NEBULAE THE MASTER PIECE

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NEBULAE By K.Shyam 3/30/2011

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3/30/2011 The Basics Of Astronomy To realize our stand in our huge and vast universe ,and to understand what nebulas are , lets take a look at our universe……………………………

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A nebula (from Latin: "cloud"; nebulae or nebulæ, with ligature or nebulas) is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases. Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromed a Galaxy was referred to as the Andromeda Nebula before galaxies were discovered by Edwin Hubble). WHAT ACTUALLY ARE THESE NEBULAS?? A nebula is an interstellar cloud of dust, hydrogen gas and plasma. It is the first stage of a star‘s cycle. Nebulae often form star-forming regions, such as in the Eagle Nebula. This nebula is depicted in one of NASA‘s most famous images, the “Pillars of Creation“. In these regions the formations of gas, dust and other materials ‘clump’ together to form larger masses, which attract further matter, and eventually will become big enough to form stars. The remaining materials are then believed to form planets, and other planetary system objects. 3/30/2011

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Evidence exists that the Maya knew about nebulae before the invention of a telescope. Support for this theory comes from a folk tale that deals with the area of the sky around the Orion constellation. The tale mentions there is a smudge around the glowing fire. Around A.D. 150, Claudius Ptolemaeus (Ptolemy) recorded, in books VII-VIII of his Almagest, five stars that appeared nebulous. He also noted a region of nebulosity between the constellations Ursa Major and Leo that was not associated with any star. The first true nebula, as distinct from a star cluster, was mentioned by the Persian astronomer, Abd al-Rahman al-Sufi, in his Book of Fixed Stars (964). He noted "a little cloud" where the Andromeda Galaxy is located. He also cataloged the Omicron Velorum star cluster as a "nebulous star" and other nebulous objects, such as Brocchi's Cluster. The supernova that created the Crab Nebula, the SN 1054, was observed by Arabic and Chinese astronomers in 1054. HISTORY OF NEBLUAE 3/30/2011

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Stellar nurseries are made of clouds of dust and gas called nebulae (singular is nebula ). All stars are born out of nebulae -- except in some rare instances when two neutron stars merge to form a black hole (however, both neutron stars and black holes are considered to be "dead" stars). There are two different origins of nebulae. The first origin for material is the universe's creation itself: Soon after its birth, atoms were created in the universe, and it is from these that the first dust and gas clouds formed. This means that the gas and dust that make up this type of nebula were not created in a star, but are the original matter from the beginnings of the universe. The second kind of nebulae are produced by the supernovas of exploding stars. The matter ejected from them created the Veil and Crab nebulae, as well as many more. Also, keep in mind that the origins of nebulae are not as clear cut as this; a nebula can be a mixture of primordial material as well as new material from previous stars NEBULAE:STELLAR NURSERIES AND CRADLES OF YOUNG STARS 3/30/2011

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3/30/2011 Emission nebulae are the most colourful of the five main types of nebulae. They are lit internally from young stars still in their stellar nursery. The different colours are caused by the different gases and the composition of the dust in the nebula. Usually a large telescope (8+ inches) will reveal most of the colours in an emission nebula. To see all of the colours, a long-exposure photograph is usually required. Pictured to the ABOVE is a section of the Eagle Nebula (top) . In the image of the Eagle Nebula, also known as M16, one can see three distinct "pillars" of gas. It took the Hubble Space Telescope to see these pillars, imaged in 1995, and they would not be visible to back-yard astronomers. Inside the pillars are newly-formed stars, whose solar winds are literally blowing away the surrounding gas and dust. The most prominent pillar is about 10 light-years tall and one light-year thick. The full nebula was discovered in 1764, and lies about 7,000 light-years away. Types Of Nebulas : EMISSION

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3/30/2011 REFLECTION Reflection nebulae are nebulae that reflect stars' light - stars from either inside or near the nebula. The Pleiades (pictured to the side) is a good example of a reflection nebula. The stars are thought to have formed at roughly the same time - about 100 million years ago, which would make them about 1/50 the age of our sun. They are believed to currently be plowing through the thin, wispy nebula that is seen as blue wisps and glows around the stars (the flares are artefacts of the camera ).They can also be called mirror nebulae because of their reflective quality.

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3/30/2011 In essence, all nebulae are in fact dark, for they produce no visual light of their own. However, when astronomers refer to a "dark nebula," they are speaking of one that blocks the light of something behind it, like a wall, and are thus only visible when they omit light from something behind them (from our line of sight). That is why we cannot see very far into our galaxy in visible light - there are too many lanes of dust and gas (dark nebulae) in the way, so astronomers must rely on other forms of light. Pictured to the right is the famous Horsehead Nebula, this image taken by the Hubble Space Telescope. The part that forms the horse's head is the dark nebula, known as Barnard 33. The dark nebula lies in front of the background emission nebula, known as IC 434. DARK…………. A dark nebula is a type of interstellar cloud that is so dense that it obscures the light from the background emission or reflection nebula (e.g., the Horsehead Nebula) or that it blocks out background stars (e.g., the Coalsack Nebula). The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust/material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy.

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3/30/2011 Planetary nebulae are created when a main sequence star grows into a red giant and casts off its outer layers. This is how they get their (usually) circular shape, for the material is thrown off the star in a roughly symmetrical manner, as seen in the upper picture of The Cat's Eye Nebula (NGC 6543). You can also see the remains of the central star in this image. In the case of the lower image of the Retina Nebula (IC 4406), we are viewing the circular disk on its side, like looking at a doughnut's edge. The star's spin and magnetic fields cause the material to expand in more of a circular disk, rather than in a spherical manner. The term "planetary" comes from the nineteenth century, when astronomers saw that they looked vaguely like the newly-discovered Uranus and Neptune in their primitive telescopes. (Remember that this was a time before people knew that there were different galaxies.) The name has stuck ever since. PLANETARY NEBULAE

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3/30/2011 These nebulae are the creations of ancient supernovas - the violent explosions of massive stars at the end of their lives. The most famous example is the Crab Nebula, created by a well-documented supernova on July 4, 1054. The supernova remnant pictured to the right was taken by the Hubble Space Telescope of nebula N132D in the Large Magellanic Cloud - a small, satellite galaxy of the Milky Way. Supernova Remnant

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3/30/2011 The first step in the birth of a star is to wait. Dust, gas, and other materials sit around in nebulae, and wait for possibly millennia until a passing star, or some other heavy body passes by and stirs things up a bit. When a heavy body passes near or through the nebula, its gravity causes swirls and ripples. It would be like spreading marbles out on a trampoline, and then rolling a large lead ball around the edge, or through the middle. The other marbles would roll around, and clump together near the path the lead one took. It is no different in a nebula when a star passes by. To add to the marble analogy: When the marbles gather in places, the dip in the trampoline causes other marbles to accumulate in the same spot until there are just a few piles of marbles, with few in between. This process is called "accretion." The "piles" of matter continue to group together in the nebula until they are gigantic clumps of dust and gas. At this stage, the clump is called a protostar . As the protostar becomes larger, gravity squeezes it tighter, causing pressure to build and for the heat to increase. If you have ever pumped a bicycle tire, you know that when the air becomes compressed, it becomes hotter. Then, when the pressure in the centre, the core , reaches a temperature of 10,000,000 K (18,000,000° F), hydrogen fusion is initiated. Now, the protostar has become a star. It shines with its own light. Its solar wind quickly pushes away the rest of the dust and gas in its vicinity. BASIC FORMATION OF NEBULAS

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3/30/2011 A supernova (plural supernovae ) is a stellar explosion that is more energetic than a nova. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. The explosion expels much or all of a star's material at a velocity of up to 30,000 km/s (10% of the speed of light), driving a shock wave into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant. ………………….SUPERNOVAE

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3/30/2011 Several types of supernovae exist. Types I and II can be triggered in one of two ways, either turning off or suddenly turning on the production of energy through nuclear fusion. After the core of an aging massive star ceases generating energy from nuclear fusion, it may undergo sudden gravitational collapse into a neutron star or black hole, releasing gravitational potential energy that heats and expels the star's outer layers. Alternatively a white dwarf star may accumulate sufficient material from a stellar companion (either through accretion or via a merger) to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it. Stellar cores whose furnaces have permanently gone out collapse when their masses exceed the Chandrasekhar limit, while accreting white dwarfs ignite as they approach this limit (roughly 1.38 times the mass of the sun). White dwarfs are also subject to a different, much smaller type of thermonuclear explosion fuelled by hydrogen on their surfaces called a nova. Solitary stars with a mass below approximately nine solar masses, such as the Sun, evolve into white dwarfs without ever becoming supernovae. TYPES………………..

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3/30/2011 Exactly what the heading says! Type 1

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3/30/2011 The Sun generates all of its heat in its core. This heat both warms the Earth and prevents gravity from forcing the Sun to undergo a catastrophic gravitational collapse. The fuel which supplies the heat is hydrogen. Hydrogen nuclei are converted to helium as heat is released. In five billion years the hydrogen fuel will have been depleted. Gravity will force the spent core, now almost pure helium, to shrink, compress, and become even hotter than at present. The high temperatures will eventually ignite the helium ashes. The result is carbon nuclei and even more heat. The "second wind" of heat release will be furious, increasing the light emitted from the future Sun's surface by a thousand fold. Meanwhile, the same heat will cause the outer layers of the present Sun to expand and form a huge "red giant". The red giant is so bloated that Mercury and Venus will find themselves orbiting inside of it. Imagine daytime on the Earth when this happens. Sunrises and sunsets will take hours, thanks to the huge apparent diameter of the swelled Sun. At noon the huge bright red Sun will fill half the sky. The view won't be very different than that within a kiln. The oceans will boil and evaporate into space, along with the atmosphere. The intense radiant heat will transform the surface to a thick layer of pottery. In all, a biblical view of hell. THE LIFE OF A STAR LIKE THE SUN

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3/30/2011 Here on Earth, we'll feel the wind of the ejected gasses sweeping past, slowly at first (a mere 5 miles per second!), and then picking up speed as the spasms continue (eventually to reach 1000 miles per second!!) The remnant Sun will rise as a dot of intense light, no larger than Venus, more brilliant than 100 present Suns, and an intensely hot blue-white colour hotter than any welder's torch. Light from the fiendish blue "pinprick" will braise the Earth and tear apart its surface molecules and atoms. A new but very thin "atmosphere" of free electrons will form as the Earth's surface turns to dust. Here's what some survivor will observe in the night sky. (After Dec 17 refer to the newly released colour images below.) Obviously our own planetary nebula will be viewed from the inside out. In addition to stars, the sky will be aflame with the wispy, colourful shapes of the nebula of ejected solar material. This spectacular show will last a few thousand years as the ejected gasses merge into the interstellar medium from which new generations of stars will form. IMAGINE THE VIEW!!!!!!!!!!!

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3/30/2011 DO NOT FORGET TO VIEW MY NEXT UPCOMING PROJECT ON MARS ROVERS……..

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3/30/2011 Thanks for watching