The Orion Nebula and Its Peculiarities - Coursework Example

Orion Nebula in Orion When the sun sets and evening falls, and all things become dark, if we look up into the clear, cloudless sky we will see countless glittering, twinkling objects that seem to baffle us. The mystery of the night sky, as Shakespeare points out “painted in unnumbered sparks” (cited in Dickinson, 1998, p. 26) has dazzled mankind right from the beginning of the human civilization and continue to so by their incomparable beauty, and by the very fact that they are beyond our grasping fingers. Not to be outdone, man from ancient times have tried to conjure figures from real, mythological and imaginary characters, thus creating constellations, galaxies and so many innumerable star patterns. One of the most well known celestial constellation is the mighty Orion hunter, with his three star belt and the prominent other four stars that mark his shoulders and legs. It is the most prominent and easily recognized stellar configuration after the Big Dipper. The Big dipper with its seven stars can be easily marked out, even by a child. The word nebula comes from the Latin word nebulae, meaning mist. It refers to the foggy appearance that a nebula has, owing to the presence of huge amount of various gases and dust. It is because of this misty appearance that a nebula is best observed under a clear, cloudless sky in a place far removed from dust, pollution and the glare of electric lights. Some nebulae have a dark appearance while others appear bright to the naked eye. The brightest of all nebulae is seen in the Orion, which is actually a gas cloud. This constellation, which is less than a million years old and therefore when compared to other stars it is relatively young. Here there are stars that are still forming, with the newly born ones right at the center of the constellation. This central region where stars are formed is the Orion Nebula of the Orion constellation. As an author describes it “Located 1,500 light-years away, along our spiral arm of the Milky Way, the Orion Nebula is located in the middle of The Sword region of the constellation Orion the Hunter, which dominates the early winter evening sky, at northern latitudes. The stars have formed from collapsing clouds of interstellar gas within the last million years. The most massive clouds have formed the brightest stars near the center and these are so hot that they illuminate the gas left behind after the period of star formation was complete. The more numerous faint stars are still in the process of collapsing under their own gravity, but have become hot enough in their centers to be self luminous bodies” ( The Orion Nebula, 2006) The Orion Nebula was first discovered by the French astronomer Nicolas-Claude Fabri de Peiresc in 1610. Since this is a bright star constellation it was independently discovered by many other astronomers too, including Christiaan Huygens in 1656 and Charles Messier in 1769. Huygens was the first to publish a sketch of the Orion in 1659. Messier along with the nebula also mentioned the presence of three stars in trapezium and in 1774 he printed the catalog of deep sky objects in which the nebula was placed at the 42nd position. Henceforth the Orion Nebula was in general, identified and termed as the M42. It is also referred to as NGC 1976. The gaseous nature of the Orion Nebula was first identified when William Huggins first did a spectroscopy in 1865. The first astro photo of the Orion Nebula was taken by Henry Draper in September 30th 1880. It was, in fact, the first astrophoto of any kind. In 2005 NASAs Hubble space telescope gave us some unprecedented photographs of Orion Nebula. As an author tells us of the photo graphs “This turbulent star formation region is one of astronomys most dramatic and photogenic celestial objects. More than 3,000 stars of various sizes appear in this image. Some of them have never been seen in visible light. These stars reside in a dramatic dust-and-gas landscape of plateaus, mountains, and valleys that are reminiscent of the Grand Canyon. The Orion Nebula is a picture book of star formation, from the massive, young stars that are shaping the nebula to the pillars of dense gas that may be the homes of budding stars” ( The Orion Nebula, 2006) Huygens had first prepared a sketch of this nebula after studying it through a telescope, and he had thought the nebula to be like a hole through which he could see a brighter, shinier background. It is interesting to note this deduction of one the pioneers in astronomy who had studied the nebula in detail during those times. This description by Huygens is partly true as, there are many stars within this nebula whose light cannot be seen owing to the heavy presence of gas and dust, in fact the nebula does look like as Clark(1990) would describe it “a hole blown in dark clouds wall, allowing us to see part way in” (Clark, 1990). Even before Huygens, we can find evidence of the mention of the Orion in the ancient Mayan (referred to as folk tale character, Xibalba) and Indian civilization (known as the Kalpurush). Strangely however, there are no mentions of this nebula in any other records. This has led to the speculation that this star constellation was not as clear in the ancient times as it is today. The Orion Nebula appears as a foggy patch to the naked eye. It is the area of the sword of the Orion, that hangs from his belt, which is actually a cluster of three stars named as the Delta Orionis, Epsilon Orionis and the Zeta Orionis. Each of these three stars are about 800 to 1400 light years away are quite easily observed under a small telescope, though Zeta Orionis being a double star may be a little tricky for amateur astronomers and small telescopes. The Orion Nebula which is at an approximate distance of 1300- 1500 light years away has a size of about 30 light years. The central region which is bright owing to the newly born stars is surrounded by a dark region, comprising mainly of dust and gases. As Clark (1990) would let us know “the dust is thought to be primarily silicate (rock) particles only a micron in diameter. The composition of the glowing gas has been given as: hydrogen 90.8%, helium 9.08%, carbon 0.05%, oxygen 0.02%, nitrogen 0.02%, sulfur 0.003%, neon 0.0009%, chlorine 0.0002%, argon 0.0001% and fluorine 0.00001%” (Clark, 1990). At the center of the Orion Nebula is a newly formed star known as Theta-1 Orionis. This Theta-1 Orionis is a small, open conglomerate which consists of four bright young stars (magnitudes varying from 5 – 8) known as the trapezium. Robert Trumpler in 1931 was the first astronomer to observe this cluster and he named it is the trapezium. These four stars are about only 100000 years old and so they are young and very hot. The brightness of this region often causes atmospheric disturbances while seeing, thus making a detailed study of this part a little difficult .This trapezium is located in a region known as the fishs mouth, which is at the tip of a wedge in the nebula. To the northern part of the nebula is M43 or NGC 1976, which is small layer of gas. There is a double wide star known as Theta-2 Orionis (magnitudes of 5 and 6.4) at the lower left part of the trapezium. The entire nebulous region that makes up the sword of the Orion consists of young and hot stars. The brightest star in the sword is the Iota Orionis (a 3 magnitude star accompanied by a 7 magnitude star). It a hot, blue and white star, seen at the tip of the sword and the southern end of the Orion Nebula. A smaller nebulous region (NGC 1977) containing a star known as 42 Orionis (of magnitude 5) is seen above the Orion Nebula. At the upper part making up the sword handle of the Orion Nebula is NGC 1981. These are 6th magnitude stars that are dim and scattered. Within the Orion Nebula region there is an area that shows infra red emissions. This part is known as Kleinman- Low nebula and is made up of stars that are extremely young and covered by dark clouds and hence not much studied. OMC 1 and OMC 2 are molecular clouds that are seen with the Orion Nebula. These dense clouds are made up of many different types of molecules (hydrogen is seen in the molecular form here). The nebula is a part of the Orion molecular cloud complex that includes the Orion constellation, the Horsehead nebula, Flame nebula, Barnards loop, M43 and M78. From the Zeta Orionis (one of the stars in the Orions belt) there is southward extension of a dim nebulous region known as IC 434, and the Horsehead nebula is on one side of this extension. This nebula is almost impossible to study as this dark gaseous formation lies in the front, with the bright burning hydrogen gas forming its backdrop. However photographs taken with long exposure have produced beautiful chess like images of it. Below the left star of the Orion’s belt lies the Sigma Orionis (a 4 magnitude star) which is surrounded by three lighter stars, somewhat similar to that of a planet with its satellites. The Barnards loop forms an incomplete elliptical ring covering the whole of the trapezium region and extends up to the center of the Orion Nebula. Photographs taken of the Orion Nebula have shown it to have red and yellow tinges. When seen with the naked eyes it however appears to be of a greenish tinge. This difference in observation occurs owing to different color sensitivity by the human eye and the film negative. The film negative produces the red and yellow color owing to the emission from hydrogen gas while the naked eye picks up the green color from ionized oxygen atoms. Since hydrogen is the main component of the Orion Nebula, we can safely assume that the photographs give a better view. As Bennett (2009) explains “Most of the striking colors in an ionization nebula come from particular spectral lines produced by particular atomic transitions. For example, the transition in which an electron falls from energy level 3 to energy level 2 in a hydrogen atom generates a red photon with a wavelength of 656 nanometers. Ionization nebulae appear predominantly red in photographs because of all the red photons released by this particular transition. Transitions in other elements produce spectral lines of different colors...starlight reflected from dust grains produce blue colors, because interstellar dust grains scatter blue light more easily than red light...” (Bennett, 2009). The greenish spectral tinge, we now know from later studies, come from an atomic transition in a doubly ionized oxygen molecule. So now during winter, when we look up at the crisp, clear evening sky we will know where to locate the second most dazzling object in the sky. When we see the hunter standing tall and erect with his sword dangling at the side from his belt, we will not make a mistake to recognize the great Orion. We know how it was formed and what it may look in the future, and yet, it never fails to thrill us every time we look up at it. As Mark Twain once said “we had the sky up there, all speckled with stars, and we used to lay on our backs and look up at them and discuss about whether they was made or only just happened (cited in Dickinson, 1998, p.26). References Bennett, J. (2009). The Essential Cosmic Perspectives. San Francisco: Pear Addison Wesley. 398-399. Clark, N, R. (1990). Visual Astronomy of the Deep Sky. New York: Sky Publishing Corporation. 98. Dickinson, T. (1998). Nightwatch: A Practical Guide to Viewing the Universe. New York: Firefly Books. 26. The Orion Nebula. (13 January 2006). Retrieved on 26th October 2009 from http://www.oarval.org/OrionNeb.htm Read More