Our universe is a place where we are constantly discovering and studying phenomenons and incredible things. One of the most researched phenomenons are supernovae. Supernovae are essentially just the explosion and fusion of a star. These tend to happen when a massive star is almost close to death and violently explodes in a fraction of a second.
Various civilizations recorded supernovae long before the telescope was invented. The oldest recorded supernova is RCW 86 which Chinese astronomers saw in A.D. 185. According to NASA, their records call the supernova a "guest star" that stayed in the sky for eight months. Before the early 17th century (when telescopes became available), there were only seven recorded supernovae as found in the Encyclopedia Britannica.
From what we know today, the Crab Nebula is the most famous of these supernovae. Chinese and Korean astronomers recorded this star explosion in their records in 1054, and some detail that southwestern Native Americans may have seen it as well. The supernova that formed the Crab Nebula was so bright that astronomers could see it even during the day.
Other supernovae that were observed before the telescope was invented occurred in 393, 1006, 1181, and 1572. Famous astronomer Tyco Brahe wrote about his observations of the "new star" in his book, "De nova Stella," which gave rise to the name "nova." However a nova differs from supernovae: both are sudden outbursts of brightness as hot gases are blown outward, but for a supernova, the explosion is more chaotic and signifies the end of the star's lifetime.
The term "supernova", as we know it today, was not used until the 1930s. Its first use was by Walter Baade and Fritz Zwicky at Mount Wilson Observatory, when talking about an explosive event they observed, called S Andromedae which was located in the Andromeda Galaxy. They also suggested that supernovas happen when ordinary-sized stars collapse into neutron stars.
There are two main types of supernovae: Type I and Type II. Type I supernovae are when a star accumulates matter from a nearby neighbor until a runaway nuclear reaction ignites. These types are characterized by the fact that they usually lack a hydrogen signature in their light spectra. Within this type, there are two subtypes: Type Ia and Type Ib. Type Ia supernovae are generally thought to originate from white dwarf stars in a close binary system. Type Ib supernovas undergo core-collapse, but they end up losing most of their outer hydrogen envelopes.
Type II supernova occurs when a star runs out of nuclear fuel and collapses under its gravity. For a star to explode as a Type II supernova, it must be at several times more massive than the sun. Like the sun, it will eventually run out of hydrogen and then helium will end up filing at its core. However, this type will have enough mass and pressure to fuse carbon. There are also sub-categories of Type II supernovae, classified based on their light curves. The light of Type II-L supernovas decline steadily after the explosion while Type II-P's light stays steady for a time before diminishing.
Typically only a tiny core of neutrons, a spinning neutron star, is left to evidence a supernova. Neutron stars give off radio waves in a steady stream or, as pulsars, in intermittent bursts. However, if the star a was so massive (at least ten times the size of our sun) that it leaves behind a large core, something different might occur. Because such a burned-out core has no energy source to fuse and produces no outward pressure, it may become engulfed by its gravity and turn into a cosmic sinkhole for energy and matter, also known as a black hole.
Supernovae are one of the many phenomenons that our incredible universe has to offer and scientists are continuing to discover more things about it every day. It is crazy to see how much technology has allowed us to advance and learn more about them. We hope that in the future we get to explore more in-depth what these phenomenons are, what causes them to form, and what are the dangers they could bring.
Comentários