Interesting Facts About Stars

http://www.youtube.com/watch?v=JJta3XuJqKs

What are Stars made of?

   Stars are made of very hot gas. This gas is mostly Hydrogen and Helium which are the two lightest elements. Stars shine by burning Hydrogen into Helium in their cores and later in their lives create heavier elements. Most stars have small amounts of heavier elements like Carbon, Nitrogen, Oxygen and Iron which were created by stars before them. After a star runs out of fuel, it ejects much of its material back into space. New stars are formed from these materials. So materials in stars are recycled.

http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/starcomp.shtml

Did you know that........

The Sun is the nearest star to us. 







Proxima Centauri is the nearest star to us after the sun.

The Sun is growing: In 5 billion years it will be 250 times bigger and close enough to swallow up the Earth.

The largest known star Canis Majoris is so big that if our Sun is a ball 117 cm wide, Canis Majoris would be 2.25 km wide.

The Pistol Star is the most luminous star known - 10 million times the power of the Sun and as big as the Earth's entire orbit around the Sun.




The star Alpha Herculis is so big that 25 of our entire solar system would have to be placed end to end to equal the star's diameter







http://www.sciensational.com/astronomy.html 

Life Cycle of Stars

The Birth of a Star

In space, there exists huge clouds of gas and dust. These clouds consist of hydrogen and helium, and are the birthplaces of new stars. Gravity causes these clouds to shrink and become warmer. The body starts to collapse under its own gravity, and the temperature inside rises. After the temperature reaches several thousand degrees, the hydrogen molecules are ionized (electrons are stripped from them), and they become single protons. The contraction of the gas and the rise in temperature continue until the temperature of the star reaches about 10,000,000 degrees Celsius (18,000,000 degrees Fahrenheit). At this point, nuclear fusion occurs in a process called proton-proton reaction. Briefly, proton-proton reaction is when four protons join together and two are converted into neutrons; an 4He nucleus is formed. During this process, some matter is lost and converted to energy as dictated by Einstein's equation. At this point, the star stops collapsing because the outward force of heat balances the gravity.

The Hydrogen Burning Stage

The proton-proton reaction occurs during a period called the hydrogen-burning state, and its length depends on the star's weight. In heavy stars, the great amount of weight puts a large amount of pressure on the core, raising the temperature and speeding up the fusion process. These heavy stars are very bright, but only live for a short amount of time. After the energy from this deuteron-hydrogen fusion process ends, the star begins to contract again, and the temperature and pressure subsequently increase. Nuclear fusion occurs between the hydrogen and lithium & other light metals in the star, but this process soon ends. Contraction starts again, and the extreme high temperature and pressure cause the hydrogen to transform into helium through the carbon-nitrogen-oxygen cycle. When all the hydrogen has been used up, the star is at its largest size, and it is called a red giant. Different things can happen to the star now.

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Scenario 1:

Planetary Nebulas One scenario is that the star will continue to make energy by using hydrogen and helium outside of the core; its surface will rise and fall and the star will become a variable star. After it gets out of control, the layers of gas will pull away, forming a shell of gas known as a planetary nebula.

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Scenario 2:

White dwarf The other scenario is that the star will continue to shine through the fusion of helium nuclei, in the triple alpha process. The star is now a white dwarf, and further contraction is prevented by the repulsion of electrons in the core.

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Supernova Very heavy stars will continue to fuse heavy elements in order to produce more energy. However, once iron is formed, it cannot be fused to make more energy since it has such a high binding energy and is therefore very stable. The core will collapse under gravity and huge amounts of gas on the surface of the star will explode out. This star is now called a supernova.

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Neutron Star After a supernova explosion, the iron core of the star may be extremely heavy, and the force of gravity may be extremely large. It then becomes a neutron star, where the repulsion between neutrons stops the contraction caused by gravity. Neutron stars consist of matter that is 100 million times denser than white dwarf matter.

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Pulsars

A neutron star may spin rapidly after a supernova explosion, and it may emit two beams of radio waves, light, and X-rays. These beams radiate in a circle because the star is spinning, and it appears that the star is pulsing on and off. Thus, it is given the name Pulsar.

Black Holes

Neutron-neutron repulsion can only counteract the force of gravity if the core of the dead star weighs less than three times the weight of the sun. In an extremely heavy core, no force can stop the matter from being squeezed into a smaller and smaller space. Nothing can escape these black holes; not even light.

http://library.thinkquest.org/17940/texts/star/star.html

Life Cycle of a Star.

   The life cycle of a star can be related to the life cycle of a human, but not exactly. So let's see how they are related. Let's look at the picture.

   In the picture we can see the comparison of human life cycle to the star life cycle. A star’s life is long compared to that of a human, but we can see the stages of stellar birth, aging, and death in the heavens. They follow a pattern similar to many of the life cycles we see here on earth. Stars are born, they “grow up,” exist many years, and then they die, and there’s an exciting battle between the force of gravity and gas pressure to that makes it exciting and potentially explosive!


http://aspire.cosmic-ray.org/labs/star_life/starlife_main.html

What are Stars

     In this video, we will know what stars are and their life cycle.


http://www.youtube.com/watch?v=pgb9OZVCqIk

What are Stars?

    

      A star is a self-luminous object that shines through the release of energy produced by nuclear reactions at its core.

     A star is also a body of matter in space that's held together by its own gravity. Stars constantly undergo nuclear reactions that emit heat & light. Although they share these things in common, they can vary in size, age, brightness, temperature & color.

     And lastly, the definition of a star is simply a huge ball of gas, with a central core that is very hot and produces lots of energy. A star is held together by gravity.

   A star is also a natural luminous body visible in the sky especially at night.

http://www.kidsastronomy.com/dictionary.htm

http://www.merriam-webster.com/dictionary/star

http://answers.askkids.com/Space_and_Stars/What_is_the_Definition_of_a_Star