2014-03-24 14:37:42
Probably the most dramatic event in our universe is the explosion of a supernova star. The explosion of some of these stars can surpass an entire galaxy in brightness. Considering that galaxies can contain between one hundred thousand and four hundred billion stars, the amount of energy we are talking about can be described, without exaggeration in the slightest, as cosmic.
Not all supernovae are the same. According to their on and off pattern, that is, according to the dynamics of their explosion, and according to whether the light signature of hydrogen can be detected in the explosion, supernovae are classified into two types: type I (not contains hydrogen) and type II (yes it does). Furthermore, within these types, there are also subtypes.
In many cases, astrophysicists today understand quite well how and why these extraordinary explosions are generated, which launch most of the star’s mass into space at speeds of up to 30,000 km per second, that is, no less than the tenth of the speed of light. Broadly speaking, most supernova explosions are caused by stars with a mass several times greater than the Sun. These stars, like all stars, maintain a nuclear fusion reaction at their center, mainly from hydrogen to helium and then from helium to carbon. and oxygen. This thermonuclear reaction generates an expansive energy that opposes the gravitational attraction of the enormous mass of the star and prevents it from collapsing towards the center. At some point in the star’s life, however, the nuclear fuel runs out, the star cannot generate enough energy to oppose gravity, and it collapses toward its center at high speed. After this collapse, a rebound effect occurs which, together with other nuclear fusion and fission phenomena generated by the collapse, lead to the enormous supernova explosion.
CRITICAL MASS
Stars with a mass up to 1.38 times the mass of the Sun do not become supernovae. These stars age until they become white dwarfs. The reason for this behavior is that, as its hydrogen is converted into helium by nuclear fusion, the core of the star becomes enriched in this element, and the less dense hydrogen is limited to a layer surrounding the core. of helium, in which nuclear fusion continues to take place. The mass of the star presses on the core by gravity, so its size decreases very substantially: the star becomes a dwarf. However, the mass of this type of star is not enough to “ignite” the fusion of helium into carbon and oxygen, nor to cause the star to collapse, so the outer layer of nuclear fusion is all that remains. This layer emits intense white light which, together with the small size that the star has acquired, gives it its name.
White dwarfs will remain in this state until they consume all their hydrogen. However, if for some reason a white dwarf could acquire matter from the outside, due to gravitational attraction, the increase in mass could cause its center to reach enough pressure to “turn on” the nuclear fusion of helium again.
Astronomers believe that this possibility can become a reality in the case of binary star systems, in which two stars orbit each other and in which at certain moments in the evolution of the life of both stars, which becomes a white dwarf first, it can steal matter from its companion. If the stolen matter increases the mass of the white dwarf above the critical mass of 1.38 solar masses, nuclear fusion could restart, which would happen very quickly throughout the star and cause a huge supernova explosion.
STELLAR COLLISIONS
However, the above scenario is not the only possible one. Another possibility, although considered to date much less likely than the previous one, is that two white dwarfs collide. The collision would momentarily generate a star that would no longer be a dwarf, would have a mass greater than 1.38 solar masses and would cause a large supernova explosion.
How could we determine which of the two possibilities actually happens? Obviously it would be necessary to observe numerous supernovae of this type in detail with powerful telescopes, and this is what is being achieved thanks to the Kepler telescope, dedicated to the discovery of extrasolar planets, but which has not failed to capture the formation of supernovae with extraordinary definition. .
The data captured by Kepler analyzed to date seem to be more compatible with the hypothesis that the collision of two white dwarfs is the cause of the formation of this type of supernovae. These observations, however, should be corroborated by other telescopes.
The Kepler mission came to an unexpected end in May 2013 due to mechanical failures that prevented the telescope from pointing with the precision necessary to observe planets around other stars. However, these failures do not prevent the observation of supernovae, which do not require such high precision due to their high intensity. What to do to reuse the telescope in the search for this type of supernovae is being studied, which, in addition to contributing to the advancement of astronomy, can be considered the best example of recycling on a universal scale carried out by Humanity.
NEW WORK BY JORGE LABORDA.
It can be purchased here:
Chained circumstances. Ed. Lulu
Other works by Jorge Laborda
One Moon, one civilization. Why the Moon tells us that we are alone in the Universe
One Moon one civilization why the Moon tells us we are alone in the universe
The intelligence funnel and other essays
#Cienciaes.com #giant #explosion #dwarfs