stars

good morning iceman

stars are mainly giant balls of gas

Stars are powered by nuclear fusion in their cores, mostly converting hydrogen into helium. they also convert helium into heavier elements, right up to the element iron.

Stars are giant nuclear reactors. In the center of stars, atoms are taken apart by tremendous atomic collisions that alter the atomic structure and release an enormous amount of energy. This makes stars hot and bright.

Nuclear fusion is an atomic reaction that fuels stars. In fusion, many nuclei (the centers of atoms) combine together to make a larger one (which is a different element). The result of this process is the release of a lot of energy (the resultant nucleus is smaller in mass than the sum of the ones that made it; the difference in mass is converted into energy by the equation E=mc2).

The production of new elements via nuclear reactions is called nucleosynthesis. A star's mass determines what other type of nucleosynthesis occurs in its core (or during explosive changes in its life cycle). Each of us is made from atoms that were produced in stars and went through a supernova.
Small stars: The smallest stars only convert hydrogen into helium.
Medium-sized stars (like our Sun): Late in their lives, when the hydrogen becomes depleted, stars like our Sun can convert helium into oxygen and carbon.
Massive stars (greater than five times the mass of the Sun): When their hydrogen becomes depleted, high mass stars convert helium atoms into carbon and oxygen, followed by the fusion of carbon and oxygen into neon, sodium, magnesium, sulfur and silicon. Later reactions transform these elements into calcium, iron, nickel, chromium, copper and others. When these old, large stars with depleted cores supernova, they create heavy elements (all the natural elements heavier than iron) and spew them into space, forming the basis for life.

stars dont twinkle..its the earths atmosphere that makes them appear to twinkle...
Earth's atmosphere is turbulent. When light from stars passes through
the atmosphere, it gets refracted from the straight line path. As a result
of this, the light reaches us from different points in the sky. These
directions are actually very close to each other but not the same. This
shifting of the image results in what we call twinkling. Twinkling can
effect objects with size smaller than the shift caused by atmosphere,
therefore, only stars twinkle and not the Sun, Moon or the Planets.

stars are the 'building blocks' of galaxies...
galaxies and galaxy clusters are the 'building blocks' of the universe

thanks col man and good morning to a fellow yorkshireman

so how long does an average star "live" for?

ah now it all depends on the definition of average star
an average star like our sun has a predicted life of around ten billion years
that 10,000 million

but there are much more massive stars
they are called O, B and A type (our star is a type G2 yellow dwarf i believe) these massive stars only last a few million years..
there are smaller stars than the sun called red dwarfs..
red dwarfs can apparently live for a very very long time maybe a hundred to a thousand billion years
no one knows exactly...

Ordered from highest temperature to lowest, the seven main stellar types are O, B, A, F, G, K, and M.
and within these seven types are ten sub-types 0-9

lots of facts on stars here :
http://www.site.uottawa.ca:4321/astronomy/index.html#star

PS The sun is middle-aged for its type. We have about another 4 - 6 billion years before it swells into a red giant (probably to the orbit of Earth or maybe Mars, thereby destroying those planets and, of course, Mercury and Venus).

So you don't need to start packing just yet. :-D

There is a mnemonic device for remembering the order of the seven main stellar types:

Oh Be A Fine Girl, Kiss Me.

I got at least something out of High School Physics.

Although heavier elements are almost certainly present in the core of stars, the outer incandescent crust is about 99%+ Hydrogen and Helium. It's the temperature that makes the difference in color.

heres a picture i found about Oh Be A Fine Girl Kiss Me
if any of u r interested..

Astronomers divide stars into different spectral types. First started in the 1800s, the spectral type was originally meant to classify the strength of hydrogen absorption lines. A few types that best describe the temperature of the star remain in use today. The seven main spectral types OBAFGKM are shown above with the spectrum of a single "O" star at the top followed by two spectra each from the progressively cooler designations, respectively. Historically, these letters have been remembered with the mnemonic "Oh Be A Fine Girl/Guy Kiss Me." Frequent classroom contests, however, have come up with other more/less politically correct mnemonics such as "Oven Baked Apples From Grandpa's/Grandma's Kitchen. Mmmm." Our Sun has spectral type "G".

Great information Col Man!!!

I am currently working on x-ray telescopes which studying the sun. One of them which is in it's last phase of development, is supposed to help clarify the difference in temperatures between the surface of the sun and the outer corona.

Right now, the surface is about 6000 degrees C, but the solar corona is in the million degree range. Currently, the latest theory is that the heating is caused from magnetic loops eminating from sun spots, hopefully our project, Solar-B will help scientists figure out this quandry.

Thanks Joe Rep.
cool thats a geeat job
may all go well for you with solar B