What the Hertzsprung-Russell Diagram Reveals about Stars

What the Hertzsprung-Russell Diagram Reveals about Stars The stars are the most amazing physical engines in the universe. They radiate light and heat, and they create chemical elements in their cores. However, when observers look at them in the night sky, all they see are thousands of pinpoints of light. Some appear reddish, others yellow or white, or even blue. Those colors actually give clues to the temperatures and ages of the stars and where they are in their life-spans. Astronomers sort stars by their colors and temperatures, and the result is a famous graph called the Hertzsprung-Russell Diagram. The H-R diagram is a chart that every astronomy student learns early on. Learning the Basic H-R Diagram Generally, the H-R diagram is a plot of  temperature vs. luminosity.  Think of luminosity as a way to define the brightness of an object. Temperature is something were all familiar with, generally as the heat   of an object. It helps define something called a stars spectral class, which astronomers also figure out by studying the wavelengths of light that come from the star. So, in a standard H-R diagram, spectral classes are labeled from hottest to coolest stars, with the letters O, B, A, F, G, K, M (and out to L, N, and R). Those classes also represent specific colors. In some H-R diagrams, the letters are arranged across the top line of the chart. Hot blue-white stars lie to the left and the cooler ones tend to be more toward the right side of the chart. The basic H-R diagram is labeled like the one shown here. The nearly diagonal line is called the main sequence. Nearly 90 percent of the stars in the universe exist along that line at one time in their lives. They do this while they are still fusing hydrogen to helium in their cores. Eventually, they run out of hydrogen and start to fuse helium.  Thats when they evolve to become giants and supergiants. On the chart, such advanced stars end up in the upper right corner. Stars like the Sun may take this path, and then ultimately shrink down to become white dwarfs, which appear in the lower left part of the chart. The Scientists and Science Behind the H-R Diagram The H-R diagram was developed in 1910 by the astronomers Ejnar Hertzsprung and Henry Norris Russell. Both men were working with spectra of stars- that is, they were studying the light from stars by using spectrographs. Those instruments break down the light into its component wavelengths. The way the stellar wavelengths appear gives clues to the chemical elements in the star. They can also reveal information about its temperature, motion through space, and its magnetic field strength. By plotting the stars on the H-R diagram according to their temperatures, spectral classes, and luminosity, astronomers can classify stars into their different types. Today, there are different versions of the chart, depending on what specific characteristics astronomers want to chart. Each chart has a similar layout, with the brightest stars stretching up toward the top and veering off to the top left, and a few in the lower corners. The Language of the H-R Diagram The H-R diagram uses terms that are familiar to all astronomers, so its worth learning the language of the chart. Most observers have probably heard the term magnitude when applied to stars. Its a measure of a stars brightness. However, a star might appear bright for a couple of reasons:   it could be fairly close and thus look brighter than one farther away; and  it could be brighter because its hotter. For the H-R diagram, astronomers are mainly interested in a stars intrinsic brightness- that is, its brightness due to how hot it actually is. Thats why luminosity (mentioned earlier) is plotted along the y-axis. The more massive the star is, the more luminous it is. Thats why the hottest, brightest stars are plotted among the giants and supergiants in the H-R Diagram. Temperature and/or spectral class are, as mentioned above, derived by looking at the stars light very carefully. Hidden within its wavelengths are clues about the elements are in the star. Hydrogen is the most common element, as shown by the work of astronomer Cecelia Payne-Gaposchkin in the early 1900s. Hydrogen is fused to make helium in the core, so thats why astronomers see helium in a stars spectrum, too. The spectral class is very closely related to a stars temperature, which is why the brightest stars are in classes O and B. The coolest stars are in classes K and M. The very coolest objects are also dim and small, and even include brown dwarfs. One thing to keep in mind is that the H-R diagram can show us what stellar type a star can become, but it doesnt necessarily predict any changes in a star. Thats why we have astrophysics - which applies the laws of physics to the lives of the stars.

The ABCs (and Ds and Es) of Plot Development

The ABCs (and Ds and Es) of Plot Development The ABCs (and Ds and Es) of Plot Development The ABCs (and Ds and Es) of Plot Development By Mark Nichol Plot develops out of conflict, either external, such as a person or an event that precipitates a series of actions the main character undertakes, or internal, driven by the protagonist’s wants and/or needs. How that character, and others, makes choices and otherwise responds to stimuli determines the course of events. The traditional structure of a plot is linear, in which the protagonist’s actions are charted in a more or less straight line, although many stories shift from that person’s point of view to that of one or more other characters as the tale progresses. Others involve one or more flashbacks, introducing new elements to the overarching plot or by explaining elements that appeared in previous acts (known as Chekhov’s Gun). In one sense, there are innumerable stories; looking at storytelling another way, various analysts have discovered variable finite numbers of basic plots (such as the quest, which is ubiquitous in all genres), though these types have a seemingly infinite number of variations, as a visit to any large bookstore or library will attest. But stories almost invariably follow a simple pattern, in which rising action propels the protagonist through a series of complications that result in a climax, followed by the falling action of the resolution. At this point, the character, or at least the character’s circumstances, have changed, though most readers (and writers) find it most satisfying if the character has experienced significant growth or change and has accomplished a palpable goal, such as a physical journey that has allowed the character to achieve some reward, or an intangible goal that still satisfies the reader’s desire for the protagonist to undergo a metamorphosis of some kind. Writer Annie Lamott created a helpful mnemonic catechism, ABCDE, to help writers remember the basics. Here are the elements: Action: Set the scene with an event that launches the series of events that constitutes a story. This scene should happen as early as possible, and though writers renowned and obscure alike have broken this rule with some degree of success, observe it unless you have an outstanding reason not to. Background: Context is essential to settle your readers into the story, though, as indicated above, it usually follows initiating action. Pay it out parsimoniously, however, and don’t let your reader get ahead of your protagonist, or you’ll likely release the dramatic tension prematurely. Conflict: Such tension is produced by your protagonist’s impetus to achieve a goal. That goal should be specific, and, for the story to be compelling, it should be something the character can’t live without. To be even more so, it shouldn’t be easy for the character to satisfy that desire. The tension is produced by desire, but it is sustained by obstacles to attainment of that desire. Development: This element constitutes the bulk of the plot; it is the journey, and all the events and incidents along the way. These happenings should bring the protagonist ever closer to resolution of the conflict, and they should steadily escalate in import and impact to heighten the suspense and keep the reader engaged in the story. End: The final step is further subdivided into a mnemonic trio: The crisis is the stage at which the protagonist must decide how to resolve the conflict, the climax is the tipping point at which the conflict is resolved, and the consequences consist of the state of affairs that exists after the crisis and the climax has the main character changed, or has the main character changed the world in some way? What is the outcome of all that has come before? This stage in a story, also called the denouement, is the final, necessary release of dramatic tension. Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Fiction Writing category, check our popular posts, or choose a related post below:Regarding Re:"Wracking" or "Racking" Your Brain?Letter Writing 101