Date: April 30, 2012
Title: Stars
Podcasters: Jeffrey Tang & Susan Tang
Organization: Astronomy For Kids
Links: www.astronomyforkids.com.au
Description: In this podcast created especially for kids we will take a look at stars, starting with our closest star, the sun. We talk about the structure of the sun and how photons are created. We then discuss other stars and what happens to stars when they run out of fuel.
Bio: Astronomy For Kids is an astronomy podcast designed especially for kids. It is presented by Jeffrey Tang who is a kid himself. Our aim is to encourage kids to be interested in science. We created the podcast because Jeffrey was interested in astronomy but we could not find a podcast that was at a suitable level for him.
Sponsor: This episode of “365 days of Astronomy” is sponsored by the Lake County Astronomical Society: Celebrating 30 years of stellar service to members and the public.
Transcript:
Hi and welcome to the 365 Days of Astronomy Podcast for the 30th of April 2012. Today we will be presenting an episode of Astronomy For Kids, a podcast created especially for kids. We hope you enjoy this episode.
Astronomy for Kids Podcast, Episode 2: Stars
Welcome to the Astronomy for Kids Podcast. I’m Jeffrey Tang. In this podcast we are going to talk about stars, starting with our closest star, the Sun.
The sun is at the centre of our solar system and all of the planets in our solar system orbit the sun. Although there are many stars much bigger than the sun, most stars are smaller than the sun. Luckily for us, the sun is there to give us light and to keep the earth at the right temperature for us to live. One important thing to remember is to never look right at the sun. The light is so bright that it can damage your eyes.
The sun is made of plasma, which is like very hot gas. There are different types of gas in the sun but most of the gas is hydrogen. There is also helium, which you would know about from floating balloons. Helium was actually found in the sun before we knew about it here on earth. Scientists discovered it by studying the light from the sun. The sun is almost 1,400,000 km across, which is the same as about 109 earths joined together in a line.
The sun has 6 layers. The centre of the sun is called the core. The core is very hot. In fact it is about 15 million degrees Celsius. The core also has all the other layers of the sun pushing down on it. The hydrogen in the core is the fuel that powers the sun. The heat and pressure in the core of the sun causes the hydrogen to get smashed together to make helium, and this produces energy.
The little particles of energy produced in the centre of the sun are called photons. Photons don’t only come from stars but we’ll talk more about that in another episode. The different photons coming from the sun have different amounts of energy. Some of the photons we see as light coming from the sun. The light can be different colours depending on the energy of the photons. Some photons with other amounts of energy we feel as heat. Other photons we only know about using different types of telescopes that can detect them.
These photons have a very long journey to get out of the sun. As they travel through the layers of the sun, they don’t often go in a straight line. They bump into everything on the way and take a zigzag path. It takes most photons thousands of years to get to the surface of the sun from the centre.
Because the sun is made of plasma, it doesn’t have a hard surface like the earth. The layer most like a surface is called the photosphere. This is where the photons leave the sun. The photosphere is also the layer where we see the dark areas called sunspots. Sunspots are patches where the surface of the sun is cooler. The sun spins around like the earth so we don’t always see the same side of it. It takes about 1 month to spin around once. Because it isn’t solid, the middle of the sun takes 25 days to spin, but the top and bottom take 34 days to spin. NASA has a space mission called STEREO, which has 2 telescopes that orbit the sun. With these telescopes and another telescope that orbits the earth, we can see all of the sun at the same time.
As well as photons, there are also many other types of particles that come out from the sun. Sometimes a lot of particles come out at once like a big explosion. The particles from the sun move outwards through the solar system and this is called the solar wind.
But our sun is only one of a universe of stars. The stars you see in the night sky are much further away than the sun, way outside our solar system, which is why they look like little dots. Some of these stars are much bigger than our sun. These stars can be a lot brighter and they burn up their hydrogen fuel much faster.
If you look up at the stars at night, you’ll notice that they can be different colours. The colour of a star depends mostly on how hot the star is. Hotter stars usually look more blue in colour and stars that are not as hot usually look more red. It’s the opposite of what we’re used to on earth as we have our cold taps coloured blue and our hot taps coloured red. The white and yellow stars are usually somewhere in between.
Scientists can learn a lot about stars by studying the light that comes from them. As well as how hot a star is, they can find out information like the age of the star, and sometimes they can even tell if there are planets orbiting the star.
Once a star uses up it’s hydrogen, it can start smashing helium together to make other things. Depending on the size of the star, it may make carbon or even iron.
When stars run out of fuel, what happens to them depends mostly on their size. The sun will be around for about another 5 billion years so we don’t have to worry about that, but when stars like the sun run out of fuel, they will firstly get bigger and then puff off their top layers into space. What is left in the centre is called a white dwarf star and this will slowly cool down.
When the very big stars run out of fuel, they end with giant explosions called supernovae. These explosions are so huge and so hot that they can smash whatever is in the star together to make other things, like silver and gold. Some of the things that make up our bodies actually come from the explosions of these giant stars. So our bodies are made from the dust of giant stars that exploded billions of years ago. Isn’t that cool?
At the centre of supernova explosions, neutron stars or black holes can be created. Neutron stars are stars where the stuff the star is made of has been squashed together so much that even a teaspoon full of the star would be really heavy and weigh something like a billion tonnes. Some neutron stars spin around and send out radio signals every time they spin, kind of like a lighthouse. These are called pulsars. Pulsars usually spin really fast. Some of them can spin hundreds of times every second.
Black holes happen when the stuff the star is made of is squashed together even more than a neutron star. Black holes have gravity that is so strong that even light can’t get away from it. But I think that’s going to have to be another episode.
I hope you’ve enjoyed taking a closer look at stars today.
And just remember, although you mustn’t look at the sun, at night you can look up in the sky and see all the other amazing stars we’re lucky enough to be able see from earth.
Before we finish this episode, we’ve got a couple of corrections for episode 1 if you downloaded it before the 28th of February. Jupiter actually takes closer to 10 earth hours to spin through a day and a night, not 8 hours and Neptune takes 16, not 19 earth hours.
If you would like to contact us you can go to our website astronomyforkids.com.au.
This podcast was presented by Jeffrey Tang and written by Susan Tang. Thanks to our Science Advisor, Mark Purver. Post production by David Kelly and Susan Tang. Until next time, bye.
End of podcast:
365 Days of Astronomy
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