Astronomy/star formation

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Question
A third grade student of mine is working on a personal learning project and she is wondering:
1. What gasses are stars made of?
2. How do stars get in the shape of a star?
3. Can astronauts touch stars?
4. How do stars get made?
If you are able to answer these in a way that an eight-year-old would be able to understand it would be greatly appreciated! Thank you so much for your time!

Answer
Hi Colleen,

I'd be happy to help. About the third grade is when I became interested in the stars - and the curiosity has never stopped. Please tell her there are more women and girls in astronomy than any other physical science. A woman named Cecilia Payne actually discovered the main thing making up stars - which is the lightest element, hydrogen - when she was still a student in her 20's. Another woman, Henrietta Levitt, discovered a new type of star which changed its brightness in such a way that it could be used like a measuring stick - to determine distances to stars and beyond! And another woman, Helen Hogg, used those same, strange, stars which changed their brightness to map that huge house of stars (shaped like a pinwheel) which we all live in - called the Milky Way. I could go on. But, for now, I'll answer those questions. Maybe, in a few years, she'll think of some questions which we can't answer, and she'll start her own lifelong search.

1. The main gas which stars are made of is hydrogen, the lightest element. Birthday balloons used to be filled with hydrogen to make them float in the air, but if they got too close to birthday candles, they'd explode! Hydrogen is very flammable. So balloons are now filled with helium, the second lightest element. It's not flammable. And that's also the second element in stars. Stars actually shine by changing hydrogen into helium. They don't really "burn" like a normal fire (which is at about 450 degrees) - stars "burn" at a temperature of 25 million degrees (Fahrenheit). But stars also have some other things found on earth - like oxygen, carbon, and in some stars, even iron. Stars are different colors (most are yellow or blue, but there's lots of red stars and even a green star or two!). The colors help tell us what the stars are made of and what their temperature is.

2. Stars are not "star-shaped". Sometimes, when we look at stars, we might see five or six points. But that's our eyes playing tricks on us! Stars are much too far away to see their shape, even with the largest telescopes. But we can study the shape of one star - our own sun. That's our nearest star! Although we should NEVER look directly at the sun, we know that its shape is nearly round. Actually, it's flattened just a little. Stars are round because all the atoms of hydrogen and other things which came together from a big cloud to make a star has gravity - the same gravity holding us to earth. So each little piece of "star cloud" tries to stick to every other piece. Gravity makes them stick! As more pieces stick to each other, they form a small ball - then, a larger ball. Eventually, it becomes a HUGE ball - many, many times the size of earth. But it's still a ball - pretty round. And it usually rotates, so the ball is slightly squashed or flattened. Just like when you spin in a circle, your arms are flung from your side. So the little pieces of "star" spinning faster at the edge of the ball get flung out just a little more. And it becomes a slightly flattened ball.

3. Astronauts can't ever touch stars, because they're just too hot - the atmosphere of stars is about 10,000 degrees. Even if she had a very good space suit to withstand the temperature, stars don't have a surface. They're balls of gas. Although the nearest star, our sun, looks like it has a solid surface, that's just an illusion. It's just a hot ball of gas.

4. In answer #2, I said that gravity makes all the little particles come together and make a big ball. Well, when the ball gets very big, the gravity starts squashing the stuff it the center of the ball. When something is squashed, it starts heating up. The next time your Dad (or Mom) fills up your car tires with air, feel the hose. It's warm. Air is being squashed or compressed. The same things happens deep inside a star. It heats up - to millions of degrees. When it gets hot enough to start "burning" hydrogen, the dark star suddenly lights up, and a new star is born.

Hope this helps. Keep wondering, and looking up..

Prof. James Gort  

Astronomy

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James Gort

Expertise

Questions on observational astronomy, optics, and astrophysics. Specializing in the evolution of stars, variable stars, supernovae, neuton stars/pulsars, black holes, quasars, and cosmology.

Experience

I was a professional astronomer (University of Texas, McDonald Observatory), lecturer at the Adler Planetarium, professor of astrophysics, and amateur astronomer for 42 years. I have made numerous telescopes, and I am currently building one of the largest private observatories in Canada.

Publications
StarDate, University of Texas, numerous Journal Publications

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