The Hertzsprung-Russel Diagram - Assignment Example

Written Assignment 3 Please answer each of the standard essay questions in this assignment in a minimum of one typed page Explain how the Hertzsprung-Russell diagram is constructed of the four main groupings of stars. Identify characteristics of the four main groupings of stars on the diagram. The Hertzsprung-Russel diagram is a diagram showing how the stars are related by their luminosity in relation to their classifications and temperatures. The diagram is constructed with two X and two Y axes. The horizontal axis on the top is Effective Temperature in Kelvin, and the one on the bottom is the star’s spectral class (O, B, A, F, G, K, or M). The Y axes measure the star’s absolute magnitude (on the left) and its luminosity (on the right). When stars are plotted on the diagram, they usually fall into one of four main star groupings, labeled with letters to keep them apart: Groups A, B, C, D. Group A is also known as the “Main Sequence” of stars. Most stars fall into this grouping, which goes diagonally down the middle of the graph. That means stars in it are pretty much average in terms of the relation of their classification and temperature to their magnitude and luminosity. Star type B are Giant type stars. These stars take up more space, and are much bigger than main sequence stars, but they’re about the same size. Because they are bigger, they put out a lot more energy than a main sequence star. Super-giants, type C stars, are like Giants only even larger. Type D stars are the opposite. They are very hot and put out a lot of energy, but they are small in terms of size and not very bright. This kind of star is called a White Dwarf. 2. "A Star is Born!" In a step-by-step fashion, reconstruct the birth of a star. In your answer, include interstellar medium, protostar, and how stellar equilibrium is finally reached. Stars often begin life in nebulae rich with materials for star construction. At some point, some sort of disturbance will go through this nebula and that will kick off the star creation process. Stars first begin to form out of the interstellar medium, the basic “stuff” that exists in outer space in the distances between the stars, planets, and other similar bodies. These distances are not simply empty, but are made up of gases and dust and other small things like that. Once something happens in the nebula as mentioned above, these various pieces of the interstellar medium in the nebula will start to clump together in little balls. This process is called accretion, and it can go on for quite a long time as dust and gas sticks to what will eventually become a star. As this accretion goes on, the star gets bigger, hotter, and more luminous. Eventually these clumps of gas and dust will become massive enough to be known as a protostar. A protostar is dense enough to keep its own heat without losing it to the nebula it is within. However, they do not yet produce energy through nuclear fusion like a real star does. Once fusion begins, the star is truly born. Two important properties of stars are equilibrium. There are two types: thermal and hydrostatic, but both are similar. Thermal equilibrium means that the amount of energy a star produces is the same as the amount it is putting out on its surface. Hydrostatic equilibrium means that the star’s core has enough pressure to stop it from collapsing in on itself. 3. "A Star Dies!" Using the same technique you applied in question 2 above, trace the elements in the demise of stars of low stellar mass, those of medium stellar mass, and those that are very massive. Stars can die in a few different ways, depending on how massive they are and other similar qualities of the stars. In other words, the way that a star dies is based on where it falls in the Hertzsprung-Russel diagram. White Dwarves, Main Sequence Stars, and Giants/Supergiants die in different ways. Basically all of these star deaths have one cause in common, though. They are all caused by the amount of energy running out and then the starts collapsing in upon themselves due to the weight of gravity and their mass. Main Sequence stars, those of medium size mass, will eventually turn enough helium into hydrogen that it begins to lose equilibrium. What happens at this point is that the star will start to die by collapsing in on itself, because the amount of energy it produces is not enough to fight gravity any longer. White Dwarf stars do not have enough energy to do much fusion, because they are so small and do not create enough gravity. They usually run out of energy at a much slower rate, and when they do they just kind of stop burning. Giants and Supergiants have a lot more stellar mass than Main Sequence and Dwarf stars, and so they die out much more quickly. This is due to gravity. Since they are more massive, they burn their helium up at a much faster rate. Like with Main Sequence stars, Giants will eventually collapse on themselves, but the difference is that when a Giant star does this, it usually causes a huge explosion called a supernova. After turning into supernovae, Giant stars become either Neutron Stars or Black Holes. 4. Explain how Type I and Type II supernovae occur. Type I supernovae occur when White Dwarves collapse upon themselves and explode. While White Dwarves are not normally massive enough to explode upon dying, sometimes they can do so. For instance, if a White Dwarf accretes matter from another partner of a binary star system, it can eventually get hot enough to begin carbon fusion. Once it begins undergoing carbon fusion, the White Dwarf can no longer maintain its stellar equilibrium and it will collapse in on itself. The supernova is what results from this collapse, as most of the matter in the star gets shot out into space. Type II supernovae occur when Giant or Supergiant type stars die. In order undergo this type of supernova, a star must have at least nine times the mass of the sun. Unlike Dwarf type stars, Giants do not need a binary partner in order to go supernova. Instead, they collapse into themselves as described above. Unlike Main Sequence stars, Giants can undergo fusion in more elements, and eventually their stellar core will turn into a solid lump of iron. The star then stops producing enough energy to do more fusion, so it eventually collapses upon itself and explodes. Read More