Stars

Getting Started

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Rubric: [[file:Space Exploration Adventure Rubric.doc]], [[file:Space Exploration Adventure Rubric.pdf]]
A star is a sphere of gas held together by its own gravity. The force of gravity is continually trying to make the star collapse, but this is counteracted by the pressure of hot gas and radiation in the star’s interior. This is called hydrostatic support. During most of the lifetime of a star, the interior heat and radiation is provided by nuclear reactions near the center, and this phase of the star’s life is called the main sequence. Before and after the main sequence, the heat sources differ slightly. Before the main sequence, the star is contracting and is not yet hot enough or dense enough in its interior for the nuclear reactions to begin. During this phase, hydrostatic support is provided by the heat generated during contraction. After the main sequence, most of the nuclear fuel in the core has been used up. The star now requires a series of less-efficient nuclear reactions for internal heat.
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Visuals Make sure to include the location of your images; add a caption with this information
 * [[image:http://www.nasa.gov/images/content/166657main_image_feature_734_ys_2.jpg width="167" height="120" caption="White dwarf stars in the Milky Way Galaxy"]] || [[image:http://www.nasa.gov/images/content/504338main_image_1818_100-75.jpg width="167" height="104" caption="NGC 6357"]] || [[image:http://www.nasa.gov/images/content/126849main_image_feature_401_ys_2.jpg width="169" height="110" caption="Protoplanetary disk around a pair of red dwarf stars"]] ||
 * [[image:http://www.nasa.gov/images/content/267554main_image_1154_100-75.jpg width="172" height="117" caption="Galactic nebula NGC 3603"]] || [[image:http://www.nasa.gov/images/content/214559main_image_1028_100-75.jpg width="175" height="122" caption="LH 95"]] || [[image:http://www.nasa.gov/images/content/378579main_image_1444_100-75.jpg width="174" height="126" caption="Cepheus B"]] ||

**Works Cited** **Sources** : =http://www.nasa.gov/audience/forstudents/5-8/features/homework-topics-index.html#s= =http://www.enchantedlearning.com/subjects/astronomy/stars/lifecycle= =http://imagine.gscf.nasa.gov/docs/teachers/lifeycles/SC_main_p1.html= =BOOK-__The Universe__-TIME LIFE student library=

**Topic: Research Focus**

What is your topic?
My topic is stars. Stars are almost like mini suns, if you think about it. A star is a sphere of gas held together by its own gravity. The force of gravity is continually trying to cause the star to collapse, but this is counteracted by the pressure of hot gas and radiation in the star's interior.

During most of the lifetime of a star, the interior heat and radiation is provided by nuclear reactions near the center, and this phase of the star's life is called the main sequence star. A star consists of a central core, convective and radiative zones, the photosphere, the chromosphere, and the corona. The core of the star is where all the nuclear fusion reactions occur to power the star. The convective and radiative zones allow the energy produced in the nuclear reactions to move outward. In the convective zone, hot gases swirling around transport energy while in the radiative zone, energy is transported by radiation. The photosphere is the part of the star in which we see visible light. We often refer to the photosphere as the "surface of the star", although it is not a real surface like the surface of the Earth. Just outside the photosphere is the chromosphere. The chromosphere is a thin layer which appears red to us when we see it because of all the hydrogen found there. The outermost part of the stellar atmosphere is the corona. It is very thin gas and over a million degrees. Stars are not alive, but they pass through stages defined as birth, life, and death. Like us, stars grow during their life. Unlike us, a star is in existence for millions of billion of years. Stars are born in nebulae. A star's life cycle is determined by its mass. A star's mass is determined by the amount of matter available in its nebula. Over time, gravity pulls the hydrogen gas in the nebula together and it begins to spin. As the gas spins faster, it heats up and is known as a protostar. The temperature reaches 15,000,000 degrees Celcius and nuclear fusion occurs in the cloud's core. The cloud begins to glow brightly at this temperature, it becomes stable. It is now called a main sequence star. As the main sequence star glows, hydrogen in the core is converted into helium by nuclear fusion. When the hydrogen supply in the core begins to run out, the core becomes unstable and contracts. The outer shell of the star, which is still mostly hydrogen, stars to expand. As it expands, it cools and glows red. The star has now reached the red giant phase. It is red because it is cooler than it was in the main sequence star stage and it is a giant because the outer shell has expanded outward. All stars evolve the same way up to the red giant stage. When a star runs out of hydrogen, it may live another 100 million years from helium gas in its core. It then shrinks and turns into a white dwarf. **Notes**
 * State the focus of your research:**
 * ====An average star-one equal to or smaller than the sun-lives a longer and dies a less violent death than a large star.====
 * A star's color tells us how hot of cold it is. For example, blue stars are the hottest and red stars are the coolest, but are still very hot.
 * Stars vary in size from tiny neutron stars just 30 kilometers (19 miles) across to red supergiants nearly 1 billion kilometers (602 million miles) in diameter.
 * A neutron star is so dense that if you took a single teaspoon of it, it would weigh 5 million tons.