Lain Miller 

Current Events March 25th 

Rao, Joe. "'Comets of the Centuries': 500 Years of the Greatest Comets Ever Seen." Space.com.              Skywatching Columnist, 23 Dec. 2013. Web. 23 Mar. 2014.

Link: http://www.space.com/24069-greatest-comets-of-past-centuries.html

            I chose to read the article “Comets of the Centuries: 500 Years of the Greatest Comets Ever Seen” by Joe Roa because I found an interest to research and investigate comets more, when we learned about them in lab. So I thought a great way to do this would be to learn about some of the most famous comets yet to be recorded. This article provides a list of the most famous comets from the sixteenth to the twentieth century. First is, The Great Comet of 1577, which appeared on November 1^st in Peru and was sighted across the world until it finally dropped out of the view of the naked eye on January 26^th 1578. It was 16.7 million miles from the sun at its perihelion (or closest point to the surface of the sun) on October 27^th and took 5 days to be sighted. The next comet is, The Great Comet of 1680, discovered by the German astronomer, Gottfried Kirch, making him the first astronomer to discover a comet with a telescope, on November 14^th 1680. At its perihelion on December 18^th it was 128 thousand miles from the sun’s surface. At its greatest magnitude, the tail measured 90 degrees. It was visible until February 1681. The Great Comet of 1744 is known to be sighted by Philippe Loys De Chesaux on November 29^th 1743 and remained visible past March of 1744. At it’s most the magnitude of the comet was -7 on February 27^th. At its perihelion on March 1^st it measured 20.5 million miles from the sun. At one point, in March, it was sighted to have 6 tails. Both Comets of 1680 and 1744 were noted to be equivalent to Venus in brightness and visibility, while the comet of 1744 rivaled Sirius, the brightest star in the sky. The Great September Comet of 1822 first spotted on September 1^st by a group of Italian sailors and was visible in daylight from September fourteenth to late December. At its Perihelion on December 17^th it measured 275 thousand miles from the sun. The comets is referred to as a “Super Comet” and perhaps one of the brightest comets ever to be seen, its radiance was described as scarcely fainter than the limb of the sun, and its magnitude registered 1,000 times brighter than the full moon. In the end it exploded, with it’s nucleus separating into at least 4 parts. Comet Ikeya-Seki of 1965 was the greatest comet of the 20^th century. At its perihelion on October 21^st it measured 744 thousand miles from the sun. It was described as “10 times brighter than the full moon” by its Japan-based discoverer. Its magnitude corresponded to -15 degrees and its nucleus broke into two parts. It was discovered just before it’s perihelion and dominated the sky until late November. Both the comets of 1965 and 1822 were members of the Kreuz Sungrazing Group of Comets. The greatest comet of the twentieth century would have been ISON thus far, but it fizzled and turned out to be a dud, but the century is only 14 years old, so we continue to wait.

            Throughout all of these amazing comets, there are many strong commonalities. Firstly the discoveries of the comets seem to always come up around October or November. These Comets stay visible into the sky until only about a month after their perihelion, making the first half of their journey (in our view) much longer than the second half. Two of them, the comets of 1680 and 1744 were noted to be equivalent to Venus in brightness and visibility. And the last two comets, the comets of 1965 and 1822, were members of the Kreuz Sungrazing Group of Comets. Meaning that some of the closest comets to the sun were the most modern. And they were both had their nucleus’ explode. The last two were described as more bright than the descriptions in the first two, suggesting that comets may be getting brighter or more powerful, which is something we should look into. Four out of the five comets were closer to the end of their centuries, which helps explain why we have yet to see a major comet in the twenty first century. It is very important for us to take not of the comets we see in the sky so that we may see the patterns of their orbits. Comets have an olyptical orbit (very oval/eccentric) where there perihelion (distance closest to the sun) and aphelion (farthest distance from the sun) are very off balance, which is why we see some comets twice in a decade and then not again for thousands of years. Their orbits can range from 200-100000000 years. Their orbits help give us an idea of the vastness in the solar system. It allowed us to discover that comets came from other parts of the solar system, which are millions of miles away and yet to be seen, such as The Oort Cloud and The Kuiper Belt.

            I thought this article was an interesting approach to an article on comets. I think it is very important to be aware of some of the most famous comets in history, but I also recognize that they are slightly opinion based and bias toward the author’s favorites, not an official “most popular” comet. I also realize that this article is one year old so there may have been more popular comets after the ISON comet. I believe the author had a good division between the centuries, but it was written more so in sections than an actually essay format which makes it look less professional. I liked the author’s consistency in putting the statistics for their discovery, visibility dates, and their perihelion distance, but I thought he was inconsistent with the degree of the comet’s tail, which he mentioned in the first centuries, but should have continued in the other centuries. I also thought he could have gone on to analyze some of the commonalities such as the similar times of year they are in the sky and lack of visibility soon after the perihelion. He also could have given some background on comets by saying something like; “Sir Edmund Halley first proposed the idea of comets in 1704 as re-occurring objects in the sky from leftover debris from the formation of the solar system. They are known as ‘dirty snowballs’ because they are small icy objects with rock”. Overall I though it was a very unique article and enjoyed the author’s friendly yet informative and descriptive writing style.