe is _____
➢ The galaxy of which we are part is _____
➢ The Indian name of Milky way is ______
➢ The diameter of milky way is _____ light years
➢ The theory that explains the origin of universe satisfactorily is
____
➢ The sun will eventually ends up as ______
➢ The spinning neutron star is called ______
➢ A pulsar emits ______ waves
➢ Light year is a unit of ____________
Evaluation

30. Thank You
Prepared by
Gulzar . I . D
Government P.U.college
(High School)
Thyamagondlu
Nelamangala tq
Bangalore rural dist
Mob no : 8277367100