This document discusses the life cycle of stars from their formation to their death. It begins by explaining that stars are giant balls of exploding gas made up mainly of hydrogen and helium. The document then outlines the various stages of a star's life: nebula, protostar, main sequence star, red giant, white dwarf, supernova, neutron star, and black hole. For each stage, it provides a brief description of the physical changes occurring within the star. The document emphasizes that stars much more massive than our sun will end their lives as neutron stars or black holes through the supernova process.

1. Prepared By - OM BIKASH DAS
Roll no - PH1217
Msc Physics in
BERHAMPUR UNIVERSITY

2.  Stars are essentially giant balls of exploding gas,
which mainly consists of hydrogen and helium. The
nearest star to Earth, the Sun, is constantly
explodingin a nuclear reaction with the element
hydrogen,which makes the explosion similar to a
hydrogenbomb. These nuclear reactions are
constantlyreleasing energy into the universe, along
with solarwinds and solar flares (QRG, n.d.). The
onlyprotection the earth has from the solar winds
andflares is the magnetic field surrounding the
Earth(Association, N. E. (n.d.).
What is a Star ?

3.  Nebula
 Proto star
 Main sequence
star
 Red Giant
 White Dwarf
 Supernova
 Neutron Star
 Black Hole

4.  In Space, there are huge clouds
of gas and dust called nebulas .
 These clouds are made up of
hydrogen and helium and are the
birthplace of new stars .
 Gravity pulls the hydrogen gas in
the nebula together and it begins
to spin .
 As the gas spins faster and faster,
it heals up and is known as a
protostar .

5.  The second stage of star creation .
 At this point the temperature
eventually reaches 15,000,000°C and
nuclear fusion occurs in the clouds core
 The cloud begins to glow brightly .
 At this stage, it contracts a little and
becomes stable and is called a main
sequence star .

6.  A star will remain in this stage, shining
for millions or billions of year to come .
 As the main sequence star glows,
hydrogen in the core is converted into
helium by nuclear reaction .
 Our Sun is a main sequence star,
Although the sun is extremely large
compared to Earth, it is only a medium-
sized star .

7.  When the hydrogen supply in the core begins
to run out, the core becomes unstable and contracts .
 The outer shell of the star starts to expand,
As it expands it cools and glows red .
 The star has now reached the
red giant phase .
 All star evolve the same way
up to the red giant phase; the amount of
mass a star has determines which of the
following life cycle paths it will take after the red giant phase .

8.  Gravity causes the last of the star‘s matter to
collapse inward and compact, this is the white
dwarf stage .
 At this stage the star‘s matter is extremely dense .
 White dwarfs shine with a white hot light .
 Once all their energy is gone, they no
longer emit light
 The star has now reached the black
dwarf phases in which it will forever
remain
 This is the last stage in the life cycle of a star

9.  Once massive starts reach the red giant phase , the core
temperature increases .
 Gravity continues to pull carbon atoms
together as the temperature increases
forming oxygen, nitrogen, and
eventually iron .
 At this point, fusion stops and the
iron atoms start to absorb energy .
 This energy is eventually released in
powerful explosion called as supernova .

10.  A Supernova is the explosive death of a star, that
often results in the star obtaining the brightness of 100
million suns for a short time. There are two main types
of Supernova which will occure:-
 Type I - The fist type of Supernova will occur in
binary star systems. As a result the gas from one star
will fall on to a white dwarf, in turn causing it to
explode .
 Type II - The second type will occur in stars which
are ten times larger than our own star. These are
known as Super-Giant Stars. When the Stars nuclear
fuel is exhausted the iron core will collapse and then
rebound, creating a massive explosion .

11.  The core of a massive star that us 1.5 to 4
times as larger as our Sun ends up as
a neutron star after the supernova
 Neutron stars spin rapidly giving of
radio waves if the radio waves are
emitted in pulses(due to the star‘s
spin), the neutron star is called a pulsar

12.  No nuclear fusion is taking place to support the core,
so it is allowed by it own gravity
 It has now become a black hole which readily attracts
any matter and energy that comes near it
 The core of a massive star that has 8 or more times the
mass of our Sun remains massive after the supernova
 Black holes are not visible they are detected by the X-
ray which are given off as matter falls into the hole

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