Astronomy

Could Pluto and Charon have extra-Solar origin?

Could Pluto and Charon have extra-Solar origin?


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Pluto and Charon seem to have surprisingly young surfaces, considering that resurfacing events were expected to be rare for them.

Could the explanation be that they actually are young? Formed later than the Solar system at some other star and then ejected and captured? Or that they are ancient but have extra-Solar origin and have little cratering because they have spent billions of years as a vagabond planet system in empty interstellar space? Sedna is believed to be captured.


(Edit, I think my original conclusion here was wrong, having read up about it).

While it seems probable that Pluto and Charon were formed by collision, I gather it's unlikely that this collision was so recent as to explain their lack of craters and young surface. The Collision, by most articles I've read, happened when the solar system was young, not in the last 100 million years.

Now, it's possible that none of this is certain, but I retract that part of my original post.

But, the creation of Charon by giant collision remains likely See here, and here. That would suggest formation within our solar-system, not from outside.

Pluto/Charon are also among a fairly common orbital region called Trans-Neptunian objects.

According to Wikipedia they suggest the collision that formed Charon happened 4.5 billion years ago.

Sedna (love the story, by the way), has a very elongated and distant orbit which seems more likely with capture of an object. I agree with everything James Kilfinger said. Rogue planet/Rogue object capture may happen from time to time, but the Rogue would need to get quite close to the sun for the sun to have sufficient gravitation to achieve the capture. Highly elongated orbits would seem likely for solar-system orbital capture. Pluto is only slightly elongated and not a good candidate. More massive suns should have significantly greater capture numbers, but that's kinda obvious I suppose.


The surface of Pluto is not just young, but very young, and also differentiated. The 'heart', Sputnik Planum, may be currently active, with flowing glaciers, and nitrogen snow. This area may have be resurfaced during Pluto's perihelion. Your theory cannot account for the very young age of the surface.

Next capture of a rogue planet is not easy. It would need Pluto to interact with the outer planets, to slow it down to enter solar orbit (otherwise a rogue planet would just pass through the solar system and come out the other side) A captured rogue would be unlikely to have the relatively low eccentricty of pluto.

Finally, while we don't know how common rogue planets are, they are probably not common, and given the massive distances between stars, the chances of any rogue just happening to have passed anywhere near the solar system in the last billion years in the right direction to be captured to Pluto's orbit is very low.

Conclusion. Pluto formed around the sun. A capture theory does not explain the observed young surface of Pluto, and modelling suggests a capture would be very unusual.


Pluto Statistics:

Discovered By: Clyde W. Tombaugh

Date Discovered: February 18, 1930

Diameter: 2,372 km

Mass: 1.31 × 10^22 kg (0.17 Moons)

Orbit Distance: 5,874,000,000 km (39.26 AU)

Orbital Period: 248 years

Surface Temperature: -229 degrees C

Pluto is smaller than our moon and is a mysterious world that has valleys, plains, craters, and possibly glaciers. It has five moons and the biggest moon is Charon, which is almost half the size of Pluto.

Charon and Pluto are listed as a “double planet” because they orbit so close to each other. Charon is listed as the largest satellite relative to its parent planet in our solar system.

It is thanks to the New Horizon spacecraft that we have learned so much about Pluto and its complex geology.


Contents

Charon was discovered by United States Naval Observatory astronomer James Christy, using the 1.55-meter (61 in) telescope at United States Naval Observatory Flagstaff Station (NOFS). [19] On June 22, 1978, he had been examining highly magnified images of Pluto on photographic plates taken with the telescope two months prior. Christy noticed that a slight elongation appeared periodically. The bulge was confirmed on plates dating back to April 29, 1965. [20] The International Astronomical Union formally announced Christy's discovery to the world on July 7, 1978. [21]

Subsequent observations of Pluto determined that the bulge was due to a smaller accompanying body. The periodicity of the bulge corresponded to Pluto's rotation period, which was previously known from Pluto's light curve. This indicated a synchronous orbit, which strongly suggested that the bulge effect was real and not spurious. This resulted in reassessments of Pluto's size, mass, and other physical characteristics because the calculated mass and albedo of the Pluto–Charon system had previously been attributed to Pluto alone.

Doubts about Charon's existence were erased when it and Pluto entered a five-year period of mutual eclipses and transits between 1985 and 1990. This occurs when the Pluto–Charon orbital plane is edge-on as seen from Earth, which only happens at two intervals in Pluto's 248-year orbital period. It was fortuitous that one of these intervals happened to occur soon after Charon's discovery.

Author Edmond Hamilton referred to three moons of Pluto in his 1940 science fiction novel Calling Captain Future, naming them Charon, Styx, and Cerberus. [23]

After its discovery, Charon was originally known by the temporary designation S/1978 P 1, according to the then recently instituted convention. On June 24, 1978, Christy first suggested the name Charon as a scientific-sounding version of his wife Charlene's nickname, "Char". [22] [24] Although colleagues at the Naval Observatory proposed Persephone, Christy stuck with Charon after discovering that it coincidentally refers to a Greek mythological figure: [22] Charon ( / ˈ k ɛər ən / [2] Greek Χάρων) is the ferryman of the dead, closely associated in myth with the god Hades or Plouton (Greek: Πλούτων, Ploútōn), whom the Romans identified with their god Pluto. The IAU officially adopted the name in late 1985 and it was announced on January 3, 1986. [25]

There is minor debate over the preferred pronunciation of the name. The practice of following the classical pronunciation established for the mythological ferryman Charon, with a "k" sound, is used by major English-language dictionaries, such as the Merriam-Webster and Oxford English dictionaries. [26] [27] These indicate only the "k" pronunciation of "Charon" when referring specifically to Pluto's moon. Speakers of languages other than English, and many English-speaking astronomers as well, follow this pronunciation. [28]

However, Christy himself pronounced the initial ch as a "sh" sound (IPA / ʃ / ), after his wife Charlene. Many astronomers follow this convention, [note 3] [28] [29] [30] and it is the prescribed pronunciation at NASA and of the New Horizons team. [3] [note 4]

Simulation work published in 2005 by Robin Canup suggested that Charon could have been formed by a collision around 4.5 billion years ago, much like Earth and the Moon. In this model, a large Kuiper belt object struck Pluto at high velocity, destroying itself and blasting off much of Pluto's outer mantle, and Charon coalesced from the debris. [31] However, such an impact should result in an icier Charon and rockier Pluto than scientists have found. It is now thought that Pluto and Charon might have been two bodies that collided before going into orbit about each other. The collision would have been violent enough to boil off volatile ices like methane ( CH
4 ) but not violent enough to have destroyed either body. The very similar density of Pluto and Charon implies that the parent bodies were not fully differentiated when the impact occurred. [11]

Charon and Pluto orbit each other every 6.387 days. The two objects are gravitationally locked to one another, so each keeps the same face towards the other. This is a case of mutual tidal locking, as compared to that of the Earth and the Moon, where the Moon always shows the same face to Earth, but not vice versa. The average distance between Charon and Pluto is 19,570 kilometres (12,160 mi). The discovery of Charon allowed astronomers to calculate accurately the mass of the Plutonian system, and mutual occultations revealed their sizes. However, neither indicated the two bodies' individual masses, which could only be estimated, until the discovery of Pluto's outer moons in late 2005. Details in the orbits of the outer moons revealed that Charon has approximately 12% of the mass of Pluto. [10]

Charon's diameter is 1,212 kilometres (753 mi), just over half that of Pluto. [11] [12] Larger than the dwarf planet Ceres, it is the twelfth largest natural satellite in the Solar System. Charon's slow rotation means that there should be little flattening or tidal distortion, if Charon is sufficiently massive to be in hydrostatic equilibrium. Any deviation from a perfect sphere is too small to have been detected by observations by the New Horizons mission. This is in contrast to Iapetus, a Saturnian moon similar in size to Charon but with a pronounced oblateness dating to early in its history. The lack of such oblateness in Charon could mean that it is currently in hydrostatic equilibrium, or simply that its orbit approached its current one early in its history, when it was still warm. [13]

Based on mass updates from observations made by New Horizons [12] the mass ratio of Charon to Pluto is 0.1218:1. This is much larger than the Moon to the Earth: 0.0123:1. Because of the high mass ratio, the barycenter is outside of the radius of Pluto, and the Pluto–Charon system has been referred to as a dwarf double planet. With four smaller satellites in orbit about the two larger worlds, the Pluto–Charon system has been considered in studies of the orbital stability of circumbinary planets. [32]

Interior Edit

Charon's volume and mass allow calculation of its density, 1.702 ± 0.017 g/cm 3 , [12] from which it can be determined that Charon is slightly less dense than Pluto and suggesting a composition of 55% rock to 45% ice (± 5%), whereas Pluto is about 70% rock. The difference is considerably lower than that of most suspected collisional satellites. Before New Horizons' flyby, there were two conflicting theories about Charon's internal structure: some scientists thought Charon to be a differentiated body like Pluto, with a rocky core and an icy mantle, whereas others thought it would be uniform throughout. [33] Evidence in support of the former position was found in 2007, when observations by the Gemini Observatory of patches of ammonia hydrates and water crystals on the surface of Charon suggested the presence of active cryogeysers. The fact that the ice was still in crystalline form suggested it had been deposited recently, because solar radiation would have degraded it to an amorphous state after roughly thirty thousand years. [34]

Surface Edit

Unlike Pluto's surface, which is composed of nitrogen and methane ices, Charon's surface appears to be dominated by the less volatile water ice. In 2007, observations by the Gemini Observatory of patches of ammonia hydrates and water crystals on the surface of Charon suggested the presence of active cryogeysers and cryovolcanoes. [34] [35]

Photometric mapping of Charon's surface shows a latitudinal trend in albedo, with a bright equatorial band and darker poles. The north polar region is dominated by a very large dark area informally dubbed "Mordor" by the New Horizons team. [36] [37] [38] The favored explanation for this phenomenon is that they are formed by condensation of gases that escaped from Pluto's atmosphere. In winter, the temperature is −258 °C, and these gases, which include nitrogen, carbon monoxide, and methane, condense into their solid forms when these ices are subjected to solar radiation, they chemically react to form various reddish tholins. Later, when the area is again heated by the Sun as Charon's seasons change, the temperature at the pole rises to −213 °C, resulting in the volatiles sublimating and escaping Charon, leaving only the tholins behind. Over millions of years, the residual tholin builds up thick layers, obscuring the icy crust. [39] In addition to Mordor, New Horizons found evidence of extensive past geology that suggests that Charon is probably differentiated [37] in particular, the southern hemisphere has fewer craters than the northern and is considerably less rugged, suggesting that a massive resurfacing event—perhaps prompted by the partial or complete freezing of an internal ocean—occurred at some point in the past and removed many of the earlier craters. [40]

In 2018, the International Astronomical Union named one crater on Charon, as Revati who is a character in the Hindu epic Mahabharata. [41] [42]

Charon has a series of extensive grabens or canyons, such as Serenity Chasma, which extend as an equatorial belt for at least 1,000 km (620 mi). Argo Chasma potentially reaches as deep as 9 km (6 mi), with steep cliffs that may rival Verona Rupes on Miranda for the title of tallest cliff in the solar system. [43]

Mountain in a moat Edit

In a released photo by New Horizons, an unusual surface feature has captivated and baffled the scientist team of the mission. The image reveals a mountain rising out of a depression. It's "a large mountain sitting in a moat", said Jeff Moore, of NASA's Ames Research Center, in a statement. "This is a feature that has geologists stunned and stumped", he added. New Horizons captured the photo from a distance of 79,000 km (49,000 mi). [44] [45]

Since the first blurred images of the moon (1), images showing Pluto and Charon resolved into separate disks were taken for the first time by the Hubble Space Telescope in the 1990s (2). The telescope was responsible for the best, yet low quality images of the moon. In 1994, the clearest picture of the Pluto–Charon system showed two distinct and well defined circles (3). The image was taken by Hubble's Faint Object Camera (FOC) when the system was 4.4 billion kilometers (2.6 billion miles) away from Earth [46] Later, the development of adaptive optics made it possible to resolve Pluto and Charon into separate disks using ground-based telescopes. [24]

In June 2015, the New Horizons spacecraft captured consecutive images of the Pluto–Charon system as it approached it. The images were put together in an animation. It was the best image of Charon to that date (4). In July 2015, the New Horizons spacecraft made its closest approach to the Pluto system. It is the only spacecraft to date to have visited and studied Charon. Charon's discoverer James Christy and the children of Clyde Tombaugh were guests at the Johns Hopkins Applied Physics Laboratory during the New Horizons closest approach.


Pluto and Charon: The Odd Couple

By: J. Kelly Beatty July 13, 2015 6

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With just one day remaining until New Horizons makes its historic flyby, missions scientists are amazed by the views of Pluto and Charon already in hand.

Normally the campus of Johns Hopkins University's Applied Physics Laboratory in Laurel, Maryland, is quiet, even pastoral. But nothing is normal about the events of this week.

New Horizons' last look at Pluto's Charon-facing hemisphere reveals intriguing geologic details that are of keen interest to mission scientists. This image, taken early the morning of July 11, 2015, shows newly-resolved linear features above the equatorial region that intersect, suggestive of polygonal shapes. This image was captured when the spacecraft was 2.5 million miles (4 million km) from Pluto.
NASA / JHU-APL / Southwest Research Institute

Tomorrow morning, at 11:49:58 Universal Time (about 7:50 a.m. Eastern Daylight Time), NASA's New Horizons spacecraft will zip past Pluto at 8.6 miles (13.8 km) per second. It's history in the making, and more than 200 news-media representatives have flocked to APL to be as close to the action as we can. So has virtually anyone who's ever had anything to do with Pluto — outer-planet researchers from across the U.S., the children of Clyde Tombaugh (Pluto's discoverer), James Christy (who found its largest moon, Charon), and a host of others.

In a way, it's The Last Picture Show in the 50-year-long exploration of our solar system by spacecraft. With all due respect to small-body missions like Dawn, Rosetta, and Hayabusa, Pluto represents a final milestone in our exploratory push outward from the Sun — "unfinished business," notes Alan Stern, the driving force behind New Horizons and its principal investigator.

(It's perhaps worth noting that, when this spacecraft left Earth in January 2006, the International Astronomical Union still considered Pluto the ninth and most distant major planet.)

And yet it's also The First Picture Show, our initial reconnaissance of a world in the frigid "third zone" of the solar system (the others being the realms of the four terrestrial and four giant planets). Stern points out that roughly 40% of all Americans weren't old enough to remember Voyager 2's encounter with Neptune in 1989. So not only are we seeing, up close, our first denizen of the distant Kuiper Belt, but we're also experiencing the thrill of seeing a sizable world revealed for the first time in a quarter century.

New Horizons captured orange-tinged Pluto and gray Charon together on July 8th. (Original LORRI image is black and white, and color information has been added from earlier images.)
NASA / JHU-APL / Southwest Research Institute

Observing from Earth and with the Hubble Space Telescope, planetary astronomers already knew basics like approximate diameters and overall surface reflectivity. They knew Pluto and Charon rotate in a gravitational coupling that keeps one hemisphere of each locked in the direction of its partner. Spectroscopy had revealed crude surface compositions (Pluto has frosts of methane and nitrogen, whereas Charon is covered in water ice), and an occultation by Pluto in 1988 showed that it has a thin atmosphere.

One basic characteristic of Pluto that has eluded astronomers until now is its diameter. However, today Stern reported a new, more accurate value based on the spacecraft's imagery: 2,370 km (1,475 miles) with an uncertainty of ± 20 km. Based on previous occultation work, researchers assumed it was at least 2,302 km but really didn't know the real value very well. That simple refinement has three immediate consequences:

  • Pluto is slightly larger than Eris (2,336 ± 12 km) the two had been in competition for King of the Kuiper Belt since the latter's discovery a decade ago. Interestingly, despite being very slightly smaller, Eris has a mass 27% greater than Pluto's.
  • Overall, Pluto's density must be lower than thought, somewhere around 1.90 g/cm³ instead of 2.05 g/cm³. The thinking had been that Pluto must be about 70% rock and 30% (mostly water) ice, but the ice fraction is apparently somewhat higher.
  • The larger radius means that the "dense" lower portion of Pluto's ultra-thin atmosphere, the part that can't be probed during stellar occultations, must be shallower than thought.

Based on the images and other data received from New Horizons in the past few days, Pluto and its cohort of five moons are not going to disappoint us. Instead, missions scientists are already talking about how so many of the results to date have been unexpected.

Two Very Different Worlds

Most obvious are the night-and-day differences between Pluto and Charon. The spacecraft has been sending a steady trickle of images and other measurements back to its handlers on Earth, and those confirm most of what we thought we knew. But now we clearly see that much of Pluto's equator is girded by an interconnected patchwork of dark features. The polar regions appear to be capped with icy frosts. At today's briefing, Stern announced that the craft's infrared spectrometer had confirmed the polar presence of nitrogen and methane ices.

Conversely, Charon is dark at its northern pole, and its surface is rather uniformly colored. Craters, fractures, and other physical features are emerging from the ever-improving resolution. One particularly obvious gash crosses the southern hemisphere and appears to be longer and and much deeper than Earth's Grand Canyon.

Chasms, craters, and a dark north polar region are revealed in this image of Pluto's largest moon Charon taken by New Horizons on July 11, 2015.
NASA / JHU-APL / Southwest Research Institute

Meanwhile, the instrument called PEPSSI (short for Pluto Energetic Particle Spectrometer Science Investigation) detected nitrogen ions — escapees from Pluto's atmosphere — five days ago and roughly 4 million miles (6 million km) on its sunward side. Apparently neutral molecules are flying away in all directions (Pluto's escape velocity is only 1.2 km per second), then become ionized either by ultraviolet sunlight or by interacting with the solar wind.

One of the mission's major scientific objectives is to determine how rapidly Pluto is losing gas to interplanetary space. But encountering nitrogen so far away defies the pre-encounter models. Maybe there's more gas in the atmosphere than believed, or the conversion to ions is unusually efficient, or some mechanism is concentrating nitrogen along the spacecraft's flight path.

While the best is yet to come, don't expect a deluge of awesome imagery right after the flyby. In fact, New Horizons will be so totally preoccupied with its preplanned observations of Pluto & Co. tomorrow that it will remain incommunicado for more than 12 hours after its closest approach. The mission team won't even know whether the spacecraft survived its encounter — let alone successfully stashed the scientific goods in its onboard memory — until 8:53 p.m. EDT tomorrow night.

That bit of news will be the most anticipated of the entire 9½-year-long mission.


Did Pluto's Weird Red Spots Result from Crash That Spawned Charon?

Mysterious dark reddish spots along Pluto's equator may be the aftermath of the giant impact that helped form the dwarf planet's largest moon Charon, a new study finds.

This finding could also help explain the strangely wide variety of colors seen in distant objects in the solar system's Kuiper belt, researchers say.

One of the most striking features of Pluto that NASA's New Horizons probe photographed during its July 2015 flyby is the dark reddish material found in giant spots along the dwarf planet's equator. The biggest example of these patches is the region informally known as Cthulhu (pronounced "k-thu-lu"), which stretches nearly halfway around Pluto's equator. [See more amazing Pluto photos by New Horizons]

Cthulhu, named after the monstrous fictional deity from the works of H. P. Lovecraft, is about 1,850 miles (3,000 kilometers) long and 450 miles (750 km) wide, and with a size of more than 700,000 square miles (1.8 million square km), Cthulhu is larger than Alaska.

These dark reddish spots may contain organic matter &mdash specifically, tar-like materials known as tholins. It remains uncertain how these patches were created. While comets might have scattered tholins onto Pluto's surface, or light or high-energy radiation could have chemically reacted with the dwarf planet's surface to create these compounds, both of these activities would have darkened the dwarf planet's surface. That, however, is not consistent with the presence of bright water-ice bedrock seen there.

Now, researchers in Japan suggest this dark reddish material was created by the giant collision that may have given birth to Charon. Just as Earth's moon likely arose from the debris of a Mars-size body's crash into the newborn Earth, so has previous work proposed that Charon was the result of a cosmic impact.

The scientists said that both Pluto and whatever struck it likely contained simple organic compounds typically found in comets, such as formaldehyde. They also reasoned that these molecules may have made their way into temporary pools of warm liquid water that would likely have existed after the impact melted a significant part of Pluto's surface.

In lab experiments, the researchers heated soups of water and simple organic compounds such as formaldehyde for many hours. The concentrations of the organic molecules in these solutions were comparable to those found in comets.

The scientists found these soups became darker and redder over time as complex organic compounds formed. After heating for more than 1,000 hours at 122 degrees F (50 degrees Celsius) or greater, they resembled the material in Pluto's mysterious equatorial dark spots.

In computer simulations, the researchers found that an impactor one-third Pluto's mass colliding with a Pluto-size object could have generated a Charon-size moon and "warm, liquid-water pools near the equatorial regions of the Pluto-sized object," said study lead author Yasuhito Sekine, a planetary scientist at the University of Tokyo. (The impact is strong enough to significantly tilt the Pluto-size object, such that the point of impact controls where the dwarf planet's new equator lies, and the warm pools form along the equator.)

The researchers suggest that in the warm pools of liquid water that would have temporarily existed after the impact, simple organic molecules from either Pluto, the impactor or both could have formed more complex organic materials, such as tholins. Therefore, the Cthulhu region and the other dark reddish spots on Pluto may be "a smoking gun of the giant impact origin of Charon," Sekine told Space.com.

The researchers suggest that high-speed giant impacts may have occurred frequently in the outer regions of the ancient solar system. These collisions may explain the mysterious variety of color, brightness and density seen in large objects in the Kuiper belt, Sekine said.

The scientists detailed their findings online today (Jan. 30) in the journal Nature Astronomy.


Pluto at 75: a uniquely American anniversary

Seventy-five years ago this month, in February of 1930, our solar system’s ninth planet, Pluto, was discovered. The discovery of Pluto𔃊,500 kilometers wide and fully a billion kilometers beyond Neptune—was made by Clyde Tombaugh (1906�), a plucky, twenty-four-year-old American astronomer working at Lowell Observatory in Flagstaff, Arizona when he made the landmark find.

News of the long-anticipated discovery of “Planet X” rocketed around the world in the spring of 1930, making Tombaugh instantly famous, and garnering a high-profile scientific achievement for what was by then routinely called the “the American Century.”

Diminutive Pluto, lying beyond both the rocky inner planet and outer gas giant planet zones of our solar system, was for many years an apparent misfit among the planets. Even after its large satellite, Charon, was discovered in 1978, Pluto’s classification and scientific value seemed problematic. Today, in 2005, that is no longer the case.

The ninth planet is the biggest, the brightest, and the first-discovered member of the solar system’s third major architectural zone—the distant and icy Kuiper Belt.

Not even Tombaugh and his mentors could have forecast how fascinating their new planet would turn out to be. For eventually, when the technology of astronomy made the detailed investigations of bodies as far away and faint as Pluto-Charon possible, this distant planet-satellite pair turned out to be full of enticing surprises. The ninth planet was revealed to be the first known world with a satellite so large it could be called a double planet, a world with complex seasons and a chaotic orbit, and the only planet with an atmosphere that freezes out and then is reborn every orbit. Pluto, replete with polar caps and fresh snows of not one, but three exotic surface ices—methane, nitrogen, and carbon monoxide—is an exotic wonderland on the ragged edge of the solar system’s vast outer wilderness.

Even beyond its own fascinating and scientifically titillating attributes, few in 1930 could have imagined that the discovery of Pluto signaled not just a new planet, but—more importantly—the opening salvo of what would become thousands of discoveries of large, icy bodies on a frontier beyond Neptune. Indeed, with the discovery of the vast population of bodies orbiting beyond Neptune in the early 1990s, Pluto’s cohort, and thus its context became clear: The ninth planet is the biggest, the brightest, and the first-discovered member of the solar system’s third major architectural zone—the distant and icy Kuiper Belt.

The discovery of the Kuiper Belt has fueled a revolution in our understanding of the origin, architecture, and richness of the deep outer solar system. Together, Pluto-Charon and the Kuiper Belt constitute an exciting frontier for scientific exploration, rich with possibilities for illuminating the origin of the planets, the formation of planetary satellites and double planet pairs, the interior properties and surface evolution of icy worlds, and the physics of tenuous atmospheres.

In fact, so valuable are the Pluto-Charon system and its Kuiper Belt companions, that their exploration was ranked as the highest priority new mission to launch in this decade by the National Academy of Sciences in its Planetary Decadal Survey report to NASA.

In the 75 years since Pluto was discovered, the United States has become the leading nation on Earth in both astronomy and space exploration. Making a history for itself that will outlast even this new millennium, the United States has sent the first spacecraft to all of the worlds of our solar system from Mercury to Neptune, and placed teams of human explorers on the Moon six times.

Today the US has robotic explorers orbiting Mars and Saturn, roving the surface of Mars, and on their way to comets, the planet Mercury, and even the boundary with interstellar space. Later in the 21st Century, America aspires to put human explorers on the deserts of Mars and on other worlds.

When the discovery of planet Pluto was announced in March of 1930, no one could have rightfully imagined this would all come to pass within the lifetime of Americans already living in that year. So too, no one might have imagined—in those days when Lindbergh’s crossing of the Atlantic was still a recent technological feat—that Pluto would, within the span of a single human lifetime, be visited by a craft from Earth.

At the time of its discovery, no one might have imagined that Pluto would, within the span of a single human lifetime, be visited by a craft from Earth.

Yet the scientific wonderland of Pluto, its giant moon Charon, and the Kuiper Belt is the destination for NASA’s New Horizons mission, which plans to launch in early 2006. If all goes as planned, New Horizons will cross the entire span of the solar system in record time and conduct flyby reconnaissance studies of the Pluto-Charon system in 2015 and then one or more Kuiper Belt objects before 2020.

In accomplishing this historic feat, America will complete the reconnaissance of all the known planets, and provide a new and vivid demonstration of the historic kinds of space exploration that only it has the technical prowess to achieve.

A planetary scientist, Dr. Alan Stern is the Principal Investigator of the New Horizons Pluto-Kuiper Belt mission and director of the Department of Space Studies at the Southwest Research Institute.


Astronomy of Planets

In this project we will investigate rogue planets, formally known as Free-Floating Planets (FFPs). We will explore how their existence was initially supposed, and how they may be detected. Most exoplanets are detected using properties related to their host star, so detecting planets that orbit no star poses significant difficulties. Techniques like transit observation, the radial velocity method, and astrometry are all inapplicable. The primary goal of this research is to determine how rogue planet detection occurs, and establish why this method of detection is reliable. The answer is that Gravitational Microlensing is the primary method used in rogue planet detection, and its credibility arises from its derivation from Einstein’s Theory of General Relativity. Research into the origins and properties of rogue planets can tell us interesting things about the formation of our own solar system, the composition of Dark Matter in our galaxy, and the conditions necessary for life.

An Exploration into the Exoplanet "Luyten B" (Winter 2018)

Exoplanets are planets that are located outside of our solar system. They were once thought to be rare but, as time has gone on, more and more are being discovered. Luyten, or GJ273, is a star located 12.36 light years away from the sun. Surrounding it, are two incredibly intriguing exoplanets that have caught the attention of many astronomers. Luyten B is a planet that is incredibly close to earth, and is categorized as a potential “Super-Earth”. While there are many variables that are unknown, which may dismiss the planets habitability, the possibility and promise of Luyten B having potential to hold liquid water on its surface makes it one that can bring excitement to research and curiosity. What our research will explore is how Luyten and its exoplanet Luyten B were discovered, the type of star it is and how this affects habitability, the habitability zone and its implications for potential life, and its orbit and rotation. Luyten C, Luyten’s inner planet, is located too close to its host star to have the chance to have liquid water.

An incredibly fascinating aspect of this exoplanet in particular is that upon the release of the hopeful likelihood that this planet could potentially support life, METI (Messaging extra-terrestrial Intelligence) International put together an encoded sonar message containing 6 different musical compositions and encoded mathematical and scientific tutorials. Doug Vakoch, president of METI states that “we’ve sent a signal we would like to receive here on earth”. They predict that if the message is received and processed we could receive a response as soon as 2042.


Courtesy of NASA, Ames, JPL-Caltech

Kepler 452b: Second Earth (Fall 2017)

The possibility for life on other planets is something that has captivated our society since we first began exploring the space that exists beyond our earth. Technology is currently limited to only viewing these planets existing outside our solar system, however, it is plausible that with technology continually advancing, in the future these planets may not seem so far out of reach. In 2015, the earth-like exoplanet Kepler 452b was discovered by the NASA Kepler telescope.1 This discovery prompted an inquisition into the possibility for this planet to sustain life. Though this concept cannot currently be accepted or denied, this research will explore the parameters necessary for life on exoplanets, and which of these may be possible for Kepler 452b.

Courtesy of Amanda J. Smith

The Search for Exoplanets: A Habitable Suitor (Winter 2017)

The hunt for exoplanets is one of the fastest-growing enterprises in astronomy, and for very good reason. An exoplanet, or extra-solar planet, is any planet that orbits a star other than our own Sun. These planets vary in size and distance from their star. If we can find planets with similar composition and features to Earth, we may discover extraterrestrial life, or a potential future home for humanity. This page will explore one of the most bountiful results of the exoplanet search, TRAPPIST-1, anaylsing the composition of this planetary system and the methods used by astronomers to discover it, and how research of this planet will proceed in the future.

The Search for Exoplanets: A Habitable Suitor (Winter 2017)

Since humanity first turned its eyes towards the night sky and gazed in awe at the infinite wonder of the universe, we have been captivated by space. Exploration and discovery is as much a part of our human nature, as our desire to observe the depths of our origins, and understand the unknown. The search for exoplanets is one of the foremost, growing fields in the exploration of space. Exoplanets are planets located in distant extrasolar systems, orbiting stars other than our own, and vary in size from larger than Jupiter, to smaller than Earth.

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Proxima Centauri B: Is there an Earth-like planet orbiting our nearest neighbour? (Fall 2016)

Proxima Centauri B is a planet that orbits a star outside of the solar system, which is known as an exoplanet. This exoplanet was thought to be previously discovered in 2012 by astronomers but proved to be a false signal due to insufficient data. Advancements in instruments allowed researchers to verify the signal which led to the discovery of exoplanet Proxima Centauri B in 2016

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Until relatively recently in human history, our observational capacity from Earth has been rather limited. Presently technological advancements and innovations have arisen allowing us to uncover and understand more of the mysteries and intricacies of the universe. Recent observational research initiatives have led to the discovery of planets outside our solar system, known as exoplanets. These discoveries have raised many questions including whether or not any planets would be capable of supporting life, which has fueled motivation for additional research


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RESEARCH ARTICLES A Giant Impact Origin of Pluto Charon Robin M Canup Pluto and its moon Charon are the most prominent members of the Kuiper belt and their existence holds clues to outer solar system formation processes Here hydrodynamic simulations are used to demonstrate that the formation of Pluto Charon by means of a large collision is quite plausible I show that such an impact probably produced an intact Charon although it is possible that a disk of material orbited Pluto from which Charon later accumulated These findings suggest that collisions between 1000 kilometer class objects occurred in the early inner Kuiper belt The Pluto Charon pair shares key traits with the Earth Moon system Each satellite mass is substantial compared to its planet Charon s mass is 10 to 15 of Pluto s mass and the Moon s mass is 1 of Earth s mass All other satellite to planet mass ratios in our solar system are less than 2 10j4 The orbits of Charon and the Moon are consistent with a scenario in which each satellite formed much closer to its planet and torques due to tides raised on the planet by the satellite subsequently caused the satellite s orbit to expand to its current separation The angular momentum of both pairs is large within a factor of several of the critical angular momentum for rotational stability of a single object containing the total system mass In both cases an origin by Bgiant impact in which a large oblique collision with the growing planet produced its satellite and provided the system with its angular momentum is favored 1 4 However to date the viability of this mode of origin has only been demonstrated for the Earth Moon case Models of lunar forming impacts 4 7 produce disks orbiting the planet containing about 1 to 3 of the planet s mass and as such the feasibility of forming the proportionally more massive Charon has been unknown Although giant impacts are believed common in the final stage of terrestrial planet formation in the inner solar system 8 their role in the outer solar system and the Kuiper belt Ea disk of objects orbiting exterior to Neptune between about 30 and 50 astronomical units AU is more uncertain 9 The origin of Pluto Charon provides a key constraint to this issue and to the population of objects in the primordial Kuiper belt Properties of the distant Pluto Charon pair Esupporting online material SOM Southwest Research Institute Boulder CO 80302 USA and Division of Geological and Planetary Sciences California Institute of Technology Pasadena CA 91125 USA E mail robin boulder swri edu 546 text remain somewhat uncertain Pluto and Charon have physical radii of RP 1150 to 1200 km and RC 590 to 620 km and their densities are rP 1 8 to 2 1 g cm3 and rC 1 6 to 1 8 g cm3 indicating rock ice compositions with about 50 to 80 rock by mass 10 Scaling the angular momentum of the Pluto Charon binary LPC by the quantity q 3 R L K GMPC PC where RPC is the radius of an equivalent spherical object containing the total Pluto Charon system mass MPC and G is the gravitational constant gives the normalized system angular momentum JPC K LPC L which is in the range 0 33 G JPC G 0 46 for a Charon to Pluto mass ratio q in the range 0 1 G q G 0 15 Here I present smooth particle hydrodynamic SPH simulations to show that giant impacts can produce Pluto Charon type systems with q 9 0 1 and J 0 4 In SPH an object is described by a multitude of overlapping particles each of which represent a three dimensional 3D distribution of matter of a specified composition whose properties are tracked in time in a Lagrangian manner In these simulations particles are evolved due to gravity compressional heating and expansional cooling and shock dissipation 11 and the Analytic Equation of State M ANEOS 12 13 is used with material constants by Pierazzo and Melosh 14 For a full description of the SPH technique see 15 from whose work the code used here is directly descended The SPH simulations involved between N 0 2 104 and 1 2 105 particles and a simulated time of 1 to 4 days Given that the appropriate differentiation state and composition of the colliding objects is uncertain I considered three initial compositions i SER 100 undifferentiated serpentine EMg3Si2O5 OH 4 a hydrated silicate containing 14 H2O by weight ii IDI 40 water ice 42 dunite and 18 iron by mass and differentiated into 28 JANUARY 2005 VOL 307 SCIENCE an ice mantle rock core and iron inner core and iii SIM 50 serpentine and 50 water ice in an undifferentiated mixture These objects range from uniform to highly differentiated with rock mass fractions between 43 and 86 and bulk densities between 1 5 to 2 5 g cm3 I modeled a variety of impacts that were all capable of providing an angular momentum within the range for Pluto Charon The collision of two nonspinning equal density objects delivers a normalized angular momentum 16 Jcol K p Lcol vimp 0 2 f g b vesc L 1 where b K sin x is the scaled impact parameter x is the angle between the surface normal and the impact trajectory a grazing impact has b 0 1 g is the impactor to total mass q ratio f g K g 1 j g g1 3 1 j g 1 3 and vimp vesc is the ratio of the impact velocity to the mutual escape velocity with v2imp K v2esc vV2 where vV is the relative velocity at large p separation Here vesc K 2GMT Rimp Rtar where MT is the total colliding mass and Rimp and Rtar are the impactor and target radii respectively A preimpact spin Edue to earlier impacts 8 17 that had a component in the same rotational sense as the impact Bprograde would increase Jimp For the case of prograde spin vectors normal to the plane of the impact the additional contribution is Jspin 0 Kimp Tmin 5 3 Tmin g Ktar 1 j g 5 3 Timp Ttar 2 where Jimp 0 Jcol Jspin Kimp and Ktar are the moment of inertia constants of the colliding objects Timp and Ttar are the preimpact spin periods of the impactor and target and the minimum period for rotational stability is Tmin K p 3p Gr 0 2 3 hours r 2g cm3 j1 2 where r is the density of the objects Here collisions with 0 5 G b G 1 1 G vimp vesc G 2 5 or 0 G vV G 2 5 km s 0 13 G g G 0 5 and with 18 and without preimpact spin are simulated Results An impact between predifferentiated IDI composition identical objects each of which contained 0 53 MPC so that g 0 0 5 and had an initial prograde 7 hour day produces a planet disk system Fig 1 This b 0 0 83 collision had vimp 0 vesc and Jimp 0 0 43 …


Pluto-Charon origin may mirror that of Earth and its Moon

The evolution of Kuiper Belt objects, Pluto and its lone moon Charon may have something in common with Earth and our single Moon: a giant impact in the distant past.
Dr. Robin Canup, assistant director of Southwest Research Institute's® (SwRI) Department of Space Studies, argues for such an origin for the Pluto-Charon pair in an article for the January 28 issue of the journal Science.

Canup, who currently is a visiting professor at the California Institute of Technology, has worked extensively on a similar "giant collision" scenario to explain the Moon's origin.

In both the Earth-Moon and Pluto-Charon cases, Canup's smooth particle hydrodynamic simulations depict an origin in which a large, oblique collision with the growing planet produced its satellite and provided the current planet-moon system with its angular momentum.

While the Moon has only about 1 percent of the mass of Earth, Charon accounts for a much larger 10 to 15 percent of Pluto's total mass. Canup's simulations suggest that a proportionally much larger impactor - one nearly as large as Pluto itself - was responsible for Charon, and that the satellite likely formed intact as a direct result of the collision.

According to Canup, a collision in the early Kuiper Belt - a disk of comet-like objects orbiting in the outer solar system beyond Neptune - could have given rise to a planet and satellite with relative sizes and angular rotation characteristics consistent with those of the Pluto-Charon pair. The colliding objects would have been about 1,600 to 2,000 kilometers in diameter, or each about half the size of the Earth's Moon.

"This work suggests that despite their many differences, our Earth and the tiny, distant Pluto may share a key element in their formation histories. This provides further support for the emerging view that stochastic impact events may have played an important role in shaping final planetary properties in the early solar system," said Canup.

The "giant impact" theory was first proposed in the mid-1970s to explain how the Moon formed, and a similar mode of origin was suggested for Pluto and Charon in the early 1980s. Canup's simulations are the first to successfully model such an event for the Pluto-Charon pair.

Simulations published by Canup and a colleague in Nature in 2001 showed that a single impact by a Mars-sized object in the late stages of Earth's formation could account for the iron-depleted Moon and the masses and angular momentum of the Earth-Moon system.

This was the first model to simultaneously explain these characteristics without requiring that the Earth-Moon system be substantially modified after the lunar forming impact.