The great orion nebula it is an emission nebula, the center of which resembles a butterfly. It is south of the constellation Orion and is easily visible to the naked eye, as a faint whitish spot in the middle of Orion's belt..
Nebulae, named for their diffuse shape, are vast regions in space filled with interstellar material: dust and gas. The Orion Nebula was first described by the French astronomer Nicolas-Claude Fabri de Peiresc in 1610, although ancient civilizations such as the Maya, for example, have records of similar objects. However, it is not possible to ensure that it was indeed the same Orion nebula.
In fact, Galileo does not mention it, although it is known that he examined the region with his telescope and detected some stars within it (known as the Trapeze). Neither did other notable astronomers of antiquity.
But since it can now be easily seen with the naked eye, the nebula may have increased in brightness due to the birth of new stars..
Charles Messier cataloged it in 1771 as object M42, a name by which it can also be searched on the web and in astronomy applications for telephones..
From an astronomical point of view, nebulae such as Orion are important, since stars are continuously formed there.
By virtue of the force of gravity, it is there that the aggregates of matter arise that later condense and constitute the seed of the stellar systems. Stars are continuously forming inside the nebula.
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The Great Orion Nebula is relatively close to the solar system, 500 parsecs (1 parsec = 3.2616 light years) or 1270 light years. As we said, it is located in Orion's belt, made up of the three bright stars diagonally in the center of the constellation's quadrilateral..
Those three stars are Mintaka, Alnilam and Alnitak, although colloquially they are called the Three Marys or the Three Wise Men..
From Earth, the angular diameter (the size of the angle at which the object is viewed from Earth) of the nebula in the sky is approximately 60 arc minutes..
By comparison, that of Venus, an easily visible celestial body, ranges from about 10 to 63 arc minutes, depending on the time, but the appearance of Venus is brighter for reasons of proximity.
You can get an idea of the size of the nebula and its true brightness by comparing the distances: 1270 light years = 1.2 x 1016 km, against the Venus-Earth distance of just 40 x 106 km.
The Orion Nebula is an emission nebula, which means that it emits light in the visible range. It is visible in the east, towards dawn from July, but the best time to observe is during the winter months in the northern hemisphere or in the summer in the southern hemisphere.
It is visible to the naked eye if the sky is dark and clear. And while it is true that it can be visible from a large city, it is best to get as far as possible from light pollution.
Through binoculars or a small telescope, the nebula appears as a small pearly spot, although a slight pinkish tint is sometimes observed. This is not the most usual, because the eye is not as sensitive to colors as photographic film..
So the observer will not see it as in the photograph shown in figure 1. This requires larger telescopes or taking long exposure photographs, which also usually receive post-processing to bring out details..
Despite this, even if it is observed only with binoculars, the nebula is an image of astonishing beauty, even more so knowing that stars are being born inside it at this precise moment..
Finding the nebula is easy, as mentioned before, since Orion is one of the best-known constellations. Similarly, an application like Sky Map will show your location immediately. And with modern telescopes you can program the search so that the focus is automatic and locate the Trapezoid inside..
At the center of the Orion Nebula are four stars known as The Trapeze (Θ-Orionis). Galileo discovered three of them in 1610, but curiously, he did not leave a record of the nebulosity that surrounded them, which Fabri de Peiresc did..
The stars that make up the Trapezoid are bluish-white and very bright. They are also massive, having between 15 and 30 times the mass of the Sun.
They are relatively close: 1.5 light-years apart roughly separates each. They are part of a much larger stellar conglomerate, about 10 light years across and of about 2,000 stars, called Trapezium Cluster.
The Trapezium can be observed with the help of a small telescope and in very clear skies an additional fifth star is distinguished. Larger telescopes allow up to 8 stars to be distinguished.
To the naked eye, the nebula is whitish in color, although sometimes, under suitable conditions, the human eye is able to detect a slight pinkish hue..
True colors are seen in images taken with long exposures and come from the energy emitted by excited gas molecules.
Indeed, the stars inside the nebula have temperatures of around 25,000 K. Therefore, they are capable of emitting enough ultraviolet radiation to ionize hydrogen, which is the majority component in the region..
The combination of wavelengths emitted by the molecular excitation of the gas (in red, blue and violet) produces the distinctive pink color.
In some photographs it has also been possible to see green areas, corresponding to different energy transitions that only occur in places with the physical conditions of the nebula.
Due to the great stellar activity in its interior, the Orion Nebula is of great astronomical interest. Inside it there are a large number of stars in formation, called protostars.
Since this is a very short stage in the life of a star, it is not easy to find protostars for study. And since the Great Orion Nebula is far from the plane of the galaxy, what it contains is not easily confused with other objects..
For all these reasons astronomers and astrophysicists have studied it exhaustively..
-The age of the nebula is estimated to be less than 2 million years, which is the same age as the stars in the clusters that make it up..
-Hydrogen is the most abundant element in the nebula and for this reason we see it in a reddish or pinkish color, because the red light from the hydrogen emission lines is the most intense..
-The stars are surrounded by bright filaments that extend 8 parsecs apart. Some of these filaments are meeting fronts between particles that move slowly with others that move more slowly..
-Stars with protoplanetary disks and brown dwarfs, among other objects, have been detected inside the nebula..
The protoplanetary disks are made of material that rotates around newly formed stars and gives rise to planetary systems like ours.
About 85% of the stars in the nebula are surrounded by disks of gas and dust, although this does not necessarily mean that they develop a planetary system like ours..
For their part the brown dwarfs they are bodies halfway between stars and planets, because they did not have enough mass to create the fusion reactor that gives rise to a star.
Given the high rate of stellar births, there are numerous brown dwarfs in the Great Orion Nebula..
-The Orion Nebula is a visible part of the large Orion Molecular Cloud or Orion Molecular Complex, which groups together different types of nebulae and other astronomical objects, such as Barnard's loop (horn-shaped in the image below) and the well-known Dark Horsehead Nebula.
-The Orion Nebula is gradually dispersing and is expected to become extinct in a few hundred thousand years, a blink from the point of view of the universe. There is still time to enjoy such a spectacular celestial phenomenon.
The following schematic shows the structure of the Great Orion Nebula and the adjacent regions.
By means of infrared shots, the structure is much better distinguished, since gas and dust are transparent at these wavelengths, while visible light is totally scattered or absorbed..
The stars of the Trapezoid, already described, shifted to the left in the image.
Inside the nebula we can also distinguish the external molecular cloud and within it, the following objects, visible in infrared:
-The Becklin-Neugebauer object, visible in infrared, is an intermediate mass protostar, that is, a star at a very early stage that is not yet incorporated into the main sequence..
-Masers or natural sources of microwave emission, are typical formations of molecular clouds.
-The Kleinmann-Low Nebula, a highly active star-forming region in the middle of the Orion Nebula. Contains a star cluster surrounded by dust and gas that also includes protoplanetary disks.
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