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The term supernova is used to refer to the explosion of a very huge star. When such a star explodes, it can release energy of up to 1044 joules. This amount of energy can be equated to the energy that the sun has given out since it came into existence. This form of an explosion has the capacity to give out brightness equivalent to the one that 10 billion suns can produce.
Supernovae have the capacity to outshine the whole galaxy before they start fading after several weeks. Supernovae are normally split depending on the attributes of light that human beings see coming from the different stars that explode. To enable people understand the elements that light from the stars contains, a special technique referred to as spectroscopy is normally used (Koupelis 56). This technique enables people to view the spectrum that light creates on its way to earth.
There are different types of supernovae that are known to exist. These are type I and type II supernovae. Type I supernovae is further classified into Type Ia, Type Ib, and Type Ic (Howell 34). There are two ways through which these supernovae can be formed. The ways in which supernovae are formed is when the nuclear fusion process does not produce energy and vice versa.
For example, there is an instance whereby a massive aging star can cease to generate energy through the process of nuclear energy. This makes the star to experience gravitational downfall making it to become a black hole or a neutron star. This process results to a release of gravitational potential energy which then heats and dismisses the outer layer of the star (Koupelis 43).
The other way through which supernovae can result is when a white dwarf star gathers enough material through merging with a stellar companion thus raising the core temperature of the star.
The high temperature then ignites a carbon fusion process which then makes the star to experience runaway nuclear fusion thus disrupting the star completely. White dwarfs can also undergo a different type of thermonuclear explosion. This type of explosion is usually powered by hydrogen present on the surfaces of the stars (Koupelis 44). The sun falls in the category of solitary stars.
These types of stars are said to have a solar mass that is below 9 solar masses thereby making it possible for these types of stars to develop into white dwarfs even before they convert to supernovae. This analysis will therefore give a report of Type Ia supernova and give its results on whether it can be used to act as secondary standard candle.
Formation Process of Type Ia supernova
There are various ways in which the Type Ia supernovae are formed but the main process is associated with the eruption of the white dwarfs in a very vigorous manner thereby releasing extreme heat. A white dwarf is described as the remnant of a star whose lifecycle is completed and has thus terminated nuclear fusion.
The white dwarfs that are associated with the carbon and oxygen are said to have the capacity to undergo additional fusion reactions thereby releasing a lot of energy when their temperatures rise to significant levels. The white dwarfs whose solar masses are below the 1.38 limit rotate at a slow rate while the white dwarfs whose solar masses are above the 1.38 limit rotate at a faster rate.
The 1.38 solar masses is the limit with which electron degeneracy pressure can support white dwarfs efficiently (Chaisson and McMillan 45). If the mass exceeds beyond this limit, the white dwarfs begin falling. When the white dwarf starts accumulating in mass as a result of binary companion, the core of the white dwarf reaches the temperature that is just enough to facilitate carbon fusion (Howell 34).
There are also instances when a star can merge with another star though this is a very rare occurrence. However, when the merging occurs, the mass of the white dwarf will go beyond the limit momentarily thereby making it to begin collapsing. This state of affairs then raises the temperature of the white dwarf to a level beyond the point of ignition of nuclear fusion.
After a few seconds when the nuclear fusion process begins, a significant amount of matter in the white dwarf experiences runaway reaction. The runaway reaction then releases an amount of energy that is approximately equal to 1-2×1044 joules. This amount of energy is enough to make the star explode into a supernova (Chaisson and McMillan 89). Type Ia supernovae have white dwarfs that have uniform mass thereby making them to produce constant uttermost luminosity.
The explosions associated with Type Ia supernovae are said to yield stable values. The distance to the galaxies that host the Type Ia supernovae can therefore be easily estimated when astrologers treat Type Ia supernovae as standard candles (Foley 21). The measurement of distance becomes possible because the ability to see the supernovae mostly depends on its distance from the earth.
In the supernova classification system, Type Ia supernova falls in the subcategory of Minkowski- Zwicky supernova. There various ways through which this type of a supernova can form. To begin with, it is possible for a slowly rotating white dwarf that is associated with the carbon-oxygen variable to accumulate matter from another companion.
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However, this white dwarf cannot exceed the 1.38 solar masses limit. Whenever the white dwarf is unable to sustain its own heaviness, it starts falling thereby forming neutron star. This scenario is observed especially if the white dwarf comprises of oxygen, neon, and magnesium (Foley 24).
However, most astronomers argue that the 1.38 solar masses index is never attained meaning that the white dwarfs do not collapse. Instead, what happens is that density and pressure increase because of the increased weight. As a result, the temperature of the core rises and when the white dwarfs come close to about 1 percent of the limit, a bonding process occurs and it lasts for about 1000 years.
At this stage, the fusion of carbon leads to the emergence of a deflagration flame. However, it is not known what ignites the carbon present in the dwarfs. Oxygen fusion is then then initiated shortly after carbon fusion. However, the carbon fusion is consumed completely whereas oxygen fusion is consumed partially (Niemeyer and Truran 102).
Once the fusion process starts, what follows is that the white dwarfs become extremely hot. The increase in thermal energy is balanced by the expansion and cooling of the star that is in the main sequence. On the other hand, degeneracy pressure is not influenced by rise in temperature.
As a result, the white dwarfs cannot regulate the burning process at this phase thereby exposing them to the runway fusion reaction. The various instabilities experienced in this phase make the flame to accelerate uncontrollably. This flame then converts to supersonic detonation (Foley 72).
Many astrologers are not yet in a position to explain the nuclear fusion process. However, once oxygen and carbon are ignited, the temperatures rise to very high degrees. The energy released from this process is estimated to be about 1-2×1044 joules. This amount of energy is extremely high in that it gives all the individual particles that make up the white dwarfs enough kinetic energy which then makes all the particles to fly away from each other (Niemeyer and Truran 34).
The explosion that results ejects a shockwave that moves at speeds of between 5,000-20,000 Km/s. This speed is approximately 6 percent higher than the speed of light. This amount of energy also leads to an extreme rise in luminosity. Type Ia supernovae have a visual magnitude of Mv= -19.3 (Koupelis 67). The amount of mass that is ejected by the white dwarfs is the one that determines whether the remnant of the supernova would continue being joined to its companion.
Binary Star Formation
The dual star concept is also an important process that illustrates the manner in which Type Ia supernovae can be molded. In this system, the major stars are observed to be heavier than the minor stars. Since the major stars possess more weight, they evolve first thereby making the resulting envelop to expand significantly.
The system fails to acquire a substantial amount of mass once the two stars are enclosed together. This reduces the period, orbital radius, and the angular momentum of the system. The major star first degenerates into a white dwarf after which the secondary star advances into a red giant. The minor red giant then deposits its own mass to the primary star. As the angular momentum diminishes, the two stars coil towards each other.
If the deposit of mass to the white dwarf becomes a continuous process, then the mass of white dwarf comes close to the 1.38 solar masses limit. During this accretion phase, the evolution process depends on the accretion rate as well as the rate at which angular momentum is transferred to the white dwarf companion (Niemeyer and Truran 65).
Double Degenerate Progenitors
The other way in which a Type Ia supernova can be triggered is when two white dwarfs merge. This makes the combined mass of these two white dwarfs to exceed the Chandrasekhar limit. In this perspective therefore, the total mass would not be restrained by 1.38 soar masses index. The collisions of solitary stars in the galaxy are estimated to occur once every 107 years (Koupelis 98). They then lead to the formation of a binary system.
The track that the stars follow also decays thereby making the stars to unite together in one envelope. It has also been noted that there is a possibility of two white dwarfs to merge once in every 100 years. The double degenerate scenario makes astrologers to doubt whether Type Ia supernovae can be applied as standard candles (Chaisson and McMillan 78). This is because the mass of the star that result from the two white dwarfs vary greatly meaning that luminosity also varies.
Type Ia supernovae are the most common types of supernovae. There are those supernovae that show preference for certain regions but Type Ia supernovae can occur in almost any type of galaxy thereby making them more common. Most white dwarfs are formed when stars attach themselves to the long-lived stars in the universe.
Before the bonding takes place, the long-lived stars may have wondered in the universe since the time they were formed. When the bonding process takes place, the transmission of mass to the white dwarfs takes millions of years. This long duration makes the environment conducive for the formation of Type Ia supernova (Niemeyer and Truran 67).
The major problem that has faced many astrologers today is how to identify supernova progenitors. Astrologers say that if they can manage to observe a progenitor which can provide constrains that they need directly, they would be able to come up with useful models that would enable them to classify the different types of supernovae effectively.
The search for such a progenitor has been ongoing for more than a century with no avail. However, though it has not been possible to identify a progenitor star having such constrains, the observation of supernova SN 2011fe proved to be very useful in providing some useful constrains that astrologers use to categorize the different types of supernovae. For example, there was a time when a team of astrologers carried out an observation with a Hubble Space Telescope.
However, astrologers said that the red giant could not have been the source. They said this because their believe was that they should have a seen a star when they were conducting the observation. However, the expanding plasma that resulted from the explosion contained both oxygen and carbon (Chaisson and McMillan 54). This observation made it more likely that the observed carbon and oxygen came from a white dwarf progenitor.
All the known Type Ia supernovae are observed to have similar luminosity characteristics. This has made many astrologers to heavily rely on them as secondary standard candles. However, the cause of similarity in the luminosity of these supernovae is still unknown. However, an observation that was conducted on Type Ia supernovae in 1998 concluded that the universe is presently experiencing an accelerating expansion (Foley 103).
Chaisson, Eric and Steve McMillan. Astronomy Today. Redwood: Benjamin-Cummings Publishing Company, 2010. Print.
Foley, Ryan Joseph . Type Ia Supernova Evolution and Dark Energy. Berkeley: ProQuest, 2008. Print.
Howell, Dale Andrew . Type Ia Supernovae: Constraints on Progenitors and Asphericity. Texas: University of Texas at Austin, 2000. Print.
Koupelis, Theo. In Quest of the Stars and Galaxies. New York: Jones & Bartlett Learning, 2010. Print.
Niemeyer, Jens and James Truran. Type Ia Supernovae: Theory and Cosmology. Cambridge: Cambridge University Press, 2000. Print.