A Stellar Explosion

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 1^st 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 1007^th 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.