When you begin a new research project, you usually have expectations about where it will lead. Most projects take you or less to the expected destination. Some go nowhere. However, every now and then a project picks you up and makes you feel like you’re just coming along for the ride.
Today, in the journal Nature, we have published the results of a research project that fits solidly into the third category.
Our original plan was straightforward. We had recently discovered two small moons of Pluto, now known as Kerberos and Styx. We wanted to publish a short discovery paper that would just cover the basics: How did we find the moons? What are their orbits? How big are they? What are the implications of the discovery?
The Pluto system had other ideas.
Pluto also has two much brighter moons nearby, Nix and Hydra. They had been discovered years earlier and much had been written about them. I had no reason to think there was anything new to be said about either of them. For me, they could just be my “reality checks” to confirm that I was obtaining valid results.
However, my early efforts to determine the size–or at least the brightness–of each moon took a very strange turn. Most moons in the Solar System are in “synchronous rotation”, meaning that they rotate once about their own axis every time they circle the planet. This is why we only ever see one face of our own Moon. The “de-spinning” of a moon happens very quickly, because the gravity of the central planet creates tides, which dissipate energy inside the moon as it rotates. The dissipation can only end when the moon reaches synchronous lock.
If Nix and Hydra were in synchronous lock, we would have seen a distinct relationship between how bright they appear and where they fall along their orbits. We didn’t. There was no pattern at all. Neither moon is in synchronous rotation! The same is probably true of Styx and Kerberos, but it has been harder for us to get good measurements of these dim points of light.
It finally dawned on me to start thinking about the double-planet in the middle of the system. The moons orbit not one object but two. Pluto has a very large, close moon called Charon, and the two orbit around each other like two unequal weights at the ends of a dumbbell. I could imagine that this might prevent the moons from ever reaching synchronous lock.
Imagining it and proving it are two different things. Most orbit simulators track the position but not the orientation of the bodies in the system. I had to re-learn the physics of rigid body rotation and build my own simulator. The movie published today shows the results of that study. Caution: May cause vertigo.
After that, I knew this was not going to be just a short discovery paper. I also knew that I had better check every other detail of the system just in case the Pluto system held more surprises. I was not disappointed.
For example, we have determined that Kerberos is an oddball–an extremely dark object in the midst of much brighter moons–a charcoal briquette surrounded by dirty snowballs. Hypothesis #1: A snowman broke apart and Kerberos was one of the eyes. Hypothesis #2: Kerberos is a monolith. Seriously, we don’t know what to make of this result. If the moons all formed at the same time, then we would have expected them to look alike. They don’t.
In the end, the paper is sort of a grab-bag of strange results about the Pluto system. The best I can do to summarize it is to make an analogy. Imagine that you are an archeologist and have just recovered a few fragments of an ancient scroll. The pieces themselves are hard to interpret, but you know they have to fit together in some way that tells a bigger story. In this case, the story is how the Pluto system formed. The full story remains to be told, but now we know that it will have at least a few very interesting paragraphs.
We have added three new historic explorers to the OurPluto ballot today. Keep those great ideas coming in! I have been learning so much.
Several people nominated the renowned 10th-century explorer and cartographer Muhammad al-Idrisi. He traveled as far west as Ireland and as far east as China, mapping much of the known world in the process. His exquisite maps were still being used centuries later. The title of his compendium of geographic information roughly translates from the Arabic as The Pleasure of Him Who Longs to Cross the Horizons. How appropriate it will be for a spacecraft named New Horizons to memorialize his work!
We also learned about for Hyecho, a Korean Buddhist monk who lived in the 8th century. The nomination from East Asia reads as follows: Hyecho was the first man to travel across the Asian continent, from far east to far west, by sea and land and to record his journey. He wrote a travelogue, consisting of originally 11,300 characters, called Memoir of the pilgrimage to the five kingdoms of India during his journey. The work of Hyecho offers a full account of a long journey that lasted four years spanning 9,000 kilometers in distance by ship, and 11,000 kilometers by land. To this day, It is praised as a valuable archeological and anthropological reference for its unprecedentedly comprehensive scope and depth.
Looking back to the way home under the reflection of moonlight
I see only the clouds floating
Though a letter was sent on a cloud
a gusty wind blows away its answer
-Hyecho (704-787 CE)
Finally, this is the nomination for a remarkable woman named Isabella Bird: Born in Yorkshire England in 1831 she holds a special place in history. Isabella was the first woman to be elected Fellow of the Royal Geographical Society. Isabella battled with ill health all her life. However this did not stop her traveling the world and writing many incredible books about her travels. She visited Australia, Hawaii, America (where she traveled over 800 miles on horseback and met some very interesting characters including one-eyed outlaw Jim Nugent “Rocky Mountain Jim”). Battling ill health she went traveling to Asia: Japan, China, Vietnam, Singapore and Malaysia. At nearly 60 years of age she set off for India covering Ladakh on the borders of Tibet, and then travelled in Persia, Kurdistan and Turkey. In India, she worked with Fanny Jane Butler to found the John Bishop Memorial Hospital in memory of her recently deceased husband. The following year she joined a group of British soldiers traveling between Baghdad and Tehran. She remained with the unit’s commanding officer during his survey work in the region, armed with her revolver and a medicine chest supplied – in possibly an early example of corporate sponsorship – by Henry Wellcome’s company in London. By now Isabella was a household name in the Royal Geographical Society. Her final great journey took place in 1897 where she travelled up the Yangtze and Han rivers which are in China and Korea, respectively. Later still, she went to Morocco, where she travelled among the Berbers and had to use a ladder to mount her black stallion, a gift from the Sultan. She died in Edinburgh within a few months of her return in 1904, just shy of her seventy-third birthday. She was still planning another trip to China. What an amazing achievement for a person who battled with severe illness her entire life. Horizons exploration of Pluto should give credit to this amazing explorer by having a piece of Pluto named after her.
We continue to receive a fascinating collection of nominees for the OurPluto campaign. Here are a few that we recently added to the ballot.
Several wrote to remind us of the iconic prints by Gustav Doré, a French artist from the 19th century who illustrated an 1861 edition of Dante’s Inferno.
In the category of historical explorers, we learned about Michał Boym: “He is notable as one of the first westerners to travel within the Chinese mainland and his Flora Sinensis was the first description of an ecosystem of the Far East published in Europe. Boym also published the first dictionary to translate between Chinese and European languages.
Another historic explorer reminds of the roles that serendipity and patience play in all of science: Marcelino Sanz de Sautuola, who discovered the first prehistoric cave paintings known to the modern world. “He was a Spanish amateur archaeologist and explorer of the Cave of Altamira. These caves provide a window into human development, much as Pluto provides a window into Solar System development. Although Sautuola’s discoveries were discredited by experts early on, he was later completely vindicated and his discoveries appreciated, albeit after his death.”
Finally, a New Jersey professor provided a very good reason for his endorsement of Krun, a monster of the darkness. “I’m trying to raise awareness of the Mandaean community of Iraq and Iran. They are one of the few communities from the Middle East that still preserve the ancient Babylonian tradition of divination by the stars and heavenly bodies (astrology), directly from the source (they even retain the traditional Akkadian names for the stars and the visible planets). [….] Unfortunately, with the Second Gulf War, their community (a minority faith in both Iraq and Iran) has become progressively endangered, and much of it has gone into a global diaspora. The lives of those that remain and their ancient culture are threatened by religious extremists, such as ISIS, who seek to eliminate anything pre-Islamic in the Middle East. I hope that OurPluto can establish a monument to them in the heavens, where these extremists cannot reach them.”
The OurPluto naming campaign has been an exhilarating experience for me so far. The amount of thought that our site visitors have been putting into their nominations astounds me. You can visit the Site News page for regular updates. Today I would just like to highlight a few of the new names that we added to the ballot last night.
On the list of scientists and engineers, we have added Carl Pulfrich, 1858-1927. Although he died before the 1930 discovery of Pluto, he contributed in a critical way—he invented the blink comparator. This is a device that lets you switch back and forth between two sky plates, looking for subtle changes. Clyde Tombaugh discovered Pluto using a blink comparator. The discovery would not have been possible without the device.
From Europe, we were reminded of the importance of the Soviet The Luna Program: “Luna was a series of robotic spacecraft missions sent to the Moon by the Soviet Union between 1959 and 1976. Fifteen were successful, each designed as either an orbiter or lander, and accomplished many firsts in space exploration. They also performed many experiments, studying the Moon’s chemical composition, gravity, temperature, and radiation. Twenty-four spacecraft were formally given the Luna designation, although more were launched.”
Two prominent women explorers were also nominated. For Alexandrine Tinné, who explored the Nile and the Sahara in the 1860s, the nomination reads, “It is rare that we take the opportunity to praise some of the women who have contributed to the exploration of our world. Ms. Tinné was courageous, dedicated, and passed on a legacy of adventure for today’s women to aspire to.”
We also learned about Jeanne Baré who, a century earlier, became the first woman to circumnavigate the globe. She was naturalist studying the world’s plants. However, times being what they were, she had to impersonate a man for the journey.
Our fictional explorers now include several popular nominees. Among others, we include a pair of the great travelers in literature, Don Quijote and his patient squire Sancho Panza.
In the category of Underworld beings, we learned that the King of the Underworld in Vietnam has a Pluto connection. “Diem Vuong is the King of Hades. Demons obey and serve him. He is the ruler of the underworld and the judge of the bad souls after death. Diem Vuong once upon a time has been added to form “Diem Vuong Tinh” to name for Pluto in Vietnamese.”
In Inuit mythology, we learned that the realm of the dead has an astronomical connection. The souls of the dead first spend time under ground in Adlivun, but later ascend to a permanent home in Quidlivun, on the Moon.
Pluto is just 3.5 pixels across in the latest images from the New Horizons spacecraft. That’s nine square pixels. You can’t do much with nine pixels. You might be able to see crude patterns of light and dark, but you probably wouldn’t call it a map. Still, it’s a start.
In a few months, this will all change. Craters, mountains and other landforms will take shape before our eyes. When New Horizons flies past Pluto in July, we will see a new, alien landscape in stark detail. At that point, we will have a lot to talk about. The only way we can talk about it is if those features, whatever they turn out to be, have names.
Today we are beginning a campaign called “Our Pluto”. The goal is to gather together the names that we will eventually use to label the maps of Pluto and its large moon, Charon. After discussions with the International Astronomical Union (IAU), we have defined a set of broad themes for these names, related to mythology, literature and history.
The New Horizons science team is doing something unprecedented. Naming campaigns have been held before, but on a different scale. Today, the entire landscapes of Pluto and Charon is open to the public. We have called the campaign “Our Pluto” because we think that everyone should have a say in the names we use on those strange and distant worlds. At ourpluto.seti.org, you can vote for your favorite names, talk about them, and nominate names that we might have overlooked.
After the campaign ends, the New Horizons science team will select your best ideas and pitch them to the IAU. The IAU will have final say over the names on the maps of Pluto and Charon.
Let the conversation begin!
The name Eadweard James Muybridge does not roll off the tongue, but we have all seen his images. In the earliest days of photography, he pioneered the use of the newly-invented camera to study animals and people in motion. In his classic studies of horses, for example, he demonstrated for the first time that there exists a moment in the cadence of a trotting horse when it is airborn–all four feet are off the ground. The technical setup required to obtain one of these sequences was substantial. Each image was taken by a different camera, which was triggered by a separate thread as the horse passed by.
Needless to say, the cameras of the 19th century lacked “burst mode”, or even auto-advance, or even film. These are the features that have made it trivial for 20th- and 21st-century photographers to capture a similar sequence of images. Today, I can just set my iPhone on video mode and let it do all the work.
However, one truth about action photography has never changed–you need to follow the motion. Otherwise, you will get nothing but a blur. Save your tripod for subjects that are willing to sit still. Had Muybridge attempted the same photo sequence without all those separate triggers, his image would have looked something more like this. All background, no horse!
So it is, strangely enough, when trying to take pictures of distant moons. Like fidgety children, moons are unwilling to sit still for the camera. This is the challenge we dealt with in finding a tiny moon of Neptune whose discovery was announced today. It has a special distinction–it never sits still long enough to have its picture taken. Neptune is a big planet with a strong gravity field, and moons whip around it very fast. This one circles the entire planet, following a path of over 600,000 km, in less than a day.
The moon is also very small and dark. We estimate that it is no more than 20 km across and as dark as if it were paved with dirty asphalt. Naturally, taking its picture requires long exposures. But there’s the rub. If you expose it for too long, the moon vanishes in a blur, much like the disappearing racehorse above.
The images in which we found tiny “S/2004 N 1″ (don’t worry, it will get a better name soon!) were taken by the Hubble Space Telescope between 2004 and 2009. In fact, these images have been freely available to anyone in the world, some for almost a decade. However, what they have in common is that they were all taken by keeping the camera fixed on Neptune. In the past, we have always discovered moons just by stacking up images like this, or perhaps animating them into a movie, and seeing what turns up. This actually works fine for Pluto, a dwarf planet with a weak gravity field. The small moons of Pluto, including the recently-named Kerberos and Styx, take weeks to circle Pluto, so summing up a few hours of data works just fine. Not so at Neptune.
Once the images are on the ground, it is too late to track the motion of a tiny moon. Besides, if we don’t know where a moon is, how could we know how to track it? The solution we found builds on the fact that moons are a bit more predictable than racehorses and fidgety children. We might not know where the moons are, but we do know how they move. As a result, we were able to write software to do all the motion-tracking, by letting a computer shift and add up the images after the fact. The procedure I devised predicts where any given moon ought to move from one image to the next, and then combines the images with a “twist” that compensates for the expected motion. I developed this procedure (and I am certainly not the first) to study some peculiar arcs in the rings of Neptune. However, I soon realized it could be useful for moons as well. It was only when I expanded my analysis out to regions well beyond Neptune’s ring system that an extra little dot turned up, over and over again. In less than a week, we went from our first detection to ten.
The discovery of one little moon might not be Earth-shaking, but somehow it is has to fit into the big picture of how the Neptune system formed. Astronomers had long noted that the moons of Neptune get progressively smaller as you go inward. However, this little rock, orbiting between 200-km Larissa and 400-km Proteus, throws a bit of a wrench into that simple story.
What we do know is that Triton, a very large moon, got captured into orbit around Neptune eons ago. Triton’s distinction is that it orbits backwards, circling the planet opposite to the planet’s rotation and opposite to the direction of the other moons. We can be pretty sure that when Triton arrived, it disrupted whatever system of moons was originally circling Neptune. The moons that we see today somehow re-formed after that event. With the discovery of S/2004 N 1, the key points of this story have not changed, but we now have one more piece of the puzzle to fit into place.
Pluto needs more moons!
In addition to surpassing 220,000 votes in just a bit over three days, we have received about 15,000 nominations for alternative names. Today I have just added eight more to the ballot, selected from among the most popular nominees. (more…)
We have made our first addition to the ballot. Vulcan is the Roman god of lava and smoke, and the nephew of Pluto. (Any connection to the Star Trek TV series is purely coincidental, although we can be sure that Gene Roddenberry read the classics.). Thanks to William Shatner for the suggestion!
So what do you think of the idea of naming the two moons of Pluto Vulcan and Romulus?You have mythology, pos and neg plutorocks.com/ground-rules
— William Shatner (@WilliamShatner) February 12, 2013
The naming of a moon is a rare privilege for any astronomer. Fewer than 200 moons have been discovered orbiting the Solar System’s planets (dwarf or otherwise).
Over the centuries, the astronomical community has established standards for the naming of moons. Most names come from ancient mythologies. The moons of Uranus are the exception, with names coming primarily from the works of William Shakespeare.
These rules ensure that newly-discovered moons receive names that have already stood the test of time. The same names will still be in use centuries and even millennia from now. Whereas today’s literature might be long forgotten, we can be confident that future generations of astronomers (and maybe even astronauts) will still recall the stories from Mount Olympus and Stratford-upon-Avon.
I suspect these naming traditions did not arise by accident. For whatever reason, we humans seem to have a deep-seated, pre-scientific need to interpret the night sky in terms of stories. Naturally, we choose the big stories, involving grand themes, great powers and deep mysteries.
I was previously involved in the naming of three moons: Pan at Saturn, plus Mab and Cupid at Uranus. In each case, the process was simple and straightforward. We pulled out our dusty old copies of Bullfinch’s Mythology or the Riverside Shakespeare and started browsing. (In each case, I also experienced a wistful regret that I had not spent more time studying literature in college, back when I still had the opportunity.)
When we announced the discoveries of Pluto’s fourth and fifth moons, it became clear to me that the naming process might have to be different. This time, I received hundreds of spontaneous, unsolicited suggestions. I suspect that some of the world’s affection for Pluto comes from its so-called “demotion” to dwarf planet status. Perhaps it is also because the names of Pluto’s moons are all associated with Hades and the Underworld, the stuff of so many of our most primal fears. Whatever the reason, the discovery team has decided that it would be unfair to keep the naming process to ourselves.
Starting today, we are trying something new. We are asking the public to help us name the moons. Visit plutorocks.seti.org and tell us what you think. We have seeded the ballot with a few names, or you can propose your own. The names will still have to be approved by the International Astronomical Union, but we will use your votes to help us decide the names we propose.
Please join us in adding the next chapter to the story of Pluto.