Glizdka
Key Member
- Joined
- Apr 13, 2019
- Member Type
- Other
- Native Language
- Polish
- Home Country
- Poland
- Current Location
- Poland
Writing this article is meant to test my ability to use English to explain a scientific topic comprehensively, such that you understand the idea. The text should meet all your teacherly standards; please tell me if it doesn't. ;-) In this article, I will explain why I think the star Sun is "the biggest of the smallest", and also why iron is the perfect element.
Our star is a G2 class star. This means that it's somewhere in the middle of stellar classification, that classifies stars by color and temperature, closer to the low end. (↑OBAF[G]KM↓) If the Sun were more massive, it could sustain the CNO cycle, and become an F class star. The CNO cycle is revolutionary in stellar evolution because it allows stars a quick and spectacular life the Sun will never have; it will live a long and peaceful life among many other stars too small to sustain it. The Sun isn't small when compared to other stars, though, as it is in the top 10% of stars in terms of mass; it's just that it takes a lot of mass to sustain the cycle.
The CNO cycle allows nuclear fusion to produce elements heavier than hydrogen and helium, which is all other elements. Stars like our sun use the gravity from their mass to squash hydrogen inside. This process splices hydrogen, and makes it fuse into helium, but helium is where it stops for such small stars. Only bigger, more massive stars can go further, from helium to carbon, nitrogen, and oxygen, hence the name, the CNO cycle. Once the cycle is sustainable, there's no return; the star is on its way to a positive feedback loop that will eventually overload its fusing capacity, use up all its fuel, and end it in a supernova.
Not all configurations of matter are equally stable. Helium has four nucleons closely packed together inside its core, a more stable configuration than if the four nucleons were separate. Higher stability of an atom means that less energy is required to hold its core together, and that energy can be released if we transform an atom into another, more stable. That's how the Sun extracts energy from hydrogen in nuclear fusion. However, adding more nucleons would produce lithium, beryllium, and boron, all of which are less stable than helium, and the product would only quickly fall apart back into the subtracts. This is where fusion cannot progress any further, unless the star has a strong enough gravitational pull to squash twelve nucleons together in short time, producing carbon.
Carbon is the first on the list of elements more stable than helium; Nitrogen and Oxygen are next. The CNO cycle is more efficient than fusing hydrogen into helium, and once sustainable, becomes the predominant source of nuclear energy for the star. The CNO cycle is the first step towards fusing iron, the most stable element in terms of binding energy of a nucleon configuration. From carbon (12) to iron (56), each next element is more stable than the previous one, meaning that fusing these elements will allow for releasing energy. Past iron, each next element is less stable, and fissioning them, rather than fusing, is the way to release energy. This is what makes heavy, unstable elements like uranium good fissile but terrible fusile materials. Once fusion reaches iron, it's reached its limit, and the star is on its way to death, the fate our star will not share, luckily.
Our star is a G2 class star. This means that it's somewhere in the middle of stellar classification, that classifies stars by color and temperature, closer to the low end. (↑OBAF[G]KM↓) If the Sun were more massive, it could sustain the CNO cycle, and become an F class star. The CNO cycle is revolutionary in stellar evolution because it allows stars a quick and spectacular life the Sun will never have; it will live a long and peaceful life among many other stars too small to sustain it. The Sun isn't small when compared to other stars, though, as it is in the top 10% of stars in terms of mass; it's just that it takes a lot of mass to sustain the cycle.
The CNO cycle allows nuclear fusion to produce elements heavier than hydrogen and helium, which is all other elements. Stars like our sun use the gravity from their mass to squash hydrogen inside. This process splices hydrogen, and makes it fuse into helium, but helium is where it stops for such small stars. Only bigger, more massive stars can go further, from helium to carbon, nitrogen, and oxygen, hence the name, the CNO cycle. Once the cycle is sustainable, there's no return; the star is on its way to a positive feedback loop that will eventually overload its fusing capacity, use up all its fuel, and end it in a supernova.
Not all configurations of matter are equally stable. Helium has four nucleons closely packed together inside its core, a more stable configuration than if the four nucleons were separate. Higher stability of an atom means that less energy is required to hold its core together, and that energy can be released if we transform an atom into another, more stable. That's how the Sun extracts energy from hydrogen in nuclear fusion. However, adding more nucleons would produce lithium, beryllium, and boron, all of which are less stable than helium, and the product would only quickly fall apart back into the subtracts. This is where fusion cannot progress any further, unless the star has a strong enough gravitational pull to squash twelve nucleons together in short time, producing carbon.
Carbon is the first on the list of elements more stable than helium; Nitrogen and Oxygen are next. The CNO cycle is more efficient than fusing hydrogen into helium, and once sustainable, becomes the predominant source of nuclear energy for the star. The CNO cycle is the first step towards fusing iron, the most stable element in terms of binding energy of a nucleon configuration. From carbon (12) to iron (56), each next element is more stable than the previous one, meaning that fusing these elements will allow for releasing energy. Past iron, each next element is less stable, and fissioning them, rather than fusing, is the way to release energy. This is what makes heavy, unstable elements like uranium good fissile but terrible fusile materials. Once fusion reaches iron, it's reached its limit, and the star is on its way to death, the fate our star will not share, luckily.
Last edited: