Ryan Chen #10236, Sam Grace #10196
Mr. Constantinides
Science 8, Period 6
19 April 2014
The Life of Stars
Stars are the night-lights of the universe. Although they may seem infinite, they do not last forever. Each star follows its own unique life cycle. The life of a star can be broken down into six phases, and there are three paths of phases a star can follow in its life.
Nebulae are the first stage in a star’s life cycle. Nebulae act as the nursery of the universe. A nebula is a massive cloud made of dust and gas. They can stretch light years across and have a very fuzzy appearance. The primary gases found in a nebula are hydrogen and helium gases. Not all nebulae are the same. They can range from blue to red to pink in color, and can be shaped like crabs, eagles, or just a large ball of dust.
There are several types of nebulae. Emission nebulae are nebulae that occur when the gas and dust collapse upon itself, and the young star begins to release ultraviolet radiation. These types of nebulae have very high temperatures because newborn stars zap the area around them with sizzling rays of particles filled with energy. Reflection nebulae do not have enough energy contained to release radiation like emission nebulae. However, they are still visible, for the clouds of gas they sit in help reflect their light. Another type of nebulae is the planetary nebulae, which occurs near the end of a star’s lifetime. Although planetary nebular have “planet” in their name, the only thing they have to do with planets is looking similar to them. These nebulae occur when an average size star runs out of fuel and dispels its gas into rings of colorful light. Another type of nebulae, called dark nebulae, are interstellar clouds with dust so com...
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... low-mass or high-mass protostar forms. The low mass-protostar then goes on to form your average star, just like our Sun. The high-mass protostar goes on to form blue giant stars. Average stars, after burning all of their hydrogen, begin burning helium, forming a red giant. The blue giants undergo the same process but instead become red supergiants. Once the red giant burns all of its helium, the star stops burning and dispels its gas into a planetary nebula. The red supergiant goes out with a bang once it runs out of fuel, and explodes into a supernova. The planetary nebula then slowly fades away into a white dwarf. This white dwarf burns out the rest of its energy until it becomes a black dwarf. The supernova then can become either a neutron star or a black hole. The life of stars is one of the most complex yet majestic processes the universe can display.
The Lagoon Nebula featured as Nasa’s astronomy picture of the day was photographed by John Nemcik using various filters to capture the light emitted by the Hydrogen, Sulfur, and Oxygen. While photographed showing beautiful vibrant, eye-catching colors, the Nebula would appear naturally appear gray to human eye due to poor color sensitivity existing at low-light levels (spacetelescope.org). The Lagoon Nebula is home to the formation of new stars, as well as several other interesting phenomena such as Bok globules, and the hourglass nebula. It is these regions of the nebula that make it a continuous area of interest and study for astronomers.
Brown dwarfs are objects in space that sit between the lines of being a star and a planet. This object is dim and hard to distinguish from low mass stars at the early stages of the dwarf’s life. They are often called failed stars because they start their life the same way as regular stars. However, in some stage, they just didn’t have enough mass gathered to generate the fusion-powered energy of a star. Scientists are certain that brown dwarfs are the missing link between stars and planets but the formations of dwarfs are still a mystery.
Imagine a massive celestial object in space, so densely packed with matter that nothing can ever escape it, not even light- that’s what black holes are. They are formed by large stars- stars that are way larger in size (20 times or more) than the sun. When such massive stars run out of fuel in its course, it can no longer sustain its heavy weight. They rapidly collapse causing colossal of explosions called supernova.
However, galactic interactions do often share many characteristics. The most notable feature associated with interacting galaxies is often the “starburst” phenomenon. A starburst is an extremely high rate of star formation over part or all of a galaxy over a cosmologically short period of time (possibly a few billion years as opposed to several billion years). Galaxy interactions cause gravitational instabilities in interstellar gas clouds, which compress the gas in the clouds and trigger star formation (Mouri 2003). When astronomers look at an ongoing starburst in a distant galaxy, they see the starburst as a bluer region than the surrounding parts of the host galaxy. That is due to the extremely hot and energetic, yet short lived, O-type stars produced in the burst, which outshine all of the other stars being born around them as well as the older, redder stars that populate the galaxy.
The American scientist John Wheeler coined the phrase “black hole” in 1969 to describe a massively compact star with such a strong gravitational field that light cannot escape. When a star’s central reserve of hydrogen is depleted, the star begins to die. Gravity causes the center to contract to higher and higher temperatures, while the outer regions swell up, and the star becomes a red giant. The star then evolves into a white dwarf, where most of its matter is compressed into a sphere roughly the size of Earth. Some stars continue to evolve, and their centers contract to even higher densities and temperatures until their nuclear reserves are exhausted and only their gravitational energy remain. The core then rushes inward while the mantle explodes outward, creating neutron stars in the form of rapidly rotating pulsars. Imploding stars overwhelmed by gravity form black holes, where the core hits infinite density and becomes a singularity (some estimate it at 10^94 times the density of water).
Stars are born and reborn from an explosion of a previous star. The particles and helium are brought together the same way the last star was born. Throughout the life of a star, it manages to avoid collapsing. The gravitational pull from the core of the star has to equal the gravitational pull of the gasses, which form a type of orbit. When this equality is broken, the star can go into several different stages. Some stars that are at least thirty times larger than our sun can form black holes and other kinds of stars.
Nebula away so that it can avoid certain things. In the short story, “The Star,” the priest stated,
The Orion Nebula is an emission nebula because of the O-type and B-type stars contained within it. These high-temperature stars emit ultraviolet (UV) light that ionizes the surrounding hydrogen atoms into protons (H+) and electrons (e-). When the protons and electrons recombine, the electrons enter a higher energy level (n=3). Then, when the electron drops from the n=3 level to the n=2 level, an Hphoton is emitted. 2 This photon has a wavelength of 6563 Å, and therefore corresponds to the red portion of the visible spectrum. It is these H photons which give the nebula the distinctive red color which we see.
Solar nebula is a rotating flattened disk of gas and dust in which the outer part of the disk became planets while the center bulge part became the sun. Its inner part is hot, which is heated by a young sun and due to the impact of the gas falling on the disk during its collapse. However, the outer part is cold and far below the freezing point of water. In the solar nebula, the process of condensation occurs after enough cooling of solar nebula and results in the formation into a disk. Condensation is a process of cooling the gas and its molecules stick together to form liquid or solid particles. Therefore, condensation is the change from gas to liquid. In this process, the gas must cool below a critical temperature. Accretion is the process in which the tiny condensed particles from the nebula begin to stick together to form bigger pieces. Solar nebular theory explains the formation of the solar system. In the solar nebula, tiny grains stuck together and created bigger grains that grew into clumps, possibly held together by electrical forces similar to those that make lint stick to your clothes. Subsequent collisions, if not too violent, allowed these smaller particles to grow into objects ranging in size from millimeters to kilometers. These larger objects are called planetesimals. As planetesimals moved within the disk and collide with one another, planets formed. Because astronomers have no direct way to observe how the Solar System formed, they rely heavily on computer simulations to study that remote time. Computer simulations try to solve Newton’s laws of motion for the complex mix of dust and gas that we believe made up the solar nebula. Merging of the planetesimals increased their mass and thus their gravitational attraction. That, in turn, helped them grow even more massive by drawing planetesimals into clumps or rings around the sun. The process of planets building undergoes consumption of most of the planetesimals. Some survived planetesimals form small moons, asteroids, and comets. The leftover Rocky planetesimals that remained between Jupiter and Mars were stirred by Jupiter’s gravitational force. Therefore, these Rocky planetesimals are unable to assemble into a planet. These planetesimals are known as asteroids. Formation of solar system is explained by solar nebular theory. A rotating flat disk with center bulge is the solar nebula. The outer part of the disk becomes planets and the center bulge becomes the sun.
When itBetelgeuse cannot fuse anymore anything over iron, the star will not have enough energy to make heat. Eventually, the core will collapse. When Betelgeuse collapses, it is so strong and powerful that it causes the outer layers to rebound. With the rebound it will have an explosion, which is called a Supernova (Type two). The explosion has so much energy and power that the temperature becomes really hot. The temperature is so hot that it can use the fusion process much heavier than iron. The elements that were given off from the explosion are sent throughout space and are now new nebula. When the Supernova is done, it has left behind a star called a Neutron star. They form when atoms of the core of a dead star are crushed together and the end result produces neutrons. The neutrons are with electrons that are degenerate on the surface. Many Neutron stars have magnetic fields and they give off strong waves of radiation from their poles. These types of Neutron Stars are known as Pulsars.
A star begins as nothing more than a very light distribution of interstellar gases and dust particles over a distance of a few dozen lightyears. Although there is extremely low pressure existing between stars, this distribution of gas exists instead of a true vacuum. If the density of gas becomes larger than .1 particles per cubic centimeter, the interstellar gas grows unstable. Any small deviation in density, and because it is impossible to have a perfectly even distribution in these clouds this is something that will naturally occur, and the area begins to contract. This happens because between about .1 and 1 particles per cubic centimeter, pressure gains an inverse relationship with density. This causes internal pressure to decrease with increasing density, which because of the higher external pressure, causes the density to continue to increase. This causes the gas in the interstellar medium to spontaneously collect into denser clouds. The denser clouds will contain molecular hydrogen (H2) and interstellar dust particles including carbon compounds, silicates, and small impure ice crystals. Also, within these clouds, there are 2 types of zones. There are H I zones, which contain neutral hydrogen and often have a temperature around 100 Kelvin (K), and there are H II zones, which contain ionized hydrogen and have a temperature around 10,000 K. The ionized hydrogen absorbs ultraviolet light from it’s environment and retransmits it as visible and infrared light. These clouds, visible to the human eye, have been named nebulae. The density in these nebulae is usually about 10 atoms per cubic centimeter. In brighter nebulae, there exists densities of up to several thousand atoms per cubic centimete...
Stars are born in the interstellar clouds of gas and dust called nebulae that are primarily found in the spiral arms of galaxies. These clouds are composed mainly of hydrogen gas but also contain carbon, oxygen and various other elements, but we will see that the carbon and oxygen play a crucial role in star formation so they get special mention. A nebula by itself is not enough to form a star however, and it requires the assistance of some outside force. A close passing star or a shock wave from a supernova or some other event can have just the needed effect. It is the same idea as having a number of marbles on a trampoline and then rolling a larger ball through the middle of them or around the edges. The marbles will conglomerate around the path of the ball, and as more marbles clump together, still more will be attracted. This is essentially what happens during the formation of a star (Stellar Birth, 2004).
Supernovas are extremely powerful explosions of radiation. A supernova can give off as much energy as a Sun can within its whole life. A star will release most of its material when it undergoes this type of explosion. The explosion of a supernova can also help in creating new stars.
One thing us as humans have never been able to fully understand is astronomy. Always having an unexplained mystery, astronomy also has served as a way to keep time and predict the future. The word “astronomy” is defined as the study of heavenly bodies, meaning anything in the sky such as stars, galaxies, comets, planets, nebulae, and so on. Many people, if not everyone, is amazed by the night sky on a clear, moonless night.
The education system in India is based on forced learning that kills student’s spirit and zest of learning. In the film “Like Stars on Earth,” we look specifically at the draw backed role played by parents and teacher in Indian education system. We follow the story of a dyslexic Indian boy, Ishaan, who always had trouble coping with his studies, but in the end with the help of an understanding teacher he is able to study normally and catch up with his peers. We will analyze this film using the concepts from Practices of Looking to explain our thesis. Eddie will cover the concepts of encoding and the ideology surrounding Indian education; Kiranjot Singh will explain the concepts of punctum, negotiated reading and producer’s intended meaning;