Astrophiz Podcast #1 9 June 2016
Listen: https://soundcloud.com/astrophiz/astrophizpodcast1
Our first feature interview is with Robert Arrowsmith, curator of the Victorian Astronomical Society’s Heathcote Radio astronomy site.
The seminal work of James Clerk Maxwell, and the four famous ‘Maxwell equations’ which ultimately paved the way for the science of radio astronomy.
News Roundup: about The Australian Compact Array and Murchison Widefield Array and what’s in the night sky via Dr Ian Musgrave’s Astroblog site, and links to Adelaide Radio Astronomy Group.
TRANSCRIPT:
Brendan: Hello, my name’s Brendan O’Brien and welcome to the first Astrophiz podcast episode. The title of today’s podcast is Exploring the Leon Mow Dark Sky Site with Robert Arrowsmith.
In each episode we’ll have a special guest in astrophysics and/or optical astronomy.
And now it gives me great pleasure to Skype down to Melbourne in Australia to speak with Robert Arrowsmith. Robert is the IT guru who runs the systems at the Astronomical Society of Victoria at their Dark Sky site and quiet zone up at Heathcote in Victoria. So, Robert, can you tell us about your initiation into radio astronomy? How did it all begin for you?
Robert: Yes, Brendan. Well, I was actually a ham radio operator back in the start of the 80s, and I was living up in a town called Gunnedah in New South Wales, and I’d always had an interest in radio astronomy. And, of course, being in that area, I was often travelling through parks and stopping in at the radio telescope there.
Brendan: Let’s get an idea, Robert. Did you watch the first landing on the moon that came down via Parkes?
Robert: Yes, I did, Brendan. I must admit I was about nine or ten at the time.
Brendan: Very good, Robert. So it would have been a landmark event, I’m sure, in your life. Tell us a bit more about how it all began for you then.
Robert: Yeah, I started off with an interest in radio and my career path initially began with CB radio back in the late 70s and early 80s and moved on to computing in the 90s and had a position for 10 years writing software. So I sort of moved from radio into computers and with the current trend now in radio astronomy, it’s all about computers really. It’s a matter of pointing an antenna at the sky, and seeing what you can do with the computer to extract the data.
Brendan: Yes, well, we’re going to talk about that in detail a bit later. Now, your early days with computers, Robert, were you a DOS jock?
Robert: Oh, yeah. Like many people, we played around with Microsoft software in the early days, and I didn’t actually get into Linux till the early 2000s, but certainly in the 1990s, it was all about Windows back then.
Brendan: Yes, well, we’re recording this. I’m using a Linux machine as we speak, Robert. I’ve really enjoyed the transition from Windows to Linux. It’s been surprisingly smooth.
Robert: So there is a wealth of information to help people transition into Linux and it’s so much more versatile than Windows. So a lot of people tend to use it for problem solving, whereas people using Windows, of course, as a purely a desktop environment.
Brendan: Okay, Robert, so does that mean that Linux is the platform of choice for radio astronomies, both professional and amateur?
Robert: Well, I think some people would say different, but most people seem to agree that Linux is the best platform to use. There is a wealth of software ready-made out there that will run in Linux and give you the results that you need to obtain, especially with radio astronomy. So there’s some amazing software out there.
Brendan: Okay, let’s move on to our next area. Can you tell us a bit about your partnerships with various organisations?
Robert: Well, I joined the Astronomical Society of Victoria four years ago. It was in need of, I guess, a bit of a kick in the pants because the membership management was… done via paper. Recently, Astronomical Society has introduced an electronic system, which has been really good. So the partnership with other organisations, I guess the Astronomical Society itself has always been ready to partner with any other organisations around Australia, and we regularly do. We have a lot of conversations with societies in other states, South Australia and Western Australia in particular.
Brendan: Yes, I’ve noticed that South Australia’s got a very active radio astronomy group.
Robert: Yes, they do. They have a lot of great projects that are happening and they seem to be quite keen to produce good science, which is what it’s all about, really. Two ways to approach radio astronomy. There is the curiosity, learning, finding out process.
And of course, once you’ve done all of that, then you can get into some more meaningful things. So many of the societies around Australia are producing some good work.
Brendan: Very good. Let’s talk about then some of the things that you’re doing up at your Heathcote site. I’ve had a look at your website. And for our listeners, if they go to tinyearl.com forward slash radioastro101 … That’s all lowercase. They can go straight to the Astronomical Society Heathcote site and find out what’s going on there. But could you talk us through some of the things that are happening up at Heathcote?
Robert: Yeah, sure, Brendan. What I guess happened was in the early days, the Astronomical Society of Victoria had a radio astronomy section that were working out of a outer Melbourne suburb called Officer. And the group were attempting to get a three-metre dish working out there on a property and didn’t have a great amount of success.
Recently, in the last six years, they’ve moved.to the site out at Heathcote at the Leon Mow Dark Sky site … it’s about 20k out of Heathcote, so it’s a great area for dark sky astronomy … optically speaking … but as it turns out it’s also a great place for radio astronomy, because it’s relatively quiet from a RF point of view, so you don’t have a huge amount of interference from other radio sources … you can only just get mobile phone coverage there.
So we got a shipping container delivered to the site many years ago and fitted it out into a radio lab and we have been doing quite a few projects out there over the years … the main one would probably be Radio JOVE which was a NASA implemented project which basically means that you receive radio noise from Jupiter that’s just awesome…
Brendan: … that’s a 20 megahertz frequency
Robert: Yes, that’s correct. It was discovered back in the 50s, I believe, that there was some strange signals coming from the direction of Jupiter, and it turned out to be the moon Io that was causing all the fuss. And to put it simply, an electrical discharge between Io and Jupiter… in a magnetic field, in Jupiter’s magnetic field, create synchrotron radiation.
And it’s receivable around 20 megahertz, not specifically right on 20 megahertz. So what you’ll find is that the synchrotron radiation coming from Jupiter as it swings past Earth will go up and down in frequency. So most radio systems for Radio JOVE will listen to a very narrow frequency and the signal will basically sweep through the receiver.
So what we’re doing is recording that and we also use that as a very useful galactic receiver in that when the centre of our galaxy comes across overhead the noise level increases so we get quite a nice increase and decrease as the galactic centre crosses over the sky.
Brendan: That sounds awesome Robert … and you don’t need a dish for that you just use a hunk of wire basically what’s called a dipole antenna.
Robert: Yes, that’s correct. It’s a very easy system to set up and one reason that NASA was promoting it as a high school project and with the simple receiver being built and a simple dipole antenna tuned to 20 megahertz or 21 megahertz probably, you could receive both the synchrotron radiation from Jupiter and other galactic sources.
Brendan: Fantastic. And I see also on your website there that you’re constructing a magnetometer at the moment.
Robert: Yes, we have a magnetometer being built. One of our members, John, has been working on that and we’re hoping to install that before the end of the year. It’s taken a little bit of engineering to put it together. We’ve also got other projects, of course. We’ve got a radiation detector, which is detecting gamma particles. We have a fairly decent weather station which gives us update on, you know, air pressure, temperature, wind direction, amount of rain etc … so we’ve probably got about eight or nine projects running at the moment … we have a an all-sky camera looks fantastic at night when you have a clear sky … the all-sky camera is quite sensitive and you can you can even see colours in the different stars in the sky
Brendan: Beautiful. The hot ones and the cold ones. Now, just getting back to the magnetometer for a moment, what is a magnetometer, Robert?
Robert: Well, it basically detects the Earth’s magnetic field in three dimensions. Most magnetometer readouts will show basically X, Y and Z fields on the magnetometer. And when the sun is quite active and you get charged particles hitting the Earth, you’ll see quite a jump in the Earth’s magnetic field. And you’ll see that in the magnetometer signals.
Brendan: Right. I’m just looking at your data output at the moment, and I notice that two of the fields seem to follow each other, but one seems to be off on its own. What’s all that about?
Robert: Well, it does vary, of course. It really depends on the time of year, and it also depends on, as I said, the solar activity. The Earth’s magnetic field varies greatly as it gets hit with energetic particles from the Sun. So you will see both X and Y or Z fields changing depending on the amount of energy from the Sun.
Brendan: Now, we’re a fair way from a south pole where the auroras are really strong. Could you use the magnetometer data to predict when auroras are going to reach us up here in Victoria?
Robert: Well, you can do. The magnetometer information will show you the amount of auroral discharge, in fact, at the South Pole, and the more discharge you get, of course, the greater the swings on the magnetometer feels.
Brendan: Okay. Now, I see you’ve also got a seismometer there. How do they work? Have you made that yourself? I see you’ve got it 80 centimetres deep in the ground. That’s a bit less than a metre. Tell us a bit about your seismometer, please, Robert.
Robert: Well, it is a commercial device and it measures the seismic waves in the ground. You’ll find that when there is an event around the world, the disturbance can travel in several different ways through the Earth. And seismometer is great for showing that because it will primarily measure the up and down motion of the ground.
The amount that we receive there with the seismometer is very small … you wouldn’t notice it but we can detect earthquakes around the world from our location up at Heathcote so it’s quite a sensitive device.
We often have weekends with members coming up to the site to do optical astronomy. And of course, they’re stamping around the place to create a lot of noise on the seismometer.
Brendan: Yes. Well, I can see on your printout at a moment that there’s a couple of events here. One’s a very strong one. Maybe you’ve had T-Rex stomping around there or it could have been an event. thousands of kilometres away.
Robert: We have a reference there to other seismometers around the world. So when you see an event on our grid, you can actually correlate that with other measuring stations around the world. So we normally have a chart there from Toolangi here in Victoria.
Brendan: They grow beautiful potatoes at Toolangi.
Robert: They do. They also have a really good seismometer there.
Brendan: Okay, up at Heathcote, you’ve obviously, for Radio JOVE, you’ve got your dipole antenna. Have you got that three-meter antenna established up there yet?
Robert: We have quite an array of antenna at the moment we have a three meter dish that is in the process of having a receiver mounted into it … we’ve got some hardware that we’re trying to finish off … we have a horn antenna … and likewise we’re putting a 1.4 Gigahertz hydrogen line receiver on the horn antenna … the three meter dish we’re primarily going to be using for solar tracking so that’ll track the sun …
And the three-metre dish will be receiving at 2.7 Gigahertz, I think it is … which is a good frequency to receive the sun at.
Brendan: So when you’re looking at a sun Robert, will you be able to tell the difference when there’s sunspot activity and when there’s not … will it be that sensitive?
Robert: Oh yeah absolutely! I think it’s a 10 centimetre radius … 10.7 centimetres which is perfect for picking up sunspots and coronal activity on the sun etc … so you see a huge noise burst on the receiver when you get sunspot activity.
What we’ll also be doing since that three-meter dish will be tracking the sun we’ll also be having a solar camera mounted there as well … and of course when the weather’s nice you’ll be able to actually see the sun disk and sunspots … so that’s another project that we’ve got in the pipeline as well.
Brendan: Fantastic, Robert. So we’ve talked about the different sort of antennas you use. Now what happens is that those signals come into the antenna and then you need some sort of receiver to grab that signal. What sort of receivers do you use?
Robert: We currently have a 1.4 gigahertz receiver that we obtained from a company in the US and that’s being set up with a filter so that it’s only receiving at that frequency … because obviously it’d be affected by the frequencies outside of where you’re interested in.
That receiver has an output frequency of about 70 megahertz, I think. So we would feed the output of that receiver into a communications receiver or basically a scanner-type radio, but a special one that we have that is perfect for receiving on that frequency ihat would be mounted on the horn antenna.
We’re also in the process of building an 8-metre aluminium dish antenna. That’s an antenna that was originally purchased many years ago by the, not Telstra, but the previous organisation before Telstra, which I can’t remember.
Brendan: Yeah, PMG.
Robert: It was originally purchased by the PMG many years ago. I think they bought maybe 10 of them, and the 8-metre dishes were assembled on site and then used for point-to-point testing. We managed to purchase one off somebody that had purchased it originally off the PMG many years ago.
Brendan: So are you going to make that steerable, or is that going to be a fixed antenna?
Robert: It’ll be a steerable antenna … it came with struts and mounting for the original testing of a point-to-point system so we’re developing a control system to actually to motorize it so that we can swing at azimuth and elevation and be able to point at objects in the sky.
Brendan: Beautiful. I look forward to watching that develop. Now, radio astronomers like to look at things and visualize what they’re seeing. We’ve talked about your hardware. We’ve talked about your receivers. Now, what do you use to visualize the signals that you’re receiving, Rob?
Robert: There’s a number of ways to do it. It really depends on what you want the end result to be. If
You might be interested in visually seeing an object using radio waves. And in that case, you really need to have quite a large dish. And in most cases, what you would do is scan the particular part of the sky or sweep with the dish across the particular object you’re interested in.
We’re using a number of software packages. There is some really great Linux-based software that was produced many years ago. Government organizations like CSIRO use it.
Brendan: Is that open source?
Robert: It is, actually. You can actually download the software source and build your own visualization package. I’ve had some work to do on that, but it’s quite involved and even places like the Australian Telescope Compact Array in Narrabri, ATCA. In Narrabri they still use those packages that were developed many years ago.
Brendan: What’s your special area of interest Robert? What drives you to radio astronomy at the moment?
Robert: I think my own pet project would be what is driving me. I became interested a few years ago in antenna arrays by combining the signals of lots of small antennas, you can electronically steer an array to point a particular area in the sky.
Brendan: Is that interferometry?
Robert: Yes. There is a number of different projects around the world that are using electronically steerable antennas. There is one at Murchison in Western Australia.
Brendan: Yes, that’s on my go-to list. I have to go. All of those spiders look awesome.
Robert: Yeah, they do. They do. They have a 4×4 antenna, and by combining those 16 antennas together and delaying the signals in each antenna, you can actually look at a particular part of the sky. So that’s one project I’m hoping to be able to build. We’re in the process at the moment of setting up the infrastructure. I was actually at Heathcote this weekend, actually on Saturday, digging holes.
We’ve got a long-standing joke up there that radio astronomy is all about digging.
Brendan: Yep.
Robert: Everything we seem to do up there involves a pick and shovel
Brendan: Well, everything needs a stable platform.
Robert: It does. It’s really true. Nothing better than digging holes for piles.
Brendan: Okay, Robert, can you tell me about how amateur radio astronomy … and what’s happening up at Heathcote, how can that contribute to research in general? I know that it’s more than just a hobby. It’s generating genuine science.
Robert: Yes, it is. Well, I mean, in most cases… A lot of the advances in radio astronomy have come about as a result of people that are just curious about the whys and wherefores. We’re very lucky to have a band of people that are curious about it., and as a result make interesting discoveries. So I think there’s a lot to be said for people that are experimenting towards a particular area of research.
Brendan: Okay, that sounds fantastic, Robert, and it sounds like you’re doing wonderful work up there.
Robert: Well, we’re quite lucky that we have a fantastic group in the radio astronomy group in the Astronomical Society. We’ve got probably about a dozen of us that meet the third Monday of every month. We have people that bring to the table all their different skills to enable us to accomplish some fantastic things.
We’ve got an engineer that is quite particular about how he does things, and we’ve got a carpenter who has built some of our amazing structures.
Clint Jeffrey is our leader. He’s the section director of the Radio Astronomy Group, and Clint has a very clear vision for where we’re heading. He is also a ham radio operator and he has the target of listening to a pulsar with his eight-metre dish. So we’re hoping that we can get that up and running and tune into a pulsar for him quite soon.
Brendan: Fantastic. Well, there’s some nice bright ones around, so he’ll probably start with some of the brighter ones.
Robert: Yes. Oh, yeah. There’s a few that we can see here from the Southern Hemisphere, so we hope to be able to actually have a speaker so people can listen to it. We have quite a few field days up at Heathcote, and what we want to do is for people to walk past going … “Wow! What’s that noise?” And the noise of a pulsar in a radio is quite distinct, so hoping that’ll be happening soon.
Brendan: Fantastic, Robert … and two websites that we’re recommending to our listeners at this stage. One is tinyurl.com forward slash radioastro101. That’s the Astronomical Society of Victoria Radio Astronomy Group. And there’s also tinyurl.com forward slash astrophiz … all lowercase as well, which takes us to the Astrophiz podcast site.
Is there anything you’d like to say at this stage that we could put in there as well, Robert?
Robert: No, I’d just like to thank you, Brendan, for taking the time out to talk to me. We’re a small group, but we’re hoping to achieve quite a lot. And we welcome people to come up and see what we’re doing at the Leon Mow Dark Sky site and welcoming people to join the Astronomical Society because we can always do with more members.
Brendan: Very good, Robert. It’s been fantastic talking to you. You’re doing wonderful stuff there and it’s inspiring.
Robert: Thanks, Brendan. I appreciate the comments.
Brendan: Okay … so we’re living in the golden age of astrophysics. But today, first podcast, I’m going to take you back to another golden age that provided a solid foundation for astrophysics.
And that is the 1780s to the 1830s. It’s a 50-year period. In the 1780s, first we had French physicist Charles Augustine de Coulomb. He was working with electrostatic charges and their attraction and repulsive effects. and he developed Coulomb’s Law, which is still a foundation stone of modern physics.
Then, 40 years later, in 1820, we had Danish physicist Hans Christian Ørsted announced his discovery that the flow of an electric current through a wire produced a magnetic field around the wire.
Next, French physicist André-Marie Ampère followed on, and he showed that Magnetic forces are circular in nature and produced, in effect, a cylinder of magnetic field around the wire carrying current. No such circular force had ever before been observed. Ampere then further developed Ørsted’s experimental work and showed that two parallel wires carrying electric currents attract or repel each other depending on whether the current flow is the same, or in opposite directions.
And this laid the foundation of electrodynamics. He also applied mathematics. He generalised the physical laws from these experiments that he did. And the most important of these was the principle that came later to be called Ampere’s law.
Then came English scientist…Michael Faraday. He was the first to understand what these discoveries really implied. If a magnetic pole could be isolated, he thought, it ought to move constantly in a circle around a current carrying wire. So, in 1821, Faraday set about devising his own experiment, and he was using a small bath of mercury as a frictionless electrical conductor.
And this device transformed electrical energy into mechanical energy. And that was the first electric motor.
And Faraday continued making electric motors through the 1820s and 1830s.
Then came James Clerk Maxwell, who was a genius who took a set of known experimental laws, Gauss’s two laws, Faraday’s law and Ampere’s law, and he unified them into a beautiful coherent set of equations known as Maxwell’s equations.
And Maxwell, he is very famous for being the first to determine that the speed of propagation of electromagnetic waves was the same as the speed of light. And thus, he concluded that electromagnetic waves and visible light were really the same thing.
Now, this is pretty profound. Maxwell’s equations, well, they’re a set of quite complicated equations that I’m not going to go into. They describe our electromagnetic universe. These four equations describe how electric and magnetic fields travel through both space and through objects, how these electric and magnetic fields are related to each other, how they interact with each other, and how they interact with objects.
These four beautiful equations can then be distilled down into two even more elegant equations and they’re very powerful and they provide a solid foundation to all of modern physics.
In science, we say that the great discoveries are made standing on the shoulders of giants. Maxwell had Coulomb, Ørsted, Gauss, Faraday, and Ampere to provide his inspiration.
And then Einstein definitely stood on Maxwell’s shoulders.
… and that’s our introduction to modern astrophysics.
We are in a golden age, and there is so much happening. We’re going to look at Australia and Europe to start with. In Australia, we’ve got the ATCA Compact Array. It’s a radio telescope made up of six 22-meter antennas, and they’re operated by the Australian Telescope National Facility, and that’s part of the CSIRO.
The telescope is located on Gomeroi country about 25 kilometres west of the town of Narrabri in New South Wales. The latest telescope weather station report gives the temperature at a cool 13 degrees Celsius and the wind from the south at 5 kilometres per hour.
This is a fantastic facility and you can look at their data live. If you go to tinyurl-DOT-com forward slash A-T-C-A-L-I-V-E, that’s ATCA live, then you can interrogate their data and you can see what the telescope is actually doing. The antenna are tracking at a moment and this afternoon the compact array controllers are observing a black hole.
The telescope is set up to observe at 6,658 megahertz. The telescope’s been configured and the placement of the antennas can be seen on the website. And you can see that five of the six antennas are pretty close together. And another one is located about three kilometers away. And so that gives a wide base for the antennas and creates a virtual antenna which is about three kilometers wide.
So it’s fantastic the maths that goes into creating these virtual antennas. Another huge thing that is happening is the MWA, the Murchison Wide Field Array which is being put in place and that will be linking in or at least working in parallel with the SKA … which is a Square Kilometre Array.
And this project is shared between Australia and South Africa. And it’s going to be an amazing facility where we’ll be dedicating a whole episode to that.
Likewise, the huge news about LIGO discovering gravity waves. A second candidate has just been confirmed and we’ll be dedicating another episode to that as well.
There’s also a couple of very interesting Facebook groups. that are following astrophysics. One is Aurora Hunters Victoria. They’re very interested in taking photos, but they’re also interested in how auroras are generated. So go and look at them in Facebook, Aurora Hunters Victoria.
Also, the Murchison Widefield Array has a very strong presence on Facebook, and you can find them just by doing a search for Murchison Widefield Array. Check them out.
Now we’re going to cross over and look at what’s in the night sky.
And we can begin by finding heavensabove-dot-com. Now heavensabove-dot-com is a fabulous website that’s got a very comprehensive database of all the satellites and iridium flares and everything that passes over your house, wherever you happen to be on the planet.
So to find out all the satellites that are visible each night, go to heavensabove-dot-com.
Now, I haven’t got permission from Dr. Ian Musgrave to quote directly from his website. He’s got a wonderful website called AstroBlogger. So if you Google that, you’ll find it easily. He puts up information about what’s up in the sky each week.
Current feature is you can see a comet called PanSTARRS, and he’s got all the directions to how you can observe PanSTARRS and he’s also got the information on what’s in the sky this week. So check out Astroblogger. Just Google the single word Astroblogger. So that’s it for Episode 1 of Astrophiz. See you next week. Good night.
