One of the most enduring questions about Earth regards the origins of its water. Where did it come from? One widely-held theory gives comets the honor of bringing water to Earth. Another one says that Earth’s water came when a protoplanet crashed into early Earth, not only delivering a vast quantity of water, but creating the Moon.
Now a new study shows that the minor planet Vesta got its water from space dust. Could that help explain the origin of Earth’s water?
Hey Pluto, Sedna, Haumea, Makemake Et al.: You’ve got company!
While searching for distant galaxies and supernovae, the Dark Energy Survey’s powerful 570-megapixel digital camera spotted a few other moving “dots” in its field of view. Turns out, the DES has found more than 100 previously unknown trans-Neptunian objects (TNOs), minor planets located in Kuiper Belt of our Solar System.
A new paper describes how the researchers connected the moving dots to find the new TNOs, and also says this new approach could help look for the hypothetical Planet Nine and other undiscovered worlds.
Guess you never know what you’ll find once you start looking!
Within the Main Asteroid Belt, there are a number of larger bodies that have defied traditional classification. The largest among them is Ceres, which is followed by Vesta, Pallas, and Hygeia. Until recently, Ceres was thought to be the only object in the Main Belt large enough to undergo hydrostatic equilibrium – where an object is sufficiently massive that its gravity causes it to collapse into a roughly spherical shape.
A unique opportunity to study the dwarf planet Haumea has led to an intriguing discovery: Haumea is surrounded by a ring.
Add this to the already long list of unique things about the weird-shaped world with a dizzying rotation and a controversial discovery.
On January 21, 2017 Haumea passed in front of a distant star, in an event known as an occultation. The background star can – pardon the pun – shine a light on the object passing in front, providing information about a distant object — such as size, shape, and density — that is otherwise difficult to obtain. Since an occultation with Haumea had never been observed before, scientists were first eager, and then surprised.
“One of the most interesting and unexpected findings was the discovery of a ring around Haumea,” said said Pablo Santos-Sanz, from the Institute of Astrophysics of Andalusia (IAA-CSIC) in a statement.
This is the first time a ring has been discovered around a trans-neptunian object, and the team said this discovery shows that the presence of rings could be much more common than was previously thought, in our Solar System as well as in other planetary systems.
“Twelve telescopes from ten different European observatories converged on the phenomenon,” said José Luis Ortiz, who led the observational effort, and is also from IAA-CSIC. “This deployment of technical means allowed us to reconstruct with a very high precision the shape and size of dwarf planet Haumea, and discover to our surprise that it is considerably bigger and less reflecting than was previously believed. It is also much less dense than previously thought, which answered questions that had been pending about the object.”
The team said their data shows that the egg-shaped Haumea measures 2,320 kilometers in its largest axis. Previous estimates from various observations put the size at roughly 1,400 km. It takes 3.9 hours for Haumea rotate around its axis, much less than any other body in the Solar System that measures more than a hundred kilometers long. This rotational speed likely caused Haumea to flatten out, giving it an ellipsoid shape. It orbits the Sun in an elliptical loop that takes 284 years to complete. Additionally Haumea has two small moons.
Ortiz and team say their data shows the newly discovered ring lies on the equatorial plane of the dwarf planet, and it “displays a 3:1 resonance with respect to the rotation of Haumea, which means that the frozen particles which compose the ring rotate three times slower around the planet than it rotates around its own axis.”
Ortiz says there might be a few possible explanations for the formation of the ring; it may have originated in a collision with another object, or in the dispersal of surface material due to the planet’s high rotational speed.
Of course, other objects in our Solar System have rings: all the giant planets have rings, with Saturn’s being the most massive and well know. But small centaur asteroids located between Jupiter and Neptune were found to have rings, too.
“Now we have discovered that bodies even farther away than the centaurs, bigger and with very different general characteristics, can also have rings,” said Santos-Sanz.
You may recall there was great controversy over the discovery of Haumea. The discovery was originally announced in 2005 by Mike Brown from Caltech, along with his colleagues Chad Trujillo of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz, of Yale University.
But then Ortiz and Santos-Sanz attempted to scoop Brown et. al by sending in their claim to discovery to the Minor Planet Center before Brown’s paper was published. It was later learned that Ortiz and colleagues had accessed the Caltech observing logs remotely, looking at when and where Brown was looking with his telescopes. Ortiz and team initially denied the claims, but later conceded accessing the observation logs, maintaining they were just verifying whether they had discovered a new object in observations from 2003.
I asked Brown today if anything was ever officially resolved about the controversy.
“I think the resolution is that it is generally accepted that they stole our positions, but no one wants to think about it anymore,” he said via email.
But the discovery of a ring Haumea, Brown said, looks solid.
“I will admit to being wary of anything Ortiz says, so I checked the data very carefully,” Brown said. “Even I have to agree that the detection looks pretty solid. Haumea is weird, so it’s less surprising than, say, finding rings around something like Makemake. But, still, this was not something I was expecting!”
An isolated 3-mile-high (5 km) mountain Ahuna Mons on Ceres is likely volcanic in origin, and the dwarf planet may have a weak, temporary atmosphere. These are just two of many new insights about Ceres from NASA’s Dawn mission published this week in six papers in the journal Science.
“Dawn has revealed that Ceres is a diverse world that clearly had geological activity in its recent past,” said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
Ahuna Mons is a volcanic dome similar to earthly and lunar volcanic domes but unique in the solar system, according to a new analysis led by Ottaviano Ruesch of NASA’s Goddard Space Flight Center and the Universities Space Research Association. While those on Earth erupt with molten rock, Ceres’ grandest peak likely formed as a salty-mud volcano. Instead of molten rock, salty-mud volcanoes, or “cryovolcanoes,” release frigid, salty water sometimes mixed with mud.
Learn more about Ahuna Mons
“This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past,” Ruesch said. Estimates place the mountain formation within the past billion years.
Dawn may also have detected a weak, temporary atmosphere; the probe’s gamma ray and neutron (GRaND) detector observed evidence that Ceres had accelerated electrons from the solar wind to very high energies over a period of about six days. In theory, the interaction between the solar wind’s energetic particles and atmospheric molecules could explain the GRaND observations.
A temporary atmosphere would confirm the water vapor the Herschel Space Observatory detected at Ceres in 2012-2013. The electrons that GRaND detected could have been produced by the solar wind hitting the water molecules that Herschel observed, but scientists are also looking into alternative explanations.
While Ahuna Mons may have erupted liquid water in the not-too-distant past, Dawn found probable water ice right now in the mid-latitude Oxo Crater using its visible and infrared mapping spectrometer (VIR).
Exposed water-ice is rare on the dwarf planet, but the low density of Ceres — 2.08 grams/cm3 vs. 5.5 for Earth — the impact-generated ice detection and the the existence of Ahuna Mons suggest that Ceres’ crust does contain a significant amount of water ice.
Impact craters are clearly the most abundant geological feature on Ceres, and their different shapes help tell the complex story of Ceres’ past. Craters that are roughly polygonal — shapes bounded by straight lines — hint that Ceres’ crust is heavily fractured. In addition, several Cerean craters display fractures on their floors. There are craters with flow-like features. Bright areas are peppered across Ceres, with the most reflective ones in Occator Crater. Some crater shapes could indicate water-ice in the subsurface.
All these crater forms imply an outer shell for Ceres that is not purely ice or rock, but rather a mixture of both. Scientists also calculated the ratio of various craters’ depths to diameters, and found that some amount of crater relaxation must have occurred as icy walls gradually slump.
“The uneven distribution of craters indicates that the crust is not uniform, and that Ceres has gone through a complex geological evolution,” Hiesinger said.
Ceres’ crust also appears loaded with clay-forming minerals called phyllosilicates. These phyllosilicates are rich in magnesium and also have some ammonium embedded in their crystalline structure. Their distribution throughout the dwarf planet’s crust indicates Ceres’ surface material has been altered by a global process involving water.
Now in its extended mission, the Dawn spacecraft has been increasing its altitude since Sept. 2 as scientists stand back once again for a broader look at Ceres under different lighting conditions now compared to earlier in the mission.
A new dwarf planet has been discovered beyond Neptune, in the disk of small icy worlds that resides there. The planet was discovered by an international team of astronomers as part of the Outer Solar Systems Origins Survey (OSSOS). The instrument that found it was the Canada-France Hawaii Telescope at Maunakea, Hawaii.
The planet is about 700 km in size, and has been given the name 2015 RR245. It was first sighted by Dr. JJ Kavelaars, of the National Research Council of Canada, in images taken in 2015. Dwarf planets are notoriously difficult to spot, but they’re important pieces of the puzzle in tracing the evolution of our Solar System.
Dr. Michele Bannister, of the University of Victoria in British Columbia, describes the moment when the planet was discovered: “There it was on the screen— this dot of light moving so slowly that it had to be at least twice as far as Neptune from the Sun.”
“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the Sun. They let us piece together the history of our Solar System. But almost all of these icy worlds are painfully small and faint: it’s really exciting to find one that’s large and bright enough that we can study it in detail.” said Bannister.
As the New Horizons mission has shown us, these far-flung, cold bodies can have exotic features in their geological landscapes. Where once Pluto, king of the dwarf planets, was thought to be a frozen body locked in time, New Horizons revealed it to be a much more dynamic place. The same may be true of RR245, but for now, not much is known about it.
The 700 km size number is really just a guess at this point. More measurements will need to be taken of its surface properties to verify its size. “It’s either small and shiny, or large and dull.” said Bannister.
As our Solar System evolved, most dwarf planets like RR245 were destroyed in collisions, or else flung out into deep space by gravitational interactions as the gas giants migrated to their current positions. RR245 is one of the few that have survived. It now spends its time the same way other dwarf planets like Pluto and Eris do, among the tens of thousands of small bodies that orbit the sun beyond Neptune.
RR245 has not been observed for long, so much of what’s known about its orbit will be refined by further observation. But at this point it appears to have a 700 year orbit around the Sun. And it looks like for at least the last 100 million years it has travelled its current, highly elliptical orbit. For hundreds of years, it has been further than 12 billion km (80 AU)from the Sun, but by 2096 it should come within 5 billion km (34 AU) of the Sun.
The discovery of RR 245 came as a bit of a surprise to the OSSOS team, as that’s not their primary role. “OSSOS was designed to map the orbital structure of the outer Solar System to decipher its history,” said Prof. Brett Gladman of the University of British Columbia in Vancouver. “While not designed to efficiently detect dwarf planets, we’re delighted to have found one on such an interesting orbit”.
OSSOS has discovered over 500 hundred trans-Neptunian objects, but this is the first dwarf planet it’s found. “OSSOS is only possible due to the exceptional observing capabilities of the Canada-France-Hawaii Telescope. CFHT is located at one of the best optical observing locations on Earth, is equipped with an enormous wide-field imager, and can quickly adapt its observing each night to new discoveries we make. This facility is truly world leading.” said Gladman.
A lot of work has been done to find dwarf planets in the far reaches of our Solar System. It may be that RR 245 is the last one we find. If there are any more out there, they may have to wait until larger and more powerful telescopes become available. In the mid-2020’s, the Large Synoptic Survey Telescope (LSST) will come on-line in Chile. That ‘scope features a 3200 megapixel camera, and each image it captures will be the size of 40 full Moons. It’ll be hard for any remaining dwarf planets to hide from that kind of imaging power.
As for RR 245’s rather uninspiring name, it will have to do for a while. But as the discoverers of the new dwarf planet, the OSSOS team will get to submit their preferred name for the planet. After that, it’s up the International Astronomical Union (IAU) to settle on one.
What do you think? If this is indeed the last dwarf planet to be found in our Solar System what should we call it?
In an ‘Independence Day’ gift to a slew of US planetary research scientists, NASA has granted approval to nine ongoing missions to continue for another two years this holiday weekend.
The biggest news is that NASA green lighted a mission extension for the New Horizons probe to fly deeper into the Kuiper Belt and decided to keep the Dawn probe at Ceres forever, rather than dispatching it to a record breaking third main belt asteroid.
And the exciting extension news comes just as the agency’s Juno probe is about to ignite a do or die July 4 fireworks display to achieve orbit at Jupiter – detailed here.
“Mission approved!” the researchers gleefully reported on the probes Facebook and Twitter social media pages.
“Our extended mission into the #KuiperBelt has been approved. Thanks to everyone for following along & hopefully the best is yet to come.
The New Horizons spacecraft will now continue on course in the Kuiper Belt towards an small object known as 2014 MU69, to carry out the most distant close encounter with a celestial object in human history.
“Here’s to continued success!”
The spacecraft will rendezvous with the ancient rock on New Year’s Day 2019.
Researchers say that 2014 MU69 is considered as one of the early building blocks of the solar system and as such will be invaluable to scientists studying the origin of our solar system how it evolved.
It was almost exactly one year ago on July 14, 2015 that New Horizons conducted Earth’s first ever up close flyby and science reconnaissance of Pluto – the most distant planet in our solar system and the last of the nine planets to be explored.
The immense volume of data gathered continues to stream back to Earth every day.
“The New Horizons mission to Pluto exceeded our expectations and even today the data from the spacecraft continue to surprise,” said NASA’s Director of Planetary Science Jim Green at NASA HQ in Washington, D.C.
“We’re excited to continue onward into the dark depths of the outer solar system to a science target that wasn’t even discovered when the spacecraft launched.”
While waiting for news on whether NASA would approve an extended mission, the New Horizons engineering and science team already ignited the main engine four times to carry out four course changes in October and November 2015, in order to preserve the option of the flyby past 2014 MU69 on Jan 1, 2019.
Green noted that mission extensions into fiscal years 2017 and 2018 are not final until Congress actually passes sufficient appropriation to fund NASA’s Planetary Science Division.
“Final decisions on mission extensions are contingent on the outcome of the annual budget process.”
Tough choices were made even tougher because the Obama Administration has cut funding for the Planetary Sciences Division – some of which was restored by a bipartisan majority in Congress for what many consider NASA’s ‘crown jewels.’
NASA’s Dawn asteroid orbiter just completed its primary mission at dwarf planet Ceres on June 30, just in time for the global celebration known as Asteroid Day.
“The mission exceeded all expectations originally set for its exploration of protoplanet Vesta and dwarf planet Ceres,” said NASA officials.
The Dawn science team had recently submitted a proposal to break out of orbit around the middle of this month in order to this conduct a flyby of the main belt asteroid Adeona.
Green declined to approve the Dawn proposal, citing additional valuable science to be gathered at Ceres.
The long-term monitoring of Ceres, particularly as it gets closer to perihelion – the part of its orbit with the shortest distance to the sun — has the potential to provide more significant science discoveries than a flyby of Adeona,” he said.
The funding required for a multi-year mission to Adeona would be difficult in these cost constrained times.
However the spacecraft is in excellent shape and the trio of science instruments are in excellent health.
Dawn arrived at Ceres on March 6, 2015 and has been conducting unprecedented investigation ever since.
Dawn is Earth’s first probe in human history to explore any dwarf planet, the first to explore Ceres up close and the first to orbit two celestial bodies.
The asteroid Vesta was Dawn’s first orbital target where it conducted extensive observations of the bizarre world for over a year in 2011 and 2012.
The mission is expected to last until at least later into 2016, and possibly longer, depending upon fuel reserves.
Due to expert engineering and handling by the Dawn mission team, the probe unexpectedly has hydrazine maneuvering fuel leftover.
Dawn will remain at its current altitude at the Low Altitude Mapping Orbit (LAMO) for the rest of its mission, and indefinitely afterward, even when no further communications are possible.
Green based his decision on the mission extensions on the biannual peer review scientific assessment by the Senior Review Panel.
Dawn was launched in September 2007.
The other mission extensions – contingent on available resources – are: the Mars Reconnaissance Orbiter (MRO), Mars Atmosphere and Volatile EvolutioN (MAVEN), the Opportunity and Curiosity Mars rovers, the Mars Odyssey orbiter, the Lunar Reconnaissance Orbiter (LRO), and NASA’s support for the European Space Agency’s Mars Express mission.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
The dwarf planets in our Solar System are some of the most interesting objects around. Of course, all of the Solar System objects–and anything in nature, really–are fascinating when you really focus on them. Now, a new study puts the focus squarely on the dwarf planet Haumea, and deepens the mystery surrounding its origins.
Dwarf planets Pluto and Haumea are considered cousins. Both of them, and their respective moons, are thought to be collisional families. This means they have a common origin in the form of an impact event. But the study, from Luke D. Burkhart, Darin Ragozzine, and Michael E. Brown, shows that Haumea doesn’t have the same kinds of moons as Pluto, which has astronomers puzzling over Haumea’s origins.
Pluto and Haumea are the only two bodies in the outer Solar System that have more than one Moon. Pluto has five moons (Charon, Styx, Nix, Kerberos, and Hydra) while Haumea has two moons, Hi’iaka and Namaka. Haumea is also the parent of a number of icy bodies which were parts of its surface, but now orbit the Sun on their own. The two other dwarf planets in the Kuiper Belt, Eris and Makemake, each have only one moon.
One thing that differentiates Haumea from Pluto is Haumea’s family of small icy bodies that came from its surface. While Pluto has a number of small icy moons, Haumea’s icy bodies orbit the Sun independently, and are not moons. Other properties of Haumea, like its inordinately high rate of spin, make Haumea a very interesting object to study. They also differentiate Haumea from Pluto, and are leading to questions about the cousin relationship between the two. If they are indeed cousins, then shouldn’t they share the same formation method?
Haumea’s lack of icy moons similar to Pluto’s was noted by researcher Darin Ragozzine. “While we’ve known about Pluto’s and Haumea’s moons for years, we now know that Haumea does not share tiny moons like Pluto’s, increasing our understanding of this intriguing object,” Ragozzine said.
There are definite similarities between Pluto and Haumea, but this study suggests that the satellite systems of the icy cousins, or former cousins, formed differently. “There is no self-consistent formation hypothesis for either set of satellites,” said Ragozzine.
Two things were at the heart of this new study. The first is the workhorse Hubble Space Telescope. In 2010, the Hubble focussed on Haumea, and captured 10 consecutive orbits to try to understand its family of satellites better.
The second thing at the heart of the study is called a “non-linear shift and stack method.” This is a novel technique which allows the detection of extremely faint and distant objects. When used in this study, it specifically ruled out the existence of small moons like the ones that orbit Pluto. This method may allow for future detection of other moons and Kuiper Belt Objects.
The study itself outlines some of Haumea’s properties that make it such an object of fascination for astronomers. It’s the fastest-rotating large body in the Solar System. In fact it rotates so quickly, that it’s near the rate at which the dwarf planet would break up. Haumea also has an unexpectedly high density, and a high albedo resulting from a surface of water ice. It’s two moons are in dynamically excited orbits, and its family of icy fragments is not near as dispersed as it should be. As the paper says, “There is no simple high-probability formation scenario that naturally explains all of these observational constraints.”
In the paper, the authors emphasize the puzzling nature of Haumea’s formation. To quote the paper, “Though multiple explanations and variations have been proposed, none have adequately and self-consistently explained all of the unique features of this interesting system and its family.”
Some of the explanations proposed in other studies include a collision between objects in the scattered disk, which overlaps the Kuiper Belt and extends much further, rather than objects in the Kuiper Belt itself. Another proposes that Haumea’s two largest moons–Hi’iaka and Namaka–are themselves second generation moons formed from the breakup of a progenitor moon.
Though the study shows that the Pluto system and the Haumea system, erstwhile cousins in the Solar System, have followed different pathways to formation, it also concludes that a collision was indeed the main event for both dwarf planets. But what happened after that collision, and where exactly those collisions took place, are still intriguing questions.
Depending on shifting definitions of what exactly is or isn’t a dwarf planet, our Solar System has about half a dozen dwarf planets. They are: Pluto, Eris, Haumea, Makemake, Ceres, and 2007 OR10.
Even though 2007 OR10’s name makes it stand out from the rest, dwarf planets as a group are an odd bunch. They spend their time in the cold, outer reaches of the Solar System, with Ceres being the only exception. Ceres resides in the asteroid belt between Mars and Jupiter.
Their distance from Earth makes them difficult targets for observation, even with the largest telescopes we have. Even the keen eye of the Hubble Telescope, orbiting above Earth’s view-inhibiting atmosphere, struggles to get a good look at the dwarf planets. But astronomers using the Kepler spacecraft discovered that its extreme light sensitivity have made it a useful tool to study the dwarves.
In a paper published in The Astronomical Journal, a team led by Andras Pal, at Konkoly Observatory in Budapest, Hungary, have refined the measurement of 2007 OR10. Using the Kepler’s observational prowess, and combining it with archival data from the Herschel Space Observatory, the team has come up with a much more detailed understanding of 2007 OR10.
Previously, 2007 OR10 was thought to be about 1280 km (795 miles) in diameter. But the problem is the dwarf planet was only a faint, tiny, and distant point of light. Astronomers knew it was there, but didn’t know much else. Objects as far away as 2007 OR10, which is currently twice as far away from the Sun as Pluto is, can either be small, bright objects, or much larger, dimmer objects that reflect less light.
This is where the Kepler came in. It has exquisite sensitivity to tiny changes in light. Its whole mission is built around that sensitivity. It’s what has made Kepler such an effective tool for identifying exo-planets. Pointing it towards a tiny target like 2007 OR10, and monitoring the reflected light as the object rotates, is a logical use for Kepler.
Even so, Kepler alone wasn’t able to give the team a thorough understanding of the dwarf planet with the clumsy name.
Enter the Herschel Space Observatory, a powerful infrared space telescope. Herschel and its 3.5 metre (11.5 ft.) mirror were in operation at LaGrange 2 from 2009 to 2013. Herschel discovered many things in its mission-span, including solid evidence for comets being the source of water for planets, including Earth.
But the Herschel Observatory also bequeathed an enormous archive of data to astronomers and other space scientists. And that data was crucial to the new measurement of 2007 OR10.
Combining data and observations from multiple sources is not uncommon, and is often the only way to learn much about distant, tiny objects. In this case, the two telescopes were together able to determine the amount of sunlight reflected by the dwarf planet, using Kepler’s light sensitivity, and then measure the amount of that light later radiated back as heat, using Herschel’s infrared capabilities.
Combining those datasets gave a much clearer idea of the size, and reflectivity, of 2007 OR10. In this case, the team behind the new paper was able to determine that 2007 OR10 was significantly larger than previously thought. It’s measured size is now 1535 km (955 mi) in diameter. This is 255 km (160 mi) larger than previously measured.
It also tells us that the dwarf planet’s gravity is stronger, and the surface darker, than previously measured. This further cements the oddball status of 2007 OR10, since other dwarf planets are much brighter. Other observations of the planet have shown that is has a reddish color, which could be the result of methane ice on the surface.
Lead researcher Andras Pal said, “Our revised larger size for 2007 OR10 makes it increasingly likely the planet is covered in volatile ices of methane, carbon monoxide and nitrogen, which would be easily lost to space by a smaller object. It’s thrilling to tease out details like this about a distant, new world — especially since it has such an exceptionally dark and reddish surface for its size.”
Now that more is known about 2007 OR10, perhaps its time it was given a better name, something that’s easier to remember and that helps it fit in with its peer planets Pluto, Ceres, Eris, Haumea, and Makemake. According to convention, the honor of naming it goes to the planet’s discoverers, Meg Schwamb, Mike Brown and David Rabinowitz. They discovered it in 2007 during a search for distant bodies in the Solar System.
According to Schwamb, “The names of Pluto-sized bodies each tell a story about the characteristics of their respective objects. In the past, we haven’t known enough about 2007 OR10 to give it a name that would do it justice. I think we’re coming to a point where we can give 2007 OR10 its rightful name.”
The Universe is vast, and we need some numbered, structured way to name everything. And these names have to mean something scientifically. That’s why objects end up with names like 2007 OR10, or SDSS J0100+2802, the name given to a distant, ancient quasar. But objects closer to home, and certainly everything in our Solar System, deserves a more memory-friendly name.
So what’s it going to be? If you think you have a great name for the oddball dwarf named 2007 OR10, let us hear it in a tweet, or in the comments section.
Planetary scientists using the Hubble Space Telescope have spotted a dark mini-moon orbiting the distant dwarf planet Makemake. The moon, nicknamed MK 2, is roughly 160 km (100 miles) wide and orbits about 20,000 km (13,000 miles) from Makemake. Makemake is 1,300 times brighter than its moon and is also much larger, at 1,400 km (870 miles) across, about 2/3rd the size of Pluto.
“Our discovery of the Makemakean moon means that every formally-designated Kuiper Belt dwarf planet has at least one moon!” said Alex Parker on Twitter. Parker, along with Mark Buie, both from the Southwest Research Institute, led the same team that found the small moons of Pluto in 2005, 2011, and 2012, and they used the same Hubble technique to find MK 2. NASA says Hubble’s Wide Field Camera 3 has the unique ability to see faint objects near bright ones, and together with its sharp resolution, allowed the scientists to pull the moon out from bright Makemake’s glare.
Previous searches for moons around Makemake came up empty, but Parker said their analysis shows the moon has a very dark surface and it is also in a nearly edge-on orbit, which made it very hard to find.
This moon might be able to provide more details about Makemake, such as its mass and density. For example, when Pluto’s moon Charon was discovered in 1978, astronomers were able to measure Charon’s orbit and then calculate the mass of Pluto, which showed Pluto’s mass was hundreds of times smaller than originally estimated.
“Makemake is in the class of rare Pluto-like objects, so finding a companion is important,” Parker said. “The discovery of this moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion.”
Parker also said the discovery of a moon for Makemake might solve a long-standing mystery about the dwarf planet. Thermal observations of Makemake by the Spitzer and Herschel space observatories seemed to show the bright world had some darker, warmer material on its surface, but other observations couldn’t confirm this.
Parker said perhaps the dark material isn’t on Makemake’s surface, but instead is in orbit. “I modeled the emission we expect from Makemake’s moon, and if the moon is very dark, it accounts for most previous thermal measurements,” he said on Twitter.
The researchers will need more Hubble observations to make accurate measurements to determine if the moon’s orbit is elliptical or circular, and this could help determine its origin. A tight circular orbit means that MK 2 probably formed from a collision between Makemake and another Kuiper Belt Object. If the moon is in a wide, elongated orbit, it is more likely to be a captured object from the Kuiper Belt. Many KBOs are covered with very dark material, so that might explain the dark surface of MK 2.