I once wrote an article about a Supernova. It was just a little over a year ago for my Writing studies. I had to write an article commemorating any interesting and little known anniversary and because I like space so much, i decided to write an article about the anniversary of one of the brightest Supernova's in Earth's history. So tonight when i read
this article (and
this one and on
this site) about a new Supernova (SN 2014J) in the M82 galaxy that was first seen this week (21st Jan), i got so excited and decided to post my article from my studies. The article explains, for those who want to/don't know, how Supernovas are formed. I think it's one of the most spectacular events that can happen in the universe. It reminds me of how dangerous outer space can be and i sometimes can't believe that we (Earth) are still here! Only by the grace of God.
A Stellar Explosion known as SN 1006
About a thousand
years ago on 30 April 1006, the brightest supernova in Earth’s recorded history
first appeared in the constellation Lupus. The stellar
explosion – known as supernova SN 1006 – was discovered a day later on the 1st
of May.
This magnificent
light show was documented in China, Japan, Europe and the Arab world, with the
Chinese and Arab astronomers providing the most complete historic descriptions
of the supernova.
The first known North
American representation of the supernova was an explanation of a rock engraving
by the Hohokum – American
Southwest ancient culture traditions - in White Tank Mountain Regional Park,
Maricopa County, Arizona.
The Egyptian Arabic
astronomer Ali Ridwan stated that the display was 2½ to 3 times as large as
Venus. It is said that if you position this supernova in the place of the sun,
it would destroy everything around it, stretching as far as Jupiter. Which of
course means Earth would seize to exist.
It was brighter than
Venus and visible during the day for weeks. Some sources state that the star
was bright enough to cast shadows and the modern-day astronomer Frank Winkler
has said that “in the spring of 1006, people could probably have read
manuscripts at midnight by its light”. According to Songshi –
official Chinese historical works – the size of the visual explosion was half
that of the moon and shone so brightly that objects on the ground could be seen
at night.
There seems to have
been two distinct phases in the early evolution of this supernova. There was a
three-month period at which it was at its brightest; after this phase it
diminished, then returned for an episode of about eighteen months.
While most
astrologers interpreted the event as an omen of warfare and famine, the Chinese
astrologer – and astronomer – Zhou Keming, described the star to the emperor on
30 May as a lucky star that is yellow in colour and brilliant in its brightness
that would bring great prosperity to the state over which it appeared.
The distance to the
supernova is about 7000 light-years. This means that the explosion actually
happened 7000 years before the light reached Earth in 1006; round about 6000 BC.
Early observers were
fortunate to experience this heavenly display, but they didn’t understand its
cause or implications. Astronomers now know that SN 1006 was caused by a white
dwarf star that captured mass from a companion star until the white dwarf
became unstable and caused a thermonuclear explosion that destroyed it.
A nova is a dreadful
nuclear explosion in a white dwarf star. A supernova is a cosmological
explosion that is more
energetic than a nova.
White
dwarfs are considered to be the final evolutionary form of all stars that aren’t
heavy enough to become neutron stars. Over 97% of the stars in our galaxy are
neutron stars.
A white dwarf star is
very dense and its mass is similar to that of the sun and its volume is equivalent
to that of the Earth. After the hydrogen-fusing
existence of a dwarf star, with low or medium mass, it will expand to a red
giant which fuses helium to carbon and oxygen in its core by a set of nuclear fusion
reactions.
If a red giant has
insufficient mass to generate the core temperature required to fuse carbon, a motionless
ball of carbon and oxygen will build up at its centre.
After shedding its
outer layers to form a glowing shell of gas, it will leave behind this core, which
forms the remnant white dwarf. Therefore white dwarfs are composed of carbon
and oxygen.
The material in a
white dwarf no longer undergoes fusion reactions, so the star has no source of
energy.
A white dwarf is very
hot when it is formed, but since it has no source of energy, it will gradually
emit its energy and cool down. This means that its radiation will diminish with
time. Over a very long period, a white dwarf will cool to temperatures at which
it will no longer produce significant heat or light, and it will become a cold
black dwarf. According to astronomers, however, black dwarfs don’t exist – yet.
But wait! There is an
alternate ending to a white dwarf’s existence – it is possible for a
carbon-oxygen white dwarf to capture material from a companion star. If this
transfer causes the white dwarf to approach the limit of 1.4 solar masses
(solar mass is the mass of the sun), it may explode as a supernova through the
process known as carbon detonation. This is exactly how supernova SN 1006 came
about.
The supernova remnant
from this explosion was not identified until 1965, when Doug Milne and Frank
Gardner used the Parkes radio telescope in Australia to demonstrate that the
previously known radio source near the star Beta Lupi, had the appearance of a
30-arcminute circular shell. It is now
known as the ‘SN 1006 supernova remnant’ and the remains appear to be about 60
light-years across.
Recent observations
of the remnant reveal the release of elements such as iron that were previously
locked up inside the star. And because no material falls back into a neutron
star or black hole after this type of supernova explosion, the deliverance of
this star’s contents is complete.
Over the next few
years, both X-ray and optical discharge from this remnant were also detected,
and in 2010 a gamma-ray observatory announced the detection of very high-energy
gamma-ray emission from the remains. In the visible spectrum the remnant is yellow,
in X-ray it is blue and at radio it is red in colour.
Humans don’t always
grasp the sheer size of the cosmos compared to the relatively small size of the
Earth within the universe. We think that it is only astronomers who should
occupy themselves with the activities of the stars and galaxies, yet we are all
a part of it.
1 May 2013 will be
the 1007th anniversary of supernova SN 1006. It is important for
people to remember such universal happenings as it illustrates the magnificence
of our heavens. Since stars appear as small white dots from here, we forget
that they significantly surpass the size of Earth. When you start to perceive
the world as part of a massive universe, you begin to understand the bigger
picture and realise what is important in life.