it.gen.nz

Writings on technology and society from Wellington, New Zealand

Thursday, August 27, 2009

Starlight

Today on Radio New Zealand National I talk about stargazing, and how you can use cheap or free technology to help you understand what you’re seeing when you look into the night sky. I’ll be on after the 11am news.

Read on for my speaking notes, or after the broadcast you’ll be able to download the audio as ogg or mp3.

Q: Stargazing! Are you talking about the bid for the new telescope which New Zealand and Australia are doing?

A: We’ll get to that, but what really caught my eye was Neptune.

Q: Neptune?

A: Yes, it’s up at the moment. Now, I’m not a stargazer – I’m impressed by a good starfield as much as the next person, but I’m certainly not an astronomer. And I knew that Neptune is the hardest to see of the planets – quick recap, Neptune is the furthest from the Sun of all the planets which makes it very hard to spot.

Q: What about Pluto?

A: Pluto is further again from the Sun than Neptune, most of the time anyway, but it really doesn’t behave like a regular planet. It goes the wrong way round the Sun, it dives inside Neptune’s orbit sometimes, and it’s very small. A few years ago some august international astronomical body reclassified it as a dwarf plant, whatever that means, so there are only eight regular planets, with Neptune as the furthest.

Q: How did you know Neptune was visible at all?

A: A friend with far better astronomical knowledge than mine pointed it out to me. There’s Jupiter, he said – and I knew that, Jupiter is a bright object low in the North East at the moment – and look, there’s Neptune next to it.

Q: How did you know he was right?

A: I checked it on my phone. I used Stellarium software on my iPhone, which showed me the night sky in the direction I was looking and helpfully labeled all the planets and stars.

Q: That’s an iPhone thing, then

A: Not really. I used to have an entirely different phone called the Palm Treo – the descendent of the Palm Pilot pocket computers people used to have – and that had a star map on it, which knew where you were and what the time was and showed you what you could see. And there are equivalent available for other phones and computers.

Q: So it’s like a Planetarium?

A: Really quite like that. When I was young, growing up near London, I’d occasionally get to the Planetarium at Baker Street. That was spectacular and taught me a lot about stars. It was a really dramatic way of presenting astronomy. Unfortunately its now been completely taken over by the Madam Tussauds gallery next door, which is owned by the Dubai government, and no longer has anything to do with astronomy. The use the dome for showing films about celebrities. Cynics might suggest that all films are about celebrities, by definition.

And in Wellington there always used to be a small planetarium connected tot eh Carter Observatory – actually, I remember it used to be downtown next to the public library but that was demolished in about 1990 and moved up the hill. Anyway, the one up at the Carter in Kelburn is currently closed, waiting for enough donations to refurbish it, or that’s what the website says.

Q: But you can get computer software to do this?

A: You can indeed. It’s not as immersive as projecting onto the inside of a large concrete dome, but it’s still pretty impressive. And if you are lucky enough to live somewhere where you can really see the stars, like the back blocks of New Zealand, and you have a fancy phone which shows you what you can see, you can have a wonderful experience stargazing on a moonless night. Stellarium software, as its called, can let you identify what you are looking at outside your window, or predict what you can see at some other time or place. It can tell you when some object will rise or set.

Q: This is astronomy, not astrology, right?

A: Absolutely. Astrology is about the notion that the stars visible at anyone time have an impact on life on Earth.

Q: Where did that come from?

A: Astrology has actually got a sound foundation. Don’t get me wrong – I’m not saying that horoscopes have any validity – they don’t. But if you want to see how a heavenly body influences life on Earth, just think about the tides for a moment. If you look at each zodiac constellation, it rises at a different time of year depending on where it is in the sky. And the zodiac constellations rise at times when, in the Babylonian era, it was relevant to do certain agricultural things. So, Taurus the bull is the symbol of fertility, who came in the spring. An effect called “precession of the equinoxes” has changed the Earth’s rotation over the years so that the constellations now rise later than the Babylonians would have seen them two and half thousand years ago, but the principle is the same.

Q: So that’s how any of us can look at stars – what about the big telescope that was in the news last week?

A: That’s the SKA, or square kilometre array. That’s a bid rather than a reality, but it will be quite a stunning telescope if gets built. It will comprise a large collection of dishes, many of them in the Western Australia desert, and some in New Zealand. That gives what’s called a baseline of 5,000 kilometres, which means that the telescope will have a very high resolution.

Q: This is a radio telescope, then?

A: Yes. It’s hard to get optical ones much better on the surface of the Earth. You need a huge mirror, and you also need an area as free as possible from air pollution, and of course from light pollution. New Zealand has optical telescopes at Mt John, near Tekapo, and you do get a fine view of the stars from around there on a clear night. There are several really big optical telescopes high up on the big island of Hawaii, where there are virtually no street lights and very clear air. But the really good optical images these days are taken by the Hubble telescope which is in Earth orbit. There are some wonderful images from that online.

A radio telescope uses a different part of the radio spectrum from visible light. The radio waves it uses are generally less prone to interference from the atmosphere than visible light astronomy. And you have the trick of using multiple dishes some distance apart to get a better resolution, that’s called interferometry and it relies on analyzing the differences between what the different dishes are seeing to get a very detailed picture of what they are looking at.

Q: And what do all these telescopes tell us?

A: Wonderful science about the beginning of our universe – where we all come from, ultimately. After all, only hydrogen and perhaps helium were originally formed from the big bang – everything else comes from stars ‘cooking’ those light elements into the ones planets, our atmosphere, and even ourselves are made of. The old song says “we are stardust” – this is literally true!

Links

Farewell the London Planetarium. Let’s hope the Carter Observatory gets back in business soon.

The Zodiac constellations.

Free Stellarium software for Windows, Mac and Linux.

The Square Kilometre Array – the planned new radio telescope

We are stardust.

posted by colin at 7:14 pm  

3 Comments

  1. Pluto does not go the wrong way round the Sun.

    Comment by Lawrence D'Oliveiro — 27 August 2009 @ 11:49 am

  2. Laurence

    Doesn’t it? Bother, I was sure it did. Anyway it exhibits enough other pathological behaviour not to be a real planet. There’s a great XKCD cartoon about it somewhere.

    Colin

    Comment by colin — 27 August 2009 @ 12:37 pm

  3. Pluto’s orbit is highly inclined to the ecliptic (17°) and highly eccentric. Also it’s very small—smaller than our Moon. So once Xena/Eris was discovered, and shown to be bigger, a decision had to be made: either that, too, was a “planet” (along with potentially dozens or hundreds of similar bodies that seem likely to be discovered in the future), or Pluto was not.

    So the term “planet” was reserved for really major bodies—well, at least as major as Mars and Earth. These smaller bodies—still large enough to be round rather than odd-shaped like most asteroids—are now to be called “dwarf planets”, or possibly “plutoids”, or something like that.

    Comment by Lawrence D'Oliveiro — 27 August 2009 @ 10:06 pm

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