Category: Podcasts

A 20-metre solar sail being tested. Image credit: NASA. Click to enlarge.
Listen to the interview: NASA Tests a Solar Sail (3.7 mb)

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Fraser Cain – Can you give me some background on solar sails in general?

Edward Montgomery ? This is a technology that our agency has been interested in for some time, but the history goes back several hundred years to Fredrick Sander at the turn of the century (19th). In more recent times, we have found that advances in a couple of particular areas have made it something that we really have to look into. The composite materials that have been coming out in the last couple of years, such as in sports equipment that is made out of ultra, lightweight rods, and film technology which in some ways is related to the materials industry and integrated circuits fields for instance and paint additives. These fields have made it possible to build structures in space that are gossamer-like and we have never really been able to do that till a couple of decades before (now) and once you can get the kind of mass down really low, then it doesn’t take a lot for force to get some acceleration and some good propulsion out of it.

How can light provide propulsion to aluminum foil in space?

That’s a very fascinating property that light has; it doesn’t really have mass, so it can’t bounce off of something, but in fact it does interact with obstructions; it does impart momentum to it and this was theorized by Einstein and it has been proven in a number of laboratory experiments.

What is the technology that you are testing at NASA right now?

We are taking one particular solar sail concept which is a square sail; it has 4 booms that come out and in between the booms are triangular sails and that system is designed to carry payloads that are relatively modest in size: the Robotic Science payload. We’re looking at several missions to the inner solar system to study the physics of the Sun and how it interacts with the Earth.

So you would be sending your solar sail in from our position; the Earth’s orbit, closer into the Sun? Sounds kind of backwards to me.

Well, the thrust that the sail can produce is proportional to the strength of the sunlight and as you go closer to the Sun, the strength of that propulsion goes up as the square of the distance as you get closer so actually, it works much more efficiently close to the Sun. The missions that have been planned to look at the outer solar system; almost all of them have involved first going to the inner solar system flying close to the Sun and getting a good boost and then going out. But the near term missions that we are looking at are missions that hover; they don’t go really fast. There is a balance point between the Earth’s gravitational pull and the Sun’s gravitational pull called the Lagrange point, and we have satellites that site there now. That doesn’t require any particular propulsion, but if you want to sit and hover at some point closer to the Sun (to get to) that particular point in space, then you have to have some propulsion capabilities and our scientists have an intense interest at wanting to be at that point. You can imagine how that might be an advantageous place to put some instruments in between the Earth and the Sun to understand how that physical property is.

Ok, so I understand; it would be as if the Sun was a fan and you had your sail and you let it drift down towards the Sun to the point that the force of the Sun’s energy coming off of it is perfectly balanced to hold the solar sail at the point. It wouldn’t go any further or go any closer.

Right. That is correct.

What kind of experiments would you be interested in doing if you could get that close and be able to station keep?

I’m a propulsion engineer, not a research scientist; they can do a much better job of explaining what exactly they’re studying, but some of the instruments that they plan to put on it measure the magnetosphere, they measure high energy particles as they go by. Of particular interest is sensing coronal mass ejections; these are the large flare events that happen on the Sun, that once they reach Earth can really disrupt our communications and they actually can harm and destroy sensitive electronic equipment. Such a flare in 1986 caused several million dollars of damage in North America alone so we want to be able to predict those events when they are happening and if we have enough warning time, we can turn our equipment off or in particular conditions, keep them from getting hurt so it is important to know when a coronal mass ejection is coming.

What could the future hold for this technology, with being able to explore the outer solar system?

Well, that’s a good point. As I just mentioned, these coronal mass ejections also can be very harmful to our astronauts so NASA is looking in the near future to going back to the Moon and Mars which there has been a lot of discussion of. We’ll need to be able to predict when these events (coronal mass ejections) happen so that our astronauts can get to safe havens from those events, so we will probably need to have these warning satellites positioned near the moon and mars and possibly around the solar system for a warning in doing that. (After that) eventually in the future there is an intense interest in wanting to understand the structure of our solar system outside the orbit of Pluto, particularly the Heliopause, now the Voyager space craft has just entered that region; there’s been some interesting results coming back in there; and there is a lot that we’d like to know about in that region of space. Just beyond that is something called the Oort Cloud which is supposedly the area of space where a lot of the comets that we see live most of their lives, but occasionally they come into the Sun. So there’s quite a bit of science to be done; observing and exploration just beyond the edges of the solar system.

Would anything be different in building a solar sail to that could travel out into the outer solar system then what you are working on right now?

It doesn’t have to be. You could take the technology that we are pursuing now to do these coronal mass ejection signals and you could send that sail on a mission. The problem is that it would take or more to get to those Oort Clouds and out into the Heliopause. If we can build a sail that is a order of magnitude or a tenth of the weight for the same amount of area; that is performs 10 times better if you will, then we can make that same mission in half the time, so to really start considering that mission, we will want to build higher performing sails to really do it and to do it within our lifetime, if you will.

What is the time frame now on forward with the prototype you are testing and your future plans?

That’s something that there is a lot of studying going on in the agency right now; particularly, there is a science advisory committee that’s meeting and determining what their science priorities are and that will set the need date for when sails need to be ready. When it can be ready?, well what we’ve been doing over the last 3 years that has culminated in these tests at Plumbrook is to do the best we can on the ground to design and operate a solar sail in a simulated space environment. The next step is to go up into space and that’s going to be an important step. We really have to have a flight of the solar sail and see how it operates in space: the loads on the structure of the sail are much, much less than they are here on the ground. Gravity puts a load on the sails 4000 times higher than what the Sun will do. So a really true environment is in space and we have to take it (the sail) up to test it out. That’s another 3-5 years to do that sort of thing, and then it will be ready to be infused into a science mission; 3-5 years nominal space mission planning and development phase. So, within the next decade, certainly, I expect to see a solar sail flying.

Image credit: SDSS
Listen to the interview: Alpha, Still Constant After All These Years (3.3 MB)

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Fraser Cain: Can you give me the primer on Alpha?

Jeffery Newman: So Alpha is one of the constants that describes the strength of a fundamental force; there are 4 fundamental forces: electromagnetism, the weak force, the strong force and gravity and Alpha basically determines the strength of the electromagnetic force compared to the other 4. As such, it’s a very basic part of the quantum theory of how these forces work and how they scale with energy (and) how they scale with time in the universe.

Fraser: What in the universe depends on it; how would the universe be different if Alpha was different?

Newman: Because Alpha determines how strong the electromagnetic force is; that’s the force that holds atoms together; that’s the force that causes things to interact with light, so if the force (Alpha) had different strength, atoms wouldn’t hold together, as well or they might hold together too strongly to allow chemical interactions. As well, if light and atoms didn’t interact very well, it would be very hard to see for instance, as we do. It is essential to our life. Because it’s so fundamental, it has ramifications all over the place that you wouldn’t even expect that can have affects on almost every interaction an atom undergoes or how an atom is structured.

Fraser: Where did the prediction come from that Alpha should remain constant since the Big Bang? Why was this even open to speculation?

Newman: It was generally expected that it was a universal constant of the universe. There were predictions in fact, that it was not just a constant, but a very simple constant that would be an integer; whatever 136 or whatever 137. For a while it was thought to be the value; not a 137.1, but a 137 even. That turned out to be numerology; it didn’t hold true, but it’s a value that comes out of nowhere, but is a fundamental part of the standard model of particle physics and all the other standard values of particle physics are things like the mass of an electron, the very basic thing. We would expect that there would be numbers that would describe the universe as a whole and if they describe the universe as a whole, they should describe they should describe it at any time or any place. Only in the last 20 or so years, when there have been unification theories, that predict many extra dimensions; there are theories that also predict that the constants of the universe as we perceive them are influenced by the presence of these extra dimensions and over time or over space, the values of these constants could actually change because of the extra degrees of freedom provided by these dimensions. Dark energy theories today also can predict changes in Alpha over time.

Fraser: Now I had reported a week before your story had come out that some Australian researchers had found that Alpha had been changing which I guess was a pretty big announcement. Do you know what research they had done to determine that it had changed?

Newman: So they’re using ? again an astrophysical method; trying to look at observations of very distant objects, deep in the past; in the distant universe, and tried to use those observations to look at quantities that should depend on Alpha; in their case, they’re looking at the wavelengths of light that are absorbed by gasses between us and quasars that are very bright objects, very far away. They have a method that tried to use many different kinds of elements counterbalancing each other trying to get as much sensitivity to Alpha as possible, but because it’s a complicated method, it requires a lot of complicated calculations. It’s certainly a more complicated method than the one we’ve tried. We’ve tried to keep things simple. So there are actually some groups who have used the same method and some of them have found changes in Alpha and some of them have found no change in Alpha with the method the Australian group is using.

Fraser: What was the method that you had used?

Newman: We are looking, not at quasars, not at the very brightest objects, but rather at galaxies which are more abundant. So we can look at greater numbers of objects. And it turns out that we are looking at a particular simple set of measurements, set of wavelengths; transitions in atoms that we can use to measure Alpha. It depends in a very straightforward way on the value of Alpha over time, so by making a pretty simple measurement, we were able to set a constraint on how Alpha could evolve without having to worry about lots of atomic physics and nuclear physics, but just the simplest thing we can do. Alpha is called the Fine Structure Constant, and we were actually measuring the strength of a Fine Structure transition in oxygen atoms.

Fraser: How precise is the calculations that you’re coming up with?

Newman: The precision is mostly limited by the just the number of objects we have in the DEEPTWO Redshift Survey; the dataset we’ve used to do this. Now, out of 50,000 objects in the survey, we have about 500 we can use for this test. That gives us a precision of about a part in 30,000 on the value of Alpha.

Fraser: Because I recall the Australians, it (Alpha) had changed in 1 in 100,000 or something like that?

Newman: Yes, so we can’t yet rule out their measurement. It’s modestly discrepant at this point. No scientist would look at these values and say one rules out the other because their nominal precision is high. The question is could there be something systematically wrong with the measurement; could there be something that goes wrong with that technique? Given that different groups have gotten different values it’s likely that something is wrong with one of the groups or the other; either the group that defines a change in Alpha or the group that doesn’t. We can’t yet rule that out, but with a larger sample, using our simple method, we can make a determination.

Fraser: What would it take then for you to be able to come to a conclusive answer that both you; the changers and the static people come to an agreement?

Newman: I think that more data coming from us would certainly help because currently we are able to show that we are not limited by any sort of systematic error or systematic uncertainty in what we’re doing. We are limited just by random errors and random errors, you can make better if you have a larger sample. The other techniques, the other groups are also trying to get more data to reduce their errors and to try to do measurements of a couple of different types to see if they can get consistent answers, not just with this more complex version of the method of looking at quasars, but now they are taking a step back and trying to use a slightly simpler method of that as well. So, hopefully these will converge and try to come to a common answer once their data sets come in.

Fraser: Right. Let’s say that you are wrong and it (Alpha) has been changing over time, what could that mean for the future of the universe? If it keeps going.

Newman: So the changes that are found are relatively slow; even the groups that do find significant changes and the changes that are found would be expected to get slower and slower as time goes on. Most predictions are that if Alpha does change, that it’s mostly changing in the first seconds of the universe. It just gets slower and slower and slower after that. So a secondary effect in the end, if it’s very slowly changing, the stars will burn out before it changes enough to affect the chemistry and interactions of atoms.

I’ve just wrapped up my fifth audio interview for Universe Today, and I was hoping to get some feedback from listeners. My goal with this is to focus on specific breaking research and chat with the researchers – it’s very minimalist, though, not a lot of rambling about the weather here at the Cain Cottage in Courtenay. I’ve been having a fun time, and should be able to produce 2-3 of these a week. So, give me any feedback. Who do you want to interviews with? I’m not crazy about the audio quality, and I’ve got my eyes on some new equipment that should improve things greatly.

If you like longer, more in-depth radio interviews, I highly recommend the Space Show, hosted by Dr. David Livingston, which spends 1+ hours talking to a single guest about a range of topics – no subscription link, yet. I can’t believe the quality of guests he’s had on the show in the past, especially this guy. Another great audio show is Slacker Astronomy. They tend to focus on a single topic, and explain it more comprehensively – with silly humour.

I’ve become a huge fan of Podcasting in the last few months (although, I despise the term… we seem to be stuck with it). I love being subscribed to various audio programs, so they just show up on my computer whenever they’ve been updated. It helps to have a portable audio player, but you can just play shows from your computer too; the point is that you’re subscribed. You can download the free subscription software here, and then start subscribing to various Podcast feeds. Here’s what I’m subscribed to: Quirks and Quarks (feed), In Our Time (feed), Reith Lectures (feed). Got any you like? Drop me an email with your suggestions.

Fraser Cain
Publisher
Universe Today

Image credit: ANU
Listen to the interview: Oldest Star Discovered (2.5 mb)

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Fraser Cain: How old is this star that you’ve found?

Anna Frebel: Well, that’s a bit of a problem because we cannot actually place an exact age on the star. You would need to measure radioactive elements in the star and if you said already that the star if very primitive, it is mint condition, so we don’t see any radioactive elements and hence we can only make a good guess on how old it is.

Fraser: How does it look different from our own sun?

Frebel: It’s very different from our Sun. We found the star because it had very low iron as compared to the Sun and this is also the reason why we think it is the oldest star because it has the lowest iron ever observed, and not only the iron, but also many other elements; carbon and nitrogen are very low as compared to the Sun.

Fraser: Why does our Sun have larger amounts of iron and this one doesn’t?

Frebel: If you consider the chemical evolution of the galaxy, and the entire universe, and you might know that after the Big Bang, the universe started out only with hydrogen and helium, and a little bit of lithium, and all the time, the heavy elements were synthesized in the stars themselves, now, certain elements such as carbon, nitrogen, oxygen and iron were synthesized during the lifetime of stars, but other elements, especially the heavy ones, were produced in supernova explosions; the death of a big star. So over time, the stars got enriched more and more in heavy elements; the Sun is not very old by astronomical standards, hence it has much more heavy elements than the star 183027, which was what we found.

Fraser: So you are saying that normal stars like our Sun have been through the wash cycle several times, and they have had their matter recycled through several stars, and that’s why they have some of the higher elements in them. How can a star remain untouched from such a long period?

Frebel: Well the density of stars in some areas is rather low and others, it’s higher; this star is a field halo star, so it’s in an area of our galaxy which is not very populated, so it’s just been sitting there for many, many, many years, and because it’s a low mass star, it is still very unevolved, so it’s just waiting there for us to find it.

Fraser: What kind of star is it, because I understand that our Sun is several billion years old, but definitely not the age of the universe, so what kind of star is it that it could be as old as the Big Bang?

Frebel: The star is a low mass star, it’s a bit lighter than the Sun and that means that it evolved very very slowly. I mean the Sun, well, it’s still in its teenage years, so it hasn’t burned much. High mass stars burn very very fast, and they explode quickly as a supernova enriching the surrounding gas; the interstellar medium with heavy elements, but this star, because it is so low in mass has just been sitting there and burning its hydrogen slowly and we think the hydrogen has just finished burning. So helium should be the next stage.

Fraser: How early on do you think it actually formed? How long after the Big Bang?

Frebel: Well, we have 2 scenarios; one would be that it formed in the second generation of stars and the first generation formed within one billion years after the Big Bang. So that star should have formed very quickly, probably about one billion years after the Big Bang. And the second theory which we cannot exclude, although I personally don’t favor it, is that the star indeed is a first star itself, meaning that it formed as one of the very, very first stars in the universe and presumably that happened then within the first billion years.

Fraser: Do you think that there are many of these types of stars in the Milky Way?

Frebel: Good question; probably not because they are very old and hence they are very rare because it seems that there is a certain type of these low mass stars which are actually able to survive that long and astronomers have been searching for these types of stars for the last 30-40 years and so far, we’ve only found 2 in huge efforts, so we are really looking for the needle in the haystack I would say.

Fraser: In the last couple of years, I have been covering the fires at Mount Stromlo. How is the observatory doing?

Frebel: It’s doing very well. We haven’t been affected from a science point of view. We have been very much productive since the fires. The reconstruction has now started; we are getting an new advanced, technological instrumentation building so we have a lot of noise here, but that also means things are progressing. Everyone is doing very well and we’ve, I think psychologically, we’ve put the fires way behind us.

In case you missed the news, NASA is headed back to the Moon in the next decade. A permanent lunar base could be down the road, so scientists are starting to consider where we should build. Ben Bussey, with Johns Hopkins University Applied Physics Laboratory in Maryland likes the Moon’s North Pole. It’s got everything you might need for a long-term stay: permanent sunlight, relatively stable temperatures, and lots of lunar soil. And as an added bonus, there might be plenty of frozen water hiding in lunar craters.

Listen to the interview: North Pole Lunar Base (2.9 mb)

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