Artist's impression of Planet Nine, blocking out the Milky Way. The Sun is in the distance, with the orbit of Neptune shown as a ring. Credit: ESO/Tomruen/nagualdesign
Finding a ninth planet in our Solar System this late in the game would be fascinating. It would also be somewhat of a surprise, considering our observational capabilities. But new evidence, in the form of small perturbations in the orbit of the Cassini probe, points to the existence of an as-yet undetected planet in our solar system.
Back in January, Konstantin Batygin and Mike Brown, two planetary scientists from the California Institute of Technology, presented evidence supporting the existence of a ninth planet. Their paper showed that some Kuiper Belt Objects (KBOs) display unexpected behaviour. It appears that 6 KBOs are affected by their relationship to a large object, but the KBOs in question are too distant from the known gas giants for them to be responsible. They think that a large, distant planet, in the distant reaches of our Solar System, could be responsible for the unexpected orbital clustering of these KBOs.
The calculated orbit of Planet Nine. Credit: Nature/K. Batygin and M. E. Brown Astronom. J. 151, 22 (2016)
Now, the Ninth Planet idea is gaining steam, and another team of researchers have presented evidence that small perturbations in the orbit of the Cassini spacecraft are caused by the new planet. Agnès Fienga at the Côte d’Azur Observatory in France, and her colleagues, have been working on a detailed model of the Solar System for over a decade. They plugged the hypothetical orbit and size of Planet Nine into their model, to see if it fit.
Planet Nine is calculated to be about 4 times as large as Earth, and 10 times as massive. It’s orbit takes between 10,000 and 20,000 years. A planet that large can only be hiding in so many places, and those places are a long way from Earth. Fienga found a potential home for Planet Nine, some 600 astronomical units (AU) from here. That much mass at that location could account for the perturbations in Cassini’s orbit.
There’s more good news when it comes to Planet Nine. By happy accident, it’s predicted location in the sky is towards the constellation Cetus, in the southern hemisphere. This means that it is in the view of the Dark Energy Survey, a southern hemisphere project that is studying the acceleration of the universe. The Dark Energy Survey is not designed to search for planetary objects, but it has successfully found at least one icy object.
There are other ways that the existence of Planet Nine could be confirmed. If it’s as large as thought, then it will radiate enough internal heat to be detected by instruments designed to study the Cosmic Microwave Background (CMB). There is also an enormous amount of data from multiple experiments and observations done over the years that might contain an inadvertent clue. But looking through it is an enormous task.
As for Brown and Batygin, who initially proposed the existence of Planet Nine based on the behaviour of KBOs, they are already proposing a more specific hunt for the elusive planet. They have asked for a substantial amount of observing time at the Subaru Telescope on Mauna Kea in Hawaii, in order to examine closely the location that Fienga’s solar system model predicts Planet Nine to be at.
For a more detailed look at Batygin’s and Brown’s work analyzing KBOs, read Matt Williams’ article here.
Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL
Neptune is a truly fascinating world. But as it is, there is much that people don’t know about it. Perhaps it is because Neptune is the most distant planet from our Sun, or because so few exploratory missions have ventured that far out into our Solar System. But regardless of the reason, Neptune is a gas (and ice) giant that is full of wonder!
Below, we have compiled a list of 10 interesting facts about this planet. Some of them, you might already know. But others are sure to surprise and maybe even astound you. Enjoy!
New Horizons’ Long Range Reconnaissance Imager (LORRI) took this image on Nov. 2, 2015 of a 90-mile (150-kilometer)-wide ancient Kuiper Belt Object named 1994 JR1, moving against a background of stars. Credit: NASA/JHUAPL/SwRI
The New Horizons spacecraft is already 209,437,000 km (130,138,000 miles) past Pluto (as of Dec. 4, 2015), making it 5,226,950,000 km (3,247,880,000 miles) from Earth. So, yes, it’s way out there. Recently, it took the closest images ever of a distant Kuiper Belt object, setting a record by a factor of at least 15, according to NASA. The team says this image demonstrates the spacecraft’s ability to observe numerous similar bodies over the next several years. Continue reading “New Horizons Takes Closest Image Ever of a Kuiper Belt Object”
Gerard Kuiper, founder of the Lunar and Planetary Laboratory. Credit: lpl.arizona.edu
In the outer reaches of the Solar System, beyond the orbit of Neptune, lies a region permeated by celestial objects and minor planets. This region is known as the “Kuiper Belt“, and is named in honor of the 20th century astronomer who speculated about the existence of such a disc decades before it was observed. This disc, he reasoned, was the source of the Solar Systems many comets, and the reason there were no large planets beyond Neptune.
Gerard Kuiper is also regarded by many as being the “father of planetary science”. During the 1960s and 70s, he played a crucial role in the development of infrared airborne astronomy, a technology which led to many pivotal discoveries that would have been impossible using ground-based observatories. At the same time, he helped catalog asteroids, surveyed the Moon, Mars and the outer Solar System, and discovered new moons.
This composite image is based on observations from the New Horizons Ralph/LEISA instrument made at 10:25 UT (6:25 a.m. EDT) on July 14, 2015, when New Horizons was 50,000 miles (81,000 kilometers) from Charon. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
Just like Luke and Leia, two craters named for the Star Wars twins (Skywalker and Organa) have many similarities. They look about the same size and shape, and appear to have been created at the same time, and therefore are about the same age. But instruments on the New Horizons spacecraft detected one major difference: Organa and its surrounding area are laced with ammonia.
“Why are these two similar-looking and similar-sized craters, so near to each other, so compositionally distinct?” asked Will Grundy, who leads the New Horizons Composition team. “We have various ideas when it comes to the ammonia in Organa. The crater could be younger, or perhaps the impact that created it hit a pocket of ammonia-rich subsurface ice. Alternatively, maybe Organa’s impactor delivered its own ammonia.”
Both craters are roughly 5 kilometers (3 miles) in diameter, with similar appearances, such as bright rays of ejecta. One apparent difference is that Organa has a central region of darker ejecta, though from the map created with data from New Horizons’ Ralph/LEISA instrument, it appears that the ammonia-rich material extends beyond this dark area.
The nearby Skywalker crater, however, shows an infrared spectrum that is similar to the rest of Charon’s craters and surface, with features mostly dominated by ordinary water ice.
“This is a fantastic discovery,” said Bill McKinnon, deputy lead for the New Horizons Geology, Geophysics and Imaging team. “Concentrated ammonia is a powerful antifreeze on icy worlds, and if the ammonia really is from Charon’s interior, it could help explain the formation of Charon’s surface by cryovolcanism, via the eruption of cold, ammonia-water magmas.”
The New Horizons team is informally naming features after various sci-fi characters. So maybe – like their Star Wars namesakes – the craters Skywalker and Organa actually are different ages, as students at the University of Leicester calculated in a paper published earlier this year. The students said that Leia would be about 2 years old than Luke because of relative velocity time dilation – which describes the bending of spacetime due to differences in speed. Their different journeys through space in various craft would change how fast they are aging.
But we digress…
A new map of Pluto’s ‘heart.’ This image released on October 29, 2015, provides fascinating new details to help the science team map the informally named Krun Macula (the prominent dark spot at the bottom of the image) and the complex terrain east and northeast of Pluto’s “heart” (Tombaugh Regio). Pluto’s north pole is on the planet’s disk at the 12 o’clock position of this image. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Meanwhile, as New Horizons continues to send back more imagery and data, the spacecraft’s hydrazine-fueled thrusters completed the third of four maneuvers to direct the spacecraft towards an ancient and distant Kuiper Belt Object named 2014 MU69.
As we explained in our previous article, the four maneuvers are designed change New Horizons’ path to send it toward a close encounter with the KBO on Jan. 1, 2019. Even though the New Horizons spacecraft hasn’t officially been approved to do this flyby as an extended mission, the team is taking advantage of being able to do the maneuvers early, thereby saving fuel.
The science team hopes to bring the spacecraft even closer to MU69 than it came to Pluto this summer, which was approximately 7,750 miles (12,500 kilometers)
The fourth and final KBO targeting maneuver is scheduled for next week, Nov. 4, 2015.
Another image released this week from the New Horizons team:
This image was made just 15 minutes after New Horizons’ closest approach to Pluto on July 14, 2015, as the spacecraft looked back at Pluto toward the sun. The wide-angle perspective of this view shows the deep haze layers of Pluto’s atmosphere extending all the way around Pluto, revealing the silhouetted profiles of rugged plateaus on the night (left) side. The image was taken with New Horizons’ Multi-spectral Visible Imaging Camera (MVIC) from a distance of 11,000 miles (18,000 kilometers) to Pluto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
In September, the New Horizons team released a stunning but incomplete image of Pluto’s crescent. Thanks to new processing work by the science team, New Horizons is releasing the entire, breathtaking image of Pluto.
Alex Parker, one of the science team members who worked on the image said on Twitter, “The haze over Pluto’s dark limb were frustratingly run through with instrumental artifacts. This version is my latest destripe and denoise.” He also noted a few things: look closely, and you can see background stars behind Pluto. Additionally, look at Pluto’s shadowed limb:
Another wonderful thing about that new image: the bright haze gives us a look at how bumpy Pluto's shadowed limb is! pic.twitter.com/hUSGIZB8Bw
This color image of Pluto taken by NASA’s New Horizons spacecraft shows rounded and bizarrely textured mountains, informally named the Tartarus Dorsa, rise up along Pluto’s terminator and show intricate but puzzling patterns of blue-gray ridges and reddish material in between. This view, roughly 330 miles (530 kilometers) across, combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC) on July 14, 2015, and resolves details and colors on scales as small as 0.8 miles (1.3 kilometers). Credits: NASA/JHUAPL/SWRI
Data from that priceless, once in a lifetime flyby is now trickling back to Earth.
The ‘snakeskin’ feature on Pluto’s utterly bizarre surface was unveiled to “astonished” scientists scrutinizing the latest data dump received over the past week, that included images taken by the Ralph instruments Multispectral Visual Imaging Camera (MVIC).
Features as small as 0.8 miles (1.3 kilometers) are resolved in detail.
The MVIC image stretches about 330 miles (530 kilometers) across the ‘snakeskin’ like landscape composed of rounded and bizarrely textured mountains that are informally named Tartarus Dorsa and that borders the bodies day-night terminator.
It shows intricate patterns of blue-gray ridges and reddish material in between that are puzzling researchers.
“It’s a unique and perplexing landscape stretching over hundreds of miles,” said William McKinnon, New Horizons Geology, Geophysics and Imaging (GGI) team deputy lead from Washington University in St. Louis.
“It looks more like tree bark or dragon scales than geology. This’ll really take time to figure out; maybe it’s some combination of internal tectonic forces and ice sublimation driven by Pluto’s faint sunlight.”
The Ralph/MVIC image is actually a composite of blue, red and infrared images.
The image of Tartarus Dorsa reveals a “multitude of previously unseen topographic and compositional details. It captures a vast rippling landscape of strange, aligned linear ridges that has astonished New Horizons team members,” say officials.
NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto on July 14, 2015. The image combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). Pluto’s surface sports a remarkable range of subtle colors, enhanced in this view to a rainbow of pale blues, yellows, oranges, and deep reds. Many landforms have their own distinct colors, telling a complex geological and climatological story that scientists have only just begun to decode. The image resolves details and colors on scales as small as 0.8 miles (1.3 kilometers). The viewer is encouraged to zoom in on the image on a larger screen to fully appreciate the complexity of Pluto’s surface features. Credit: NASA/JHUAPL/SwRI
Another wider angle global view of Pluto downlinked on Sept. 19 shows a new “extended color” view of Pluto with an the extraordinarily rich color palette of the planet.
“We used MVIC’s infrared channel to extend our spectral view of Pluto,” said John Spencer, a GGI deputy lead from Southwest Research Institute (SwRI) in Boulder, Colorado.
“Pluto’s surface colors were enhanced in this view to reveal subtle details in a rainbow of pale blues, yellows, oranges, and deep reds. Many landforms have their own distinct colors, telling a wonderfully complex geological and climatological story that we have only just begun to decode.”
The image resolves details and colors on scales as small as 0.8 miles (1.3 kilometers).
High-resolution images of Pluto taken by NASA’s New Horizons spacecraft just before closest approach on July 14, 2015, reveal features as small as 270 yards (250 meters) across, from craters to faulted mountain blocks, to the textured surface of the vast basin informally called Sputnik Planum. Enhanced color has been added from the global color image. This image is about 330 miles (530 kilometers) across. For optimal viewing, zoom in on the image on a larger screen. Credits: NASA/JHUAPL/SWRI
Beyond MVIC, additional new images taken by New Horizons’ narrow-angle Long Range Reconnaissance Imager (LORRI) during the July 14 were downlinked on Sept. 20.
They focus on the Sputnik Planum ice plains on the left side of the famous heart shaped Tombaugh Regio feature and are the highest resolution yet – as seen below. The team added color based on the global MVIC map shown above.
High-resolution images of Pluto taken by NASA’s New Horizons spacecraft just before closest approach on July 14, 2015, are the sharpest images to date of Pluto’s varied terrain—revealing details down to scales of 270 meters. In this 75-mile (120-kilometer) section of the taken from a larger, high-resolution mosaic, the textured surface of the plain surrounds two isolated ice mountains. Credits: NASA/JHUAPL/SWRI
Barely 5 or 6 percent of the 50 gigabits of data captured by New Horizons has been received by ground stations back on Earth.
“With these just-downlinked images and maps, we’ve turned a new page in the study of Pluto beginning to reveal the planet at high resolution in both color and composition,” added New Horizons Principal Investigator Alan Stern, of SwRI.
“I wish Pluto’s discoverer Clyde Tombaugh had lived to see this day.”
Stern says it will take about a year for all the data to get back. Thus bountiful new discoveries are on tap.
This new global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Right side mosaic comprises twelve highest resolution views of Tombaugh Regio heart shaped feature and shows objects as small as 0.5 miles (0.8 kilometers) in size. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/ Ken Kremer/kenkremer.com/Marco Di Lorenzo
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Just 15 minutes after its closest approach to Pluto on July 14, 2015, NASA’s New Horizons spacecraft looked back toward the sun and captured this near-sunset view of the rugged, icy mountains and flat ice plains extending to Pluto’s horizon – shown in this colorized rendition. The smooth expanse of the informally named icy plain Sputnik Planum (right) is flanked to the west (left) by rugged mountains up to 11,000 feet (3,500 meters) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. To the right, east of Sputnik, rougher terrain is cut by apparent glaciers. The backlighting highlights more than a dozen layers of haze in Pluto’s tenuous but distended atmosphere. The image was taken from a distance of 11,000 miles (18,000 kilometers) to Pluto; the scene is 780 miles (1,250 kilometers) wide. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. Colorized/Annotated: Marco Di Lorenzo/Ken Kremer/kenkremer.com
This new global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This new mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Marco Di Lorenzo/Ken Kremer/kenkremer.com
This new global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This new mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Marco Di Lorenzo/Ken Kremer/kenkremer.com
See annotated version and new hi res Tombaugh Regio mosaic below[/caption]
But because of limited bandwidth the new image data sets were stored onboard the probe until days ago when they were transmitted back to Earth and released by the New Horizons team late in the day on Friday, Sept. 11.
This best yet view of far flung Pluto comes from raw images taken as New Horizons conducted the history making first flyby past Pluto on July 14, 2015, at a distance of 50,000 miles (80,000 kilometers).
The global Pluto mosaic was generated from over two dozen raw images captured by New Horizons’ Long Range Reconnaissance Imager (LORRI) and stitched together by the image processing team of Marco Di Lorenzo and Ken Kremer.
See also our expanded hi res Tombaugh Regio mosaic below showing features as small as 0.5 miles (0.8 kilometers) in size.
After transmitting carefully selected high priority images and science measurements across over 3 billion miles (about 5 billion kilometers) of interplanetary space in the days around the history making flyby, the team elected to temporarily pause the transmission of new images for several weeks in favor of sending other data important for helping place the entire Pluto planetary system into context.
Altogether, over 50 gigabits of data were collected during the July 14 encounter and flyby periods of the highest scientific activity – which includes the most critical hours before and after the spacecrafts closest approach to Pluto, its largest moon Charon and its quartet of smaller moons.
Highest resolution mosaic of ‘Tombaugh Regio’ shows the heart-shaped region on Pluto including ice flows and plains of ‘Sputnik Planum’ (center) and icy mountain ranges of ‘Hillary Montes’ and ‘Norgay Montes.’ This new mosaic combines the eleven highest resolution images captured by NASA’s New Horizons LORRI imager during history making closest approach flyby on July 14, 2015. It shows features as small as 0.5 miles (0.8 kilometers) in size. Credit: NASA/JHUAPL/SWRI/Ken Kremer/kenkremer.com/Marco Di Lorenzo
Data from the flyby continues streaming back to Earth, but rather slowly due to limited bandwidth amounting to an average “downlink” of only about 2 kilobits per second via its two transmitters.
New Horizon’s unveiled Pluto as a surprising vibrant and geologically active “icy world of wonders” as it barreled past the Pluto-Charon double planet system on July 14 at over 31,000 mph (49,600 kph) and collected unprecedented high resolution imagery and spectral measurements of the utterly alien worlds.
Since the flyby, the team has been busy analyzing the science data returned thus far and “making some discoveries” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado, during the Weekly Space Hangout on Sept 11.
The team is ecstatic with all the new images and created what they call a synthetic global view of a portion of Pluto.
“We created a synthetic global mosaic view of more than a dozen frames from the LORRI camera, and wrapped it on a sphere and then projected the view as if you were suspended about a thousand miles above the planet – looking back.”
Each LORRI frame is about 400 km across.
This new mosaic of Pluto is from the latest high-resolution images sent to Earth from the New Horizons spacecraft shows what you would see if you were approximately 1,100 miles (1,800 kilometers) above Pluto’s equatorial area, looking northeast over the dark, cratered, informally named Cthulhu Regio toward the bright, smooth, expanse of icy plains informally called Sputnik Planum. The entire expanse of terrain seen in this image is 1,100 miles (1,800 kilometers) across. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
“It gives a breathtaking view of how diverse the geology is and also how diverse the seasonal volatile transport must be across the surface.”
“It’s just absolutely magical and breathtaking. There is a lot going on there.”
“The big bright area on the left side of the heart shaped feature is informally called Sputnik Planum after the first spacecraft – Sputnik. Surrounding the Texas sized plain are steep mountain ranges that are as tall as the Rockies in Colorado.”
What are Pluto’s plains and mountains comprised of?
“We know that the mountain ranges are not made of the same stuff as the planum, or plains. The plains are made of nitrogen. But nitrogen is too soft a material to build mountains out of, even in Pluto’s weak gravity.”
“So the mountains must be made of something else stronger. Rock and water ice are the two most likely possibilities. But they are most likely water ice, the lighter stuff. Because the rock has almost certainly sunk to the center of Pluto and the ice has floated to the top and formed the mantle and perhaps the crust of Pluto.”
“So we think the volatiles like the nitrogen, methane and carbon monoxide you see there and that shifts around with the seasons and interacts with the atmosphere – is just a veneer. It’s just a coating on the surface. And in some places its very thin and looks like it is breaking up on the margins. In other places it may be quite thick, maybe even kilometers thick.”
“We’ll see when we have more data!” exclaimed Stern.
“The data downlink will take over a year to get all the data to the ground [on Earth].”
“Over 50 gigabits of science data from the Pluto system needs to be sent back. The Pluto flyby took place on the 50th anniversary of NASA’s first flyby of Mars by Mariner IV. New Horizons dataset amounted to several thousand times more data collected compared to what Mariner IV sent back during its first flyby of Mars,” Stern elaborated.
“The surface of Pluto is every bit as complex as that of Mars,” says Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging (GGI) team at NASA’s Ames Research Center in Moffett Field, California. “The randomly jumbled mountains might be huge blocks of hard water ice floating within a vast, denser, softer deposit of frozen nitrogen within the region informally named Sputnik Planum.”
How much data has been returned so far varies by instrument.
“The average across all the entire science payload is only about 5 or 6 percent so far,” Stern explained.
“All the flyby data from the two plasma instruments – PEPSI and SWAP – and the Student Dust Counter instrument is back on the ground, because they were small datasets.”
“But less than 3% of the ALICE UV spectrometer data is back so far. And for the other imaging instruments its similar.”
“So it’s going to take about another year to send all the data back!”
This new global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This new mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Annotated with informal place names. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Marco Di Lorenzo/Ken Kremer/kenkremer.com
Stern informed that the team has submitted a paper to the journal Science and plans a large series of technical scientific presentations at upcoming meetings, including the Division of Planetary Sciences Meeting in Washington in November.
And New Horizons is in excellent shape to get those 50 gigabits of data back to the eagerly waiting researchers since all the spacecraft systems are operating normally.
“The spacecraft is doing very well,” said Alice Bowman, New Horizons Mission Operations Manager of the Johns Hopkins University Applied Physics Laboratory (APL), during the Weekly Space Hangout.
“It’s very healthy and we are getting back gobs of data – causing a flurry of emails among the science team.”
“It’s been a good ride and we had a good flyby of Jupiter too [along the way].”
This new global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Right side mosaic comprises twelve highest resolution views of Tombaugh Regio heart shaped feature and shows objects as small as 0.5 miles (0.8 kilometers) in size. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/ Ken Kremer/kenkremer.com/Marco Di Lorenzo
New Horizons also discovered that Pluto is the largest known body beyond Neptune – and thus reigns as the “King of the Kuiper Belt!”
As of today, Sept. 14, New Horizons is 2 months past the Pluto flyby and already over 73 million kilometers ( over 45 million miles) beyond Pluto and continuing its journey into the Kuiper Belt, the third realm of worlds in our solar system.
The science team plans to target New Horizons to fly by another much smaller Kuiper Belt Object (KBO) in 2019 after recently selecting the object dubbed PT1, for Potential Target 1, based on images taken by NASA’s Hubble Space Telescope.
“Since the flyby, we have been planning for the extended mission which we will propose to NASA next year,” Stern explained. NASA will then decide whether to approve and fund the new KBO mission proposal.
“We expect to do an engine burn for that [new KBO target] next month [in October]. The KBO flyby will take place about a billion miles beyond Pluto at about 44 AU.”
The actual flyby distance of New Horizons from the KBO is yet to be determined. Stern thinks it could perhaps be much closer, but all those details still need to be worked out.
NASA Associate Administrator for the Science Mission Directorate John Grunsfeld, left, New Horizons Principal Investigator Alan Stern of Southwest Research Institute (SwRI), Boulder, CO, second from left, New Horizons Mission Operations Manager Alice Bowman of the Johns Hopkins University Applied Physics Laboratory (APL), second from right, and New Horizons Project Manager Glen Fountain of APL, right, are seen at the conclusion of a press conference after the team received confirmation from the spacecraft that it has completed the flyby of Pluto, Tuesday, July 14, 2015 at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Credit: Ken Kremer/kenkremer.com
Watch for Ken’s continuing coverage of the Pluto flyby. He was onsite reporting live on the flyby and media briefings for Universe Today from the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Pluto Explored at Last
The New Horizons mission team celebrates successful flyby of Pluto in the moments after closest approach at 7:49 a.m. EDT on July 14, 2015. New Horizons Principal Investigator Alan Stern of Southwest Research Institute (SwRI), Boulder, CO., left, Johns Hopkins University Applied Physics Laboratory (APL) Director Ralph Semmel, center, and New Horizons Co-Investigator Will Grundy Lowell Observatory hold an enlarged print of an U.S. stamp with their suggested update after Pluto became the final planet in our solar system to be explored by an American space probe (crossing out the words ‘not yet’) – at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Credit: Ken Kremer/kenkremer.comHighest resolution mosaic of ‘Tombaugh Regio’ shows the heart-shaped region on Pluto focusing on ice flows and plains of ‘Sputnik Planum’ at top and icy mountain ranges of ‘Hillary Montes’ and ‘Norgay Montes’ below. This new mosaic combines the seven highest resolution images captured by NASA’s New Horizons LORRI imager during history making closest approach flyby on July 14, 2015. Inset at right shows global view of Pluto with location of mosaic and huge heart-shaped region in context. Annotated with place names. Credit: NASA/JHUAPL/SWRI/ Marco Di Lorenzo/Ken Kremer/kenkremer.comThis new global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This new mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Right side inset from New Horizons team focuses on Tombaugh Regio heart shaped feature. Annotated with informal place names. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Marco Di Lorenzo/Ken Kremer/kenkremer.com
Artist's impression of Pluto and its moons. Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Over the course of the past decade, many amazing discoveries have been made at the edge of the Solar System. Thanks to the work of astronomers working out of Earth-based observatories, with the Hubble Space Telescope, and those behind the recent New Horizons mission, not only have new objects been discovered, but additional discoveries have been made about the ones we already knew about.
For example, in 2005, two additional satellites were discovered in orbit of Pluto – Hydra and Nix. The discovery of these moons (which has since been followed by the discovery of two more) has taught astronomers much about the far-flung system of Pluto, and helped to advance our understanding of the Kuiper Belt.
Discovery and Naming:
Nix was discovered in June of 2005 by the Hubble Space Telescope Pluto Companion Search Team, using discovery images that were taken on May 15th and 18th, 2005. The team was composed of Hal A. Weaver, Alan Stern, Max J. Mutchler, Andrew J. Steffl, Marc W. Buie, William J. Merline, John R. Spencer, Eliot F. Young, and Leslie A. Young.
The discovery images of Nix (and Hydra) obtained by the Hubble Space Telescope. Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI)
Nix and Hydra were also independently discovered by Max J. Mutchler on June 15th, 2005, and by Andrew J. Steffl on August 15th, 2005. At the time, Nix was given the provisional designation of S/2005 P 2 and casually referred to as “P2”. Once pre-recovery images from 2002 were confirmed, the discoveries were announced on October 31st, 2005.
In accordance with IAU guidelines concerning the naming of satellites in the Solar System, the moon was named Nix. Derived from Greek mythology, Nix is the goddess of darkness and night, the mother of Charon and the ferryman of Hades (the Greek equivalent of Pluto) who brought the souls of the dead to the underworld.
The name was officially announced on June 21st, 2006, in an IAU Circular, where the designation “Pluto II” is also given. The initials N and H (for Nix and Hydra) were also a deliberate reference to the New Horizons mission, which would be conducting a flyby of the Pluto system in less than ten years time after the announcement was made.
Images acquired by the New Horizon’s probe of Nix (left) and Hydra (right) on July 14th, 2015. Credit: NASA/JHUAPL/SWRI
Size, Mass and Orbit: Based on observations with the Hubble Space Telescope of Nix’s geometric albedo and shape, the satellite was estimated to measure 56.3 km (35 mi) along its longest axis and 25.7 km (16 mi) wide. However, images provided by the New Horizons’ Ralph instrument on July 14th, 2015, indicated that Nix measures 42 km (26 mi) in length and 36 km (22 mi) wide.
Nix follows a circular orbit with very little eccentricity (0.0020) and a low inclination of approximately 0.13°. It is in the same orbital plane as Charon, is in a 3:2 orbital resonance with Hydra, and a 9:11 resonance with Styx. Its orbital period is roughly 24.9 days, meaning it takes about 25 days to complete a single orbit of Pluto.
As with Hydra and perhaps the other small Plutonian moons, Nix rotates chaotically, which is due mainly to its oblong shape. This means that the moon’s axial tilt and day length vary greatly over short timescales, to the point that it regularly flips over.
Composition: Early observations conducted by Marc W. Buie and William M. Grundy at the Lowell Observatory appeared to show that Nix has a reddish color like Pluto, but unlike any of its other moons. However, more-recent studies conducted by S. Alan Stern et al. using the Hubble Space Telescope’s Advanced Camera for Surveys (ACS), have indicated that it is likely as grey as the remaining satellites.
From these observations, it is likely that the surface of Nix is composed primarily of water ice (like Hydra) and may or may also have trace amount of methane ice on its surface. If true, then the exposure of these deposits of methane ice to ultra-violet radiation from the Sun would result in the presence of tholins, which would give it a reddish hue.
However, when the New Horizons space probe photographed Hydra and Nix during its flyby of the Pluto system, it spotted a large region with a distinctive red tint, probably a crater. The appearance of this surface region – a spot of red against an otherwise grey landscape – may explain these conflicting results.
Exploration: Thus far, only one mission has been performed to the Pluto system that resulted in close-up and detailed photographs of Nix. This would be the New Horizons mission, which flew through the Pluto-Charon system on July 14th, 2015 and photographed Hydra and Nix from an approximate distance of 640,000 km (400,000 mi).
Until July 13th, 2015, when NASA’s Long Range Reconnaissance Imager (LORRI) on board New Horizons determined Nix’s dimensions, its size was unknown. More images and information will be downloaded from the spacecraft between now and late 2016.
Prior to the discovery of Hydra and Nix in 2005, Pluto was believed to share its orbit with only the satellite of Charon – hence why astronomers often refer to it as the “Pluto-Charon system”. However, since the discovery of these two additional satellites in 2005, two more have been discovered – Kerberos in July of 2011 and Styx in July of 2012.
This raises the number of bodes in the Pluto-Charon system to one primary and five satellites. And thanks to the recent New Horizons flyby, we got to see all of them up close for the first time!
Like most large bodies in the Kuiper Belt (not to mention their satellites) much remains to be learned about Nix and its companions. In time, and with more missions to the outer Solar System, we are sure to address many of the mysteries surrounding this particular satellite, and will probably find many more waiting for us!
We have written many interesting articles on Pluto, its system of moons and the Kuiper Belt here at Universe Today.
Artist's impression of the Trans-Neptunian Object (TNO) 90482 Orcus. Credit: NASA
Since the early 2000s, more and more objects have been discovered in the outer Solar System that resemble planets. However, until they are officially classified, the terms Kuiper Belt Object (KBO) and Trans-Neptunian Object (TNO) are commonly used. This is certainly true of Orcus, another large object that was spotted in Pluto’s neighborhood about a decade ago.
Although similar in size and orbital characteristics to Pluto, Orcus is Pluto’s opposite in many ways. For this reason, Orcus is often referred to as the “anti-Pluto”, a fact that contributed greatly to the selection of its name. Although Orcus has not yet been officially categorized as a dwarf planet by the IAU, many astronomers agree that it meets all the requirements and will be in the future.
Discovery and Naming: Orcus was discovered on February 17th, 2004, by Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University. Although discovered using images that were taken in 2004, prerecovery images of Orcus have been identified going back as far as November 8th, 1951.
Provisionally known as 90482 2004 DW, by November 22nd, 2004, the name Orcus was assigned. In accordance with the IAU’s astronomical conventions, objects with a similar size and orbit to that of Pluto are to be named after underworld deities. Therefore, the discovery team suggested the name Orcus, after the Etruscan god of the underworld and the equivalent of the Roman god Pluto.
90482 Orcus. The location of Orcus is shown in the green circle (top, left). Credit: NASA
Size, Mass and Orbit: Given its distance, estimates of Orcus’ diameter and mass have varied over time. In 2008, observations made using the Spitzer Space Telescope in the far infrared placed its diameter at 958.4 ± 22.9 km. Subsequent observations made in 2013 using the Herschel Space Telescope at submillimeter wavelengths led to similar estimates being made.
In addition, Orcus appears to have an albedo of about 21% to 25%, which may be typical of trans-Neptunian objects approaching the 1000 km diameter range. However, these estimates were based on the assumption that Orcus was a singular object and not part of a system. The discovery of the relatively large satellite Vanth (see below) in 2007 by Brown et al. is likely to change these considerably.
The absolute magnitude of Vanth is estimated to be 4.88, which means that it is about 11 times fainter than Orcus itself. If the albedos of both bodies are the same at 0.23, then the diameter of Orcus would be closer to 892 -942 km, while Vanth would measure about 260 -293 km.
In terms of mass, the Orcus system is estimated to be 6.32 ± 0.05 ×1020 kg, which is about 3.8% the mass of the dwarf planet Eris. How this mass is partitioned between Orcus and Vanth depends of their relative sizes. If Vanth is 1/3rd the diameter Orcus, its mass is likely to be only 3% of the system. However, if it’s diameter is about half that of Orcus, then its mass could be as high as 1/12 of the system, or about 8% of the mass of Orcus.
Orcus compared to Earth and the Moon. Credit: Wikipedia Commons
Much like Pluto, Orcus has a very long orbital period, taking 245.18 years (89552 days) to complete a single rotation around the Sun. It also is in a 2:3 orbital resonance with Neptune and is above the ecliptic during perihelion. In addition, it’s orbit has a similar inclination and eccentricity as Pluto’s – 20.573° to the ecliptic, and 0.227, respectively.
In short, Orcus orbits the Sun at a distance of 30.27 AU (4.53 billion km) at perihelion and 48.07 AU (7.19 billion km) at aphelion. However, Pluto and Orcus are oriented differently. For one, Orcus is at aphelion when Pluto is at perihelion (and vice versa), and the aphelion of Orcus’s orbit points in nearly the opposite direction from Pluto’s. Hence why Orcus is often referred to as the “anti-Pluto”.
Composition: The density of the primary (and secondary assuming they have the same density) is estimated to be 1.5 g/cm3. In addition, spectroscopic and near-infrared observations have indicated that the surface is neutral in color and shows signs of water. Further infrared observations in 2004 by the European Southern Observatory and the Gemini Observatory indicated the possible presence of water ice and carbonaceous compounds.
This would indicate that Orcus is most likely differentiated between a rocky core and an icy mantle composed of water and methane ices as well as tholins – though not as much as other KBOs which are more reddish in appearance. The water and methane ices are believed to cover no more than 50% and 30% of the surface, respectively – which would mean the proportion of ice on the surface is less than on Charon, but similar to that on Triton.
Another interesting feature on Orcus is the presence of crystalline ice on its surface – which may be an indication of cryovolcanism – and the possible presence of ammonia dissolved in water and/or methane/ethane ices. This would make Orcus quite unique, since ammonia has not been detected on any other TNO or icy satellite of the outer planets (other than Uranus’ moon Miranda).
Moon: In 2011, Mike Brown and T.A. Suer detected a satellite in orbit of Orcus, based on images taken by the Hubble Space Telescope on November 13th, 2005. The satellite was given the designation S/2005 (90482) before being renamed Vanth on March 30th, 2005. This name was the result of an opinion poll where Mike Brown asked readers of his weekly column to submit their suggestions.
The name Vanth, after the Etruscan goddess who guided the souls of the dead to the underworld, was eventually chosen from among a large pool of submissions, which Brown then submitted to the IAU. The IAU’s Committee for Small Body Nomenclature assessed it and determined it fit with their naming procedures, and officially approved of it in March of 2010.
Vanth orbits Orcus in a nearly face-on circular orbit at a distance of 9030 ± 89 km. It has an eccentricity of about 0.007 and an orbital period of 9.54 days. In terms of how Orcus acquired it, it is not likely that it was the result of a collision with an object, since Vanth’s spectrum is very different from that of its primary.
Therefore, it is much more likely that Vanth is a captured KBO that Orcus acquired in the course of its history. However, it is also possible that Vanth could have originated as a result of rotational fission of the primordial Orcus, which would have rotated much faster billions of years ago than it does now.
Much like most other KBOs, there is much that we still don’t know about Orcus. There are currently no plans for a mission in the near future. But given the growing interest in the region, it would not be surprising at all if future missions to the outer Solar System were to include a flyby of this world. And as we learn more about Orcus’ size, shape and composition, we are likely to see it added to the list of confirmed dwarf planets.
For more information on Orcus, Vanth, check out the Planetary Society’s page on Orcus and Vanth. To learn more about how they were discovered, consult Mike Brown’s Planets.
Astronomy Cast also has a great interview with Mike Brown from Caltech.
