Planetary Radio: Space Exploration, Astronomy and Science - Far Out Sedna

Episode Date: March 22, 2004

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Her name is Sedna, and she's far out, man. This is Planetary Radio. Hi, everyone, and welcome back. I'm Matt Kaplan. Officially, her name is still 2003 VB-12, but her discoverers want to name her after the Inuit goddess of the cold deeps. One of them, Principal Investigator Mike Brown, joins us to talk about this mysterious member of the solar system family.

And speaking of deep space, Emily will be telling us where it begins in this week's Q&A. Later, it's Bruce Betts with What's Up and our new trivia contest from deep in the heart of Texas. Stay tuned, y'all. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, where does deep space begin? Deep space is a slang term that seems to have originated among amateur astronomers.

The earliest use of the term was in the 1940s in Sky and Telescope magazine. It has come to mean beyond the solar system. But as amateur telescopes have grown larger, deep space has become deeper. The general notion is that deep space objects are dim ones requiring relatively large telescopes or magnification. Anything visible to the naked eye is not a deep space object, including nearby galaxies. There are more technically exact terms out there. You can describe the space within the moon's orbit as cis-lunar, and the space outside as trans-lunar, and the

meaning of the terms interplanetary, interstellar, and intergalactic space are pretty obvious. But none of these terms captures the romance of the term deep space. For an alternative way of looking at what this term means, stay tuned to Planetary Radio. They first saw her last November, but the announcement that she is farther than any other object circling our sun came just a week ago. Sedna may be three-fourths the size of Pluto, but her three discoverers say she isn't a planet. Mike Brown, David Rabinowitz, and Chad Trujillo work with a state-of-the-art CCD camera, sophisticated automatic search software, and a 60-year-old telescope at Mount Palomar in California. They use them to systematically search for the most distant members of our solar system family.

Their successes may just rewrite our knowledge of the outer limits. Principal Investigator Mike Brown is Associate Professor of Planetary Astronomy at Caltech in Pasadena, California. Mike Brown, congratulations. How does it feel to be following in the footsteps of Clyde Tombaugh and so many other of your progenitors? Oh, it's been great. I have to admit, I don't quite feel like I'm in the footsteps of Clyde Tombaugh and so many other of your progenitors. Oh, it's been great. I have to admit, I don't quite feel like I'm in their footsteps yet

because I've been admiring those guys for a long time. But it's been a lot of fun nonetheless. Well, Sedna has been getting most of the attention in the last couple of weeks, and it is certainly worthy of congratulations and pride on your part, yours and your two co-discoverers, as well as the rest of your team. But it hardly stands alone. You guys have been at this since what?

Did the survey start in 1991? No, not this part of the survey. We started a preliminary survey probably about five years ago, but we really have been going strong for the past two and a half years. And when you say going strong, what are we talking about? And how does this survey work? It's automated, I understand. Yeah, it's absolutely automated, which is the only reason it actually works.

Because otherwise, we would never be able to have the manpower to keep this going. And there are a couple of key ingredients to the survey. One of the other ones is a very large CCD camera. When I say we really got started in earnest, that was two and a half years ago. We got our first moderately large CCD camera, but over the summer, we got a 172 megapixel CCD camera, which as far as I know is the largest CCD camera on an astronomical telescope in the world. So almost 60 times the number of pixels that I have in my little camera that takes pretty good pictures. Yeah, absolutely. So that is times the number of pixels that I have in my little camera that takes pretty good pictures.

Yeah, absolutely. So that is really the key to having this project work. People have said, and maybe expressed surprise, that yes, you have this incredible camera, incredibly sensitive device, but you're using a 60-year-old 48-inch telescope. And I think maybe there's this feeling that, oh, well, if it's like most things, cars, computers, if it's 60 years old,

it can't be very good. Not really true, is it? The amazing thing about that telescope, the Samuel Ocean Telescope down at Palomar, is that all of these telescopes that they built back 50, 60 years ago, mechanically are so amazingly sound that we can go back now and retrofit them now for CCD cameras and for robotic use, and they just work night after night after

night. They're just amazing machines. And good optics, too. That's absolutely true. Certainly, the 100-inch Wilson telescope that's even older is still quite a powerful instrument. Yeah, it's still going strong. It's just an amazing thing to see. So back to this camera, though, which really, it and the automation that have made the difference,

is that fair to say? Oh, those are both absolutely true. And the one other aspect that's been critical is the very nice support from Caltech, which owns the telescope, and letting you use large quantities of time on that telescope, because otherwise we wouldn't cover nearly enough sky and be able to find things like this. Well, only a month before you announced the discovery of Sedna, you also, your team, found this other object that I guess is still called 2004 DW, one of those very romantic International Astronomical Union names.

Yeah, that's right. At the time we found 2004 DW, we were in the middle of a very intensive study of Sedna, so we actually didn't really have time to think very hard about it, so it just sort of dribbled out as 2004 DW. But it's actually a very interesting object. We actually call it the anti-Pluto amongst ourselves. It has an orbit almost exactly a mirror image of Pluto, which is a very interesting thing. You had actually first detected Sedna several months before that, November 14, 2003?

That's right. It was about four months ago, and we've been studying it very intensely ever since then to try to learn as much as we could. And did it take some time to figure out that this object was just as far away as it proved to be? Well, it's funny. As soon as you see it in the data, and the way we look at the data is we take three images of the sky in a row, and we look for something that's moving. And as soon as you see the data, you realize it's the most slowly moving object that we've ever seen in the sky. And the speed with which it moves is simply related to the distance. So we knew as soon as we saw it that it was the most distant thing that we'd ever seen.

But because it was moving so slowly and because it looked like it was so distant, we actually thought something was wrong and we didn't believe it. Like so many world-changing scientific discoveries in the past, you thought you'd made a mistake, only to find that this object is incredibly far away. Your website, and we'll give the URL, the address for your website, at the end of this conversation. We'll also post it where this radio show can be heard,

on the Planetary Society website. There is an animation on your website that you are links to that animation. It is probably the best way to get a feel for just how incredibly far out there this object is. You know, it's quite funny that we have been in our heads dealing with how far away it is for a long time, and then when that animation was put together and I first watched the animation, even I was just amazed to see how far it it is for a long time. And then when that animation was put together and I first watched the animation, even I was just amazed to see how far it really is. Yeah, I recommend to people that they click over to that from your site. We are talking about an extremely elliptical orbit, 76 astronomical

units to 900 astronomical units. And we should add, even though we have a very sophisticated audience, that 1 AU, of course, is what the mean distance from the Earth to the sun, about 93 million miles. That's right. So 900 AU? I think the first time I sat down and calculated that, I was stunned. I just stared at the piece of paper and again thought, this just can't be right.

Are you still amazed also that you were even able to find this object, which is at most apparently about three-fourths the size of Pluto? Again, it's a testament to that fabulous camera that we have and the great telescope. It was not the brightest thing of all the things we've found in the past two and a half years, but it was still very obvious crawling across the sky there when we saw it. And you know quite a bit more about this, not nearly as much as you'd like, I'm sure,

but you've learned a lot more about Sedna. You know it's a rotational period, and I guess from that you've deduced that it has a friend out there, a companion. Well, we think that that might be true. It rotates once every 40 days, and that is a remarkably slow rotation period. In the solar system, the only things that rotate more slowly are Mercury, which is locked to the sun in a complicated way, and Venus, which presumably rotates slowly because of something to do with its atmosphere. A 40-day rotation period, we think the only way to explain it is if there is a moon that's also in a 40-day orbit

and that it's locked to it, just like Pluto and Charon are locked to each other with a six-day period. But it's possible that that's not the real answer. We have observations from the Hubble Space Telescope that we're going to be looking at soon, which will really answer that question pretty much instantaneously. I didn't know that you were getting some time on the Hubble. Whencope that we're going to be looking at soon, which will really answer that question pretty much instantaneously.

I didn't know that you were getting some time on the Hubble. When is that going to happen? It actually already happened, and I'm waiting for those data to come down to my computer sometime very soon. We're going to need to take a break in just about a minute, but let's talk a little bit more about what you've learned about Sedna and then sort of its status in the solar system when we come back. You've learned that, well, I guess now we have a red planet and a red planetoid in our system.

That's right. It's one of the most red objects out there in the solar system, and that's one of the big mysteries that we're still trying to understand. No idea why? We thought we knew at first. The more we learn, the more we realize we just don't know. We're talking with Mike Brown of Caltech, also the principal investigator for the survey that has come up

with a number of incredibly far-out-there planetoids, most recently Sedna, the primary topic that we're talking about on today's Planetary Radio. Mike, when we come back, let's do talk a little bit about how we define and place this planetoid or planet that you and your colleagues have discovered. This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth

asteroids and comets. We sponsor the search for life on other worlds, and we're building the first-ever solar sail. You can learn about these adventures and exciting new discoveries from space exploration in the Planetary Report. The Planetary Report is the Society's full-color magazine. It's just one of many member benefits. You can learn more by calling 1-877-PLANETS. That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments at our exciting and informative website, planetarysociety.org. The Planetary Society, exploring new worlds.

PlanetarySociety.org. The Planetary Society. Exploring new worlds. Its discoverers call it Sedna, and they hope that the International Astronomical Union will accept that name, as it usually allows discoverers to name the objects that they find out there in the universe. Our guest is Mike Brown. He is the principal investigator of the ongoing survey looking for these kinds of objects that are still a part of our solar system, although maybe just barely. Mike Brown is an associate professor of planetary astronomy at Caltech, the California

Institute of Technology. Mike, let's talk a little bit more about Sedna. We already mentioned that it has this incredibly elliptical orbit, which, again, people can see on your website, including in that great animation that shows just how far out it is, bringing it as close as 76 AU, certainly not close, and as far out from the sun as 900 astronomical units. Why such a weird orbit? You know, the interesting thing about this orbit is, first off, it's the only object ever seen in the solar system that never comes in close to the planets.

Every single other object does. There are comets. They come in close to the planets, even though they come from very far away. There are objects out of the Kuiper Belt, some of which can travel quite far out in the solar system, but they always come back into the planets. back into the planets. The only thing that we know of in the solar system, or that we think we know of in the solar system that never comes close to the planets, are protocomets out in the Oort cloud. And we think that Sedna is actually telling us that the Oort cloud is much, much closer than we used to think. If you had asked me or any other astronomer six months ago, I would have told you that an object had to be 10 or even 100 times further away to be part of the Oort cloud.

But now I think the answer is that there are so many objects out there that there's a continuous sphere of these sorts of objects from Sedna all the way out to almost the distance of the nearest star. If you're right about this, it's going to be a fairly large rewriting of our knowledge, our belief about the solar system. I think you're absolutely right. I think that for a long time we would have predicted that this region where we found Sedna would be relatively unpopulated. To find something out there and something so large really implies that the population is quite big

and that the total mass out there is tremendous. Now, the other interestingly named region out there, of course, which some people, I guess, would try to classify Sedna as part of this other region, is, of course, the Kuiper Belt, and I think I'm pronouncing it correctly. But I think you believe that actually Sedna never really comes close to that belt. Yeah, one of the interesting things we've been learning for the past five years about the Kuiper Belt is that it is very strongly truncated at about 50 astronomical units. Just cuts right off.

It just cuts right off. There are objects that go out a little further, and sometimes much further, but if you look at all the objects in the sky, there's really quite a strong edge right there. but if you look at all the objects in the sky, there's really quite a strong edge right there. Sedna never comes closer than 76 astronomical units, and that's really quite a big distance away from where the Kuiper Belt is. What is all this stuff doing out there? And I take it that you believe we're going to find a lot more of these guys.

I do think it's true. The interesting thing about the orbit of Sedna is that we found it when it was almost as close as it could be to the sun. Sedna has a 10,000-year orbit around the sun, so it spends most of its time far enough away that we would never see it. What that means to me is either we were extremely lucky, which I never like to think I'm very lucky, so what I think it means is that there must be a lot of these objects, and we just happen to find the one that's really close. So the question of how it gets out there, well, I think the answer is, just like comets get out to the Oort cloud, and that's a complicated process, but it starts out by having an object form in the inner solar system

or in the region of the giant planets, and it's generally in a circular orbit. It goes around and around, and eventually it has an encounter with one of the giant planets, and it's generally in a circular orbit. It goes around and around, and eventually it has an encounter with one of the giant planets, and it gets slingshot out into the outer solar system. But sort of just like the what goes up must come down, if you get slingshot out to the outer solar system, well, you still come back to the same place. And when that happens, you get slingshot out again and slingshot out again, and eventually you can be slingshot all the way out until you're gone and you leave the solar system entirely. But it's possible that on your way out you can have an encounter with a star

which can change your orbit. You're talking about Alpha Centauri and beyond. That's right. Absolutely. So their gravitational influence is enough to help to stabilize the orbits of these folks? Only when one of the objects is really far away, so that it's no longer very tightly bound to the sun at all. And when that happens, they get essentially stuck out in the very outer part of the solar system,

and they become what we call the Oort cloud. That's why astronomers have always thought the Oort cloud is very, very far away, because that's how far you have to be before you can be affected by these passing stars. So the question to ask yourself right now is, why is Sedna so close? Now, it seems far away, but compared to the Oort cloud, it really is quite close. And we think the answer is that it formed by the same process, but that it formed back in the very earliest history of the solar system. And we think that the sun formed in a cluster of stars,

that there were stars much, much closer, and many more of them, and that these are the stars that affected the orbit of Sedna. And these stars have now drifted slowly away from the sun and basically just left this fossilized remnant of the initial place where we were formed. That suggests to me that we may have more reason to be interested in Sedna or objects like it. This is the part that excites me the most. I mean, finding something large, finding a planet is great, and it's a lot of fun. But scientifically, I am fascinated by the formation of the solar system

and the initial conditions that were there at the time. And this is one of the best ways that I've found that we can now probe at those very early times. Now, I want to note that you said finding a planet, but you insist that Sedna is not a planet. You're right. There are those out there who are saying that Sedna should be considered a planet, but I just don't think it's true. I'm actually quite strict in my definition of a planet, and it's because I think planets are very special things. I think a planet should be something that is significantly larger than anything else in its vicinity. And while Sedna

is currently the only thing we know in its vicinity, I suspect within the next five or ten years, we'll have many other objects known out there. And if I were to tell you today that Sedna is a planet, I'd have to come back in ten years and say, well, okay, I guess we're going to have to reclassify Sedna as something else because there are more objects out there. Otherwise we, what, eventually end up with hundreds of planets. And there's nothing scientifically wrong with that. If your definition of a planet, as one definition is,

that it's anything that's round in the solar system, well, then there are hundreds. And scientifically, that's fine, too. But culturally, I don't like that definition very much because, again, I feel like a planet should be special as opposed to having hundreds of them out there. We have only a couple of minutes left. Talk about your team, and in particular your co-discoverers, the two gentlemen who are sharing credit for this discovery with you. Everybody's had a very important role to play in this discovery. Chad Trujillo at the Gemini Observatory in Hawaii has been working with me on this project since the very beginning for the past two and a half years.

And he really is the person who is responsible for putting together this very sophisticated robotic program that finds these moving objects out of these massive CCD images. And without his work, we would have never been able to have gotten this accomplished. So I'm very happy that he's still involved in this project. And the other co-discoverer is David Rabinowitz, and he has worked very hard on building that 172 megapixel camera, and without that camera, we just couldn't have done it at all. Not only that, he's now taking prime responsibility for following Sedna and the other objects that we find once we find them

with some telescopes that he's using down in Chile, also robotically. It's actually one of the interesting stories here is that objects that we find, once we find them with some telescopes that he's using down in Chile, also robotically. It's actually one of the interesting stories here is that everything that we do is robotic. We don't actually go to the telescopes much at all these days. And without his efforts following these things, we would never know what the orbit really is. And so this has just been a fabulous collaboration

of people with very different skills, very different responsibilities. It keeps us going and finding more and more of these things. Which you intend to keep doing. We will definitely find more. I don't know if we'll find more bigger ones, but we certainly hope so, and we certainly hope that at some point we'll be able to find something that even we are willing to call a planet. Well, good luck. You certainly have the right team.

willing to call a planet. Well, good luck. You certainly have the right team. I did say, as we run out of time, that I would give the address for your website, and it is one of those long ones, folks, so you may still want to go to planetary.org or planetary.org slash radio and check it out there.

We'll have the link up. It is www.gps.caltech.edu slash tilde, a little curvy line, mbrown slash sedna slash, and that's it. And so you can see why I say you're going to want to go to planetary.org to find it. The easiest way is to go to Google and type sedna. That's the very first one. The easiest way is to go to Google and type Sedna. That's the very first one. And while you're on Mike Brown's website,

be sure to look up the Go Girl pinball machine, of which I don't know if you want to say anything at all. I think everyone can look at it for themselves. Best seen. Best experienced, I guess. Mike Brown, thank you very much. I know that you've been spending a lot of time with the media lately, and so we are even more appreciative that you could join us on Planetary Radio. It's been my pleasure.

Mike Brown is an associate professor of planetary astronomy at Caltech, also principal investigator of the survey that has discovered Sedna, easily the object farthest away in our solar system so far. And we'll be back right after this from Emily. I'm Emily Lakdawalla, back with Q&A. Deep space may be a slang term, but it's part of a rich store of concepts and words carried over from the great ocean wanderings

of our species here at home. We imagine crews of space explorers navigating among the planets or stars, coming finally to planetfall at the end of a long voyage through a space deeper and darker than the deep blue of the ocean a thousand miles from land.

So it's no wonder that deep came to be the word for space beyond our neighborhood. So deep space is a romantic term, but it's also good public relations. Among Earth's many tracking and data systems, the deep space network holds a special place. For a time, it seemed that the moon would become another home for humans. Hence, the term deep would no longer be appropriate for lunar missions. But today the moon, as inaccessible as it was in 1959, remains an object of our yearnings. Deep space begins there.

Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Time for What's Up. Bruce Betts, why are you in Houston? Why, why, why? I'm afraid there's a very rational and boring reason, which is I'm here for the Lunar and Planetary Science Conference, a yearly event here in Houston,

one of the big planetary science conferences of the year, learning about stuff that's going on in the planetary science world. Well, I'm glad that you're still able to join us for What's Up. What's up? Speaking of planets, there are planets up. It's finally happened, Matt. It's here. There are five naked-eye planets, naked-eye in the sky.

All five of them, one time in the evening. It's so cool. So we're talking about what? Mars, Venus, excuse me, let's start on the inside. Mercury, Venus, Mars, Jupiter, Saturn. Nice. Good job. Thank you, thank you. Yes, yes, Saturn. Nice. Good job. Thank you.

Thank you. Yes, yes, we are. So look for them in the evening sky, not too long after sunset. Venus is that really bright thing that's been over there for a while after sunset in the west. Below Venus, closer to the horizon, below and to the right of Venus, you can find Mercury. If you've got a clear view to the horizon, not nearly as bright as Venus, but still fairly bright. And going the other direction from Venus, you've got Mars, a yellowish-looking, looks like a star to the upper left of Venus. You keep going across the sky, Saturn's almost directly overhead in the early evening, and

then Jupiter's the really, really bright thing over in the east, and you'll notice that they're all in a line going across the sky. So if you can find any two of them, you can follow the line and find the other three, we hope. Also, don't order yet, because the moon is going to play with them all during this week. I'm just kidding. If I was an astrologer, I would just be falling off my chair right now. I'd be freaking out. Fortunately, we're not.

Heaven forbid. Heavens forbid. Wait, I have a joke here. I have a joke here. Heavens forbid. Get it? Oh, I'm embarrassed. I have no good response.

I'll just go on with the moon. Moon. You can watch it. It's one of those times, you know So I'll just go on with the moon. Moon. You can watch it. It's one of those times, you know, people usually just kind of ignore the moon out there. You can actually track it moving from night to night relative to the planet. It moves in the sky from west to east. So at the beginning of the week on the 22nd,

it is about two-thirds of the way from Venus to Mercury and then moves closer and closer to Venus. It will be really close to Venus on the night of the 24th. It should be really cool looking. And even closer to Mars on the 25th. And then three days later, it's made it all the way to Saturn. And then a few days after that, on the 2nd, it will be near Jupiter. Watch that moon going across the sky.

Find your planets. Have a good time. By the way, you're probably asking yourself, how unusual is this, Bruce? How unusual is this, Bruce? Well, it's pretty unusual. The last time that the five naked-eye planets were together in the evening sky, January 2002.

You know, not that long ago. But the next two times will not be until August of 2008, July of 2016. So get out there, play with your planets. I'm going to do it tonight. All right. Let's move on to random space facts. The planets appear in a line in the sky.

Why? Because they are all orbiting in roughly the same orbital plane. The plane of the Earth's orbit is called the ecliptic. So they're all very similar in their orbital plane to the ecliptic. Makes a nice line across the sky. Good stuff. On to the trivia contest. We asked you last week, at least in the context of astronomy, is what I was looking for is

what does the Japanese word Subaru mean? How'd we do, Matt? What'd we learn? I'm sure we learned things. And what I had to resist blurting out last week, of course, is that if you look at the logo on every Subaru car,

it gives it away. And here is the answer from this week's winner, a long-time listener to Planetary Radio, who I don't think has won. I look back through the records. I don't think he's won the contest

for months and months and months and months, at least eight or so. Subaru is not only the name of a car company, but also, now here's the other one, a telescope. It's this big Japanese telescope, but it means to bring together in Japanese and is also the Japanese name for the Pleiades star cluster. So, Per Keeland Lund, you will be getting your Planetary Radio t-shirt up there in Eugene, Oregon. Congratulations.

Cool. And you can also see Mars is near the Pleiades right now, which is what got us off on this whole Pleiades thing last week. Bruce, you want to hear some other interesting stuff people sent in? Oh, yes, I would. We've got a minute or so. Does it have anything to do with the trivia contest? Yes, it does, actually.

Here's one from another regular, Lee Valance, who happens to live in Japan. Most common name for the Pleiades in Japan, also visualized as a strainer, kozaru, a square sake cup, matsuboshi, pouring out sake, and an elbow joint, which I won't try to pronounce. Then a little more detail

from another regular, Dominic Turley, who talked a lot about the Pleiades themselves, but also about the Seven Sisters, the name of the Pleiades. In 1953, five Japanese car companies merged to form Fuji Heavy Industries Limited. The new corporation adopted the Subaru Cluster of Stars as its official logo for its automobiles. Bruce, what do you have for us in a new contest? A new contest. Another tricky one to phrase, but something a little different.

I want to know, what is the shape that an object follows if it has exactly enough energy to escape its parent body's gravitation? Something gets on a trajectory where it is just at escape velocity for that, whatever its parent body is, whether it's the sun or earth or whatever. What is the shape of its orbit? And this is assuming it's not influenced by third bodies, because that always makes things complicated. So how should folks enter the contest?

Go to planetary.org slash radio and follow the directions to enter the contest. And remember, we're looking for when it has exactly just enough, no more, no less energy to escape its parent body. Sounds like an important clue. Get those entries into us by Thursday, Thursday of this week at noon Pacific time, so that your entry can be among those chosen for the winner of next week's Planetary Radio T-shirt. Bruce, got anything else for us? Oh, just a little wish for everyone, which is look up in the night sky and picture the moon revolving around the Earth in its orbit, going across the sky.

Thank you. Good night. He leaves us with a lovely image tonight. That's Bruce Betts, the director of projects for the Planetary Society, joins us each week here on What's Up, this week from Houston, Texas. Say something Texan. Yee-haw! Thanks, y'all. Take care. That's all the time we have this week.

Come on back for another probing of the outer limits of knowledge, next time on Planetary Radio.