The heavenly body of the universe has originated for different reasons. There are also stars in these heavenly objects. After creation, the stars pass through different stages and are lost forever in the infallible laws of nature. Today we will try to recognize the star in a new way through the various stages of its birth and evolution.
Stars are basically divided
into eight classes based on the course of evolution after birth. In these eight
classes some more subcategories have originated based on different subjects. Now
we will know the names of those eight classes and will discuss about them very
briefly.
1. 1. Proto star:
The
birthplace of the star is the Nebula. Hydrogen particles are in a molecular
state there, hence this region is called Molecular Cloud. These clouds contain
large amounts of dust. As long as the pressure and gravitational force are in
balance, the cloud remains stable. But when the equilibrium state is disturbed,
dust and molecular hydrogen particles move closer to each other due to gravity
and continue to rotate around each other. As a result of this phenomenon, the
mass of that rotating body continues to increase, and as the mass increases, so
does the force of attraction. As a result of the attraction of the object, the
surrounding dust and hydrogen runs towards it and gradually the size of the
object increases further. As this phenomenon continues, the
pressure at the center of the object increases and so does the density of the
material inside the object. In this way, when the material size of the object
is 8 percent of that of our sun, the temperature inside it reaches 10 million
Kelvin or 1 crore Kelvin (99,99,626.85 degrees Celsius) due to the increase in
pressure inside its center, and the Nuclear Fusion Reaction begins at the
center of the object. This is the initial stage of the star. This phase of our
sun lasted for about 5 million or 5 lakh years. ‘HH34’ is an example
of a Proto Star.
2. Herbig Ae /Be Star or T Tauri Star:
According
to the evolutionary trend in the star, this type of star is a short-lived
intermediate phase between the Proto Star and the Main Sequence Star. Hence
this phase is called Pre-Sequence Star. At this point, the young star reaches a
certain temperature by increasing its mass and density. Stars that have more
than twice the mass of the sun are called Herbig Ae/Be Stars, and stars that
have mass less than twice the mass of the sun are called T-Tauri stars. The
stability of this intermediate phase is much less than other phases. ‘IRAS-12196-6300’
and ‘V-1025’ are examples of such stars.
3. Main Sequence Star:
The
main phase of the star comes after the intermediate phase. This is the main
effective stage of the life of the star. There are a total of seven categories
in this phase and a total of 68 types of stars have been found. This
classification of stars was done by astronomer Annie Jump Cannon. These seven
types of categories are identified by the seven letters of the English
alphabet. Below is a brief description of them.
a. O
Category:
The
number of such stars is very rare in space (only 1 in every 30,000,000 stars).
They are the brightest and hottest stars in space and emit the most ultraviolet
rays. Their mass can be at least 16 times the mass of the Sun and at least
30,000 times their luminosity. The stars in this subcategory are further
divided into 17 subcategories. They are called Blue Supergiant Stars
for their intense brightness and huge size. ‘Cygnus X-1’ is an example of an O
Category star.
b. B Category:
The
stars of this class are also very bright and warm in nature. Although their
number is not rare in space, it is small (about 0.13 percent). They range from
2.1 to 16 times the mass of the sun and from 25 to 30,000 times the luminosity.
These type of stars are divided into 9 subcategories based on their physical
and chemical properties. ‘Kappa Andromedae’ is an example of this type of star.
c. A Category:
These
white light stars, the most visible from our Earth, are not too much of a
presence in space (0.6 percent). Their mass is 1.4 to 2.1 times the mass of the
sun and 5 to 25 times the luminosity. They are divided into 7 subcategories
based on their physical and chemical properties. An example of such a star is ‘Vega’.
d. F Category:
They
are the fourth class of stars in the original phase. Their mass is between 1.04
to 1.4 times the mass of the sun and 1.5 to 5 times the brightness. They occupy
3 percent of the space in terms of presence. The rays emitted by them are
usually yellowish-white in nature. The stars of this class are divided into 10
subcategories. ‘Beta Virginis’ is an F class star.
e. G Category:
Our
most familiar sun is in this category of yellow light-scattering stars. The
mass of stars in this class varies from 0.4 to 1.4 times the mass of the sun
and from 0.6 to 1.5 times the brightness. In terms of numbers, they occupy 7.6
percent of the space. The stars in this class are divided into 10 subclasses
and our sun falls in the G2V class. In addition to the Sun, another example of
this class of stars is ‘Alpha Centauri’
f. K Category:
The
number of these light-orange stars in space is quite good (12.1 percent). Their
mass is 0.45 to 0.8 times the mass of the sun and their luminosity is 0.08 to
0.6 times. The stars of this class are further divided into 8 subcategories.
The search for life is usually carried out on the satellites of all these
stars. ‘Epsilon Eridani’ is an example of a star in this category.
g. M Category:
This
orange-red star is the most abundant in space (76.45 percent). Of all the types
of stars, they are the lowest in size, warmth, and brightness. They are also
known as red stars, and many also know them as Red Dwarf Stars. Their mass is
between 0.08 to 0.45 times the mass of the sun and less than 0.8 times the
brightness. The number of their subcategories is 10. An example of a star in
this category is ‘Wolf-359’.
4. Red Giant Star:
The
original energy source of a star is the process of nuclear fusion through which
hydrogen is converted to helium, and with it a great deal of light and heat are
radiated around. But over time, little by little, hydrogen is depleted, leaving
a heavy centre filled with helium. As a result, the gravitational force of the
star increases so much that the nuclear fusion reaction of helium begins due to
which the radiation of the star becomes more and more intense. This phenomenon
further enhances the outer layer of the star, giving it a monstrous shape. It
is estimated that our sun will reach around Jupiter during the phase of turning
into a red giant star. The nuclear fusion of helium produces carbon in the
centre of the star and the temperature decreases rapidly. Ionized particles
from the extended layer of stars begin to scatter far into space. Another name
for this condition is Planetary Nebula. ‘Alpha Tauri’is an example of a red
giant star.
5. White Dwarf Star:
This
phase is obtained by further decreasing the temperature of the red giant star.
At this time the stars radiate heat and light, albeit in small quantities. It
can be said that this is the last illuminated phase of the star, except for the
giant star. The concentration of stars is very high at this time. When stars
like the sun reach this stage, they will take on the size of the earth. Since
no nuclear fusion process takes place at the centre of the star at this time,
no new heat energy is generated. By letting go off the heat that has
accumulated in the star little by little, the white dwarf star becomes cooler
and moves towards its end. 'Sirius-B' is an example of a white dwarf star.
6. Red Super Giant Star:
This
phase is seen in the case of giant stars and is similar to the aforementioned
red monster star. But the stars are so named because of their large size. Here,
too, in the process of nuclear fusion, when hydrogen form helium and hydrogen
are depleted in the centre of the star, the process of nuclear fusion of new
elements continues and more new types of elements begin to be produced. Helium
is produced from hydrogen and then carbon, neon, oxygen, silicon and finally iron
gets produced. Iron is a very dense, strong and stable substance so the process
of nuclear fusion stops and with it the process of heat generation ceases.
However, the size, volume and radiation of the star increased during this
event. The stagnation of the nuclear fusion process completely destroys the
stability in the centre of the star and after the center of the star collapses,
there is an intense explosion called a supernova explosion. This explosion
marks the end of this phase and the beginning of the next stage. ‘Betelgeuse’
is an example of this.
7. Neutron Star:
If
the mass of the remnants of a star after a supernova explosion is 1.4 to 2.16
times the mass of our sun, then that star reaches a very dense state called a
Neutron Star. The name itself suggests that all the protons and electrons in a
star merge under the influence of intense gravitational force to form a
neutron-rich star. But if the mass is greater than that, it turns into a Black
Hole which is not the subject of our discussion today. Neutron stars have very
high densities as well as very high velocity. They revolve around their centre
10 to 700 times per second. As a result of this, all matter around the neutron
star are attracted and rushed towards its centre. This type of star can have a
diameter of about 25 km. Neutron star is probably the smallest and densest star
in the universe. So far, a total of 9 types of neutron stars have been found.
They are mentioned very briefly below so that we can get a little idea about
them.
A. Radio Pulsar:
It
is a highly magnetic, fast-moving neutron star that emits vibrating light at
intervals of a few seconds without scattering drawn light. ‘PSRJ-1803-6202’ is
an example of a radio pulsar.
B.
Reusable Pulsar:
Many
people call this type of neutron star a Millisecond Pulsar. They move from one
state to another very quickly and return to normal. ‘PSRB-1937+21’
is an example of such a star.
C.
Magnetar:
This
type of neutron star is considered to be the most dynamic star in space with
the strongest magnetic field. It emits very high potential X-rays and gamma
rays. ‘SGR
0525−66’ is an example of such a star.
D. Soft Gamma Ray Repeater or SGR:
These
types of neutron stars emit large amounts of X-rays and gamma rays at irregular
intervals. It is thought to be a magneter. ‘SGR-1608-20’ is an example of a star in this class.
E. Anomalous X-ray pulsar or AXP:
They
are considered to be the high-magnetized neutron stars of young nature. Here
the two stars are held as one and one is a normal star and the other is a
receiving neutron star or black hole. However, their speed of rotation is
slightly lower than that of other neutron stars. But at present they are
considered as magneter. ‘XTEJ1810-197’ is a star in this category.
F. Low Mass X-ray Binaries: or LMXB:
It
is a kind of dual neutron star system which is a faded nature star illuminated
by X-ray. Here the process of mass transfer from one star to another goes on.
‘LMXB-4U-1636-536’
is considered a star in this category.
G. Intermediate Mass X-Ray Binaries or IMXB:
It
is also a kind of double neutron star system which is a faint nature star
illuminated by X-ray light. One of the two stars is a normal star and the other
is a neutron star or black hole. Here too the process of transferring mass from
one star to another is going on. ‘PSRJ-1614-2230’ is an
example of such a star.
H. High-Mass X-Ray Binaries or HMXB:
In this system, if the mass of the second
star, in addition to the neutron star or the black hole, is 10 times the mass
of the sun, it will be placed in this category. Here, too, intense X-rays are
scattered and the mass is transferred to neutron star or black hole. We
can consider ‘Vela X-1’ as a star in this class.
I. Accretion Powered Pulsar:
It
is also a type of binary neutron star system which has a high magnetic neutron
star that emits X-rays of varying intensity at different times. ‘IGRJ-00291+5934’
is an example of such a star.
Even though we know so much about
neutron stars, we still can't say for sure about their consequences, and so we
often hear many different theories from different scientists.
8. Variable Star:
All
the stars visible from Earth that change in light intensity over time are
called Variable Stars. Stars whose light intensity change for the star itself
are called Intrinsic Variable Stars and the stars whose light intensity change
for reasons other than star itself are called Extrinsic Variable Stars. 'R
Scooty' is an example of such a star.
Apart from this, the forms
of many other types of stars have not been discussed here as their relationship
with the evolutionary trend of stars has not yet been determined. In this
context, it can be said that the brown dwarf star, black dwarf star or black
hole is not a star in the real sense, so they are not discussed here. But last
but not least, scientists are constantly working to find out if there are any
other unknown sources of evolution of stars among the millions of stars of
billions of light-years away from us in space.
DECLARATION:
All The Images Have Been Sourced From Google.
