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Summary:
The following video segments form part of the Fred Watson masterclass. The masterclass was filmed at the UWS observatory where Fred presents his ‘Stargazer’ talk to a group of students from Western Sydney Region schools associated with Lachlan Macquarie College.
You will find the Fred Watson Masterclass on the Teaching and Learning exchange (TaLe). www.tale.edu.au
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Fred: I'm absolutely thrilled to be here especially talking to you folks and hopefully this will be something that...
might be useful to other educators and people like you who are educatees, being educated.
That's a picture you don't have to worry about it's supposed to be an old 14th century woodcut but it actually was done in the 19th century,
and David Malin who is a friend of mine who I'll no doubt mention later on says it's a picture of a man trying to escape from a planetarium
whereas, you know, everybody thinks actually no it's human kind trying to explore the mechanisms of the heavens which are here...
and that's what we see and its trying to understand what's behind it and that's really what astronomy is all about.
Summary:
Fred outlines the content of his Stargazer talk which is available as a masterclass:
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Fred Watson: Stargazer, that's what the talk's about. And it's about, the past, present and future of the telescope.
So, it's about the way astronomers use telescopes and the kinds of things, not only that they have discovered with telescopes
but that they hope to discover in the future. Because the way telescopes are going it's big stuff.
That's me and that's where I work and they pay my salary so it's very important that I get a mention of the Anglo-Australian Observatory.
Summary:
As Fred outlines the process of mirrors production in reflecting telescopes, think about:
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Mahasan: My question is about the mirrors in the reflecting telescopes. They're coated in aluminium. So how do you actually coat them and how do you get them so accurate?
Fred: Yeah, that's another great question. The process is that you first of all make this what's called a substrate that's the layer that's the surface the really important bit of the mirror.
So you do that with grinding, polishing the optical process. Then you've got to put something shiny on top of it and the old fashioned way of doing that was to coat,
to put the mirror in a bath of a solution containing silver and a chemical process takes place when you take the mirror out it's got a layer of silver on it.
Which is nice and messy and lovely but it doesn't work for large mirrors. Since the 1930s what has happened is that you take your mirror and you put it in a huge tank
which you pump all the air out of. It's called a vacuum tank because at the end of it there's a vacuum in there and then you
actually boil little coils of aluminium on heating elements inside the tank and what happens is the aluminium first of all it melts when you pass the current through these elements
then it evaporates and because there's a vacuum there the atoms of aluminium basically behave just like light, they travel in straight lines they don't hit anything
and so they fall uniformly on the mirror and you get this beautiful coating of aluminium, now it's only something like a hundred atoms thick
so it's quite a thin layer and what you do is you engineer these tanks so that the deposit of aluminium is as uniform as you can make it.
But even if it's slightly non-uniform that non-uniformity is at a lower level than the accuracy of the mirror, so you don't spoil the accuracy of the mirror.
But that's a great question because people do think oh if you've got a big lump of aluminium here doesn't it put a bump on it.
Which is what it would do, but in fact the deep position is at a much lower level than that.
Summary:
As Fred describes how different radiations provide a new way of looking at the universe, consider:
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Fred: Here's just a little snapshot of why we need to look at the universe through these different eyes. Look at the universe with these different radiations.
Picture of, you all know what this is, the planet Jupiter. The biggest planet in the Solar System, about 10 or 11 times the diameter of the Earth. It's got a beauty spot in this picture.
That, which is actually the shadow of one of its bigger moons which the sun is lighting up that moon and causing a shadow on the surface of Jupiter.
Except it's not really a surface, what we see when we look at Jupiter is its a cloud layer the upper deck of its cloud layer. And perhaps you're familiar with this as well.
This is a thing called The Great Red Spot. Which is a storm that Jupiter has been suffering for the last 300 years.
We have bad storms here in Australia but they don't go on for 300 years. So, what you see when you look at Jupiter with an ordinary visible light telescope,
which is the way this image was made, is the top of Jupiter's cloud layer. So you see all this structure and you see the occasional shadow of satellites and things of that sort.
But what could we learn by looking at Jupiter, for example, with a telescope that is sensitive, not to visible light, but to infra-red radiation that's long wave length light.
It's radiation whose wave length is redder than red. And it looks like this on the same scale. So I can sort of toggle between them and this is rather interesting.
It's of course a false colour image because you know we don't really relate to colours in the infra-red. But it's been colour coded and what you can see is, you can see
the cloud layers again, these bands of dark and light. But you might notice that there are sort of bright regions peeping through the cloud layers what it's telling you
is actually that there is a source of infra-red radiation within Jupiter. Now, you might know that infra-red radiation is how we feel radiant heat. It's basically heat radiation.
When you stand in front of something hot and feel like a fire, we still have fires occasionally, and things of that sort and feel the radiant heat coming from that.
That's being brought to you by infra-red radiation. So, what this is telling you is that the inside of Jupiter is actually hot.
And we now know that Jupiter actually radiates 1.7 times more heat than it receives from the sun. Which is quite interesting.
And sort of suggests that perhaps there's things going on in Jupiter that we didn't know about. So, that tells you something
looking at Jupiter in infra-red tells you something immediately. Here's another picture which is of Jupiter again but this time it's seen with micro-waves,
at a wave length of about of about 20 centimetres and it looks quite different. The planet itself sits in here. And what you're looking at here are emissions
from the charged particles which are around Jupiter. Jupiter has a very strong magnetic field, it's more than a hundred thousand times stronger than the Earth's magnetic field.
Imagine what that would do to your compass. You hold your compass up and it would get sucked down straight away into the ground because the magnetic field is so strong.
What that does is collects particles, energetic particles from the sun, and they radiate in the radiant region of the spectrum. So, quite a different picture of Jupiter but
nevertheless one that tells us things about the planet that we didn't know before. So that's one of the reasons why we like to look at the universe in many different wave-bands.
Summary:
Fred describes infra-red radiation on Jupiter, think about:
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Shiela: My question’s about something you said about Jupiter, about how it gives of more light than it actually receives about 1.7 times more. How does that actually work?
Fred: Yeah that's a good question. Thank you for thinking of Jupiter, Jupiter gets neglected in these discussions.
It's actually, it's not correct to say it gives off more visible light than it receives but it does give off more infra red radiation so there's a source of heat there
and it is almost certainly residual heat left over from a process called gravitational collapse. The way the Solar System formed was from a cloud of gas and dust
which basically collapsed on itself. The biggest blob in the middle became the Sun which is the most important thing in the Solar System the rest is just cinders kind of spread
around the edge. But Jupiter is the next biggest object in the Solar System and if it had been rather bigger than it is now it would have become a star rather than a planet.
It is or it was for a long time collapsing under its own gravity and we still see the residual heat from that process. This is not part of the answer but we'll talk about it anyway.
If Jupiter had been, it's actually 13.7 times bigger. Then it would have allowed, the temperature would have been high enough for nuclear reactions to start. There wouldn't have been
the same energetic nuclear reactions that you get in the Sun which is a process called hydrogen fusion there would have been a process called deuterium burning
and it's a nuclear reaction but it's a much lower level one and that would have made it actually into a thing we call a Brown Dwarf Star.
So it would have been a warm star rather than a hot one. But it's not big enough to do that.
Shiela: Alright, thank you.
Fred: Fabulous question
Summary:
For more information on the Stargazer talk don’t forget to check out Fred’s masterclass.
You will find the Fred Watson Masterclass on the Teaching and Learning exchange (TaLe). www.tale.edu.au
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Fred: Thanks ever so much for being a very attentive audience and thank you for putting up with the Stargazer talk
which went on rather longer than it was, is it still Tuesday? No, it’s Monday. That's alright. Thank you very much.
Students: Applause