The most detailed image of Ultima Thule yet. Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute, National Optical Astronomy Observatory
On December 31st, 2018, the New Horizons probe conducted the first flyby in history of a Kuiper Belt Object (KBO). Roughly half an hour later, the mission controllers were treated to the first clear images of Ultima Thule (aka. 2014 MU69). Over the course of the next two months, the first high-resolution images of the object were released, as well as some rather interesting findings regarding the KBOs shape.
Just recently, NASA released more new images of Ultima Thule, and they are the clearest and most detailed to date! The images were taken as part of what the mission team described as a “stretch goal”, an ambitious objective to take pictures of Ultima Thule mere minutes before the spacecraft made its closest approach. And as you can no doubt tell from the pictures NASA provided, mission accomplished!
Graphic of Ultima Thule showing its true shape. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
On December 31st, 2018, NASA’sNew Horizons mission made history by being the first spacecraft to rendezvous with the Kuiper Belt Object (KBO) named Ultima Thule (2014 MU69). This came roughly two and a half years after New Horizons became the first mission in history to conduct a flyby of Pluto. This latest encounter led to some stunning images of the KBO as the spacecraft made it’s approach.
But of course, these were not the last images New Horizons was going to capture of this object. While making its flyby of Ultima Thule on New Year’s Day, the spacecraft took a number of images that revealed something very interesting about Ultima Thule’s shape. Rather than consisting of two spheres that are joined together, Ultima Thule is actually made up of two segments – one that looks like a pancake, the other a walnut.
An artist's illustration of the newly-detected object. Image Credit: Ko Arimatsu
The Kuiper Belt, or the Edgeworth-Kuiper Belt, is home to ancient rocks. Kuiper Belt Objects, or KBOs, are remnants of the early planet-formation days of our Solar System. Small KBOs, in the 1 km. diameter range, have been theorized about for decades, but nobody’s every found one.
This image taken by the Long-Range Reconnaissance Imager (LORRI) is the most detailed of Ultima Thule returned so far by the New Horizons spacecraft. It was taken at 5:01 Universal Time on January 1, 2019, just 30 minutes before closest approach from a range of 18,000 miles (28,000 kilometers), with an original scale of 730 feet (140 meters) per pixel. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
On December 31st, 2018, NASA and the New Horizon‘s team (plus millions of people watching the live stream at home) rang in the New Year by watching theNew Horizons mission make the first rendezvous in history with a Kuiper Belt Object (KBO). About thirty minutes after the probe conducted its flyby of Arrokoth (2014 MU69), the mission controllers were treated to the first clear images ever taken of a KBO.
Since the first approach photographs were released (which were pixilated and blurry), the New Horizons team has released new images from the spacecraft that show Ultimate Thule in color and greater detail. It’s appearance, which resembles that of a snowman, beautifully illustrates the kinds of processes that created our Solar System roughly four and a half billion years ago.
Composite image (left) produced by adding 48 different exposures from the News Horizons Long Range Reconnaissance Imager (LORRI) taken on Aug. 16, 2018 and a magnified view (right) of the region in the yellow box taken by LORRI in September 2017. Credits: NASA/JHUAPL/SwRI
In July of 2015, NASA’s New Horizons mission made history when it became the first spacecraft to conduct a flyby of Pluto. Since that time, the spacecraft’s mission was extended so it could make its way farther into the outer Solar System and become the first spacecraft to explore some Kuiper Belt Objects (KBOs). It’s first objective will be the KBO known as 2014 MU69, which was recently given the nickname “Ultima Thule” (“ultima thoo-lee”).
Artist's concept of the hypothetical "Planet Nine." Could it have moons? Credit: NASA/JPL-Caltech/Robert Hurt
In January of 2016, astronomers Mike Brown and Konstantin Batygin published the first evidence that there might be another planet in our Solar System. Known as “Planet 9” (or “Planet X”, to those who contest the controversial 2006 Resolution by the IAU), this hypothetical body was believed to orbit at an extreme distance from our Sun, as evidenced by the fact that certain Trans-Neptunian Objects (TNOs) all seem to be pointing in the same direction.
Since that time, other lines of evidence have emerged that have bolstered the existence of Planet 9/Planet X. However, a team of researchers from CU Boulder recently proposed an alternative explanation. According to their research, it could be interactions between Kuiper Belt Objects (KBOs) themselves that might explain the strange dynamics of “detached objects” at the edge of the Solar System.
The researchers presented their findings at the 232nd meeting of the American Astronomical Society, which ran from June 3-7 in Denver, Colorado. The presentation took place on June 4th during a press conference titled “Minor Planets, Dwarf Planets & Exoplanets”. The research was led Jacob Fleisig, an undergraduate studying astrophysics at CU Boulder, and included Ann-Marie Madigan and Alexander Zderic – an assistant professor and a graduate student at CU Boulder, respectively.
Artist’s conception of Sedna, a dwarf planet in the Solar System that only gets within 76 astronomical units (AUs) of our Sun. Credit: NASA/JPL-Caltech
For the sake of their study, the team focused on icy bodies like Sedna, a minor planet that orbits the Sun at a distance ranging from 76 AU at perihelion to 936 AU at aphelion. Along with a handful of other objects at this distance, such as Eris, Sedna appears to be separated from the rest of the Solar System – something which astronomers have struggled to explain ever since it was discovered.
Sedna was also discovered by Michael Brown who, along with Chad Trujillo of the Gemini Observatory and David Rabinowitz of Yale University, spotted it on November 14th, 2003, while conducting a survey of the Kuiper Belt. In addition to orbiting our Sun with a period of over 11,000 years, this minor planet and other detached objects has a huge, elliptical orbit.
What’s more, this orbit does not take them Sedna or these other objects anywhere near to Neptune or any other gas giant. Unlike Pluto and other Trans-Neptunian Objects (TNOs), it is therefore a mystery how they achieved their current orbits. The possible existence of a as-yet-undiscovered planet (Planet 9/Planet X), which would be about 10 times the size of Earth, is one hypothetical explanation.
After years of searching for this planet and attempting to determine where its orbit would take it, astronomers have yet to find Planet 9/Planet X. However, as Prof. Madigan explained in a recent CU Boulder press release, there is another possible explanation for the gravitational weirdness going on out there:
“There are so many of these bodies out there. What does their collective gravity do? We can solve a lot of these problems by just taking into account that question… Once you get further away from Neptune, things don’t make any sense, which is really exciting.”
While Madigan and her team did not originally set out to find another explanation for the orbits of “detached objects”, they ended up pursuing the possibility thanks to Jacob Fleisig’s computer modelling. While developing simulations to explore the dynamics of the detached objects, he noticed something very interesting about the region of space they occupy.
Having calculated the orbits of icy objects beyond Neptune, Fleisig and the rest of the team noticed that different objects behave much like the different hands on a clock. Whereas asteroids move like the minute hand (relatively fast and in tandem), larger objects like Sedna move more slowly like the hour hand. Eventually, the hands intersect. As Fleisig explained:
“You see a pileup of the orbits of smaller objects to one side of the sun. These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape.”
What Fleisig’s computer model showed was that Sedna’s orbit goes from normal to detached as a result of those small-scale interactions. It also showed that the larger the detached object, the farther it gets away from the Sun – something which agrees with previous research and observations. In addition to explaining why Sedna and similar bodies behave the way they do, these findings may provide clues to another major event in Earth’s history.
Artistic rendition of the Chicxulub impactor striking ancient Earth, which is believed to have caused the Cretaceous–Paleogene extinction event. Credit: NASA
This would be what caused the extinction of the dinosaurs. Astronomers have understood for a long time that the dynamics of the outer Solar System often end up sending comets towards the inner Solar System on a predictable timescale. This is the result of icy objects interacting with each other, which causes their orbits to tighten and widen in a repeating cycle.
And while the team is not able to say that this pattern was responsible for the impact that caused the Cretaceous–Paleogene extinction event (which resulted in the extinction of the dinosaurs 66 million years ago), it is a fascinating possibility. In the meantime, the research has shown just how fascinating the outer Solar System is, and how much remains to be learned about it.
“The picture we draw of the outer solar system in textbooks may have to change,” said Madigan. “There’s a lot more stuff out there than we once thought, which is really cool.”
The research was made possible thanks to the support of the NASA Solar System Workings and the Rocky Mountain Advanced Computing Consortium Summit Supercomputer.
Artist’s impression of NASA’s New Horizons spacecraft encountering 2014 MU69, a Kuiper Belt object that orbits one billion miles (1.6 billion kilometers) beyond Pluto, on Jan. 1, 2019. With public input, the team has selected the nickname “Ultima Thule” for the object, which will be the most primitive and most distant world ever explored by spacecraft. Credits: NASA/JHUAPL/SwRI/Steve Gribben
In July of 2015, NASA’s New Horizons mission made history when it became the first spacecraft to conduct a flyby of Pluto. Since that time, the spacecraft’s mission was extended so it could make its way farther into the outer Solar System and explore some Kuiper Belt Objects (KBOs). Another historic first, the spacecraft will study these ancient objects in the hopes of learning more about the formation and evolution of the Solar System.
By Jan. 1st, 2019, it will have arrived at its first destination, the KBO known as 2014 MU69. And with the help of the public, this object recently received the nickname “Ultima Thule” (“ultima thoo-lee”). This object, which orbits our Sun at a distance of about 1.6 billion km (1 billion miles) beyond Pluto, will be the most primitive object ever observed by a spacecraft. It will also be the farthest encounter ever achieved in the history of space exploration.
Artist’s concept of Kuiper Belt object 2014 MU69, the next flyby target for NASA’s New Horizons missionCredits: NASA/JHUAPL/SwRI/Alex Parker
In 2015, MU69 was identified as one of two potential destinations for the New Horizons mission and was recommended to NASA by the mission science team. It was selected because of the immense opportunities for research it presented. As Alan Stern, the Principle Investigator (PI) for the New Horizons mission at the Southwest Research Institute (SwRI), indicated at the time:
“2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by. Moreover, this KBO costs less fuel to reach [than other candidate targets], leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen.”
Originally, the KBO was thought to be a spherical chunk of ice and rock. However, in August of 2017, new occultation observations made by telescopes in Argentina led the team to conclude that MU69 could actually be a large object with a chunk taken out of it (an “extreme prolate spheroid”). Alternately, they suspected that it might be two objects orbiting very closely together or touching – aka. a close or contact binary.
Given the significance of New Horizons‘ impending encounter with this object, its only proper that it receive a an actual name. In medieval literature and cartography, Thule was a mythical, far-northern island. Ultima Thule means “beyond Thule”, which essentially means that which lies beyond the borders of the known world. This name is highly appropriate, since the exploration of a KBO is something that has never been done before.
This artist’s impression shows the New Horizons spacecraft encountering a Pluto-like object in the distant Kuiper Belt. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Steve Gribben)
As Alan Stern, the principal investigator of the New Horizons mission at the Southwest Research Institute, said in a recent NASA press release:
“MU69 is humanity’s next Ultima Thule. Our spacecraft is heading beyond the limits of the known worlds, to what will be this mission’s next achievement. Since this will be the farthest exploration of any object in space in history, I like to call our flyby target Ultima, for short, symbolizing this ultimate exploration by NASA and our team.”
The campaign to name this object was launched by NASA and the New Horizons team in early November, and was hosted by the SETI Institute and led by Mark Showalter – an institute fellow and member of the New Horizons science team. The campaign involved 115,000 participants from around the world who nominated 34,000 names – 37 of which were selected for a final ballot based on their popularity.
These included eight names suggested by the New Horizons team and 29 nominated by the public. The team then narrowed its selection to the 29 publicly-nominated names and gave preference to names near the top of the polls. Along with Ultima Thule, other names that were considered included Abeona, Pharos, Pangu, Rubicon, Olympus, Pinnacle and Tiramisu.
This chart shows the path of NASA’s New Horizons spacecraft toward its next potential target, the Kuiper Belt object 2014 MU69, (aka. Ultima Thule). Credit: Alex Parker/NASA/JHUAPL/SwRI
After a five-day extension was granted to accommodate more voting, the campaign wrapped up on Dec. 6th, 2017. Ultima Thule received about 40 nominations from the public and was among those that got the most votes. “We are grateful to those who proposed such an interesting and inspirational nickname,” Showalter said. “They deserve credit for capturing the true spirit of exploration that New Horizons embodies.”
This name, however, is not a permanent one, but a working one which reflects the fact that MU69 is beyond Pluto – once held to be the most distant planet of the Solar System. Once the flyby is complete, NASA and the New Horizons team will submit a formal name to the International Astronomical Union (IAU). The name will depend on whether or not MU69 is a single body, a binary pair, or multiple objects.
Artist's impression of NASA's New Horizons spacecraft encountering a Pluto-like object in the distant Kuiper Belt. Credits: NASA/JHUAPL/SwRI/Alex Parker
Since it made its historic flyby of Pluto in July of 2015, the New Horizons mission has been venturing farther into the outer Solar System. With the spacecraft still healthy and its system in working order, the mission was extended to include the exploration of additional Kuiper Belt Objects (KBOs). The first target for this part of its mission is the KBO known as 2014 MU69, which New Horizons is currently making its way towards.
In the past, NASA believed this object was a spherical chunk of ice and rock measuring 18–41 km (10–30 mi) in diameter. However, a more recent occultation observation has led the New Horizon‘s team to conclude that MU69 may actually be a large object with a chunk taken out of it (an “extreme prolate spheroid”) or two objects orbiting very closely together or touching – aka. a close or contact binary.
In 2015, MU69 was identified as one of two potential destinations for New Horizons and was recommended to NASA by the mission science team. It was selected because of the immense opportunities for research it presented. As Alan Stern, the Principle Investigator (PI) for the New Horizons mission at the Southwest Research Institute (SwRI), indicated at the time:
“2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by. Moreover, this KBO costs less fuel to reach [than other candidate targets], leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen.”
Artist’s concept of a binary object, which new data suggests 2014 MU69 (the next flyby target for NASA’s New Horizons mission) could be. Credits: NASA/JHUAPL/SwRI/Alex Parker
The most recent observation of the KBO took place on July 17th, 2017, when the object passed in front of a star. This provided the New Horizon’s team with an opportunity to measure the resulting dip in the star’s luminosity – aka. an occultation – using a series of telescopes that they had deployed to a remote part of Patagonia, Argentina. These sorts of observations are performed regularly in order to obtain estimates of an asteroid’s size and position.
In the case of MU69’s occulation, the New Horizons team was able to obtain vital data that will help the mission planners to plot the trajectory of their flyby. In addition, the data revealed things about MU69’s size, shape, orbit, and the environment that surrounds it. It was because of this that the team began to question earlier estimates on the object’s size and shape.
Based on their new observations, they are confident that the object is no more than 30 km (20 mi) long, if it is an extreme prolate spheroid. If, however, it is a binary, the two objects that compose it are believed to measure about 15-20 km (9-12 mi) in diameter each. Alan Stern expanded on these new findings in a recent NASA press statement, saying:
“This new finding is simply spectacular. The shape of MU69 is truly provocative, and could mean another first for New Horizons going to a binary object in the Kuiper Belt. I could not be happier with the occultation results, which promise a scientific bonanza for the flyby.”
Artist’s concept of Kuiper Belt object 2014 MU69 as a single body (above) with a large chunk taken out of it. Credits: NASA/JHUAPL/SwRI/Alex Parker
The recent stellar occulation was the third of three observations conducted for the New Horizons mission. To prepare for the event, the New Horizons team traveled to Argentina and South Africa on June 3rd. On July 10th, a week before the occultation, NASA’s airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) provided support by studying the space around MU69.
Using its 2.5 m (100-inch) telescope, SOFIA was looking for debris that might present a hazard to New Horizons spacecraft as it makes its flyby less than 17 months from now. Last, but certainly not least, the team also relied on data provided by NASA’s Hubble Space Telescope and the ESA’s Gaia satellite to calculate and pinpoint where MU69 would cast its shadow on Earth’s surface.
Thanks to their assistance, the New Horizons team knew exactly where the occultation shadow would be and set up their “fence line” of small, mobile telescopes accordingly. Marc Buie – the New Horizons co-investigator – was responsible for leading the observation campaign. As he explained, the data it yielded will be of great help in the planning the flyby, but also indicated that their could be some surprises in the future:
“These exciting and puzzling results have already been key for our mission planning,” he said, “but also add to the mysteries surrounding this target leading into the New Horizons encounter with MU69, now less than 17 months away.”
The flyby with MU69 is scheduled to take place on Jan. 1st, 2019, and will be the most distant flyby in the history of space exploration. In addition to being 1.6 billion km (1 billion mi) from Pluto, the New Horizons spacecraft will be 6.5 billion km (4 billion mi) from Earth! What’s more, the first-ever study of a KBO is expected to yield some fantastic scientific data, and tell us much about the formation and evolution of our Solar System.
Observers Kai Getrost and Alex Parker wait to collect 2014 MU69 stellar occultation data in Argentina on June 3, 2017. Several New Horizons team members and collaborators will return to the country on July 17 for this summer's third and final MU69 occultation observation opportunity. (Image credit: Kai Getrost, via NASA)
While the New Horizons spacecraft was heading to Pluto, scientists from the mission used Hubble and other telescopes to try and find out more about the environment their spacecraft would be flying through. No one wanted New Horizons to run into unexpected dust or debris.
And now, as New Horizons prepares to fly past its next target, the Kuiper Belt Object known as 2014 MU69, mission scientists are using every tool at their disposal to examine this object and the surrounding region. The flyby will take place on January 1, 2019.
They’ve already uncovered some surprises.
On June 3, 2017, 2014 MU69 passed in front of a star – in an event called an occultation – providing a two-second glimpse of the object’s shadow.
A diagram of an occultation event, via the International Occultation Timing Association.
More than 50 mission team members and collaborators traveled to South Africa and Argentina to catch the occultation, setting up telescopes to capture the event. They are now looking through more than 100,000 images of the occultation star that can be used to assess the environment around this Kuiper Belt object (KBO). In addition, the Hubble Space Telescope and Gaia, a space observatory of the European Space Agency (ESA) also observed the event.
The team said that while MU69 itself eluded direct detection, the June 3 data provided valuable and unexpected insights that have already helped New Horizons.
“These results are telling us something really interesting,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. “The fact that we accomplished the occultation observations from every planned observing site but didn’t detect the object itself likely means that either MU69 is highly reflective and smaller than some expected, or it may be a binary or even a swarm of smaller bodies left from the time when the planets in our solar system formed.”
Mission scientist Simon Porter said on Twitter, “The upshot is that MU69 is probably not as big and dark as it could have been, and (more importantly) doesn’t seem to have rings or a dust cloud,” adding later that the “lack of dust was reassuring.”
Again, no one wants to New Horizons to run into any surprising dust or debris.
The team will be observing two more occultation events on July 10 and July 17, and Porter said they should get even better constraints from these next two events.
Projected path of the 2014 MU69 occultation shadow, on July 10 (left) and July 17, 2017. Credit: Larry Wasserman/Lowell Observatory, via NASA.
On July 10, NASA’s airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) will use its 100-inch (2.5-meter) telescope to probe the space around MU69 for debris that might present a hazard to New Horizons as it flies by in 18 months.
On July 17, the Hubble Space Telescope also will check for debris around MU69, while team members set up another ground-based “fence line” of small mobile telescopes along the predicted ground track of the occultation shadow in southern Argentina to try to better constrain, or even determine, the size of MU69.
Initial estimates of MU69’s diameter, based primarily on data taken by the Hubble Space Telescope since the KBO’s discovery in 2014, fall in the 12-25-mile (20-40-kilometer) range. However, the latest data from the June occultation seem to imply it’s at or even below the smallest estimated sizes.
“2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by,” Stern said back in August 2015 when the target was announced. “Moreover, this KBO costs less fuel to reach [than other candidate targets], leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen.”
You can see the star brightness, predicted shadow path and other tech specs for the July 10 and July 17 occultation events at the embedded links.
These two images reveal a moon orbiting the dwarf planet
2007 OR10. NASA/Hubble/ESA/STScI
These two images reveal a moon orbiting the dwarf planet 2007 OR10. NASA/Hubble/ESA/STScI
It isn’t every day we get a new moon added to the list of solar system satellites. The combined observational power of three observatories — Kepler, Herschel and Hubble — led an astronomical detective tale to its climatic conclusion: distant Kuiper Belt Object 2007 OR10has a tiny moon.
The dwarf planet itself is an enigma wrapped in a mystery: with a long orbit taking it out to a distant aphelion 101 astronomical units (AU) from the Sun, back into the environs of Neptune and Pluto for a perihelion 33 AU from the Sun once every 549 years, 2007 OR10 was discovered by Caltech astronomers Megan Schwamb and Mike Brown in 2007. Nicknamed “Snow White” by Mike Brown for its presumed high albedo, 2007 OR10 was 85 AU distant in the constellation Aquarius at the time of discovery and outbound towards aphelion in 2135. 2007 OR10 is about 1,500 kilometers in diameter, the third largest body known beyond Neptune in our solar system next to Pluto and Eris (nee Xena).
See the moon (circled?) at +21st magnitude, it’s a tough catch! NASA/Hubble/STScI
Enter the Kepler Space Telescope, which imaged 2007 OR10 crossing the constellation Aquarius as part of its extended K2 exoplanet survey along the ecliptic plane. Though Kepler looks for transiting exoplanets — worlds around other stars that betray their presence by tiny dips in the brightness of their host as they pass along our line of sight — it also picks up lots of other things that flicker, including variable stars and distant Kuiper Belt Objects. But the slow 45 hour rotational period of 2007 OR10 noted by Kepler immediately grabbed astronomers interest: could an unseen moon be lurking nearby, dragging on the KBO like a car brake?
“Typical rotation periods for Kuiper Belt Objects are under 24 hours,” says Csaba Kiss (Konkoly Observatory) in a recent press release. “We looked in the Hubble archive because the slower rotation period could have been caused by the gravitational tug of a moon.”
And sure enough, digging back through archival data from the Hubble Space Telescope taken during a survey of KBOs, astronomers turned up two images of the faint moon from 2009 and 2010. Infrared observations of 2007 OR10 and its moon by the European Space Agency’s Herschel Space Telescope cinched the discovery, and noted an albedo of 19% (similar to wet sand) for 2007 OR10, much darker than expected. The moon is about 200 miles (320 kilometers) in diameter, in a roughly 9,300 mile (15,000 kilometer) orbit.
The discovery was announced at an AAS meeting just last year, and even now, we’re still puzzling out what little we know about these distant worlds. Just what 2007 OR10 and its moon looks like is any guess. New Horizons gave us our first look at Pluto and Charon two short summers ago in 2015, and will give us a fleeting glimpse of 2014 MU69 on New Year’s Day 2019. All of these objects beg for proper names, especially pre-2019 New Horizons flyby.
This also comes on the heels of two new moons for Jupiter, recently announced last month S/2017 J1 and J2.
What would the skies from the tiny moon look like? Well, ancient 2007 OR10 must loom large in its sky, though Sol would only shine as a bright -15th magnitude star, (a little brighter than a Full Moon) its illumination dimmed down to 1/7,000th the brightness enjoyed here on sunny Earth, which would be lost in its glare.
The current position of 2007 OR10 in the night sky. Stellarium
And looking at the strange elliptical orbits of these outer worldlets, we can only surmise that something else must be out there. Will the discovery of Planet 9 be made before the close of the decade?
One thing’s for sure: this isn’t your parent’s tidy solar system with “Excellent Mothers” serving “Nine Pizzas.”
