9UNP1260HD_Sanjay_Limaye_WordPress

- Welcome everyone to Wednesday Nite at the Lab. I'm Tom Zinnen. I work here at the UW- Madison Biotechnology Center. I also work for UW-Extension Cooperative Extension and on behalf of those folks, and other co-organizers, Wisconsin Public Television, Wisconsin Alumni Association and the UW-Madison Science Alliance, thanks again for coming to Wednesday Nite at the Lab. We do this every Wednesday night, 50 times a year. Tonight, it's my pleasure to welcome back to Wednesday Nite at the Lab, Sanjay Limaye. He works at the Space Science and Engineering Center. He was born in Brunei, India. He got his high school education in Delhi. 

He got his Bachelor's in Physics at Mumbai. His Masters in Physics at Kampur, and came to the United States in 1971 to work with Vernon Swomi here at UW-Madison. And he spent a few years with Jim Hanson in New York and then came back in 1980 to the Space Science and Engineering Center here at UW-Madison. 
(phone rings)

Those are the magic words. 
(laughs)
 Tonight... that phone call's coming in from Pluto, by the way. 
(laughs)
 We get to hear about Visions of Pluto, The New Horizon's Flyby back in July of 2015. 

Please welcome me in welcoming Sanjay back to Wednesday Nite at The Lab. 
(applause)
- Good to be back here. Thank you, Tom for inviting me. As I look at the audience, I don't think I see anybody under the age of 50, if that looks like the median age is about 65. So some of you probably remember the Pluto history and I hope there's nobody in the audience who remembers reading the headline when Pluto was discovered in 1930. 
(laughs)

It's a pleasure to give a stock on Pluto. The title is "New Frontiers with New Horizons" and hope you'll enjoy what I have to relay to you. It's not going to be heavy on what we have learned about Pluto, because if you watch the television coverage, you know as much as I do. 

And if not, most of it is on the web. So I thought the way I would make it a little more interesting for you is to address the questions that I still get asked. Is Pluto a planet? 
(laughs)
 And try to show you or at least, give you a bit of the history behind that question. This is 2015 and for the last 15 years or so, the question of, "Is Pluto a planet?" has been debated and probably will be debated for the next 15, 30 years at least. At least as long as Alan Stern is around because pretty soon, I'm sure, we'll be hearing about the next mission to Pluto. So let me begin with this quote from James Christy who discovered one of the moons of Pluto.

It's a book called, "Out of the Darkness

- The Planet Pluto" intro by Clyde Tombaugh himself and Sir Patrick Moore. Jim Christy had this to say in the forward, "Discovery is where the scientist touches Nature in its least predictable aspect. It discloses to us the regularities of Nature, but in itself, discovery is fickle, striking at the unexpected moment. This is the view that I must take after my serendipitous discovery of the moon of Pluto," and that is entirely true and as you'll discover when you start exploring the history of how we got here, serendipity has been around forever. To give you a preview of the quest for Pluto and the timeline, the planets were discovered by our ancestors. Nobody knows who noticed them first, but different civilizations all over the world noticed these bright points of light moving against the background of stars and they knew they were special. They were so special, that we based our calendars on them, so that's why we have seven days in the week, five for the known planets. One for the Sun and none for Earth. What is of course, the last days for the moon and it's a mystery as to why there was no day named for Earth because certainly, the fact that, the idea that it's not a geocentric system was found in other civilizations way before the west adopted it. It may not have been usually accepted but certainly it was exposed. 

But anyway, let's move on to 1609 when Johannes Kepler had moved to Prague and he published his first two laws of Planetary Motion and those were crucial because now you could start to predict the positions of the planet in the sky. Now it had been done a little bit earlier. I know the Mayans certainly knew how to predict the positions of Venus, but this was a mathematical calculations and I think that was a big step.

And soon after that, in 1610, Galileo was observing Jupiter, but according to his observations, he recorded the positions of stars around Jupiter and lo and behold, there's Neptune. Of course, he didn't know it then. And this was the situation that went on for the next couple of centuries that people had observed these planets, unknown at that time. They didn't know what they were and they were not curious enough or something prevented them from exploring further and discovering them. So Galileo actually missed Neptune three times, but before we get to Neptune, we didn't even know about Uranus. And that was a purely accidental discovery by William and Caroline Herschel. Caroline Herschel was William Herschel's sister. 

She had moved with him and William Herschel was a musician, but he also had an interest in astronomy and he actually had built some of the largest telescopes. He had built a 40-inch refractor back in the 17th century. And on 13th of March, 1781, he discovered a fuzzy object which he thought that looked like a comet to him, and so he described it as a comet. Then when he observed it for a few more nights, it soon became apparent that it was not a comet. It didn't have a tail and so it was accepted as a planet. Some years later, the moons of Uranus, two moons, Oberon and Umbriel were... sorry, Titania and Oberon were discovered by Herschel and then about a decade later...

Delambre in France, he was able to publish positions of Uranus in the sky that people use subsequently. And he made a comment, "I leave it to the future, the task of discovering whether the difficulty of reconciling the data is connected with the ancient observations of whether it depends on some foreign and unperceived cause which may have been acting upon the planet." Because at that point, what happened was eventhough you had Kepler's Laws, you had the recorded positions, the two didn't match. 

The predictions, and if you went back, they were off a little bit. Now I think this was the clue that carried people on forward all the way to Percival Lowell and Pickering that lead to the discovery of Pluto as we shall see. Then many years later, in 1801 Ceres, an asteroid which was called a planet or a minor planet at that time, was discovered. And that filled a gap in-- some of you may be aware that it is a body, emperical law that predicts a progression of planets, planetary distances empirically from all the way. Now, you can't even fit from Mercury to Pluto. But between Mars and Jupiter, there was a missing number of origin, there was no known planet and so Ceres filled that gap, so that was a major, major...

...discovery in a sense and that lead people to keep on looking at the law to see if there were other objects beyond Uranus when it was discovered.

Anyway, people kept observing positions of Uranus and I just want to jump ahead a little bit and show you what the situation actually is, regarding, and I can't use the mouse here. So I hope you all, if you can see, the sun is at the center. 

You see the planets, the blue orbits and the wrong choice for this kind of presentation of the orbit locations, but Jupiter is the outermost circle and between Mars, the innermost... not the one inward of the Jupiter's orbit is the Mars orbit and you see a lot of dots in a circle and that's the asteroid belt. That's the main belt for the asteroids. That's where Ceres and the other asteroids fall and they have been discovered as thousands of them, 15,000 as I recall.

And pay attention to the green dots that you see in the orbit of Jupiter, the Greeks and the Projents and those will give you some clue as to why people who study planets have such a difficulty with the current definition of what a planet is without AU.

Anyway, here are those asteroids and we're fortunate enough that actually, a mission flew past Ceres and west in recent years. Also NASA Discovery missions. Ceres is the big one in the middle. Vesta on the right and for comparison, against the Moon, you can see them in the lower right and there's Palas up in the upper left. Now these pictures are a little bit misleading because their sizes are awfully comparable. 

They're about 500 kilometers in radius.

The search for a planet beyond Uranus started using Kepler's Laws because as I mentioned earlier, people were trying to predict positions of Uranus in the sky and they weren't matching and so there were ideas and at that time, remember, many things weren't known at that point. The special 
(mumbles)
 was not developed yet and there was this concept of some medium that transmits light. So one idea was that, "Gee, maybe gravity doesn't work beyond orbit of Uranus." And that was by an astronomer, George Airy in England. Maybe there was some other influence that people didn't know, that there was some medium that was resisting the movement of planets and why Uranus was not where it should be. It was lagging sometimes. But fortunately, not everybody accepted that and here's the argument behind it.

If you have two planets that come close together, depending on their position, for example in 'A', the inward planet will try to pull the outward planet towards it so it will tend to speed up. Whereas in 'B', it'll tend to pull itself back and so that's what causes the errors in the positions that are predicted by Kepler's Law and the actual positions. So that's a very simple idea, but if you don't think about it, that is not obvious. So here was the situation for orbit of Uranus and Neptune and before 1822, Uranus was trying to pull Neptune back and after 1822, it was trying to accelerate it, so that's what was going on. And to come back to my timeline again, people were trying to see why Uranus was not moving the way it should and people knew that they should be looking for a new planet, but that took almost half a century. And it was not until 1845 or 1846 that it was actually observed. But the discovery of Uranus is actually an amazing feat because it was predicted that there should be a planet and people were able to calculate where that new planet should be and then you go look for it and you find it. I mean, that's amazing and I think this was the first astronomical feat, so to speak. And the history that happened, the events that took place in those 40-50 years are a preview of what happened almost two centuries later. And since, this confirms my belief that people who don't know history, are condemned to repeat it. 

(laughs)
 And there's all sorts of jealousy, secrecy...

...and big egos, 
(laughs)
 and just plain stubborness or trying to follow procedure and not taking any risks of hampered discovery, but anyway, I don't want to bore you with all of that. It is described in the book by Patrick Moran, and Clyde Tombaugh. So in late August, September of 1846, the situation became so close that Levaye, Ervin Levaye was an astronomer in France. He writes to the director, Johann Gulle.

He was at the Berlin Observatory to look for the new planet in a specific location. 

He sensed it coordinates. That very night, they look for it, he and Gulle and Heinick Dearest and they find it. That night, Anke joins them in the search and they follow this new object throughout the night and Anke was able to measure this diameter, three arc seconds. Three seconds of Arc. So that was amazing and then he writes, "The planet was positioned, you have pointed out, actually exists." This was a confirmation. It took one night 
[laughs]
 and people in other places refused to look for it. In France, in other places, they looked for it. 

They missed it or didn't do a proper job and missed it. So going back, you can now find all observations which was actually useful because they did record the data. Then you could construct the orbit and confirm it and get a better view.

Basically, the same situation applied to Neptune as was the case with Uranus. So that's where the idea of planet X came along and until 1915, Percival Lowell and Pickering, they were calculating the positions of Planet X. Now X simply stood for the unknown planet. Not the 10th planet, at that time. I think after the discovery of Pluto, Planet X still persisted, but then it was being interpreted as the 10th planet. And the problem was that the orbits of Uranus, Neptune and now Pluto are so long. Uranus was 84 years. 

You didn't have a long enough observation timeline to really define the orbit precisely. Besides, you didn't have computers back then, you didn't have the kind of tools that we have today. Fast computers to do the orbit calculations quickly and to find the orbit. And that hampered the calculations in terms of accounting for the influence of other planets, the large planets, Jupiter, Saturn on the orbits of Uranus and Neptune. So that was the problem. Anyway, Percival Lowell carried out the search for many, many years at Lowell Observatory and the search basically stopped after his death in 1916. His younger brother was the president of Harvard University and somehow, they managed to build a new telescope at Lowell Observatory in Flagstaff. A 13-inch telescope which was dedicated to the search for Pluto. The observatory wanted to continue that work in 1949. Slipher was there, as the director and Clyde Tombaugh who had been born in Illinois, his family moved to Kansas and they were basically, he was working on a farm. 

He didn't have the money to go to college so he was not a trained astronomer, but he liked astronomy and so he built a telescope and that seems to be the key to all of the great people in the 20th century. Everyone built a telescope. 
(laughs)
 I only built a small three inch one. Not three inch, two inch basically, telescope.

But anyway, so he drew drawings of Jupiter and he sent those drawings to Slipher, the Director of Observatory at Flagstaff, and Slipher invited him, wrote to him saying, "Would you like to work on an observing program?" And so he joined Flagstaff in 1929 and then carried on the search for one year and on the 13th of March, he discovers Pluto, and then later on, in 1948 there are at Kuiper at Yerkes Observatory just 75 miles south of Madison. He discovers the fifth moon of Uranus, not of Pluto.

So let me go forward to show you a picture of what the observatory looks like. That's the 13-inch telescope in the lower right. 

The building that houses it and that's at the blinking machine. It was basically, you take two plates and you go back and forth between them and you observe for motion between the two plates of a single dot of light and that's the object that you're looking for because it starts to mean the same and something is moving. Oops, what happened here? Okay, so this was the headline.

These are the two plates. You can see the arrow pointing to where Pluto is in those two plates and, "See Another World in the Sky" was the headline in Chicago Tribune the next day.

Somehow, the same day, the news reached England and an 11-year old girl was having breakfast and her father mentioned that, "Gee, there's a new world." "I wonder what they will call it?" was the question he asked, and she said, "Pluto". After thinking about it for awhile and that name stuck, so her father knew somebody who was an astronomer and he wrote to the Astronomical Society and the name eventually was picked up as Pluto. 

Now surprisingly, the predicted position of Pluto and where it was discovered are very close together. Now that appears to be a mistake because now it turns out that...

Pluto could have been anywhere because it's mass, it's so small. Pluto is so small that those calculations could not have been correct. So this was a pure accident that Pluto just happened to be where Percival Lowell had predicted it to be. And you can see, the two predictions by Pickering and Lowell and the actual position. The mean distance was close about 40 times the distance between Earth and the Sun. The period is long. 248 years, the actual period. Lowell's prediction was 282, but what matters is the mass of Earth. 

Lowell had roughly seven times the mass of Earth and it's actual mass is 2,000 of the Earth. That was the beginning of the problem of Pluto's status because it was simply not massive enough to impact any planet. So whether or not it should be a planet or not, was it massive enough? Those questions began back then. But they were less and of course, just as what happened with Uranus and Neptune, Pluto was of course, seen in many other place including at Yerkes. This was a plate taken in 1909, almost 20 years earlier and that's the position of Pluto.

And then things sort of rested. Pluto was accepted as a planet and then only in 1978, which is not on this chart...

something interesting happened. Two astronomers at the US Naval Observatory were looking at plates of Pluto and you can see the plates. 

There are two plates at the bottom. The one on the right doesn't look like the one on the left in that image. The one on the left has a slight bump. And first, he thought that maybe this was just a smudge, so he went looking at other plates taken of Pluto around that time and found that the little bump moved around, and it moved around, it appeared about six to seven days. That's the reason why Christy made that comment. He was not looking for a moon. He just found it, but he was curious enough to wonder why that bump was there on the image and that's where the moon.

So there's the situation. Neptune and Triton and this is actually, I should have paused there. I'm going back, going forward to 1989 when Voyager II spacecraft flew past Neptune. 

By that time, we knew Neptune had a moon called Triton which is in a retrograde orbit. It goes backwards. It's inclined, so that its orbit doesn't go from west to east. It's the other way.

Triton was believed to be roughly the same size as Pluto and because of this weird orbit, it's inclined, not on the plane of the planet, and it's a general makeup, that it's icy, it's cold and a rocky surface. People thought it was the best analog for Pluto. And looking at Triton basically...

...made people feel reassured about their belief that Pluto was an icy, cold object and that maybe its status as a planet shouldn't be considered permanent.

Following the Voyager missions, the United States Postal Service published a stamp commemorating all of the missions that United States had flown and that's the stamp that they created for Pluto. 

Of course, there was no picture for Pluto and so that caption remained. Pluto had not yet explored and the other planet in that series, there was a photograph taken from the space mission, except for Pluto not yet explored. And that stamp had a lot to do with how we got to Pluto in 2015. Cause there was a group of scientists, Fran Bagenal, Alan Stern, Jeremy Gladstone, Bill McKeenan who are still active and working and many of them are actually affiliated with this mission. I think every single one of them is. There were about eight or 10. They formed a group called Pluto Underground in about 1990, and if you follow the history of space missions, there was a group called Mars Underground because after Viking, there was no mission to Mars for a long, long time. And so the people, the group of scientists working on Mars, they had formed an informal group called Mars Underground and they used to send newsletters monthly, periodically and any chance they got, they would talk to NASA people and try to encourage them to take on a mission to Mars and eventually it happened. They actually got a billion-dollar program. It's a Mars program. 

It's a line item. So this group of scientists took that approach. They called themselves Pluto Underground and started talking about undertaking a mission to Pluto because that was the only planet that had not been explored and mostly because this was an American planet. An American had discovered it and Americans discovered the moon of the planet and why won't NASA take on a mission to Pluto? So that take on a scale, but this stamp had a lot to do with getting the people motivated. At the same time, there were other developments going on in terms of what we knew about how the Solar System evolved, how the planets were formed. And to learn something from history when the Asteroids were discovered more than a century earlier, the Ceres, Palas, Juno, etcetera, people discovered there were hundreds of asteroids and so even though Ceres was first called a minor planet, it was then relegated to a new term called asteroids, and so the same idea was being formed because at that time, remember, Haley's Comet had been observed as a very amazing comet in 1910 and it was predicted to come back in 76 years, but people didn't know where comets came from. So one astronomer, Ward had suggested this idea that the long period comets, the ones which have a period of a hundred years or longer come from a reservoir called a cloud. It's now called Oort Cloud. He can call it Oort's Cloud. 

But far, far away more than a 100,000 times the distance of Earth and the Sun. Very far away.

Another astronomer, Kenneth Edgeworth, had suggested in 1941 that there are some comets, the short period comets, should also come from a cloud and this was way before Oort had published his idea in 1950. And that there should be a reservoir that should come closer to the Sun more often than the long period comets. Every maybe 10 years or 20 years or even less.

And then Kuiper proposed in 1951 that some comets could come much closer. That they could be very close to Neptune. Maybe up to hundred times the distance between the Earth and the Sun. But nobody actually called it anything specific. Nobody called it a cloud. 

Nobody called it a belt. Nobody called it a Taurus or a donut or whatever. But those were just ideas that were put out in their papers and so people started thinking about these ideas as to when you have Pluto, which is very different from the other planets, and by that time, we knew it was very small. It was cold. It was icy, too far away. Not big. Whether or not it had an atmosphere, we didn't know. But most of all, its orbit was inclined to the plane overclifted by 17 degrees. So that was the first clue that maybe it's a captured object, or maybe it was ejected from Neptune or something happened. But we knew something was different. 

And whether or not it was a comet, I don't know, asteroid. I mean, that question was not answered because we didn't know anything about asteroids and we had not yet explored a comet at that time.

But then, something happened and that was-- And so anyway, this is the Kuiper Edgeworth Belt as we now call it. Although I suspect the term will change in the next few years. The letters J, S, U and N represent the planets. The Sun is the yellow dot in the middle and the blue and the yellow dots that you see are the objects that had been seen beyond orbit of Neptune. So a better term is, for such objects is transneptunian object, but in the literature you'll still see Kuiper Belt being used. Some people call it Kuiper Edgeworth Belt.

But AU simply means Astronomic Units. It's the main distance between Earth and the Sun.

- So that's what those are?

- Yeah. So those units are basically AU. Sun is at zero and 40 is 40 AU. So 40 astronomical units multiplied by 149.7 million kilometers and then you get the distance.

Anyway, I already mentioned this so that following the success of the Voyager mission, people started thinking about a mission to Pluto. Then the Decadal Survey of Planetary Sciences was undertaken by the National Academy which also recommended that Pluto should be explored and eventually, NASA did agree to take on a mission called New Horizons under the New Frontiers Program which is a program of completed missions with the budget backed then of about 500 million dollars. This is about 2001. And Alan Stern was the leader of the team that won it. It was a completed mission and there's some people here who were affiliated with the selection program. 

And it was a long road to Pluto. Of course, JPL engineers were working on ideas themselves. In the left is the Voyager One spacecraft model. Voyager Two was an identical copy that was launched in 1977. In 1990, the Pluto 350 idea came. 350 for 350 kilograms. And the cost back then, and I believe these costs are in the 2014 dollars, so it was about $543 million. JPL being JPL, next year they came up with a bigger and better mission. Better than Mark Two.

2,000 kilograms and $3.2 billion. 

Then came 1991, because the budgets...

...were not very conducive to spending billions of dollars on the space mission. 1991 of course, is the year that you all remember. You're still arguing about the events that happened back then. The Pluto Fast Flyby was coming in at $2.1 billion and 140 kilograms. And then in 1995, Pluto Express, the evolved version of Pluto Fast Flyby came in at slightly less cost. Only $1.4 billion. NASA selected something for only $500 million back then which is now $646 million. But of course, the weight was a lot more. 

So that's the New Horizons spacecraft that actually flew past Pluto, July 15th, and this is a view of the spacecraft. This is not the actual spacecraft. I was at NASA headquarters last week and meeting with the Director of Panetary Science Division and he happened to have this scale model outside his office. I said, "What is it ?" "I don't recognize where it came from." This was built by some students in Africa. Somewhere, I do not know which country, but a very, very nice model. So I took a picture of it. I said, "I'll show it." Here it is. 

On this picture, you see the basic components of the spacecraft. You can see the radioactive power source. It has no clear batteries because you are going so far away from the sun that you cannot have solar panels because the sunlight drops as the inverse square of the distance and then you will need very large panels which means you won't have any mass left for instruments.

The saucer-like thing on the top of the spacecraft is the high gain antenna and then the three little things that you see, they are the instruments. So to go back to history and I think I'll recover this, so I'm gonna skip this and just show you the launch. To get to Pluto, the distance is so vast. Roughly, 30 astronomical units at closest approach, that to get there, you need a very fast spacecraft. To have a spacecraft moving very fast, you need a big rocket. Well, there's only a certain type of rocket that we have.

Atlas Five or something like that, unless you go buy a rocket from the Russians now.

So the spacecraft had to be very, very small. So it was a very tiny rocket on a big rocket. A tiny spacecraft on a big rocket. It was launched in 2006, January 19 and it was a direct shot. It just flew past Jupiter. Now it went to Jupiter in just about one year. The Jupiter Flyby was February 28, 2007. Voyager took two years to get to Jupiter. So this was a very fast spacecraft and then from there, it was a straight shot to Pluto. It didn't use any other gravity assist and it got to Pluto in 2015.

The launch was very successful. They didn't have any corrections needed. They had planned eight projectory corrections in between and they needed only three. So it was a very good launch and you can see the times it took... the days the spacecraft took to cross the orbits of different planets. Mars in 78 days. A normal Mars mission takes about 11 months, 11 to 18 months, like the Curiosity Rover that took 16 months. Whereas this one, we're there in 78 days. Jupiter in 404 days. Uranus in 1,884 days, roughly less than six years.

Neptune in roughly 3100 days and Pluto in less than 10 years, nine and a half years. Now as it goes away from the sun, it's speed actually decreases because it is still being pulled back by the sun. So it's speed will continue to decrease. The Pluto Flyby changed its speed only by a few meters per second because Pluto is so puny. Before it got to Jupiter, it also flew past an asteroid.

The team was able to turn on the instruments and test their instruments and observing schemes. So that was successful. It also observed Jupiter before that and that was successful also.

It turned on its cameras onto Pluto...

...

only in about May this year and what you see is the image... well, first of all, on the right, you see the images taken just for guidance to make sure that they were aimed the right way and you see Pluto in two images and that's how they, this is called optical navigation, to refine your pointing, to hit towards that. So that's the upper right image on the right, the orange image. And then, this sequence taken in the larger frame shows Pluto and it's moon, Charon rotating about each other. Because Pluto's moon is almost half as big as the planet itself, the common center of mass is outside of Pluto and so that's why they seem to revolve around each other.

This is the view of Pluto that we all saw on July 15th. This was post-processed of course, and this has been enhanced to bring out the colors of the planet. What you see, the main features of Pluto and it's basically an icy object, but the main striking thing is that as the team noted, it has a heart and you see that heart at the bottom and that region has been given the name Tombaugh Reggio to honor Clyde Tombaugh. Now what is surprising about this is that the terrain is very young because that Tombaugh Reggio has no impact craters at all. So it's a very fresh surface. 

You can see some ancient craters on that picture and the high resolution pictures taken after that show that Pluto has lots of topography as much as several miles around. The moon, Charon, is also very interesting. It has a very dark northern polar region. It has some impact craters and canyons and valleys and when you look at it on the edge, you can actually see gouges and even Charon has lots of topography. Both the surfaces, Pluto and Charon's are covered with ice and here's a map of Pluto with craters and I believe, the next map has the names on it. You can see the Tombaugh Reggio, Vena Terra, Lowell Regio and you can see that the team is honoring all the people who worked on not just Pluto, but exploring the planets in the past and many of them colleagues. But they also have named certain regions after some explorers, like the mountains are named after Tenzing Norgay who was the Sherpa who climbed up Mount Everest with Sir Edmund Hillary. There is a Hillary mountain, also...

...which we will see in this region. 

So that image is next. It's one of the moons of Pluto.

This is the Sputnik Planum on the right. Sputnik after, of course, the first spacecraft.

I guess one of the most surprising things about Pluto was that not only, it still had an atmosphere and I skipped over many details. Pluto being so far away from the sun, where most of its orbit reaches about 248 years. The timing of arrival at Pluto was designed so that it would be at a close proximity to the sun. That is at Verhelian. And what that meant was that Pluto would have developed an atmosphere and that was seen in the last decade or two, so people knew, the scientists knew that there would be an atmosphere. The question was, as it moved away from the Sun, how soon would it collapse? 

And so there was no guarantee that when it arrived in July of 2015, that most of it would still be visible. So there was some special observations planned using an Occultation experiment which is basically, wait for something to obscure your view of the planet and they use the sun. So they were able to get two measurements. One at sunset and sunrise. The sunset behind Pluto as seen from the spacecraft and they obtained this wonderful measurement. So let me explain this. Pluto is in the middle.

The yellow circle that you see, is the area within which they could detect the signal and that signal is the red and the white line that you see coming in from both sides, from the left and right, and then you see a dip in the middle and that's Occultation. That's when the sunlight is blocked because it's being blocked by the planet. But before it gets to zero at the bottom, you can see that it actually has two different slopes and those are due to the part of that atmosphere which is due to haze and clouds. 

And that portion that shows us that there's a haze that reaches up to about 100-150 some miles and I can't point to you on the screen, but you see the steeper line that goes straight up? And then it changes slope. So this was the biggest surprise that Pluto's atmosphere extends to a very large distance above its surface. Now most of it is just methane gas.

There is some haze, acetyline and some of the other exotic organic compounds. But exactly how that haze is created is unknown and in fact, how should such little sunlight produce so much atmosphere. That's the mystery and so one possibility that the team has suggested is that there's some internal heat from nuclear fission, just radioactive decay of uranium and some other radioactive elements that are found on all the planets. That heat is what's causing some of this because this atmosphere probably persists for some time and because it's clearly there even though Pluto is now past its closest approach to the Sun.

And then on the departure from Pluto, New Horizons caught this vision and you can see atmosphere all the way around and I don't know what the midpoint is of this image, but you can see that atmosphere is asymmetric. Of course, Pluto is tipped on its side. 

It's not just Uranus that's tipped on its side. It's also Uranus, and so you are seeing more of one hemisphere than the other and that's why the atmosphere looks asymmetric. There is more extended on one hemisphere than the other one.

One other surprise was right in the middle of Tombaugh Reggio, you see carbon monoxide. There's a high concentration of carbon monoxide.

Where does it come from? That's a mystery. But in this image, you can see just about below the center on the left side a beautiful crater with a central impact peak. With a ring around it even and so that...

...

is interesting because this is all ice. This is covered with water ice. And that ice is very dynamic. It's not steady and the amazing thing is that Pluto has topography that reaches several miles and we have not seen mountains made of ice. We have seen icebergs, but not mountains several miles high.

Clearly, something is happening because if you look just above, northward of that you see a crater which is filled in with material whether it's melt from the neighboring region that was thrown into the crater or what, will be debated for the coming days and years.

I'm about to end my talk here. I thought I'll give you a preview of what our impression of Pluto has been since its discovery until now. So the beginning image is just a tiny dot that was a picture taken probably by Hubble Space Telescope, I think and then this is the animation...

...

around still images from New Horizons spacecraft.

So beyond this, what happens? Of course the Pluto mission is not over. It continues. The spacecraft is on its way to explore objects in the Kuiper Belt or the transneptunian space. It did carry something special. Not only did it carry a postage stamp, and I don't know what Alan Stern was thinking of to put a stamp on a spacecraft, 
(laughs)
 but it also carries a tiny capsule with ashes of Clyde Tombaugh. And he was a very gentle person. 

He was an amazing individual who taught at the University for many, many years. So here are some more pictures of Pluto that describe some of the other regions that have been named. In the Sputnik Planum, the Norgay Mountain. Montes is at the bottom and let's see. So Hughes asteroid in the middle, and there are some names that I don't recognize, but you will see Columbia and Challenger named after the two space shuttles. And what we see in this picture is something unique. I don't think-- I've been affiiated with Planetary exploration for most of my life and every new encounter tells us something, shows us something new. This is just absolutely astounding. I don't think we would have expected to see anything like this. The cover of this book, "Out of the Darkness." 

"The Planet Pluto" has a painting, artist imagination of what Pluto might look like. And believe it or not, that picture even has the semblance of a heart and one of the craters. It's from a very famous space artist. Anyway, this is Alan Stern on the left. Jeff Moore on the right and some of the other colleagues of the New Frontier's team hoping, and of course, this is lobbying for a new postage stamp, Pluto Explorer. 
(laughs)
 But more than that, more than the stamp, they are actually rooting for a Pluto Orbiter. 
(laughs)
 I'm sure and we'll continue to see it, so in the next couple of minutes, let me just show you what's going to happen. Pluto is of course, carrying on in the same direction. 

It'll have enough power so that we can communicate with it for the next at least a decade or so. And in the next few years, it will fly past another transneptunian object or a Kuiper Belt object that was part of the selection criteria that you had to explore one more object beyond that. Of course, by now we have hundreds of objects so they actually have several candidates that will target in the next year and they'll go past it.

Hopefully, we will learn something new. So what kind of objects do we have and here's an image from Mike Brown that shows Pluto and three objects that he has discovered, Makemake, Haumea and Eris. These were taken with the Keck, a rapid optics telescope on the island of Hawaii. And the missing thing is that of these four brightest transneptunian objects 
(TNOs)
, Pluto, Makemake, Eris and Haumea, all of them have moons except one. Pluto has of course, five and so it colors the debate about what our concept of a planet should be, or is. 

So this debate is not going to be over and if you compare the properties, they are very similar. But Pluto still remains an interesting object because it is of course, the outermost or I should say, the innermost towards the sun, member of the transneptunian objects of the Kuiper Belt 
(KBOs)
 family. It is unlike any of the other TNOs of the KBOs. It has the least eccentricity and is the most planet-like object. The other objects simply aren't like that and here's a comparison of some of the largest transneptunian objects that we have. There's the Earth. You can see a Moon, Pluto, Quaoar, and Sedna and Sedna is way out there. 
(laughs)

 Even though it is comparable in size to Pluto.

And here are the rest of them. Eris, Makemake, Huamea, Quaoar, Orcus, Lanth, Sedna and Quaoar. Now there are so many units, it's hard to keep track of their names. But in any case, I think what this brings us is an opportunity to learn far more about the objects that are not easy to access. Of course, this won't happen in our lifetime again, that we'll see the discovery of a famous object because by now...

I think the debate is almost over. It doesn't matter what we call Pluto. I think to many people, it will always remain a planet and objects beyond Pluto are not easy to access, so they will always remain a fantasy because it is so expensive to mount a mission to go to a distant object and if that object is not big enough, then you cannot learn more my orbiting it. You can only fly past it. 

And I don't think any scientist anywhere will be able to convince the governments to spend lots of money to take on a mission like New Horizons again. So we should appreciate what we have and then use our imagination and see what we can learn about the rest of them. So I'll stop there and thank you for your attention. 
(audience claps)

- Welcome everyone to Wednesday Nite at the Lab.