11. The Oldest Known Star in the Universe

The oldest start we know of, HD 140283, has been discovered and dated to be 14.3 billion years old. But how can it be if the universe only has 13.82 billion years? Scientists date starts by analyzing how much metals is in them. By taking high-resolution spectra, special-filtered pictures that display quantities of substances, they calculate the metallicity of stars. "As a rule of thumb, the older the star is, the fewer metals it has in it." The HD 140283, one of the targets for this metallicity research, checked all the boxes required for it to be analyzed. It was near the sun, less than 200 light years away, there is no galactic dust in the way which may alter results, and most important, it's at the end of its life. All these characteristics have led scientists to determine the 14.3 billion years of age. However, factors such as how much oxygen is in the star (which is unknown) and how much dust is in the way interfere. As a results, an error bars of about +-0.8 billion years is taken into consideration. With this, the age of the star ends up being an approximate 13.5 billion years, which is just about right. For now, this is the oldest star in the universe. However, it is very unlikely to be so due to the number of stars out there is such vast universe.
Phil Plait, author of this article, is an astronomer and is responsible for all of Slate's astronomy related posts. His article was purely informative and straight forward. He states the processes scientists use  and explains them to the audience. His writing and word choice are simple, however, there are some specific scientific words that readers might not be familiar with. To solve this, Plait left a link attached to them in which he explains them in other detailed articles. Although he is an expert on the subject, he doesn't seem to use any quotes from researches and other experts, making the paper lack some credibility. He also seems to contradict himself at one point. He says "the sky is clear of galactic dust" which is an advantage of looking at that specific star. Later he says one of the difficulties of getting the age is that scientists don't know "how much dust is between us and it." Other than that, he is thorough in his explanations and does successfully informs the audience.

http://www.slate.com/blogs/bad_astronomy/2014/09/26/oldest_star_astronomers_have_found_the_most_ancient_known_star.html