A supernova is coined by some astronomers as the brilliant destruction of a star, and rightfully so because of the highly complex activities that resulted to the final outburst of the of the celestial body. While the typical explanation of a star explosion is a change in its core or the excessive absorption of massive matter from another star, it took years of study for astronomers to finally present it that way. It is stimulating to note that the study of supernova dated back to ancient China, the oldest known record was shortlisted from thousands of supposed supernovae. The supernova SN 185 was observed in 185 AD, 1 when Chinese astronomers observed and noted the unusual behavior of a bright star. The uncommon characteristics are associated by modern day astronomers as that of a supernova. Interestingly, a gaseous shell, the RCW 86, is believed to be a remnant of the said star 2 as proved by a study that substantiated the age of the remnant and the time of occurrence. The SN 185 was followed by other stars whose remnants are linked with bits and pieces of supernova explosions.
Classification of Supernova
There are two traditional classifications of supernovae, which is the type I and II, though the type III, IV and IV were later proposed by scholars to take on the rare types of supernovae. Accordingly, a type I supernova is characterized by a star’s exhibition of a sharp maxima that is about 10 billion solar luminosities3 as it slowly die away. These supernovae occur when a dwarf star accumulates too much matter from another star and the massive content cause it to explode. The type I supernova is further classified as such by the absence of hydrogen in its spectra.
The increase in the discovery of other supernovae during the 1980s results to the sub-classifying of type I supernovae into Ia, Ib and the Ic subcategories. The type Ia results from the accumulation of gas from a companion star into a dwarf one, leading to the nuclear reaction and finally ending in a supernova explosion. Scholars often refer to this type of supernova as a thermonuclear supernova, as a means to show its distinctive characteristic of being a white-dwarf thermonuclear explosion4. In addition to that, the type Ia supernovae is unique in that its distinguishing behavior is dependent on a specific factor. That is, the shape of the spectrum, the change in luminosity with time, and the velocity of the debris are all determined by the full expanse of energy that were released during the outburst5. Astronomers theorized that the degeneration of the white dwarf and its collapse stimulated the oxygen and carbon within the star to be subjected to nuclear fusion, and the outburst is the result of a carbon-oxygen thermonuclear bomb6. The characteristics and behavior that is unique to that of type Ia supernovae allow scholars to use it in cosmological researches to calculate distance.
The Type Ib and Ic Supernovae
While the type Ia supernovae is an explosion of a dwarf star that has accumulated an excessive mass from another, the type Ib and Ic is a stellar explosion that is initiated by the breakdown of a massive star that has been uncovered of its outer protective hydrogen7. There are two ways by which a star can lose its hydrogen layer; one is through binary mass exchange which is a frequent occurrence and another is through stellar winds which rarely happens8. Accordingly, a star's hydrogen envelope may be absorbed by a neighboring star and may further loss considerable mass content, even as a detached star in an advanced stage of stellar evolution. Still and all, the binary exchange of mass may continue even after the loss of the hydrogen envelope due to a close distance between the stars and even possible due to envelope interface.
Type II Supernova
Different circumstances lead to a supernova explosion, and remarkably, type II supernovae are elicited by a core collapse of an enormous star. For instance, the RCW 86 and SN 1987, were supernovae types II that occur when the hydrogen within the core is transformed into helium, thus putting a stop to fusion and allowing for gravity to take over causing the core to collapse9. It is to be noted that the thermonuclear fusion in stars that are within the ~0.8 and 8 solar masses are responsible for the creation of outward radiation pressure, a force that is used to control the forces of gravity for roughly ten billion years10. Consequently, the remnants that are cast out by the star forms a ring-shape nebula which extends into the nearby space between the star systems at ~17-35 km/s11. What remains after the explosion is the core of the star, more popularly called the white dwarf, a degenerated dwarf that does not have the ability to develop pressure within.
Various researches have been conducted to study the effect of supernova explosions to earth and human lives as a whole. A theory associating the extinction of ancient plants and animals to that of a supernova explosion creates an alarm to humans. Further, there is an experimental evidence that indicates the effect of the ionization of the air by Galactic Cosmic Rays in the earth’s atmosphere. Although there is an assurance from the scientific community that such an explosion is too far from earth to even cause us harm, it imposes a responsibility for science to develop further study about about these astronomical occurrences.
1. M. J. Rees and R.J. Stoneham. Supernovae: A survey of Current Research: Proceeding of the NATO Advanced Study Institute held at Cambridge, UK., June 29- July 10, 1981. Volume 90 of NATO Science Series. Publisher: Springer Science & Business Mdia, 2012. P. 364
2. European Space Agency. New Evidence Links Stellar Remains to Oldest Recroded Supernova. Sept. 18, 2006. Retrieved from www.esa.int/Our_Activities/Space_Science/New_evidence_links_stellar_remains_to_oldest_recorded_supernova.
3. Hyperphysics. Supernovae. Retrieved from hyperphysics.phy-astr.gsu.edu
4. The Astrophysics Spectator. Supernovae. May 2, 2009. Retrieved from http://www.astrophysicsspectator.com/topics/supernovae/SupernovaeThermonuclear.html
5. The Astrophysics Spectator. Supernovae. May 02, 2009. Retrieved from http://www.astrophysicsspectator.com/topics/supernovae/SupernovaeThermonuclear.html
6. The Astrophysics Spectator. The structure of our universe. Nov. 10, 2004. Retrieved from http://www.astrophysicsspectator.com/topics/overview/DistanceExtragalactic.html
7. S.E Woosley and R.G. Eastman. Type IB and Ic Supernovae: Models and Spectra. Retrieved from http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.57.3823&rep=rep1&type=pdf
8. S.E Woosley and R.G. Eastman. Type IB and Ic Supernovae: Models and Spectra. Retrieved from http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.57.3823&rep=rep1&type=pdf
9. Chandra X-Ray Observatory. Type II Supernovae. Feb. 26, 2015. Retrieved from http://chandra.harvard.edu/edu/formal/snr/bg2.html.
10. Chandra X-Ray Observatory. Type II Supernovae. Feb. 26, 2015. Retrieved from http://chandra.harvard.edu/edu/formal/snr/bg2.html
11.Chandra X-Ray Observatory. Type II Supernovae. Feb. 26, 2015. Retrieved from http://chandra.harvard.edu/edu/formal/snr/bg2.html