Planetary Radio • Feb 13, 2019

Watching the Births of Solar Systems

Please accept marketing-cookies to listen to this podcast.

Download MP3

On This Episode

20190213 sean andrews

Sean Andrews

Astrophysicist for Harvard Smithsonian CfA

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

Kaplan mat headshot 0114a print

Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

Radio telescopes are delivering stunning images that, in some cases, current optical telescopes can’t equal. Witness the 20 beautiful protoplanetary disks imaged by the DSHARP team using the ALMA radio telescope in Chile. The diversity of these proto-solar systems is astounding. Principal investigator Sean Andrews will tell us how the pictures were created, and why they are surprising and delighting astronomers. Senior editor Emily Lakdawalla is literally looking back on objects around our own solar system. She tells us how backlit images reveal their secrets. The rubber asteroids have returned! You can win one in this week’s space trivia contest.

Nearby protoplanetary disks
Nearby protoplanetary disks Four of the twenty disks that comprise ALMA's highest resolution survey of nearby protoplanetary disks. This image shows the millimeter-wavelength light emitted by the dust in the disk, giving astronomers a clearer understanding of the similarities and differences among the disks and what that has to say about planet formation.Image: ALMA (ESO/NAOJ/NRAO), S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello
Twenty nearby protoplanetary disks
Twenty nearby protoplanetary disks ALMA's high-resolution images of twenty nearby protoplanetary disks, which are results of the Disk Substructures at High Angular Resolution Project (DSHARP).Image: ALMA (ESO/NAOJ/NRAO), S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello

This week's question:

What are the two brightest stars in the asterism (think constellation) the Big Dipper?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, February 20th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

How long was the longest Skylab mission (the longest that humans were onboard in one continuous stay)?


The answer will be revealed next week.

Question from the January 30th space trivia contest question:

What planetary spacecraft (not Earth-orbiters) were launched by a Space Shuttle?


The Galileo, Magellan and Ulysses planetary missions were launched from space shuttle payload bays. (Yes, Ulysses was a solar mission, but it also visited Jupiter!)


Transcribed by Planetary Society volunteer Jake Bathman:

[Mat Kaplan]: Watching the birth of solar systems this week on Planetary Radio. Welcome. I'm Mat Kaplan of the Planetary Society with more of the human adventure across our solar system and beyond. Happy World Radio day. Sure, you may be listening to this on an un-radio, but our heritage is clear and they're still lots of people who hear PlanRad over the air. And then there are scientists who are using radio to reveal the cosmos. Sean Andrews is one of them. He leads a project that has shown us in gorgeous detail an array of protoplanetary disks revolving around young stars. I'll be talking to Sean in minutes right after we say hello again to senior editor Emily Lakdawalla. Stick around for this week's What's Up as we finally bring back one of the most popular space trivia contest prizes ever. Emily the immortal Satchel Paige said, "don't look back something may be [00:01:00] gaining on you." But that seems to be bad advice for explorers of our solar system.

[Emily Lakdawalla]: Well, it's always a good idea to look at things from every possible angle because you just never quite know what you'll see when you have the light glancing almost sideways across a planetary surface.

[Mat Kaplan]: Tell us about how this gave us a new view of 2014 MU69, which of course to many is known unofficially as Ultima Thule.

[Emily Lakdawalla]: Well when you do a flyby Mission you see things from the front for a while, from the perspective of the Sun. You see it fully lit. You can see features on the surface, but then when you fly past it, you get this view with sunlight picking out little topographic features and the the crescent shape and so you get a second chance to view the geometry of an object. And with 2014 MU69 we were able to see these what it's actually a bi-lobed crescent, looks like a letter B. It's got two curves [00:02:00] intersecting at the neck of 2014 MU69. And one of the things... I didn't even mention this in the blog post, one of the cool things you can see in this image is that there's actually a little bit of sunlight being cast into the night side of one of the lobes by light that first bounced off the sunlit side of the other lobe so you can just imagine standing on it at night on this world and looking up over your head you would see a whole 'nother world sitting right next to you.

[Mat Kaplan]: That is so cool. And the bigger of these two lobes ends up looking less like a sphere and more like a cookie.

[Emily Lakdawalla]: Yeah, it's quite flat. It's got an aspect ratio of something like 1 to 5 or something. It's very hamburger shaped. It's such a strange shape when the New Horizons team first published The Shape model on Twitter the scientists all over my Twitter feed were just going bananas at this bizarre shape. It's like, who ordered that? But it's so fun to see things that that you didn't predict and then you have the fun of trying to [00:03:00] explain them.

[Mat Kaplan]: Briefly, you provided many other lovely examples of looking back at objects around our solar neighborhood, right? What are a couple of those?

[Emily Lakdawalla]: Well, one of my favorite things has always been crescent shapes of things that are decidedly not round. So their crescents look very squashed. So in particular, I love the crescent shape of asteroid Lutetia, which was visited by Rosetta. As it has this great Bowl in the center. It's almost bi-lobed. So that one's pretty cool. And then Hyperion just looks... it looks weird from the front but it looks even weirder from the back. Looks like a sponge. So those are really fun crescents to look at.

[Mat Kaplan]: Yeah, Hyperion the the the creepy wasp nest moon that the creeps me out, anyway. There are a lot of other great examples in Emily's February 8, 2019 blog, Looking Back at MU69: The Hamburger Patty Shaped World. It really is, at least that one lobe. Thank you Emily. This is terrific.

[Emily Lakdawalla]: I decided it was too space beignets stuck [00:04:00] together, Mat.

[Mat Kaplan]: Oh, now I want some powdered sugar on mine. She is our Senior Editor, the Editor in Chief of the Planetary Report, our magazine, the Planetary Evangelist for the Planetary Society, Emily Lakdawalla. Just as there was once a time when we could not say that planets are common across the galaxy, there was a time when radio astronomy was not expected to produce images that look like photographs. That was before the creation of marvelous new internationally funded instruments like ALMA, the Atacama Large Millimeter/submillimeter Array. ALMA is on a high plane in Chile's Atacama region. You can find links to my own ALMA [00:05:00] adventure of a few years ago on this week's show page at Radio astronomers are now serving up pictures that in some cases surpass what current optical scopes are capable of. This has happened because of revolutionary advances in receivers and the ability of super computers running exquisite algorithms that can make scores of dishes work as if they were a single kilometers-wide antenna. The work of our guest today is a case in point. Sean Andrews is Principal Investigator for a project called DSHARP. As you will hear and will be able to see it has delivered results that astronomers of only a few decades ago could not dream of. Sean spoke to me from his office in Cambridge, Massachusetts at the Harvard-Smithsonian Center for Astrophysics. Sean Andrews, thank you very much for joining us on Planetary Radio and congratulations on the publication of this really stunning [00:06:00] data about protoplanetary disks, truly. Congratulations.

[Sean Andrews]: Thanks very much, and thanks very much for having me.

[Mat Kaplan]: Yeah, we wanted to do this sooner. But as you know all too well, our conversation was delayed by of all things the government shutdown. So I also congratulate you on being able to go back to work. You couldn't answer email you couldn't answer business calls. Must have been a difficult period.

[Sean Andrews]: Yeah, that's right. I work for the Smithsonian Institution and and we were furloughed just like a lot of the government. It's just part of being a government employee in some respects.

[Mat Kaplan]: Yeah. Well, let's hope it doesn't happen again anytime soon. Let's get to the science. If anybody needed more proof of ALMA's value, DSHARP has sure delivered it. Even though you're the Principal Investigator for the DSHARP project, are you sometimes as stunned by this data and and certainly by these images as as the rest of us are?

[Sean Andrews]: Oh yeah, absolutely. I mean in some [00:07:00] respects I shouldn't be surprised. I've been looking at these data for more than a year now in bits and pieces. In an overarching sense, this project is sort of exactly one of the reasons ALMA was built. The technical design of the facility itself had this kind of science in mind. It's one of the few three four five key requirements to be able to image protoplanetary disks at this kind of resolution. And we had sort of notional ideas and what we might happen to see. But I have to say that, you know, if you go back and look at the design documents from... related to this thing the sort of theoretical prediction images for what you might see are much more boring than what we do see. They're much simpler. So it is... it is kind of surprised. I have just been going over some slides to give a seminar to some of my colleagues at NRAO in New Mexico, you know, just looking over the slides again I still have [00:08:00] to be sort of in awe of what that facility can do.

[Mat Kaplan]: Yeah, awe is definitely the right word. NRAO, of course, National Radio Astronomy Observatory, which is one of the partners in operating ALMA and actually was my host when I was able to make it down there for the dedication of the ALMA array. I want to give my strongest recommendation to listeners to the show to take a look at these images. We have a link to them on the show page at At least that's where you can easily find the page, and you can find it across the net as well just by doing a simple Google search. They are so beautiful and so diverse. That diversity is is quite a revelation too, isn't it? I guess actually you might have expected.

[Sean Andrews]: I guess I personally didn't really expect to see that much diversity. Although I wasn't entirely sure when we proposed the [00:09:00] project that we would actually see these small scale features in all the disks. It wasn't unreasonable to think that it might actually just be in a sort of special subset of the disks, may be the most massive or the most evolved or something like that. But indeed they're all similar in some ways. They show similar kinds of features, but they're all quite strikingly different to the eye. Different locations for these these features and rings and gaps and different kinds of structures like spirals. Yeah.

[Mat Kaplan]: If somebody had said to me when they showed me this image, these are from some really powerful optical telescope, I'd have said yeah, okay, that makes sense. What is the resolution that that we're looking at here in the best of these images?

[Sean Andrews]: I think the sort of average number that we quote is about 35 milliarcseconds, right? So .035 arcseconds , which is basically, you know comparable or better than the spatial [00:10:00] resolution of a telescope like Hubble in the optical. The reason is basically that even though the wavelengths are much longer than the radio you can actually synthesize a much larger telescope with the interferometer array by separating the individual antennas, in these cases out to up to 16 kilometers is the sort of effective size of the telescope.

[Mat Kaplan]: And, of course, they can move these dishes around as needed by a particular project. They have those huge custom trucks that actually had some video of that pick them up and drop them on another concrete pad as needed and the supercomputer is right there. I bet it's still the highest altitude supercomputer on this planet.

[Sean Andrews]: Well, I can't imagine people would want to build a supercomputer at that altitude. That's not really a good reason aside from this, I suppose.

[Mat Kaplan]: No, I suppose not. If you and your colleagues are correct, some of these stars and the disks that surround him may be as [00:11:00] little as a million years old, which is like right after birth for a star. I mean first of all, how did you determine their age?

[Sean Andrews]: Ages of young stars are actually not particularly well known but the way you do it is you look at their stellar temperatures and their luminosities in a Hertzsprung–Russell diagram, which is sort of a classic diagram of looking at stars. And then you have to compare them to theoretical models for the evolution of the young stars as they settled down to become main sequence Stars. They're sort of notoriously uncertain at these early ages. So you have to sort of take those with a grain of salt but you know, these are in star forming regions that still are full of molecular cloud material that stars form out of, they're very young systems. Perhaps we don't know the ages that, you know, I typically say they're sort of 2 plus or minus 2 million years old.

[Mat Kaplan]: That's not bad. Not bad.

[Sean Andrews]: Yeah.

[Mat Kaplan]: From what I read, [00:12:00] there may be some surprise among a lot of researchers, a lot of theorists who have tried to figure out how planets form, that these disks look the way they do and are so young. I mean does this challenge what has been our thinking about how long it takes planets to form?

[Sean Andrews]: I would say yes and no. There's a lot of hindsight here where you know, you look back at theoretical work that's been done over the past 40 years and there were some thoughts that maybe these disks would be structured for sort of variety of reasons. I think in the context of planet formation and if these perturbations in the disc structures are actually being directly caused by young planets, that is a bit of a surprise because the sort of standard models our planet formation would take a few million years at least to be able to form large bodies like planets that could perturb the destructors. [00:13:00] There's a bit of a time scale concern in the sense that you know, the theory sort of was was pushing more towards a factor of a few to a factor of ten longer time scales to make a planetary system. I think those are still pretty open questions, while at the same time I think the community understands that while there are some alternatives that have yet to be fully vetted out the presence of young planets and planetary systems seem to be common. Trying to identify how you can increase the efficiency of the planet formation process, speed it up, is going to be a big effort going forward. I think in part thanks to these data and other observations with ALMA.

[Mat Kaplan]: As I understand it, it's the gaps in these disks, the the darker rings, where you and others expect that planets have formed or are forming. Is that correct?

[Sean Andrews]: Yeah, that's sort of the the simplest explanation. I would say that [00:14:00] there's a few important details, and that is basically you can have a situation where you have one planet that creates many gaps. This is in one of our one of our papers. This is discussed in a few other papers previously. If you have a disc that's has a particular set of properties and you have a relatively low mass planet, like the super Earths that are being found by Kepler but much further out in the disc, that can actually create a pattern that looks like multiple gaps for complicated reasons. Basically when you deposit angular momentum elsewhere in the disc. And then there's another situation where you can have pretty low-mass planets a few times an Earth-mass, and some again special physical situations. You can actually have that planet sort of on a bright ring, still relatively faint, but a ring of emission, where on either side of it sort of straddled by ga... by gaps. And we do see a couple cases like that. So it's interesting to think about these things. I mean [00:15:00] obviously with... with the planet scenario, the smoking gun really would be to image a planet...

[Mat Kaplan]: Yeah.

[Sean Andrews]: these disks, right? And I that will take some time but certainly that's being pursued now and I think you know might take sort of next generation facilities in the coming decade to actually hunt these things down, but that's sort of the the nail on the coffin.

[Mat Kaplan]: What is this data mean for the formation of even smaller worlds, worlds like our own Earth?

[Sean Andrews]: It's difficult to actually probe down to the Sun-Earth distance, in nearby star forming regions. If you want to probe disc material at a radius of one AU, for example, you need basically at the kind of resolution ALMA can get to you basically need something that's considerably closer than the nearest star forming clusters. So we've done this in one case a few years ago 2016, looking at the nearest protoplanetary disc around a star called TW Hydrae. And that also has gaps in [00:16:00] rings of emissions material. But because it's so much closer to us, you have a spatial resolution of about an AU, about one AU. And in that particular disc, we do see an actual gap at a radius... at a distance from the star of one AU which is really just remarkable. It's not clear that that particular gap is actually caused by a planet, because this is a somewhat older disc and can have a different mechanism producing. But that's sort of what you need right now, because ALMA's limitations on angular resolution again are set at about 16 kilometers. You'd like to be able to get higher angular resolution and you can do that in principle by separating the individual ALMA antennas by larger distances. The problem is well, there's sort of two problems. There's a geographical problem, up on the Atacama plane. If you start separating further and further, there's mountain, volcano, obstacles.

[Mat Kaplan]: I remember them well, yeah.

[Sean Andrews]: Well, it's that... that becomes sort of an engineering catastrophe. And when you try and [00:17:00] go in a different direction you sort of land in geopolitical problems because you'll end up starting trying to put antennas in Bolivia. This is something that's being intellectually explored at this point. We had a meeting at Kyoto a year and a half ago to discuss the potential for doing some engineering with sort of 30 to 45 meter, or 45 kilometer baselines, removing one or two antennas somewhat down the mountain to test if that would be a viable option and you could do that in principle. There's also the potential for a new facility that's sort of the successor to the Very Large Array, VLA, in New Mexico called the Next Generation Very Large Array that will operate at slightly longer wavelengths, the shortest wavelength would be about 3 millimeter which overlaps with ALMA, and that would be a really large facility where you could sort of push down to sort of 5 milliarcsecond resolution, a [00:18:00] factor of five or seven better than ALMA could do those wavelengths. So to push for real Earth's or to actually overlap with the sort of less than one AU that is probed by current exoplanet observations with radial velocities or transit is a little bit tough at this point just because of resolution limitations. The interesting point though is that if we look at these somewhat larger planets, super-Earths or sub-Neptunes or Saturns or that kind of thing out at more than ten AU with ALMA, the theory would predict that those things tend to migrate into the inner disc and maybe those are some of the things that you're seeing with Kepler and TESS and so on. Since we're seeing them at their birth sites with ALMA you might actually be able to kind of trace out their future evolution in a way.

[Mat Kaplan]: I think back to not that many years ago when we still wondered if there were planets around other stars, and we've learned so much but it's very clear from what from what you've [00:19:00] just described that we have a lot more to learn.

[Sean Andrews]: Well, you can never run out of things to do in astronomy. That's the great part. The properties of planetary systems that you observe with Kepler and TESS and radial velocity surveys and so on and so forth. Even you know direct imaging. When you look at a main sequence star, you know, a normal star in the in the in our galactic neighborhood. The properties of those planets are very strongly affected by the very early parts of their lives. Basically where they are now their masses, their compositions, those are not what they were when they formed. And the reason is basically once the planet forms, it has a very complicated short lifetime of interaction with the disc material nearby that it formed out of. Planets will migrate, they'll accrete mass, they will change their composition if they migrate over long distances, so on and so forth. If you want to make a [00:20:00] true understanding of how the planets came to be you have to be concerned about these first few million years in their in their lifetimes, and that's sort of where ALMA comes in. You measure a lot of these things and you try and compare with the mature exoplanet population and then you try and work out how you could go from point A to point B with some theoretical work.

[Mat Kaplan]: Hmm. Well the progress continues. We could talk about each of these 20 disks that have been published individually, but are you familiar with... there was one particular image that brought four of them together and they seem to be really good examples of the kind of diversity that we were talking about a few minutes ago. I'm just going to take them in order here and hope that that you're familiar enough with them to talk a little bit about them like AS 209, which is one of those that may be only about a million years old and apparently it's almost a neighbor [00:21:00] only about 400 light-years away from here.

[Sean Andrews]: Yeah. It's a really spectacular image. I mean, it's sort of... sort of took us a long time to come to grips with what we are seeing because that that system is... literally that disc is basically solely composed of little narrow rings of material in gaps in between them. There's no sort of smooth component whatsoever. It's just sort of ring after ring after ring and that sort of is a particularly striking image. You know, the interesting thing about that one is that you know at some point you run out of sensitivity to the continuum emission you're seeing which is these images are made basically from the glow of solid sort of dust particles in the disc.

[Mat Kaplan]: Being lit by the star, right? That they're revolving.

[Sean Andrews]: Yeah, they're heated up by the star and they... and they glow that heat off relatively cool temperatures that you're particularly sensitive to with ALMA. The neat thing about that particular disc is that when you go up beyond where you can see the [00:22:00] dust you continue to see gaps and rings in molecular gas as well. So it's... that is a particularly compelling system, especially in terms of those rings being caused... rings and gaps being caused by a planet. We have a one of our articles on this has discusses a particular example from a numerical simulation that shows that you can actually make this with a sort of Saturn mass planet.

[Mat Kaplan]: Let's go a little bit farther out, 540 lightyears to be precise. HD 143006, little bit older, 5 million years old. I noticed even before I read the caption that this disc has this one little brighter sort of arc shaped region, it's described as, which then reading the caption it becomes even more interesting.

[Sean Andrews]: Right. This system is interesting because it's orbiting a definitively older star. We know that just basically characterizing the cluster of stars that it [00:23:00] belongs to compared to the other clusters that we've done. So sort of a more evolved state, a solar mass that's very much like the Sun. And right, it has a series of rings and gaps and then outside one of the rings you see this sort of crescent of material accumulated. And the thinking on that is that basically you have hydrodynamic instability like a vortex basically, like a whirlpool in a body of water that sort of collects dust particles and concentrates them and you what you're seeing there is the emission from the concentration of that. So a vortex like that could actually be produced by again perturbations by a planet or there are other more complicated mechanisms that could make it as well. In our sample, in the DSHARP sample, these kind of little arc or azimuthal asymmetries are pretty rare. We only see it in two out of the 20 cases, and that's an interesting thing to follow up because there are other examples of different kinds of disks that [00:24:00] show more of these sort of asymmetries in the... as you go around the disc at a given radius. So it'll be interesting to figure out how common those things really are and if they depend on other properties of the system.

[Mat Kaplan]: Third in this image, which of course we will also include on the show page at I'm not sure how to pronounce it, is it "I-M-LUP"? Or "LOOP"?

[Sean Andrews]: It's in the consolation Lupus.

[Mat Kaplan]: Ah, no wonder. IM Lup. I did not expect to see among these disks what looks for all the world like a baby galaxy.

[Sean Andrews]: Yeah, that was quite a surprise to me too, I have to say this. This one was the one that I was sort of most stunned by, and part of the reason was that it took us a long time to actually get all the data. It was taken by ALMA and then processed because it's very large disc. It's much harder to deal with and we are folding in a lot of older ALMA observations. My graduate student Jane Huang when she finally managed to get [00:25:00] something to her liking sent me the image. I was I was completely stunned because indeed it looks like a spiral galaxy. There are a few systems like this in the DSHARP sample, but this one in my mind is the most spectacular. It's difficult to tell in these... in the images, in the stress images, but when we do the analysis in Jane's paper, we actually see is that spiral patterns pretty complicated. It has these two prominent arms, but also sort of superposed on the spiral pattern are circularly symmetric gaps and rings just like the other disks. And that to me is just completely baffling. Although I sort of raise this point a lot and and there's a bunch of bright, theroist-minded people that are... theory-minded people that are trying to figure out how you could potentially make such a thing.

[Mat Kaplan]: They're starting to build models that might account for this?

[Sean Andrews]: Well, there are trying. I think... people have ideas on what might [00:26:00] actually do it, but they have to actually do the work to figure out if they if they actually work or not.

[Mat Kaplan]: I love science. Just one more in this image and it is fascinating for another reason. AS 205, which is a pretty typical kind of star, not a star but a star system, right?

[Sean Andrews]: That's right. This is actually a triple system. There is a sort of relatively isolated primary star. That's the bright... that hosts the brighter bigger disc that you sort of in the upper left of the system. To the lower right what you see is well, I mean you can't tell because there is such a small separation but it's a very very close binary system, sort of less than an AU separation of two stars. There's a few interesting things about this image. One is that the primary... the disc around the primary star, the more massive star, actually has a fairly tightly wound spiral pattern. It's a little difficult to see sometimes depending on the stretch, but it's quite [00:27:00] prominent if you do some analysis on it. That has been a long theoretical prediction where you actually raise these spiral features due to tidal interactions amongst the three stars and their disks. The binary star system is really... was a real surprise to me because it actually is... again it's it's got gaps and rings in it. It's relatively small. It could be similar to the other systems that also could be a consequence of a dynamical interaction. The thing that's sort of interesting looking at the data from not really thinking about planet formation, but thinking more about star formation or multiple star formation, is that if you just look at the image, you can see that those disks are not aligned. They're not coplanar in the multiple system. One of them is much more tilted toward our line of sight. The disc around the primary star is almost face on and that actually has something to say about how you formed the multiple system and probably out of the relatively turbulent single core of [00:28:00] molecular cloud. I mean there's all sorts of other ancillary interesting stuff that's coming out of these things aside from the actual structures that we observed.

[Mat Kaplan]: Give it a few billion years, there might just be some astronomers living in that system who are going to have some really really interesting neighborhood to study.

[Sean Andrews]: Yeah, I suppose that's true. Yeah.

[Mat Kaplan]: Twenty protoplanetary disks. By my count ten papers that this team that you lead is it has gotten out of this data. All published, or has it been published yet?

[Sean Andrews]: It has, yeah. Published the last days of 2018.

[Mat Kaplan]: Yeah. So Special Focus Issue, it says here, of the Astrophysical Journal Letters. It is absolutely, I'll say it again, stunning work, both the images and what it tells us about our galaxy and about the formation of planets and obviously I would think if you go back far enough the formation [00:29:00] of the planet that we call home. Sean, you talked about some things that might happen quite a ways off if ALMA is upgraded or if a new array of radio telescopes is built, but what's just ahead?What are you working on now?

[Sean Andrews]: There's still quite a lot to do. One of the nice things that we did as part of this project is all this data is publicly available. All my colleagues, all other astronomers, and public if they want, can get the images and and do their own analysis on things. Some of the stuff that we're doing, we're looking into observing the same disks at different wavelengths to try and learn more about how the solids in the disks are trapped in these ring features, how to relate that to the presumably planetary perturberance. We have programs where we're trying to do a similar analysis with molecular gas instead of the solids. Those are sort of two prominent things we're doing. What we're aiming to do, I would say more as a community although myself included, [00:30:00] twenty disks is fantastic, but there's a lot more there's a lot of different angles. You could look at the sample and whether or not we could be exploring the dependence of the forms and shapes and so on of these substructures on additional parameters, like is there a dependence on the star? Do you get different kinds of planetary systems around different stars? And so on and so forth. So the key going forward, I think, is still expanding the sample. It's this is a relatively small... I mean twenty images is nice, but it's a relatively small sample in terms of the the possible parameter space you can look at. So I think there's still a... just a ton of discovery space with ALMA doing these high-resolution imaging and I think you know every year you're going to see more and more of these really spectacular sharp images of disks coming out.

[Mat Kaplan]: Absolutely fascinating work Sean. Please pass along our congratulations to the entire DSHARP team and keep up the [00:31:00] great work.

[Sean Andrews]: Thanks very much.

[Mat Kaplan]: Sean Andrews is the Principal Investigator for DSHARP, the Disk Substructures at High Angular Resolution Project. He's an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. And he also lectures in Harvard University's Department of Astronomy. Time for What's Up on Planetary Radio. The Chief Scientist of the Planetary Society is Dr. Bruce Betts, and he's here to tell us once again about the current night sky and a whole bunch of other stuff. I was going to go through the table of contents, but there's really no point. There's no need to tease it any further. These people are sufficiently teased.

[Bruce Betts]: Then let me just tell them good stuff. So in the pre-dawn East... I'm just going to move on. In the pre-dawn East, we've got three planets: bright Jupiter highest up and then to its lower left, it'll depend on when you're looking, but we've got super bright Venus and much dimmer yellowish Saturn [00:32:00] and Saturn's below Venus until about February 18th, and then it rises above Venus and you can watch it from day to day as they separate in the sky.

[Mat Kaplan]: Can we establish that Jupiter is a planet?

[Bruce Betts]: Yes. Yes. That's an important point, Mat.

[Mat Kaplan]: You know where I'm going?

[Bruce Betts]: Yes, I do. We'll find out later in the show. In the evening sky, we've got reddish Mars low in the southwest but also I encourage people to not only check out Orion which many people can recognize but if you have a good broad view of the evening sky in the winter South northern hemisphere, you've got the winter hexagon, made up of six really bright stars. If you start with Sirius the brightest star in the sky and then going counterclockwise you get Rigel and Orion, Aldebaran and Taurus, Capella, and then Pollux, and then Procyon. So it makes a lovely not-quite-regular hexagon. [00:33:00]

[Mat Kaplan]: I've got stars in my eyes.

[Bruce Betts]: On to This Week In Space History. It was 2000 that the NEAR spacecraft, later named Shoemaker NEAR, went into orbit around the asteroid Eros appropriately on Valentine's Day. And then in 2013, it's been six years since the Chelyabinsk impactor when a large asteroid object came and exploded over Chelyabinsk. We'll come back to that in just a moment. On to Random Space Fact.

[Mat Kaplan]: From the Old Prospector of the Skies.

[Bruce Betts]: [Exaggerated Prospector Voice] "Well dell, herdey here." Whatever. The Chelyabinsk meteor was roughly an 18 to 20 meter diameter asteroid object that came zipping in at over 60,000 kilometers per hour. It came in with an amount of energy equivalent to about half a megaton of TNT. So like 30 times more [00:34:00] energy than released from the Hiroshima atomic bomb.

[Mat Kaplan]: That is a great way to express it.

[Bruce Betts]: All right, we move on to the trivia contest and I asked you, what planetary spacecraft, not Earth-orbiting satellites, were launched by the space shuttle? How'd we do, Mat?

[Mat Kaplan]: Ah, this was interesting. I had to struggle because I mean first of all we had once again a lot of winners, even more than we expected, more about that in a moment. There were so many people who only came up with two of the three that you were looking for. Some of them overtly stated that they left out one of these missions and only came up with the other two because they thought that the third mission, well, we had set a "planetary ,mission" you said. And they thought this other one was a solar mission, but but but... tell us what the answer was.

[Bruce Betts]: Well the ones that apparently everyone agrees upon are the [00:35:00] Magellan Mission radar mapper Venus and the Galileo Mission, which became a Jupiter Orbiter. The one in question is Ulysses, which was indeed designed primarily to study the poles of the Sun. But in order to get over the poles of the sun it went out to Jupiter and did some Jupiter studies as it used Jupiter's gravity to sling it into a more polar orbit over the Sun. So I'd say we were looking for all three, although I'd be flexible, but you're not flexible, Mat. I won't be on this one because I think we called it fair and square even though a few people said, woo this is a little bit tricky, isn't it? And pointed out those passes past Jupiter. I think we heard Ulysses possibly going past your window a moment ago there at the office.

[Bruce Betts]: Good ear. Good ear, Mat. You can tell you're a professional.

[Mat Kaplan]: I know my spacecraft. We had not just five but six winners of the Blu-ray edition of [00:36:00] First Man, the movie that was a big hit at the box office and got a bunch of Oscar nominations about the life of Neil Armstrong and starring Ryan Gosling of course. That Blu-ray which is now available both as Blu-ray DVD and video on demand. We have a sixth winner of the disc because one of our winners from last week already has it and he said no no, no, please make someone else happy. So we will in fact here are the six people that we will try to make happy. Vincent Canonje-nhehin-yah. I came close, he said, with my previous attempt. I'm just going to say Vincent in San Jose, California who added within a span of 17 months Magellan Galileo Ulysses in that order with the pesky Hubble low earth orbiter in between but Hubble outlives them all. True. So congratulations Vincent and also congratulations to Nick Churry in Scotch Plains, New Jersey. To Scott [00:37:00] Borgesmiller in Ijamsville, Maryland. John Linedecker in Aurora, Colorado. Justin Mawson, Annatone, Washington. And Paul Hoover. He's the number six, lucky number six, in my old home town of Long Beach, California. And we do have one additional winner, Ken Adams in Dunlap, Illinois will be getting the full set the five Kick Asteroid stickers that you, Bruce, help to put together. Those are available from in the Planetary Society store, of course, and a 200 point account. Just a couple of others to mention. Sid Meecham in Scottsdale, Arizona, who said that a total of a hundred and eighty payloads of one kind or another were deployed from the space shuttle payload Bay. I imagine a lot of those were pieces of the International Space Station. Robert Cohein, Worcester, MA, Massachusetts. Here's a couple of quotes. Unlike the mediocre intrepid spirits seek [00:38:00] victory over those things that seem impossible. That is attributed to Magellan. And this from Galileo, all truths are easy to understand once they are discovered. The point is to discover them. And Robert adds their insights are still valuable today. Finally this, Galileo, Magellan, Ulysses, wouldn't that have been an interesting panel of guests? We'll find their... we'll find their agents and and put some feelers out.

[Bruce Betts]: Maybe a Celebrity Jeopardy game?

[Mat Kaplan]: Yeah. The answer is They're All Dead.

[Bruce Betts]: So I think this one's fairly straightforward, but we'll find out. What are the two brightest stars in the asterism the Big Dipper? The two brightest stars. Go to

[Mat Kaplan]: Sounds simple enough to me. You've got until Wednesday, February 20th at 8 a.m. Pacific time. That's Wednesday the 20th at 8 a.m. [00:39:00] to get us the answer. Are you ready for this? I didn't tell you this would be the week. We're going to give away that 200 point account. You can do astronomy from any small almost any spot on Earth. They've got telescopes everywhere. We are also going to give away a Kick Asteroid... [tries to do a drum roll]. I can't even do it. Help me out here.

[Bruce Betts]: Rubber asteroid.

[Mat Kaplan]: That's exactly right. So you can amaze your friends and fill them with envy and win yourself the first of the returned rubber asteroids, now that say Kick Asteroid, That's it.

[Bruce Betts]: The asteroids have returned in their orbit.

[Mat Kaplan]: They do that.

[Bruce Betts]: Speaking of hilarious jokes. All right, everybody go up there. Look up at the night sky and ponder the following: when Ryan Gosling gets older, will he be Ryan Goose? Thank you and good night.

[Mat Kaplan]: That's very good. I like that. He's [00:40:00] Bruce Betts. He's the Chief Scientist for the Planetary Society who joins us every week here for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its radioactive members. MaryLiz Bender is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Pieter Schlosser. I'm Mat Kaplan. Ad Astra.