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.

Using Sinatra in Ruby - Introduction

Using Sinatra in Ruby - Introduction In the previous article in this series of articles, we talked about what Sinatra is. In this article, well look at some real functional Sinatra code, touching on a few Sinatra features, all of which will be explored in depth in upcoming articles in this series. Before you get started, youll have to go ahead and install Sinatra. Installing Sinatra is as easy as any other gem. Sinatra does have a few dependencies, but nothing major and you shouldnt have any problems installing it on any platform. $ gem install sinatra Hello, World! The Sinatra Hello world application is shockingly simple. Not including the require lines, shebang and whitespace, its just three lines. This is not just some small part of your application, like a controller in a Rails application, this is the entire thing. Another thing you may notice is that you didnt need to run anything like the Rails generator to generate an application. Just paste the following code into a new Ruby file and youre done. #!/usr/bin/env rubyrequire rubygemsrequire sinatraget / doHello, world!end Of course this isnt a very useful program, its just Hello world, but even more useful applications in Sinatra arent much larger. So, how do you run this tiny Web application? Some kind of complex script/server command? Nope, just run the file. Its just a Ruby program, run it! inatra$ ./hello.rb Sinatra/0.9.4 has taken the stage on 4567 for development with backup from Mongrel Not very exciting yet. Its started the server and bound to port 4567, so go ahead and point your Web browser to http://localhost:4567/. Theres your Hello world message. Web applications have never been so easy in Ruby before. Using Parameters So lets look at something a little more interesting. Lets make an application that greets you by name. To do this, well need to use a parameter. Parameters in Sinatra are like everything elsesimple and straightforward. #!/usr/bin/env rubyrequire rubygemsrequire sinatraget /hello/:name doHello #{params[:name]}!end Once youve made this change, youll need to restart the Sinatra application. Kill it with Ctrl-C and run it again. (Theres a way around this, but well look at that in a future article.) Now, the parameters are straightforward. Weve made an action called /hello/:name. This syntax is imitating what the URLs will look like, so go to http://localhost:4567/hello/Your Name to see it in action. The /hello portion matches that portion of the URL from the reqest you made, and :name will absorb any other text you give it and put it in the params hash under the key :name. Parameters are just that easy. There is of course much more you can do with these, including regexp-based parameters, but this is all youll need in almost every case. Adding HTML Finally, lets spiff this application up with a little bit of HTML. Sinatra will return whatever it gets from your URL handler to the web browser. So far, weve just been returning a string of text, but we can add some HTML in there with no problem. Well use ERB here, just like is used in Rails. There are other (arguably better) options, but this is perhaps the most familiar, as it comes with Ruby, and will do fine here. First, Sinatra will render a view called layout if one exists. This layout view should have a yield statement. This yield statement will capture the output of the specific view being rendered. This allows you to create layouts very simply. Finally, we have a hello view, which generates the actual hello message. This is the view that was rendered using the erb :hello method call. Youll notice that there are no seperate view files. There can be, but for such a small application, its best to keep all the code in a single file. Though the views are sepeated at the end of the file. #!/usr/bin/env rubyrequire rubygemsrequire sinatraget /hello/:name doname params[:name]erb :helloend__END__ layouthtmlbody% yield %/body/html helloh3Hello % name %!/h3 And there you have it. We have a complete, functional hello world application in about 15 lines of code including the views. The following articles, well take a closer look at the routes, how you can store and retrieve data, and how to do better views with HAML.

The Treaty of Tordesillas

The Treaty of Tordesillas Just months after  Christopher Columbus  returned to Europe from his maiden voyage to the New World, the Spanish-born Pope Alexander VI gave Spain a head-start in the quest for domination over newly discovered regions of the world. The Lands of Spain The Pope decreed that all lands discovered west of a meridian 100 leagues (one league is 3 miles or 4.8 km) west of the Cape Verde Islands should belong to  Spain  while new lands discovered east of that line would belong to  Portugal. This papal bull also specified that all lands already under the control of a Christian prince would remain under that same control.​ Negotiating to Move the Line to the West This limiting line made Portugal angry. King John II (the nephew of  Prince Henry the Navigator) negotiated with King Ferdinand and Queen Isabella of Spain to move the line to the west. King Johns rationale to Ferdinand and Isabella was that the Popes line extends all around the globe, thus limiting Spanish influence in Asia. The New Line On June 7, 1494, Spain and Portugal met at Tordesillas, Spain and signed a treaty to move the line 270 leagues west, to 370 leagues west of  Cape Verde. This new line (located at approximately 46 ° 37) gave Portugal more claim to South America yet also provided Portugal with automatic control over most of the Indian Ocean. Treaty of Tordesillas Accurately Determined While it would be several hundred years before the line of the Treaty of Tordesillas could be accurately determined (due to problems determining longitude), Portugal and Spain kept to their sides of the line quite well. Portugal ended up colonizing places like Brazil in South America and India and  Macau  in Asia. Brazils Portuguese-speaking population is a result of the Treaty of Tordesillas. Portugal and Spain ignored an order from the Pope in enacting their treaty, but all was reconciled when Pope Julius II agreed to the change in 1506.

Global Financial Management Essay Example | Topics and Well Written Essays - 500 words - 1

Global Financial Management - Essay Example With reasons. We have an equation with only one unknown, so we can solve it to find PMT.The easy way is with a financial calculator. Input N=3, I/YR = 10, PV = 1000, FV = 0, and then press the PMT button to get PMT = 402.1148036, 10) Suppose that on January 1 you deposit $100 in an account that pays a nominal (quoted) interest rate of 11.33463%, with interest added (compounded) daily. How much will you have in your account on October 1, or 9 months later? (4) An important rule is that you should never show a nominal rate on a time line or use it in calculations unless what condition holds? (Hint: Think on annual compounding, when INom = EFF% = I per.). What would be wrong with your answers to part (1) and (20) if you used the nominal rate of 10% rather than the periodic rate Nom/2 = 10% /2 = 5%? INom can be used in the calculations only when annual compounding occurs. If the nominal rate of 10% were used to discount the payment stream, the present value would be overstated by $272.32- $247.59 = $24.73. 12) Suppose someone offered to sell you a note calling for the payment of $1000 in 15 months. They offer to sell it to you for $850 .You have $850 in a bank time deposit that pays a 6.76649% nominal rate with daily compounding, which is a 7% effective annual interest rate, and you plan to leave the money in the bank unless you buy the note. The note is not risky you are sure it will be paid on schedule. Should you buy the note? Check the decision in three ways (1) by comparing your future value if you buy the note verses leaving your money in the bank; (2) by comparing the PV of the note with your current bank account and (3) by comparing the EFF $ on the note with that of the bank

World War I Research Paper Example | Topics and Well Written Essays - 250 words

World War I - Research Paper Example However, suffice it to say that within this particular author’s understanding, the First World War was fought under the most horrific conditions imaginable. Ultimately, the reason that so many different countries became embroiled in this conflict had to do with the alliance structure that existed within Europe time. Ironically, the structure of the alliance system was engaged as a means of preserving the peace; allowing lesser powers to ally with great powers as a means of ensuring that conflict would not break out. However, as was seen, the assassination of Archduke Ferdinand in Bosnia-Herzegovina ignited the so-called â€Å"tinderbox† of the Balkans; dragging in the Austro-Hungarian Empire, Russia, France, Germany, the United States, and a litany of other actors. Sadly, the horrors of the first world war are not constrained to the years 1914 through 1918. Instead, many scholars and authors have argued that the repercussions of the First World War did not truly conclud e until 1945. This is due to the fact that the peace accords for the First World War and the Treaty upper side created a situation in which a resurgent Germany would attempt to shake itself from the shackles of financial hardship and national disgrace that the treaty of Versailles had affected upon

Business report of financial exercise Essay Example | Topics and Well Written Essays - 2000 words

Business report of financial exercise - Essay Example To increase the revenue, the owner has decided that the firm will operate six days a week which will bring gross sales of  £15,000 in the upcoming year. We will analyze the implication of this change on the profit & loss statement in the light of reasonable assumptions. If the wages are calculated on the basis of increase in variable costs than the initial work demand was for 5 days which has now increased to 6 days therefore the rate of increase in variable costs will be It is found that advertising is correlated with sales and brand value of the organization (Eng & Keh, 2007). Therefore, we will assume that Advertising will increase respect to increase in percentage sales The local garage initially agreed on vehicle maintenance at a cost of  £500 per quarter. The terms initially might include that the business will operate for 5 days. Now since the business will be operating for six days therefore the contract costs will increase to  £600 per quarter. The cash flow forecast for year 2008 and 2009 can be implemented based on the future income statements. In this section we have provided the cash flow forecast for 2007 this will serve as the guideline for future cash flows based on the future assumptions. The cash flow analysis can be and income statements have revealed important information with regards to the community travel. Although the new change seems to be feasible, but it should be implemented in the proposed way by hiring two new part-time drivers who can fulfill the needs on Saturdays. Similarly if the full time employees are willing to work on the compensation terms than they should be hired since they have relevant expertise of the organization. If the business flows in the way as it was doing without any credit sales than it will have abundant cash at the end of the cycle which can be used to expand the business. However, as we noted small changes such as delays in payments or increase in

Amazon Case Study Example | Topics and Well Written Essays - 1250 words

Amazon - Case Study Example The company, Amazon.com, Incorporation is one of the electronic commerce companies, operating on the multinational level, located in America having its headquarters in Seattle, Washington. It is one of the largest online retailers globally (Jopson, Barney, 2011). Amazon incorporation also produces the products of consumer electronics, which most prominently include the Amazon Kindle e-book reader. It also provides the services of cloud computing to its consumers. The company manages it sellers by contributing towards programs which let its consumers sell their products through the websites of the seller and also market and sell them on the website of Amazon incorporation. It earns per-unit activity fees or revenue share fees and fixed fees on such business dealings. The enterprises are served by Amazon through AWS that brings the technological infrastructure in easy access to the developers, who can utilize it to facilitate nearly every sort of business. Amazon mainly functions in the online retailing business of e-books, and has various websites in many countries across the world. They operate in United Kingdom, United States, Canada, Italy, France, Spain, Japan, Germany, and China, along with the international delivery to many other places for some of its products. The company initially came into the business by starting up an online bookstore. However, it quickly expanded into a bigger company dealing in the selling of CDs, DVDs, software, MP3 downloads, apparel, furniture, electronics, video games, toys, food, and jewelry (Rivlin, Gary, 2005). The Amazon Incorporation competes in the Internet & Mail-Order Retail industry. It provides business services in media, publishing, clothing and other retailing. The top competitors of Amazon incorporation include Apple incorporation, Columbia House Company, eBay Incorporation, Wal-Mart Stores, Incorporation, Barnes & Noble Incorporation, and Hastings