2014 MU69 revealed as a contact binary in first New Horizons data returns
It’s a contact binary, two different spherical rocks permanently touching each other and bound together by each other’s gravity. And that’s just the tip of the proverbial iceberg when it comes to 2014 MU69, the small little red world in the center of the Kuiper Belt that NASA’s New Horizons spacecraft flew by for close-range exploration less than two days ago.
New Horizons begins to unlock 2014 MU69’s mysteries:
Yesterday, Principal Investigator Alan Stern said that if he had to bet, his money would be on 2014 MU69 being a single object – a prediction agreed to by others on the panel.
But two new images of the Kuiper Belt world taken from a no-closer distance of 50,000 km by New Horizons reveal 2014 MU69 to be a contact binary, meaning it is composed of two spherical objects that formed separately before gently easing together to form the object we see today.
This easing together of the two lobes of 2014 MU69 occurred over 4 billion years ago at speeds between 1 to 2 miles per hour, according to Jeff Moore of the geography and geophysics investigation teams for New Horizons.
A primordial element from the formation of our solar system, the bilobate 2014 MU69 took a few hundred thousand years to a million years to form from a scattering of small rocky objects gravitationally swirling around each other that gradually formed two large spherical rocks.
These two rocks were then pulled together by the extremely weak gravitational forces of each other, nudging together at such slow speeds that initial observations from New Horizons do not reveal any stress fractures or damage from the “collision”.
So gentle was the initial contact between the two lobes of MU69 that Mr. Moore related it to getting into a fender bender car accident that produces no damage; you wouldn’t bother filling out the insurance claim.
Mr. Moore confirmed that the two lobes are “soundly bound” to each other, with Alan Stern adding that their mutual gravity holds the two together.
What is perhaps most exciting about the final confirmation that 2014 MU69 is a contact binary is that it begins to solidify models of solar system formation and planetary accretion.
For quite some time, this model has relied heavily on the theory that small pieces of dust in the protoplanetary nebula surrounding the Sun after its birth collided with each other and stuck together to form larger specs of dust.
Those larger specs then continued to clump together until objects greater than 1 kilometer in size formed and began attracting each other with their gravity… and so on to form the larger objects in our solar system today.
“This is what we need to move the models of planetary formation forward,” said Alan Stern. “This is how science works. The theorists have ideas, they do computer modeling, they think hard about problems. They take the available data. And different models produce different outcomes.
“But then you need more data in order to distinguish between those models. And in the last 36 hours, NASA and New Horizons have collected more data about the formation of the solar system, in particular the planetesimals in the Kuiper Belt, that now let us choose between models or tell which models are more likely to be right than others.”
While contact binaries have been observed in the solar system already, what’s exciting about 2014 MU69 is that we know definitively that this is how it formed, as a contact binary, and not what it was shaped into via interactions with planets, the Sun, or through sublimation and structural collapse changes.
The known specifics:
With the obvious warning that with only 1% of the data in-hand that some of this will change, here’s what we currently know about 2014 MU69 based on those initial science returns.
The object is composed of two distinct lobes in contact with each other, with a 3-1 ratio in terms of their respective size. The larger lobe is the “bottom” sphere and the smaller lobe is the “upper” sphere.
The team has nicknamed the larger lobe “Ultima” and the smaller lobe “Thule” – much the same way they gave unofficial names to the regions and features of Pluto and Charon before submitting the names for formal approval to the International Astronomical Union.
The New Horizons team has also been able to determine a rough calculation for 2014 MU69’s rotation period at 15 hours +/- 1 hour, meaning that more than half of the object was in daylight as New Horizons passed and was therefore observed.
The Kuiper Belt body also has an extremely low surface reflectivity, with the New Horizons team likening it to dark potting soil in a garden.
Pre-flyby observations made by the Hubble Space Telescope indicated that MU69’s surface was red in color, and that has proven true – with the reddish hue indicating the presence of tholins, which are processed volatile ices.
Exactly what ices – methane, nitrogen, or something else – is not yet known.
The less-red areas near 2014 MU69’s neck – the connection point between the two lobes – carries a higher albedo or reflectivity than the rest of the so-far-observed rockey world, indicating the presence of fine grain particles in the neck region.
The neck area is also sloped enough that objects and fine grain elements can tumble or roll down the slopes and settle in the valley where the two lobes meet – something which likely explains the higher albedo seen in the data thus far returned from New Horizons.
While much higher-resolution images will provide a better sense of the topography and geography of 2014 MU69, what is currently known is that the bottom, larger lobe (“Ultima”) contains changes in elevation greater than one kilometer and that the upper, smaller lobe (“Thule”) may contain a plateau feature.
Also interesting in the returned images is the lack of observable craters.
“Theoretical studies suggesting what the crater rate in this part of the solar system might be suggest that MU69 could be very underpopulated with small craters compared to the asteroids or something in the inner solar system,” said Jeff Moore. “We may discover that it doesn’t have many craters and we may very well find that most of the surface texture is dominated by the slow accretion processes and not the high-energy impacts that cause craters.”
Alan Stern cautioned, though, that this might change and sought to lay out why we might not be seeing craters just yet.
“Unfortunately the approach images we’re showing you that came down first just aren’t conducive to determining whether there are craters on the surface or not,” said Mr. Stern. “We’re not saying there aren’t craters. What we’re saying is that the lighting geometry on approach with the Sun behind the spacecraft’s back makes it hard to see whether the features on the surface are craters are not.”
Mr. Stern added that images acquired when New Horizons flew around the side of 2014 MU69 will create a better phase angle between the Surface and the sunlight and should allow the team to make a “definitive determination and ultimately will count the number of craters” on MU69.
Additional information will be released at 14:00 EST (1900 UTC) Thursday, 3 January 2019 by the New Horizons team.
New Horizons' Historic Flyby of Ultima Thule Reveals 'Entirely New Kind of World'
NASA’s New Horizons spacecraft has just completed its newest flyby – of the Kuiper Belt Object (KBO) called Ultima Thule (aka 2014 MU69). New Horizons sped past the small but intriguing little world at 12:33 a.m. EST on Jan. 1, 2019. The event marks a milestone for the most distant object in the Solar System ever to be visited by a spacecraft from Earth. The good news was first reported during a NASA press conference on January 1. The flyby has revealed an “entirely new kind of world” according to today’s follow-up press conference.
“This flyby is a historic achievement,” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “Never before has any spacecraft team tracked down such a small body at such high speed so far away in the abyss of space. New Horizons has set a new bar for state-of-the-art spacecraft navigation.”
“Congratulations to NASA’s New Horizons team, Johns Hopkins Applied Physics Laboratory and the Southwest Research Institute for making history yet again. In addition to being the first to explore Pluto, today New Horizons flew by the most distant object ever visited by a spacecraft and became the first to directly explore an object that holds remnants from the birth of our solar system,” said NASA Administrator Jim Bridenstine. “This is what leadership in space exploration is all about.”
Some of the basic surface features seen so far. Image Credit: Image Credit: NASA/JHUAPL/SwRI
The new images – taken from as close as 17,000 miles (27,000 kilometers) during approach – revealed Ultima Thule to be a “contact binary,” consisting of two connected spheres. End to end, the little world measures 19 miles (31 kilometers) in length. The team has dubbed the larger sphere “Ultima” (12 miles/19 kilometers across) and the smaller sphere “Thule” (9 miles/14 kilometers across).
One of the most prominent features is a distinct brighter “band” circling the “neck” where the two spheres connect. Scientists don’t know how it formed yet, but it may be composed of smaller grains of material that accumulated in the neck crevice. Scientists said the two lobes probably came into contact with each other very, very slowly, no faster than two cars in a fender-bender.
This is the first time ever that humanity has explored an object in the Kuiper Belt, the region of asteroid-like bodies in the outer Solar System, out past the orbit of Neptune.
Signals from the spacecraft reached the mission operations center at the Johns Hopkins Applied Physics Laboratory (APL) yesterday at 10:29 a.m. EST, almost exactly 10 hours after New Horizons’ closest approach to the object.
“New Horizons performed as planned today, conducting the farthest exploration of any world in history – 4 billion miles from the Sun,” said Principal Investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado. “The data we have look fantastic and we’re already learning about Ultima from up close. From here out the data will just get better and better!”
Scientists show off space snowman, Ultima Thule, in 3D
The newly visited space snowman — the most distant object ever explored — is now appearing in 3D.
At a news conference Thursday, scientists and others put on 3D glasses to see the city-size, two-sphered cosmic body in stereo, revealing possible curvy ridges. Ultima Thule, as it's known, is still not showing any signs of craters, moons or rings.
Photos taken by NASA's spacecraft New Horizons during a flyby earlier this week revealed that Ultima Thule (TOO-lee) has two reddish globes joined by a narrow neck, much like a snowman. It is 4 billion miles (6.4 billion kilometers) from Earth.
"The Prize!! For those of us who waited with bated breath for the Ultimate Stereo of Ultima Thule ... here it is!" tweeted May.
Mark Showalter of the SETI Institute in Mountain View, California, said he expects to know within weeks or months, once better images arrive, whether Ultima Thule has any tiny moons or faint, narrow rings. He suspects there might be at least a couple moons a few hundred miles (kilometers) out. The data covering that area are still aboard the spacecraft, he noted.
As for impact craters, lead scientist Alan Stern said he'd be surprised if none turn up. If they are there, they will create a window into the interior "so they're super valuable tools."
For the next several days, data transmission will be halted temporarily because of the sun's position smack between Earth and Ultima Thule, creating radio interference.
It will take nearly two years for all of the data to be transmitted to Earth, given the vast distance.
Ultima Thule is deep within the so-called Kuiper Belt, or Twilight Zone, well beyond the orbit of Neptune. In 2015, New Horizons first visited Pluto, which is barely in the Kuiper Belt, a full 1 billion miles (1.6 billion kilometers) closer to Earth.
Since Tuesday's close approach, New Horizons is already 3 million miles (5 million kilometers) deeper into that mysterious region. It will keep pressing farther out, observing other objects from afar, and measuring dust and particles.
Stern hopes to get another mission extension from NASA, so another flyby can be arranged sometime in the 2020s.
In the meantime, he'll come up with a formal name for Ultima Thule, to recommend to the International Astronomical Union, the deciding body. He acknowledged its current nickname may wind up on the short list.
"Everybody knows it as Ultima Thule," he noted.
NASA's New Horizons mission reveals Ultima Thule in 3-D
The New Horizons science team created the first stereo image of Ultima Thule, which can be viewed with blue-and-red 3-D glasses. (NASA)
Get out those blue-and-red glasses, space lovers. NASA’s New Horizons mission just revealed a new image of Ultima Thule in 3-D.
The stereo image shows the three-dimensional shape of Ultima Thule, a peanut shaped world about 20 miles long, and the most distant object ever visited by humankind.
The New Horizons spacecraft sped past the Kuiper Belt object on New Year’s Eve, filling its servers with data on Ultima Thule’s size and shape, the number of craters it has, whether it has moons or an atmosphere, and what ices appear on its frozen surface.
Three days after the historic flyby, less than 1% of the data from those observations has been sent back to Earth, and no more is expected for several days.
Beginning Friday, New Horizons will fly almost directly behind the sun in relation to the Earth, said Alan Stern of the Southwest Research Institute and the principal investigator of the mission.
Radio interference from the sun’s outer atmosphere will prevent any data transmissions from the spacecraft until Jan. 10, Stern said.
In the meantime, scientists will continue to puzzle over the images and measurements they do have of this distant and mysterious world, 4 billion miles from Earth.
As the stereo image shows, Ultima Thule is comprised of two spherical objects.
Scientists believe the two objects came together in a slow-motion impact early in the solar system’s history. Neither of the spheres is perfectly round. They both appear to have a significant number of lumps.
It is too soon to tell whether these lumps are caused by craters that excavated parts of its surface, or ridges that rise above it, said Paul Schenk, a New Horizons co-investigator from the Lunar and Planetary Institute in Houston.
“We need to be careful when interpreting images like this,” Schenk said. “We think what we are seeing could be interpreted as ridge structures, but we’ll have to get back to you on that.”
More detailed images that are expected to arrive on Earth later this month and in February should help clarify the small world’s topography, he said.
So far, the team has found no evidence of an atmosphere around Ultima Thule, which is to be expected. It is a small world, roughly the size of the city of Washington, D.C., and unlikely to have even a thin atmosphere like the one on Pluto. But scientists said they will continue to evaluate New Horizons data for any evidence of unexpected gases in Ultima Thule’s vicinity.
There has also been no evidence yet of any moons or satellites orbiting Ultima Thule, which is a bit more frustrating. The discovery of any moon on any orbit in the vicinity of the bi-lobed object would allow scientists to determine its mass and density, said Mark Showalter, a New Horizons co-investigator from the SETI Institute in Mountain View, Calif. That information would in turn offer clues to the composition of its interior, he said.
The discovery of a moon or moons would also help scientists understand Ultima Thule’s spin rate.
Ultima Thule currently takes about 15 hours to complete one full rotation on its axis, but computer models suggest that it was spinning much faster when the two objects first came together, Showalter said. It is likely that gravity from a nearby object or several objects caused it to slow down.
“Something had to put the brakes on it,” he said.
He is hopeful that images of Ultima Thule in its immediate environment will hold some answers.
“As soon as they hit the ground we will look to see if we can find a moon or two in that data set,” he said.
Future information will also reveal more details about the color differences on Ultima Thule’s surface and allow scientists to create maps of its surface composition, researchers said.
It is clear that the surface of Ultima Thule is a deep red color, but scientists cannot say definitively why. They should know soon.
For now, the science team will analyze and try to draw additional conclusions from the data it does have.
Quelle: Los Angeles Times
New Horizons probe delivers 3-D views of cosmic snowman, plus mysteries to solve
LAUREL, Md. — The science team behind NASA’s New Horizons spacecraft today released the first 3-D image of an icy object more than 4 billion miles from Earth, and the variations in the picture hint at ridges, craters and knobby features that will be more fully charted as the resolution improves.
Two pictures, separated by just a moment in time, were fused together to produce a somewhat fuzzy but depth-enabled glimpse at the object — which has the official designation of 2014 MU69 but has been nicknamed Ultima Thule by the New Horizon team.
“Features appear to be rotating into view as the object twists underneath us,” Paul Schenk, a New Horizons co-investigator from the Lunar and Planetary Institute, said during today’s briefing here at Johns Hopkins University’s Applied Physics Laboratory. “These have a knobby appearance, and could be the inside of a large impact crater that’s on the far side.”
The stereo view also appears to highlight ridge structures on the 19-mile-long object, which has been compared in appearance to a snowman or the BB-8 droid from “Star Wars.” Some of the ridges could represent elevation variations amounting to several hundred feet, he said.
Schenk said a side-by-side version of the 3-D images was created by Brian May, an astrophysicist specializing in scientific stereoscopy who also happens to be the lead guitarist for the classic rock group Queen.
New Horizons’ researchers emphasized that their findings were still highly tentative, coming only three days after New Horizons zoomed past Ultima Thule at 32,000 mph, at a distance as close as 2,200 miles.
The mission’s principal investigator, Alan Stern of the Southwest Research Institute, said the piano-sized spacecraft has already gone 3 million miles beyond Ultima, blazing a trail through a sparsely populated, icy zone of the solar system known as the Kuiper Belt.
Today the probe made its final observations looking back at the environment around Ultima Thule, a Latin term that signifies “a place beyond the known world,” and turned its instruments to the unknown worlds ahead, Stern said. He said data transmissions back to Earth will be suspended for several days due to solar interference, and resume on Jan. 10.
It’ll take 20 months to downlink several gigabytes’ worth of data from the close flyby on the night of Dec. 31-Jan. 1, due to New Horizons’ limited transmission capability and the extreme distances involved.
The Ultima encounter is the latest chapter in a saga that began with New Horizons’ launched in 2006 and reached a crescendo in 2015 when the probe flew past Pluto. Even before the Pluto flyby, the mission team identified 2014 MU69 — a billion miles beyond Pluto — as a worthy follow-up target. Part of the reason for looking ahead now could well be to identify yet another Kuiper Belt object for close study.
Along the way, New Horizons’ instruments will continue to sample the solar wind and particle flux in the solar system’s least-explored zone.
Many mysteries still surround Ultima, which scientists see as a relic of the early solar system that looks much as it did 4.5 billion years ago. One mystery has to do with the object’s snowman shape.
Mark Showalter, a New Horizons team member from the SETI Institute, said the fact that Ultima has two roundish lobes would suggest that it was once surrounded by moonlets or other debris.
That surmise is based on a series of computer simulations for the formation of planetesimals like Ultima. The outlying objects would have carried off enough angular momentum to allow the two largest objects to fuse together gently.
“A very common scenario was two objects in the center, and a few more objects outside,” Showalter said.
Showalter said “we’re looking for the objects that put on the brakes.” But no moons or rings of material have been detected in the imagery that’s been downlinked so far.
Such features could show up on imagery yet to be sent back to Earth. But there’s also a good chance that the outlying objects went their own way long ago. “It’s quite possible that we will never actually see the culprit,” Showalter said.
Other scientists are looking for any signs of a faint atmosphere or a haze of dust surrounding Ultima, but nothing has been detected yet.
Ultima Thule Animation
In this animated GIF of Kuiper Belt object Ultima Thule made from two images taken 38 minutes apart, the "Thule" lobe is closest to the New Horizons spacecraft. As Ultima Thule is seen to rotate, hints of the topography can be perceived. The images were taken by the Long-Range Reconnaissance Imager (LORRI) at 4:23 and 5:01 Universal Time on January 1, 2019 from respective ranges of 38,000 miles (61,000 kilometers) and 17,000 miles (28,000 kilometers), with respective original scales of 1017 feet (310 meters) and 459 feet (140 meters) per pixel.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons carries seven scientific instruments, which collect several types of data. (The instrument names and main functions are described in the science payload section) As an instrument makes an observation, data is transferred to a solid-state recorder (similar to a flash memory card for a digital camera), where they are compressed (if necessary), reformatted and transmitted to Earth through the spacecraft's radio telecommunications system.
The Data Rate Challenge
A major challenge for the New Horizons mission is the relatively low "downlink" rate at which data can be transmitted to Earth, especially when you compare it to rates now common for high-speed Internet surfers.
During the Jupiter flyby in February 2007, New Horizons sent data home at about 38 kilobits per second (kbps), which is slightly slower than the transmission speed was for acoustic computer modems which operated over telephone lines. The average downlink rate after New Horizons passed Pluto (and sent the bulk of its encounter data back to Earth) was approximately 2,000 bits per second, a rate the spacecraft achieved by downlinking with both of its transmitters through NASA's largest antennas. Even then, it took until late 2016 to bring down all the encounter data stored on the spacecraft's recorders.
Since NASA's Deep Space Network has to track other missions besides New Horizons, the team produced a lossy compressed browse data set that could be sent d
Pluto Probe Encounters a Pristine World in the Solar System’s Suburbs
Ultima Thule, the most-distant object ever visited by a spacecraft, is revealing our solar system’s deepest history—and, just maybe, revolutionizing planetary science
The history of the solar system is a dish best served cold. And it is so very cold on Ultima Thule.
That is the message beaming back to Earth from NASA’s New Horizons probe now that it has completed its historic exploration of a small body in the Kuiper Belt, the sprawling population of dwarf planets and cometlike objects out beyond Neptune. When New Horizons flew past at 12:33 AM Eastern time on January 1, Ultima was a hair over four billion miles from the sun. It is by far the most distant object ever visited by spacecraft, and correspondingly one of the coldest: about 35 kelvins, or nearly 400 degrees below zero Fahrenheit.
At such low temperatures, Ultima (more formally known by its scientific designation, 2014 MU69) preserves its initial, ancient composition. Ultima is also cold in another, more specialized and intriguing way. It is dynamically cold, part of what’s known as the “cold classical” Kuiper Belt, meaning that it circles the sun in a settled orbit that was undisturbed by all the chaotic events that buffeted Earth and other planets as they came together more than four billion years ago.
Prior to the encounter, the great hope of the New Horizons team was that they would see an intact survivor from the solar system’s birth. The first images of Ultima, showing its delicately stacked snowman shape, fully vindicate those hopes. It matches up exactly with models of how clouds of gas and dust around young stars clump together into larger and larger objects—a process that has been well studied in theory, but never observed in reality until now. “We’re looking at one of the first building blocks that came together to form the planets and moons,” says Jeffrey Moore, a research scientist at NASA’s Ames Research Center. “It looks like somebody left it out in the back of God's freezer for the last four-and-a-half billion years.”
LONG WAY TO THE KUIPER BELT
Being left out in the cold is an all-too-familiar feeling for Alan Stern, principal investigator of New Horizons. He had started campaigning for NASA to mount a mission like the one to Ultima in the 1980s, long before anyone even knew Ultima existed. His original goal was to visit Pluto, completing the exploration of the then-nine planets, but the plans went nowhere. Befitting their outsider status, Stern and other like-minded outer-solar system fans called themselves the “Pluto Underground.”
Scientific interest in Pluto exploded in the 1990s, when astronomers discovered it is just one part of the much grander Kuiper Belt. Even so, Stern watched three different mission concepts wither and die. It took another decade, a cancellation, and a rare resurrection before New Horizons launched on January 19, 2006.
The probe’s nominal objective was only to visit Pluto and its moons, but from the start Stern had a second act in mind. “New Horizons is a very healthy spacecraft, and it has the power to operate for another 15 or 20 years,” he says. Why waste a once-in-a-lifetime opportunity to explore more of the Kuiper Belt? A 2015 flyby revealed Pluto as an excitingly dynamic world, but in some ways it is too dynamic: Its active geology (plutology?) has erased much of its early history. A visit to a much smaller, more pristine follow-on target would fill in a huge missing piece of the reconnaissance of the solar system.
The huge catch was that there was no suitable target in astronomers’ catalogues; the New Horizons team would have to find one themselves, something the spacecraft could reach on its dwindling stores of fuel. That meant marshaling the world’s most powerful telescopes, searching for a dim dot of light moving slowly among a thicket of background stars, located in exactly the right spot for an easy interception. Marc Buie of Southwest Research Institute (SwRI) describes his work leading that search. “I spent 10 years looking for an object for New Horizons to go to,” he says with admirable sangfroid. “I’ll let you in on a little secret: When you take photographs through a telescope, they don’t come with arrows on them to tell you what to look at.”
Finally, Buie spotted it. The telltale blip consisted of just 144 photons in a survey image from the Hubble Space Telescope, “but the instant I saw it, I got a chill. I knew it was The One.” As recognition of its importance increased, the object originally catalogued as 1110113Y became Potential Target 1, then Kuiper Belt object 2014 MU69, and most recently it was informally dubbed Ultima Thule (a name which has generated some unfortunate controversy).
When the first high-resolution images of Ultima arrived from New Horizons, all those past agonies vanished from the scientists’ minds, replaced by backslaps and oversize, unshakable grins.
“It’s a snowman!” Stern laughed as he looked at Ultima’s iconic, double-lobed shape. Or in scientific terms, he notes, it is a “contact binary,” two objects that formed separately but are now held together by their mutual gravity. The larger lobe is three times the size of the smaller one; stacked together, they measure 21 miles long.
That snowman structure is precisely what the New Horizons team was hoping to find in the Kuiper Belt. “The number-one thing I wanted to get out of this mission was incontrovertible evidence that we're looking at a primordial, unaltered object,” Buie says. More specifically, he wanted to witness an object frozen time from the moment when small bodies in the solar system began accreting together and building up bigger ones.
On planets and moons all evidence of that process was wiped clean by subsequent geologic activity. Even on relatively primitive comets like 67/P Churyumov-Gerisamenko—the “rubber duck” comet studied until 2016 by the European Space Agency’s Rosetta probe—the surface has been extensively cooked and altered by the sun’s heat. Moore breezily dismisses such objects as “post-toasties.”
On Ultima it is as if the birth of the solar system happened yesterday, with two planetesimals (the first large conglomerations of rock, dust and ice to coalesce around a young star) still lumped together right before New Horizon’s digital eyes. “I looked at it and thought, ‘I see accretion happening’,” Buie says. “This is going to revolutionize our view of where we came from and how this whole process works.”
DO YOU WANT TO BUILD A PLANET?
In fact, the revolution is already well underway. On the first three days after the Ultima flyby, the members of the New Horizons analysis teams huddled near mission control at Johns Hopkins University Applied Physics Laboratory to make sense of the first data downloads. After all those decades of waiting, Stern is eager to get going. “We will begin writing our first science papers next week!” he promises. But really, nobody was waiting even that long to start digging into the lessons from Ultima.
One of the first orders of business is interpreting how Ultima’s two lobes came together so gently, with a tidy little necklace of brighter material rimming the place where they meet. Bill McKinnon, a planetary dynamics expert at Washington University in Saint Louis, notes objects in the Kuiper Belt are moving so slowly that typical encounter velocities would be around 600 miles per hour, which limits the amount of damage an impact can create.
Ultima apparently came together even more lightly than that. Most likely the two lobes initially formed as separate bodies in orbit around each other, spiraling together until they touched. “It would have been like a parking lot fender bender, walking speed. Also, these are probably very porous objects; they have energy-absorbing bumpers on them,” McKinnon says. As a result, the two lobes stuck together rather than shattering when they touched.
The jammed-together lobes of Ultima provide the most direct evidence yet of the standard hierarchical theory of how planets form: First dust grains stick together into pebbles, which gather into planetesimals. Those accrete into protoplanets, continuing all the way up to bigger things like Earth and Jupiter.
Another notable detail is that, other than the difference in size, the two lobes of Ultima look extremely similar in shape and color. “That’s also consistent with forming as a result of the merger of two objects that formed close together in the protoplanetary disk,” says Silvia Protopapa of the SwRI. In such a chemically and dynamically cold region two neighboring planetesimals should have aggregated from an essentially identical mix of raw materials.
Information still stored onboard New Horizons will reveal much about exactly what those materials are. “We’ll be looking for ammonia, water, carbon monoxide and organics,” Protopapa says. Ultima’s overall red tint already suggests it is covered with tholins (organic compounds processed by eons of radiation), similar to what is seen on many other outer-solar system objects, including Pluto’s moon Charon.
Moore is relieved, if maybe a little disappointed, that nothing about Ultima directly confounds expectations—as would be the case if, say, the two lobes had totally different colors. “To zeroth order, our ideas of how these things formed seem to be vindicated,” he says. “But there's a whole range of specific explanations that people had. It's like going into a restaurant, you can choose from any number of things on the menu. Now that we see Ultima, we know what the good choices on the menu are.”
ULTIMA’S NEXT ACT
These rapid-fire readings of Ultima are all the more impressive considering they were made by highly caffeinated scientists operating on little or no sleep, working with an initial download of just 1 percent of the total data New Horizons collected during its flyby.
Perhaps the most egregious missing data element so far is a clear look at the topography of Ultima: We can see it but we can’t really feel it. The best views released so far were taken with the sun almost directly behind the spacecraft, making it difficult to distinguish hills from depressions on the alien landscape below. Significantly sharper pictures, including ones showing deep shadows, are still sitting on New Horizons’ solid-state recorders. “It’ll take 20 months to empty the recorders of all the data we’ve taken, including hundreds of images and spectra,” Stern says. Blame the extremely limited bandwidth of a spacecraft six light-hours from home.
As the stored information trickles in, you can expect a lot more history lessons. One big hanging question for the planetary scientists is how Ultima’s individual lobes themselves were assembled. Somewhat surprisingly, there’s no unambiguous evidence for craters. There certainly are things that resemble craters, but in the calm environment where Ultima formed those poorly resolved formations might actually be hills that were built up rather than gouged-out pits. “We may find that the texture is dominated by slow-motion [accretionaary] processes,” Moore says. If so, that would reveal a lot about the early stages of planetary formation.
With that thought in mind, Cathy Olkin of SWrRI, a deputy project scientist on New Horizons, is eager to examine how the composition of Ultima varies from spot to spot. Spectral measurements from New Horizons should make it possible to identify the individual splats from ancient impact that stuck to the surface like flies on a windshield. Then she’ll do a census of the splats to understand the objects that created them. “So we will be able to look at the smallest particles in the Kuiper Belt, a population we could not see any other way,” she says.
Perhaps the most subtle but significant surprise about Ultima is that we were able to reach it at all. Recent studies of newborn stars using the Atacama Large Millimeter/submillimeter Array (ALMA) observatory in Chile show many of them seem to be forming planets across a much larger scale than what we see in our solar system, with their versions of the Kuiper Belt taking shape at far greater distances. The vast distance between our sun and Ultima does not look so vast in comparison.
McKinnon throws out another possible history lesson in there: The outer edge of our solar system may have been clipped off by radiation from neighboring stars at a very early stage, he suggests, well before even Ultima formed. “It’s probably defined by the other stars in the sun’s birth cluster, its lost brothers and sisters,” he says.
In the debate over whether our solar system is normal or a cosmic outlier, then, Ultima tips the balance a tiny bit further in the weirdo direction. “Then you consider that the sun is a single star, which is not the norm, and solar-type stars are not the most common stars,” McKinnon says. “You add it up and you think, ‘We’re not exactly a garden variety planetary system.’”
Quelle: SCIENTIFIC AMERICAN
New Horizons in solar communication blackout, team studies first flyby data
As New Horizons and its scientists prepare for the end of a solar conjunction in two days and the resumption of science data downlink from the craft of its historic flyby of 2014 MU69 on New Year’s Day, Alan Stern and his team are busy analyzing the first few datasets returned from the spacecraft before the solar conjunction began on 4 January.
New Horizons current status:
As viewed from Earth, New Horizons is now directly behind the Sun in an alignment known as a solar conjunction. During this period, communications with the spacecraft are not possible due to radio interference produced by the Sun’s atmosphere.
The cessation of communications was known well in advance of the New Year’s Day flyby of 2014 MU69, with the New Horizons science teams understanding they would only get a small amount of data back before all communication with the craft stopped for five days.
he solar conjunction and communications blackout period will end Thursday, 10 January, at which point the steady stream of data from New Horizons will resume. “The data will start to come back down again and begin this long 20-month period in which we’ll be emptying the solid-state recorder of all the different kinds of data we’ve taken – literally hundreds of images and spectra and other data types,” said Dr. Alan Stern, New Horizons Principal Investigator.
It might sound like a funny thing. One of the first things the New Horizon science team is looking for around MU69 is evidence of a moon or moons orbiting the small body.
2014 MU69 is only 21 miles long and significantly smaller in width, and looking for moons might seem counterintuitive. But in fact it is quite vital in terms of understanding the interior composition of this Kuiper Belt Object (KBO).
The importance of understanding 2014 MU69’s interior lies with the body’s importance of understanding the early formation of the solar system and would reveal what was present in the stellar disk of dust and material surrounding the Sun after its birth – the disk from which almost everything we see in the solar system today was created or formed from.
In turn, this would tell us if our current models of solar system formation and development are accurate or if they need to be adjusted based on what 2014 MU69 tells us about what was present in the earliest days of the solar system.
If there are moons orbiting MU69, and those moons were observed by New Horizons for long enough to determine their orbits, that information would be crucial to understanding the interior composition of MU69 because an object’s internal characteristics can be determined from a satellite’s orbit by observing how the orbit is changed by fluctuating gravity of the parent body – in this case 2014 MU69.
While the initial returns from New Horizons reveals no moons, Dr. Mark Showalter, a New Horizons Co-Investigator from the SETI Institute, and his team have already used approach imagery of MU69 to preclude the possibility of a moon 1 mile across at a distance of 500 miles or more from the KBO.
Already returned images of the MU69 flyby have allowed the team to tighten that search and eliminate the possibility of a moon within 100 miles of the surface of this primordial remnant of the solar system.
But that still leaves a 400-mile gap around nearly the entirety of MU69 to search. Despite the sheer amount of space left to explore, Dr. Showalter is confident that if a moon or moons exist, New Horizons will have likely observed it/them during the flyby.
For 2014 MU69, the presence of a moon or moons would not just help scientists understand and categorize the object’s interior but would also help explain its current slow rate of rotation at 15 hours +/- 1 hour.
According to Dr. Showalter, when 2014 MU69 formed as a contact binary, the object was likely rotating at a speed of 3-4 hours per rotation.
That’s much faster than the current observed rate of rotation, and the most natural way to explain such a rapid and significant decrease in the rotation rate of a solar system object is if a permanently orbiting companion were affecting its spin rate.
A closer-to-home example of how a natural satellite can slow a solar system body’s rotation can be found on Earth, where tidal interactions with the Moon have slowed Earth’s rotation from 21 hours 600 million years ago to the 24 hour rotation we enjoy today.
For 2014 MU69, the question for Dr. Showalter of how the bilobate object’s rotation slowed from 3-4 hours to 15 hours comes down to the same understanding we have of Earth’s rotation: the best way to understand this is if there “was a moon or two or three orbiting the system. Essentially, what those moons would do is put the brakes on [MU69], slow [it] down, and as a result the small moons would spiral outward a little bit but not necessarily very far.
In terms of other information already released regarding 2014 MU69 is its surface coloration.
As Dr. Silvia Protopapa related, MU69 is a cold classical member of the Kuiper Belt – a term that does not refer to the object’s temperature but rather its status as a primitive object of the early solar system.
The cold classical KBOs reside in a tightly grouped ring with a low inclination relative to the solar system’s plane – which again connects MU69 and the other cold classical objects to the very formation of the solar system from the protoplanetary disk of dust and gas.
The cold classicals have thus far all been observed as redder than the rest of the Kuiper Belt population, and MU69’s observed color is “well within the average color displayed by the cold classical Kuiper Belt Objects,” says Dr. Protopapa.
Moreover, the observed color of both lobes, Ultima and Thule, are the same – lending further evidence that the two objects formed from the same general clump of material before coming together as the bilobate object we see today.
Presently, New Horizons is 9 million miles deeper into the Kuiper Belt than 2014 MU69.
Flyby observations officially concluded on 3 January before New Horizons transitioned to its first post-flyby command load given to it by the science team.
During the solar conjunction, New Horizons is “making observations of the deeper environment of the Kuiper Belt,” related Dr. Stern, and the craft will also make additional observations of other KBOs once its MU69 data transmission resumes.
Before the end of January, Dr. Stern anticipates releasing more information of “this wondrous place in this wondrous scientifically valuable region of the solar system: the Kuiper Belt.”
Lights, camera, action! Tumbling space snowman in film debut
Lights, camera, action! Tumbling space snowman makes out-of-this-world film debut
(The Associated Press)This combination of images provided by NASA shows a series of photographs made by the New Horizons spacecraft as it approached the Kuiper belt object Ultima Thule on Jan. 1, 2019. (NASA/Johns Hopkins University Applied Physics Laboratory/Southwest
The tumbling space snowman is making its out-of-this-world film premiere.
Scientists from NASA's New Horizons mission on Tuesday released the first stitched together animation of Ultima Thule (TOO-lee), the most distant object ever explored by humans.
The small, icy object is shown spinning end-over-end like a propeller. It is about 4 billion miles from Earth and looks like a reddish snowman with two fused-together spheres, extending about 21 miles (33 kilometers) in length.
The movie was put together from photos taken New Year's Eve and New Year's Day as the spacecraft made its closest approach, but not sent back to Earth until the last few days. The same spacecraft explored Pluto in 2015.
Ultima Thule rotates about every 16 hours so the time-lapsed movie shows seven of those hours.
New Movie Shows Ultima Thule from an Approaching New Horizons