• •A star is a massive, luminous ball of plasma that is held together by it’s own gravity.

The Sun is the star at the centre of the Solar System. The Earth and other matter (including other planets, asteroids, meteoroids, comets, and dust) orbit the Sun, which by itself accounts for about 99.8% of the Solar System's mass. Energy from the Sun, in the form of sunlight, supports almost all life on Earth and drives the Earth's climate and weather.The surface of the Sun consists of hydrogen (about 74% of its mass, or 92% of its volume), helium (about 24% of mass, 7% of volume), and other elements, including iron, nickel, oxygen, silicon, sulphur, magnesiumm, carbon, neon, calcium, and chromium.

Dwarf stars

Massive Star VY Canis Majoris - Polarized Light

• Red dwarfs- are low-mass main sequence stars. • Yellow dwarfs- are main sequence (dwarf) stars with masses

comparable star which is hypothesized to be the post-main sequence form of that of the Sun. The Sun is a yellow dwarf.

• A blue dwarf- is a low-mass red dwarf. • A white dwarf- is a star composed of electron-degenerate matter,

thought to be the final stage in the evolution of stars not massive enough to undergo a Type II supernova—stars less massive than roughly 9 solar masses.

• A black dwarf- refers to a white dwarf that has cooled sufficiently such that it no longer emits any visible light.

• A brown dwarf- is a sub-stellar object not massive enough to ever fuse hydrogen into helium—less than about 0.08 solar masses.

The formation of a star begins with a collapse. Perhaps a supernova shockwave or the wind from a massive star triggers it off, but once it starts the collapse proceeds until something stops it. When a clump of material in the cloud begins to contract, the first stage of stellar life begins. As the particles in the clump get closer together the force of gravity between them increases. This in turn makes the star contract faster, pulling the particles closer together still, thus increasing gravity's pull further. A feedback loop is produced creating a self sustaining gravitational contraction.

Formation of a star

Stars expand as they grow old. As their core runs out of hydrogen and then Stars expand as they grow old. As their core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become helium, the core contacts and the outer layers expand, cool, and become less bright. This is a red giant or a red super giant (depending on the initial less bright. This is a red giant or a red super giant (depending on the initial mass of the star). It will eventually collapse and explode. A star's life span mass of the star). It will eventually collapse and explode. A star's life span and eventual fate are determined by the original mass of the star. Life span:and eventual fate are determined by the original mass of the star. Life span:The most massive stars have the shortest lives. Stars that are 25 to 50 times The most massive stars have the shortest lives. Stars that are 25 to 50 times that of the Sun live for only a few million years. They die so quickly that of the Sun live for only a few million years. They die so quickly because they burn massive amounts of nuclear fuel. because they burn massive amounts of nuclear fuel.

For example, Betelgeuse (the second-brightest star in Orion) is a red For example, Betelgeuse (the second-brightest star in Orion) is a red supergiant star that is about 20 times more massive than the Sun. It is about supergiant star that is about 20 times more massive than the Sun. It is about 14,000 times brighter than the Sun and burns nuclear fuel at a rate 14,000 14,000 times brighter than the Sun and burns nuclear fuel at a rate 14,000 times faster than than that of the Sun. The Sun will live about 7,000 times times faster than than that of the Sun. The Sun will live about 7,000 times longer than a massive star like Betelgeuse. longer than a massive star like Betelgeuse.

Stars like our Sun live for about 10 billion years. Stars less massive than Stars like our Sun live for about 10 billion years. Stars less massive than the Sun have even longer life spans. the Sun have even longer life spans.

http://www.youtube.com/watch?v=HfqcZdNnQ6s&eurl=http://video.google.ca/videosearch?hl=en&q=death%20of%20a%20star&um=1&ie=UTF-8&sa=N&tab=wv&feature=player_embedded

• What is a star?

• What supports all life on Earth and drives the Earth’s climate and weather?

• The sun is what type of dwarf?

• What is the estimated life span of the sun?

Answers

• A star is a massive, luminous ball of plasma that is held together by it’s own gravity.

• Energy from the Sun, in the form of sunlight, supports almost all life on Earth and drives the Earth's climate and weather.

• The Sun is a yellow dwarf.

• Stars like our sun live for about 10 million years