Contents
About 15 billion years ago, there was a huge explosion. Not
any old and ordinary explosion. It was a gigantic explosion that formed the
whole wide universe! This is known as the Big Bang.
Can you believe that all this began as the smallest single
point in the vast expanse of space called a singularity? Soon, this point
started expanding rapidly. This massive explosion was like a nuclear bomb. The
explosion caused protons, neutrons, electrons, etc., to form. Several clumps of
gas and dust came together and they were pulled and squeezed together by their
own gravity. All these clumps slowly formed STARS!
The wondrous10 stars that we see, glow because of
the nuclear fusion reaction which is Hydrogen turning into Helium. Without
this, we wouldn’t be able to see the number of stars in the night sky!
I have always been amazed by the stars in the night sky. I
would like to share my fascination with you. In this article, I will explain to
you all about stars and introduce you to some mysteries of space.
Like we saw in the last chapter, stars are the objects
twinkling and shining far away in the night sky. For us, stars seem very small,
like dots in the sky. You won’t believe this, but most stars are many times
bigger than the Sun! So, you can imagine how many times they are bigger than
the whole Earth!
Stars are huge, fiery balls of extremely hot gas. They are
constantly burning inside, which is what gives them their glow and shine. They
are mostly composed of Hydrogen (about 90%) and Helium (about 10%) with slight
amounts of other gases. The extremely hot temperatures helps it to have nuclear
reactions6 between Hydrogen and Helium.
Stars vary in size. Our Sun is an average-sized star. Many
stars are bigger than this, such as:
·
Red Giant Stars – 20 to 100 times bigger than the Sun
·
Supergiants such as Betelgeuse – 500 times as big as
the Sun
Some of these stars are actually so massive that they have
collapsed under own gravity4. There are also stars much smaller. For
example, there are white dwarf stars that are only 9 miles across.
Can you
guess what the brightest star that can be seen from Earth might be? It is
SIRIUS, the Dog Star. This star is about 26 times brighter than the Sun!
One of the brightest stars is the Hypergiant Cygnus OB2 No.
12. It is 810,000 times brighter than the Sun! Since it is almost 6 billion
light years5 away, it appears quite dim to us on Earth.
After our Sun, the nearest star is Proxima
Centauri. It is just over 4 light years away. There is also a star named Alpha
Centauri, which is over 4.35 light years away. This is the nearest star visible
to the naked eye.
Something to Wonder About
Even today, the universe is still expanding. Its future depends
on how much matter it contains. Some astronomers believe that there might be
enough matter to slow down the expansion so that the universe eventually
stabilizes. However, if the universe keeps expanding at this rate, galaxies3
will move further away, stars will slowly die, and all matter will
eventually DISINTEGRATE1!
In the previous chapter, you learnt about what stars are. But,
how are they formed? Well, a star’s life begins when clumps of gas and dust in
space are pulled together by their own gravity. The middle of the whole clump
is squeezed so hard by gravity that it begins to get immensely hot. This starts
the nuclear reaction between Hydrogen and Helium, which makes these objects
burn. It is now a Main Sequence Star.
After a long time, the star runs low on Hydrogen fuel. It swells into a huge Red Giant that starts pulsating9.
After a long time, the star runs low on Hydrogen fuel. It swells into a huge Red Giant that starts pulsating9.
After another 3 billion years, the expansion and pulsation
goes stronger and the vast bloated star sheds all its outer layers to form a
gaseous shell around its core, which is known as a Planetary Nebula. In less
than about 50000 years, the planetary nebula collapses. However, the core
becomes a White Dwarf, a Neutron star or even a Black Hole. Are you wondering
what Black Holes are?
However, if Red Giants swell up way too much, they can become
massive Supergiants. The end of a supergiant star is the most important part.
No one would believe this but a gigantic explosion, known as a Supernova,
finishes off a supergiant. It is like a nuclear bomb. For just a brief moment,
the supernova flashes out with such a brilliant light, it seems like it is
coming from a billion suns! These supernovas are rare and very short-lived, but
there is always one in the Universe.
FUN FACT
Supernovas can send out more energy in a few seconds than our
Sun in 200 million years!
The Supernovas and Black Holes are two amazing mysteries of
space. They are at the end of life of a Main Sequence Star. However, how a star
dies, and whether it becomes a Supernova or a Blackhole, depends on the type of
the star. In the next chapter, you will learn about some important types of
stars such as, Red Giants, White Dwarfs, etc.
There are many types of stars in the Universe. There are
three main stars that are part of a main sequence star’s life: White Dwarfs,
Red Giants, and Neutron Stars.
White
Dwarfs
White Dwarf stars are really unique.. They are formed when
stars are very dense objects, and they have an unusual faintness2
compared to other stars. They are mostly composed of Carbon and Oxygen. They
are really hot when formed, but over time, they cool down.
White Dwarfs have the densest matter and their material is
made up of plasma8 of unbound nuclei7 and electrons. But
enough of White Dwarf stars. Let us move on to the next type of star!
Red Giants
As you can guess from the name, Red Giants are massive,
luminous stars. However, compared to their size, they have a very low mass.
These stars appear a yellowish-orange to red colour, and are actually many
times more luminous than the Sun. They are cooler than most stars, mainly
because they have used up their supply of Hydrogen in their core.
Some well-known Red Giants are Arcturus, Aldebaran, and Gamma
Crucis. Even our own Sun will become a Red Giant in 5-6 Billion Years. It will
become so big that it will swallow the Earth!
Well, now, let us move on to our last (but not the least!)
type of star.
Neutron
Star
Neutron Stars are as interesting as
Black Holes and very similar too.
These Neutron Stars are the densest and also the tiniest
stars in the universe. Their radius is just about 10 km but their mass is still
few times that of the sun! This is what makes these stars so unbelievable!
They are composed entirely of Neutrons, from where they get
their name. Their whole surface is made of only Iron. Most importantly, they
have the most intense gravitational force. Objects are 100 billion times
heavier on a Neutron Star than they are on Earth!
Well, that's all I have in store for you in this edition for
the topic STARS. But overall, that was a whole lot of fun! We learnt a lot,
too. We learnt about the BIG BANG THEORY, stars in general, the whole life
cycle of a star including SUPERNOVAS and BLACK HOLES and few important types of
stars that were part of a Main Sequence Star's life!
However, this is just basics of Stars. There is a whole lot more you can learn about them. You should try STAR GAZING!
However, this is just basics of Stars. There is a whole lot more you can learn about them. You should try STAR GAZING!
2. Faintness - Lacking brightness or distinctness
3. Galaxies - Numerous large groups of stars, gas and dust that constitute the universe
4. Gravity - the natural force of attraction exerted by a celestial body, such as Earth, upon objects at or near its surface, tending to draw them towards the center of the body
5. Light year - The distance that light travels in a vacuum in one year - approximately 9.46 trillion (9.46x10*12) km
6. Nuclear reaction - A process in which the structure and energy content of an atomic nucleus are changed by in interaction with another nucleus or particle
7. Nuclei - Plural of nucleus, which is central part about which other parts are grouped or gathered; core
8. Plasma - An electrically neutral, highly ionized gas composed of ions, electrons and neutral particles
9. Pulsating - To expand and contract rhythmically; vibrate
10. Wondrous - Remarkable or extraordinary; wonderful
1. En.wikipedia.org/wiki/Star
3. Children’s
Atlas of the Universe
4. Magic Tree
House – Space
5. Fantastic
Book of Q and A
6. En.wikipedia.org/wiki/White_dwarf
7. En.wikipedia.org/wiki/Red_Giant
8. En.wikipedia.org/wiki/Neutron_Star
9. En.wikipedia.org/wiki/Galaxy
11. En.wikipedia.org/wiki/Galaxy#Ellipticals
12. En.wikipedia.org/wiki/Irregular_galaxy
13. En.wikipedia.org/wiki/Small_Magellanic_Cloud
14. En.wikipedia.org/wiki/Milky_way
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