Hello and welcome back to
episode 3 of Season 3 of this astronomy podcast. Today, we are going on another
adventure but this time it’s a journey to a Nebula called Blinking Nebula but
before we dive into this, let’s talk about what is a nebula?
Nebula is a place where
stars are born. They are usually called stellar nurseries where stars are born
in a group. It’s like cultivating seeds of plants in a nursery but in terms of
astronomy, stellar nursery is a place where stars are born in a group from a
massive cloud of gas and dust. It’s also a place where stars die. In other
words, nebula is a part of cycle in which the material gets recycled by the
universe. If it still sounds complicated then let me start by giving you an
example. Let’s take our Sun. What do you think about how it formed? Has it
always been around revolving the supermassive black hole at center of our
galaxy? Nebula can be of many types but this is not what we will dive into
today. The kind of nebula that I will talk about is a Planetary Nebula. Yes,
Blinking Nebula is a Planetary Nebula, also known as NGC 6826 in the NGC
astronomical naming catalog. It is also known as Caldwell 15 in the Caldwell catalog. Now you might be wondering about what exactly is a Planetary Nebula.
To put it into simple words, a planetary nebula is a nebula formed after the
death of a star massive than our Sun in an explosion called Supernova. If a
star’s mass is bigger than Chandrasekhar limit, then it will go and become
either a black hole or a neutron star as a result of this explosion but since
this isn’t a black hole or a neutron star, this is a planetary nebula. In other
words, this was formed after a Star with mass less than that limit. To put it
into much simpler words, a planetary nebula is an expanding shell of gas and
dust into the outer space. It happens when the star runs out of fuel and
collapses under the weight of its gravity and since the fate depends on the
mass of a star, the star then ends its life in form of a explosion by expanding
its shells outwards, leaving a core at the center, which in astronomical terms
is called a white dwarf star. It is the third stage of fate for a main-sequence
star like our Sun, which means our star too will someday face a death like
this. It is the third stage since it comes after the Red Giant phase in which
the star expands but doesn’t collapse and goes into explosion. It is after this
phase the white dwarf stage arrives. Now that you know the basics, when I’m
saying planetary nebula, I meant an expanding cloud of gas and dust after
supernova, thus leaving the core of star at the center. Now back to Blinking
Nebula.
Blinking Nebula is located
about 2200 light years from Earth in the constellation Cygnus. It is referred
as the Blinking Nebula because of its pattern of blinking from the observer’s
view when viewed through the telescope. What I meant by that is if you were to
take a small telescope and see at this nebula directly, the light from the
white dwarf HD 186924 will obscure the colorful light of the surrounding
nebula. To you, then it won’t appear as a nebula but rather a bright star.
However, you can view it with an averted vision. This causes the blinking
effect in the eyes of observer as his eyes wanders. It doesn’t actually blink
in space. This nebula was discovered in the year 1793 by the astronomer William
Herschel and is about only 1000 years old.
This is all from me for this
episode. We will meet again with a new episode!
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