Ation black dwarf its unknown if any black dwarves

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ation: Black dwarf. It's unknown if any black dwarves actually exist--scientists speculate that the universe probably isn't old enough yet for any white dwarves to have finished cooling off and dying. In high-mass stars, the red giant (technically a red supergiant) doesn't become a white dwarf. Yes, its core of carbon starts contracting, but it's so massive that as it contracts, it can cause further nuclear reactions, converting carbon into oxygen, neon, silicon, sulphur, and finally to _______. Explanation: Iron. The more mass a star has, the higher the gravitational pressure in its core. Most stars can't generate enough pressure to burn carbon--that's why once their core is converted into carbon, they turn into white dwarves and die. With a high-mass star, it keeps undergoing successive nuclear reactions, each time forming a heavier and heavier element until finally it ends with iron. Iron is the most stable element and there is no energy to be gained from converting it into a heavier element. Once the core of a red supergiant is essentially all iron, the core collapses even further and what you get is a mighty explosion known as a ______________. Explanation: Supernova. Right before the fully mature red giant explodes in a supernova, it has the structure of an onion. That's because each nuclear reaction produces a heavier element which sinks to the center, becoming fuel for the subsequent reaction. As you can see in the diagram below, the end result is a core of iron (Fe): Note: If you're feeling overwhelmed by all of these details, keep in mind that on the actual test, you really just need the "big picture" to do well. In other words, a low mass red giant becomes a white dwarf; a high mass red giant eventually explodes in a supernova.
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Supernovas are important because they result in the release of many exotic "heavier" ____________. Explanation: Elements. Supernovas are extremely powerful; during a month they outshine their entire galaxy and radiate more energy than our sun will over its entire lifespan. This energy is high enough that as it is exploding outwards it creates many elements which are heavier than iron. Without supernovas, many of the elements necessary to life as we know it would not exist. On a side note, supernovas release an abundance of X-rays and gamma-rays. Most of the time, it doesn't end with the supernova. If the core that's left after the explosion is small (i.e. less than 3 solar masses), then it will become a __________ _______. Explanation: Neutron star. A neutron star is the densest form of matter to exist. Note that a neutron star that's rapidly spinning is a pulsar--it pulses because as it's rotating, each time its magnetic poles align with the Earth, we receive a pulse of radiation. Typically that radiation is in the form of radio waves, although some have been known to emit X-ray and gamma ray pulses.
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