They are the main source of most heavy elements, from oxygen on up. If the exploding massive star is still within the molecular cloud in which it formed, the expanding remnant might compress the surrounding interstellar gas and trigger subsequent star formation.
The remnants contain strong shock waves that create filaments of material emitting gamma-ray photons with energies up to 10 14 electron volts and accelerating electrons and atomic nuclei up to cosmic-ray energies, from 10 9 up to 10 15 electron volts per particle.
In the solar neighbourhood, these cosmic rays carry about as much energy per cubic metre as starlight in the plane of the galaxy, and they carry it to thousands of light-years above the plane. Much of the radiation from supernova remnants is synchrotron radiation , which is produced by electrons spiraling in a magnetic field at almost the speed of light. Electrons of many different energies produce radiation at essentially all wavelengths, from radio through infrared , optical, and ultraviolet up to X - and gamma rays.
About 50 supernova remnants contain pulsars , the spinning neutron star remnants of the former massive star. The name comes from the exceedingly regularly pulsed radiation that propagates into space in a narrow beam that sweeps past the observer similarly to the beam from a lighthouse.
There are several reasons why most supernova remnants do not contain visible pulsars. Perhaps the original pulsar was ejected because there was a recoil from an asymmetrical explosion, or the supernova formed a black hole instead of a pulsar, or the beam of the rotating pulsar does not sweep past the solar system. Supernova remnants evolve through four stages as they expand. At first, they expand so violently that they simply sweep all older interstellar material before them, acting as if they were expanding into a vacuum. The shocked gas, heated to millions of kelvins by the explosion, does not radiate its energy very well and is readily visible only in X-rays.
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This stage typically lasts several hundred years, after which time the shell has a radius of about 10 light-years. As the expansion occurs, little energy is lost, but the temperature falls because the same energy is spread into an ever-larger volume.
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The lower temperature favours more emission, and during the second phase the supernova remnant radiates its energy at the outermost, coolest layers. This phase can last thousands of years. The third stage occurs after the shell has swept up a mass of interstellar material that is comparable to or greater than its own; the expansion has by then slowed substantially. The dense material, mostly interstellar at its outer edge, radiates away its remaining energy for hundreds of thousands of years. The final phase is reached when the pressure within the supernova remnant becomes comparable to the pressure of the interstellar medium outside the remnant, so the remnant loses its distinct identity.
In the later stages of expansion, the magnetic field of the galaxy is important in determining the motions of the weakly expanding gas. Even after the bulk of the material has merged with the local interstellar medium, there might be remaining regions of very hot gas that produce soft X-rays i.
The recent galactic supernovae observed are in the first phases of the evolution suggested above.
To a radio telescope , however, the situation is spectacularly different: the Cassiopeia remnant is the strongest radio source in the entire sky. Study of this remnant, called Cassiopeia A , reveals that a supernova explosion occurred there in approximately , missed by observers because of the obscuring dust. At the site of the supernova is one of the most remarkable objects in the sky, the Crab Nebula , now about 10 light-years across. Photographed in colour, it is revealed as a beautiful red lacy network of long and sinuous glowing hydrogen filaments surrounding a bluish structureless region whose light is strongly polarized.
The filaments emit the spectrum characteristic of a diffuse nebula. In the world of Remnant, all living creatures possess a soul, the physical manifestation of which is known as Aura : a form of innate energy that bestows its user with certain abilities and powers. Unique expressions of these abilities which are specific to individuals are known as Semblances.
Remnant is populated by two intelligent species - Humanity and Faunus , a race of Human-animal hybrids.
Legend states that mankind was born from dust into a hostile world, forced to battle for survival against soulless creatures of darkness known as the Grimm. However, man discovered a power that would help them combat the forces of darkness; they named their newly discovered power, Dust, after that from which they were formed. Armed with Dust, described as "Nature's Wrath", mankind was able to turn the tide against the Grimm.
In truth, before it was called that, Remnant was originally seeded by the brothers, the Gods of Light and Darkness , who created humanity as a joint project to bridge their differences. Humanity existed alongside their creators for ages until a time when a young woman named Salem confronted the gods, demanding that they return her lost love, Ozma to them.
After they refused, she tried to force the issue, only to be cursed with immortality. Angry and frustrated, Salem spread the word to the various kingdoms that they could overthrow the gods, and take their powers for themselves. This got humanity to rebel against their creators, but when they attempted to confront them, the God of Darkness effortlessly wiped them all out, save for Salem.
The gods then elected to leave, with the God of Darkness destroying the moon in the process, taking magic with them, leaving this world and its inhabitants a mere remnant of what they once were. Eventually, humanity recovered from its extinction and found themselves joined now by another intelligent race, the Faunus. The world, however, was not the same, and without magic, they were vulnerable to the Grimm.
The pace of plant community change is accelerating in remnant prairies.
To that end, they harnessed the power of Dust to defend themselves. In the absence of darkness, mankind was able to build civilization and spread throughout the world. The mining of Dust would continue to be a major industry, leading to the rise of large enterprises such as the Schnee Dust Company. However, having survived the Grimm menace, Humanity began to turn against itself, spiraling into a series of self-destructive conflicts. The largest of these was the Great War , fought over issues of individualism and self-expression.
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Conflict also arose between the Humans and the subjugated Faunus, eventually sparking the Faunus Rights Revolution. Through a combination of Human tenacity and the use of natural barriers, these settlements managed to survive and are regarded as "safe havens" and "beacons of hope" for Humanity. Small villages and nomadic communities do exist outside of the territories of the main Kingdoms, though they are noted as being far more vulnerable to Grimm attacks.
This serves to emphasize that Remnant is not a particularly welcoming world to Humans and Faunus. In doing so, they protect those who cannot protect themselves from the dangers of Remnant. In the World of Remnant episode, " Kingdoms ", a brief description is given on how the Kingdoms are governed - each Kingdom has a governing council that represents the needs of their people. The powers and responsibilities of these councils, as well as how members are appointed, are not stated. In the area of security, they are known to have influence over the administration of the Huntsmen of academies - in " Breach ", the council of Vale chastises Ozpin following a Grimm incursion into the city , and have demonstrated the authority to question his suitability as headmaster of Beacon.
Apart from Huntsmen, conventional militaries are also known to exist, but not all of the Kingdoms keep standing armies. The Kingdom of Atlas is known to maintain a sizable military force, fielding a large air fleet, as well as robotic soldiers and mechs. Although the world is said to be in an unprecedented state of peace, social issues seriously threaten the status quo - racial tensions between the Faunus and Humans caused by continuing prejudice in society, the immoral practices of the Schnee Dust Company, as well as agitation from the White Fang terrorist group, continue to cause friction in society.
The Grimm still thrive in the wild areas outside the territory of the four Kingdoms, whilst plotting by mysterious groups threaten them from within. The narration of "Kingdoms" implies that the future of Humanity is heavily contingent upon the continued cooperation of the four Kingdoms.
The Vytal Festival is an event at which the diverse cultures of Remnant are celebrated. Remnant has a vibrant culture owing to the diversity of its inhabitants. Each of the four Kingdoms has a unique identity and this distinctive character is encouraged by events such as the Vytal Festival , where the people of Remnant gather to celebrate their cultures. Given the importance of Huntsmen and Huntresses in mankind's continued existence, part of this celebration also includes a combat tournament between students of the Kingdoms' respective academies.
A significant part of Remnant's worldwide culture is the practice of naming children after colors. During the Great War, attempts by tyrannical oppressors to limit individualism and self-expression were met by a violent backlash from the populace. In response to persecutors' attempts to destroy art, people began to name their children after a fundamental element of art - color - sending the message that the next generation would also fight to prevent the destruction of their individuality.
After the end of the War and the defeat of this subjugation, the practice continued into the present day, and virtually all citizens of Remnant have names derived from colors. There is a significant amount of discrimination towards Faunus in Remnant's past and present. Since the Faunus War, in which they gained freedom by law, Faunus have continued to face discrimination and exploitation from Humans.
Whether this is the norm or the actions of a minority is unknown; however, it is enough to cause some Faunus to turn to the terrorist group, the White Fang. By contrast, Remnant appears to be a very egalitarian world when it comes to the sexes, as seen at Beacon Academy.
Both sexes share locker rooms, and teams that have both sexes in them share dorm rooms. There never appears to be animosity from men towards women or women towards men on the basis of sex. Remnant has a wide variety of advanced technologies. The Kingdom of Atlas, in particular, is known for its technological advances in numerous fields. Most technology is powered by Dust, which is the primary source of energy in Remnant. One of the most significant examples of Remnant's technology are the weapons of huntsmen and huntresses. Unique weapons are designed and manufactured by their users on an individual basis and use a variety of techniques to increase their effectiveness, such as in-the-field transformations for versatility, and the harnessing of Dust.