Title: Searching for Distant Hydrogen from the Australian Outback
Podcaster: Nicole Gugliucci
Description: Astronomers are looking back to the earliest epoch of star and galaxy formation in our universe by mapping distant hydrogen gas. As the first stars and galaxies “turn on,” they ionize the intergalactic hydrogen, and a new generation of low frequency radio telescopes are coming online to watch it happen! Hear from the PAPER team (where PAPER stands for the Precision Array to Probe the Epoch of Reionization) as they prepare for the next phase of building a novel instrument for probing the early universe.
Bio: Nicole Gugliucci is a graduate student at the University of Virginia, working at the National Radio Astronomy Observatory. When not helping with the construction and data analysis for PAPER, she enjoys public outreach activities, especially those that allow her to talk about the fascinating discoveries to come out of radio astronomy.
Today’s Sponsor: This episode of “365 Days of Astronomy” is sponsored by Wilson Afonso.
Part 1 – Nicole Gugliucci
Hello and welcome. My name is Nicole Gugliucci, and I will never get tired of that fantastic theme song! I am a graduate student in the astronomy department at the University of Virginia. I also work with the National Radio Astronomy Observatory, based in Charlottesville, Virginia, and they’ve been putting out a great series of 365 Days podcasts, so check those out. Today, I’m going to be talking about a wonderful project that I am involved in at the NRAO, along with collaborators at the University of Berkeley, Curtin University, and University of Pennsylvania. This project is called PAPER, or the Precision Array to Probe the Epoch of Reionization. What is that, and why is it important?
You may have seen one of the earliest images of the universe in the Cosmic Microwave Background map from the time when the universe, now 13.7 billion years old, was only 300,000 years old. At that time, there were no stars or galaxies, just a universe filled with hydrogen and a bit of helium. Eventually, stars, and then galaxies, began to form, but the earliest galaxies that we can see with our telescopes are from a time when the universe was one billion years old. How did the first stars form? What were the first galaxies like? How did this all begin? These are the questions that astronomers want to answer.
We cannot yet see these first stars and galaxies, but we may be able to detect the effects that they have on the environment around them. The first stars were so large and hot that they gave off lots of ultraviolet light. It turns out that this UV radiation can ionize hydrogen, that is, it breaks apart the electron from the nucleus of the atom. Today, all of the hydrogen between galaxies is ionized. Now, the original, neutral hydrogen, gives off a radio signal, or light, with a frequency of 1.4 GHz. What radio astronomers, such as the PAPER team, hope to do is detect the hydrogen from the early universe before it was ionized, and study and map it as bubbles of ionized hydrogen form around the first galaxies. We’ll be watching the neutral hydrogen effectively disappear from our data as we get closer to the present day. This happened so long ago that the radiation has been stretched, or redshifted, but the expansion of the universe, so the signal will arrive somewhere between 100 and 200 MHz. This is a familiar place in the radio spectrum, since that’s right near your radio FM dial!
This is a faint signal, this epoch of reionization signal, and we need to escape as much of the manmade radio “noise” as we can. That is why PAPER is building its telescope in the outback of Western Australia! Our radio telescope will consist of 128 radio antennas in the outback, acting together as an interferometer. This telescope will take data all the time, adding up enough data to see this faint cosmological signal. In order to thoroughly test our system and make sure we can calibrate it really well and get it really stable, we’ve been using a prototype array at the National Radio Astronomy Observatory’s site in Green Bank West Virginia.
Part II – Nicole Gugliucci interviews Erin Benoit
NG: So I’m sitting here at the NRAO Technology Center with Erin Benoit who works for the NRAO, and, why don’t you tell us a little bit about the PAPER Green Bank Array.
EB: Well, the PAPER Green Bank Array is an array of sixteen cross-dipoles out in the field. It’s sitting behind the GBT, which is the world’s largest fully steerable radio telescope, the Green Bank Telescope. They basically sit back there and we’re taking data continuously, been doing so for several years, and it’s our test array that we’re using to prepare for our deployments in the outback of Western Australia. This array in Australia, very much like the one we have in Green Bank, is in a “radio quiet zone.” So it’s very important when we’re doing observations in the band that we are, which is 100 to 200 MHz, that we’re blocking out as much man-made radio frequency interference as possible. It’s [Green Bank] an ideal location, and it has served as a really nice test array to work out some engineering problems before we ship it out to the outback where we really don’t have any recourse if we run into a problem. So we’re solving a lot of things and pre-empting a lot of issues and it’s going really well.
NG: Yeah, it’s nice. It’s only a two and a half hour drive to Green Bank. And it’s one of the most radio quiet sites you are going to find on the eastern seaboard, so it’s very convenient for us.
EB: Yes, that’s true.
NG: Why don’t you tell us a little bit more about the environment in Green Bank, kind of what it is like working there?
EB: Well, the fact that it’s a radio quiet zone tells you already that we’re dealing with a remote site. It’s a high mountain plateau. It’s a little cooler, a little drier. It’s basically out there in the middle of nothing, except for all of the other telescopes that we have operating at the research site out there. It’s quiet.
NG: Not just radio quiet, it’s quiet quiet!
EG: Quiet quiet! It’s not like being in a city, you know. At night you can actually see the stars.
NG: I love it!
EB: You can see the galaxy overhead! It’s sort of a very calm and serene place. So when we go there, we tend to work very hard and we have goals in mind for our field work and usually stay one to two days at a time. We’ll go out there and do some field maintenance. It’s really nice because in between we get to stay in the nice residence halls and eat the great mountain food.
NG: Oh, yes. We love the cafeteria here. Awesome!
EB: I highly recommend the cinnamon rolls. I think it’s a wonderful place to work! I’ve really thoroughly enjoyed it and the drive there is beautiful. You end up going over, I think it’s seven mountain ranges to get there. You get this gorgeous view of West Virginia countryside and then once you get there you are out there and you are surrounded by all these telescopes and it’s just a really quiet nice place to be.
NG: Yeah, yeah, cool. So what have you been working on recently with the array?
EB: Recently we’ve been upgrading some of our instrumentation. We have a groundscreen and the antenna which serves as the basic functional units of our antenna stations. We have been in the process of updating both of those so we have a whole new look and feel to our groundscreen. We also have been updating our antenna design. We’ve been working on that to prepare for our next Australia deployment and it looks like that’s wrapping up. It’s going very well. We have sixteen of these new groundscreens with the new design and they are deployed and they are out there. We have one of our new antenna prototypes out there as well. We’ve been working on upgrading some of our instrumentation. Right now the data analysis team is working on looking at some of this data that’s coming out of the array. We’ve got data coming in all the time, and we’re getting out techniques down for how we want to tackle this data stream once we get out there to Australia.
NG: Yeah, lately we’ve got some new sixteen antenna data, relatively new sixteen antenna data as of this recording. We’re fitting the positions of all the antennas from the data and comparing them to the surveyed positions, and hopefully this week putting out some long-baseline outriggers, too, to include. So, what work have you been doing to prepare for this Australia deployment that’s coming up?
EB: For the Australia deployment, there’s a lot that goes on behind the scenes. What we have to do now is worry about getting 32 antenna stations, which are quite large, the weigh about 200 pounds apiece, and all of the related equipment that goes with them, and we have to get them in a container, transport them over the ocean, deal with the logistics of getting all this equipment transported by truck on these unsealed roads out to the middle of nowhere, and how to get these things off the trucks and dodge kangaroos on the way and try not to run over any emus, and just try to get out there and not disturb the land out there. This land is protected by the Australian government for Aboriginal use. These people have been living there for 50,000 years and are still there. We have to be mindful of their traditions and respectful of them. So there are things like we can’t drive any stakes into the ground. We can’t have large bulky things that are destroying the natural landscape, so everything we do has to go through them. But, that’s just one aspect of it. We have to worry about our own lodging there, setting up camp, and getting our infrastructure built, and getting a fiber line run out to a hut in the middle of nothing.
NG: Well, yeah, we need our internet. That’s important.
EB: The internet is important and out there everything is done by satellite, there’s no other way to do it. There’s a fair amount of logistical detail that goes into something like this. It takes months to plan but we’re making progress.
NG: Awesome. Very cool stuff. Well, that’s it from the PAPER team. Check out the show notes for links about the various topics that we’ve talked about, and thanks for listening!
End of podcast:
365 Days of Astronomy
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