Hi Know more about one of the familier constallations ORION

Orion (pronounced /ɒˈraɪən/), a constellation often referred to as The Hunter, is a prominent constellation, one of the largest and perhaps the best-known and most conspicuous in the sky^[1]. Its brilliant stars are found on the celestial equator and are visible throughout the world. Its three prominent "belt" stars - three stars of medium brightness in the mid-section of this constellation - make this constellation easy to spot and globally recognized. From mid-northern latitudes, Orion is visible in the evening from October to early January and in the morning from late July to November.^[2][3]

According to the most common contemporary imagery: Orion is standing next to the river Eridanus with his two hunting dogs Canis Major and Canis Minor, fighting Taurus the bull. Other prey of his, such as Lepus the hare, can be found nearby.

There are other contemporary names for Orion. In Australia, the belt and sword of Orion are sometimes called the Saucepan, because the stars of Orion's belt and sword resemble this kitchen utensil as seen from the Southern Hemisphere. Orion's Belt is called Drie Konings (Three Kings) by Afrikaans speakers in South Africa ^[4], and French les Trois Rois (the Three Kings) in Daudet's Lettres de Mon Moulin (1866). The appellation Driekoningen (the Three Kings) is also often found in 17th- and 18th-century Dutch star charts and seaman's guides.

Historically it has had other names, perhaps the earliest known is the Babylonian "Shepherd of Anu", corresponding to an apparent representation of the constellation Auriga or an element of it, as a shepherd's crook.

HISTORY

The configurations of the constellation Orion roughly formed about 1.5 million years ago, because of relative slow movements of stars within the constellation from earth's perspective (especially the belt of Orion). Orion will remain visible in the night sky for the next 1 to 2 million years, making it one of the longest observable constellations, parallel to the rise of human civilization.

Being so bright and distinctive, the pattern of stars that forms Orion was recognized as a coherent constellation by many ancient civilizations, though with different representations and mythologies.

The ancient Sumerians saw this star pattern as forming part of an image of a shepherd (sometimes in a chariot) with his sheep and in some versions a shepherd's crook, while in China, Orion was one of the 28 lunar mansions Sieu (Xiu) （宿）. Known as Shen （參）, literally meaning "three", it is believed to be named so for the three stars located in Orion's belt. (See Chinese constellation)

The stars were associated with Osiris, the god of death and underworld, by the ancient Egyptians. The Giza pyramid complex, which consists of the Great Pyramid of Giza, the Pyramid of Khafre and the Pyramid of Menkaure, is said to be a sky-map of the Belt of Orion, that is, of Osiris. In archeoastronomy, Graham Hancock and Robert Bauval describe this arrangement as central to the Orion Correlation Theory or OCT.

References in ancient Middle Eastern and Mediterranean literature to the "belt and sword" imagery of Orion are those most often echoed in modern western literature and for this reason this imagery has found its way into popular western culture, for example in the form of the shoulder insignia of the 27th Infantry Division of the United States Army during both World Wars, probably owing to a pun on the name of the division's first commander, Major General John F. O'Ryan.

Around October 21 each year the famous Orionid meteor shower reaches its peak. Coming from the border to the constellation Gemini as much as 20 meteors per hour can be seen.

Stars in the Constellation

The constellation is extremely rich in bright stars and in deep-sky objects. Here are some of its stars. ^[5]

Star	Magnitude	Open Clusters	Nebulae
Rigel	0.12	NGC 1981	NGC 1976
Betelgeuse	0.5	NGC 2175	NGC 1982
Bellatrix	1.64	Nil	NGC 2068
Alnilam	1.70	Nil	IC 434
Alnitak	1.77	Nil	Nil

• λ Ori (Meissa) is Orion's head.
• α Ori (Betelgeuse), at its right shoulder, is a red star with a diameter larger than the orbit of Mars. Although it is the α-star, it is somewhat fainter than Rigel.
• γ Ori (Bellatrix), is at Orion's left shoulder.
• ζ Ori (Alnitak), ε Ori (Alnilam) and δ Ori (Mintaka) make up the asterism known as Orion's Belt: three bright stars in a row; from these alone one can recognize Orion.
• η Ori (Eta Orionis), between Delta Orionis and Rigel.
• κ Ori (Saiph) is at Orion's right knee.
• β Ori (Rigel), at the constellation's left knee, is a large blue-white star, among the brightest in the sky. It has three companions, invisible to the naked eye.
• ι Ori (Hatsya) is at the tip of Orion's sword.

In common with many other bright stars, the names Betelgeuse, Rigel, Saiph, Alnitak, Mintaka, Alnilam, Hatsya and Meissa originate from the Arabic language.

How was general theory of relativity proved?

The eclipse has been the subject of scientific interest ever since the time of the Ancient Babylonian astronomers, but of all the thousands of eclipses studied by scientists, the most important one was the eclipse of 1919, which was able to provide the clinching evidence in favour of one of the most revolutionary ideas in the history of physics, namely Einstein’s theory of general relativity.

Although general relativity was a radically new formulation of gravity, its predictions were largely consistent with Newton’s highly successful theory of gravity. However, Einstein’s theory did make one or two predictions which distinguished it from Newton’s theory, and, if true, these predictions would show that Einstein’s model was closer to reality. For example, Einstein predicted that a gravitational field should bend rays of light much more than was expected by Newton’s theory of gravity. Although the effect was too small to be observed in the laboratory, Einstein calculated that the immense gravity of the massive sun would deflect a ray of light by 1.75 seconds of arc – less that one thousandth of a degree, but twice as large as the deflection according to Newton, and significant enough to be measured.

Einstein pictured a scenario whereby the straight line of sight between a star and an observer on earth would be just blocked by the edge of the sun. Einstein believed that the star would still be visible because gravity would bend the rays of light around the sun and towards the earth. The sighting of a star that should have been blocked by the sun would prove Einstein right, but it is generally to impossible to see starlight that passes close to the sun, because it is swamped by the brilliance of the sun itself. However, during an eclipse, the sun is blacked out by the moon, and under such conditions a gravitationally distorted star should be visible.

General relativity was born in 1915 during the First World War, and as soon as the war ended the Astronomer Royal Sir Frank Dyson began preparing for the next total eclipse, which would occur on 29 May 1919, and which would be an opportunity to test Einstein’s theory. He had already recruited Arthur Eddington, Plumian Professor of Astronomy at Cambridge, to make the observations, a decision that was largely a consequence of Eddington’s pacifist beliefs. The son of devout Quakers, Eddington had nearly spent the war as a conscientious objector peeling potatoes in an army camp, but instead Dyson had arranged for a letter of deferment, which allowed him to carry on his astronomical research. However, in return, Eddington had to promise to make the trek to the island of Principe, off the coast of West Africa, one of the best locations for observing the 1919 eclipse.

The eclipse seemed almost too good to be true. Totality would last for 410 seconds, almost seven minutes, which is extraordinarily long for an eclipse, and which would provide plenty of opportunity for measurements to be taken. Also, the eclipse would occur against the rich background of the Hyades constellation, increasing the likelihood for an appropriately positioned star. However, as the vital day approached a cloud, or rather several, loomed on the horizon. It rained every day for the nineteen days prior to the eclipse, and as the eclipse began on 29 May, the sun was obscured by clouds. For 400 seconds the eclipse was hidden from view, and throughout this period Eddington prayed. Then with only ten seconds of the eclipse remaining, the skies miraculously cleared, and he was able to take just one meaningful photograph.

Eddington compared his eclipse photos with images taken when the sun was not present, and announced that the sun had caused a deflection of roughly 1.61 seconds of arc, a result that was in agreement with Einstein’s prediction, thereby validating the theory of general relativity. In recent years, scientists have questioned Eddington’s margin of error, arguing that his equipment was not sufficiently accurate to discriminate between the predicted effects of the rival gravitational theories.

In other words, Eddington believed in Einstein’s theory and wanted to prove that it was true, and therefore he subconsciously minimised his errors in order to get the right result. Regardless of whether or not this was the case, Eddington’s result was hailed as a wondrous piece of science, experimental validation of the greatest intellectual achievement of the of the youthful twentieth century, a sign of optimism in a world that had been torn apart by war. J.P. McEvoy, author of the “Eclipse”, encapsulated the significance of the announcement: “A new theory of the universe, the brain-child of a German Jew working in Berlin, had been confirmed by an English Quaker on a small African island.”

Next week’s eclipse will resonate with the 1919 eclipse, because it will follow an uncanny path that seems to pay homage to Einstein. The science journalist Marcus Chown noted that the eclipse, the last one of the millennium, will pass over the German city of Ulm, the birthplace of Einstein, arguably the greatest intellect of the millennium. An eclipse occurs somewhere in the world every eighteen months, but the time between eclipses above the same location is typically three centuries. Hence, the fact that this particular eclipse passes over Ulm appears to be a special celestial tribute to the physicist who concocted the general theory of relativity, the theory that dictates the motions of the stars and planets.

Some Pictures of famous nebulae

HorseHead Nebulae

Ring Nebulae



Eagle Nebulae



Cat's eye nebulae



Crab Nebulae

Regarding Astronomy and Modern physics

Hi I am Sudharsan from Anna University. I am basically interested in astronomy and modern physics. This blog is created particularly to discuss about various topics which come under the above mentioned areas and to say interesting facts.. I think the entire astronomy field is a fascinating one and I hope let us know more information about it by sharing mutual information that we know...