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  • richardmitnick 11:29 am on November 18, 2016 Permalink | Reply
    Tags: , , Kuiper belt objects,   

    From Sky & Telescope: “Big Kuiper Object 2007 OR10 Has a Moon” 

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    Sky & Telescope

    October 21, 2016
    Kelly Beatty

    1
    Little is known about the moon of Kuiper Belt object 2007 OR10, seen here in a Hubble Space Telescope image taken September 18, 2010.
    NASA / ESA / W. Fraser / G. Marton

    Hubble images reveal a satellite orbiting one of the Kuiper Belt’s biggest objects.

    An interesting trend has emerged concerning the largest objects in the distant Kuiper Belt: they have moons.

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Most notable is Pluto, with five. Haumea has two. Eris, Orcus, Quaoar, and Makemake each have one. In fact, of the eight largest known trans-Neptunian objects, only Sedna and yet-to-be-named 2007 OR10 were considered moonless — and now it’s just Sedna.

    Astronomers Gábor Marton and Csaba Kiss (Konkoly Observatory, Hungary), and Thomas Müller (Max Planck Institute, Germany) have identified a moon orbiting 2007 OR10. They spotted it in Hubble Space Telescope images taken in September 2010 as part of a survey of trans-Neptunian objects. Marton announced the discovery this week at a joint meeting of the AAS’s Division for Planetary Sciences and the European Planetay Science Congress.

    Although 2007 OR10 itself has been known for almost a decade, only recently have researchers realized that it’s surface is quite dark and therefore that it must be quite sizable, with an estimated diameter of 1,535 km (955 miles). This makes it the third-largest dwarf planet, after Pluto and Eris. It also ranks third for distance — 13 billion km or 87 astronomical units away — drifting among the stars of central Aquarius at a dim magnitude 21.

    For now, not much is known about its companion. Aside from HST’s 2010 survey, the discoverers report a tentative detection of the moon in images from 2009. It orbits at a distance of at least 15,000 km, but more specifics are lacking. However, Marton’s team has requested more HST time for follow-up observations. As soon as a reliable orbital radius and period are found, quick calculations will yield the mass of 2007 OR10 and its overall density.

    Meanwhile, the orbit of 2007 OR10 itself is now known well enough that the Minor Planet Center has assigned this body the number 225088. This means it can be officially named, but discoverers Megan Schwamb, Michael Brown, and David Rabinowitz have yet to submit one. For a while it had the nickname “Snow White,” because the discovery team believed it to be much smaller and more reflective.

    Infrared spectra show that the surface, despite being dark, must be quite red (perhaps stained by organic compounds) and generously coated with water ice.

    See the full article here .

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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 7:38 am on October 15, 2016 Permalink | Reply
    Tags: , , , , Kuiper belt objects, Mike Brown   

    From Caltech Astronomer Mike Brown: “How many dwarf planets are there in the outer solar system? (updates daily)” 

    Caltech Logo
    Caltech

    1

    Mike Brown

    How many dwarf planets are there in the outer solar system? (updates daily)
    (As of 1 Nov 2013 also includes latest thermal and occultation results)
    As of Sat Oct 15 2016
    there are:
    10 objects which are nearly certainly dwarf planets,
    30 objects which are highly likely to be dwarf planets,
    75 objects which are likely to be dwarf planets,
    147 objects which are probably dwarf planets, and
    695 objects which are possibly dwarf planets.

    In 2006, when the vote on the definition of “planet” was made, and the eight dominant bodies in the solar system were declared (quite rationally) a class separate from the others, a new class of objects was defined. The “dwarf planets” are all of those objects which are not one of the eight dominant bodies (Mercury through Neptune) yet still, at least in one way, resemble a planet. In other words, a dwarf planet is something that looks like a planet, but is not a planet. Specifically this means that dwarf planets are bodies in the solar system which are large enough to become round due to their own gravitational attraction.

    Why do astronomers care about round? If you place a boulder in space it will just stay whatever irregular shape it is. If you add more boulders to it you can still have an irregular pile. But if you add enough boulders to the pile they will eventually pull themselves into a round shape. This transition from irregularly shaped to round objects is important in the solar system, and, in some ways, marks the transition from an object without and with interesting geological and planetary processes occuring (there are many many other transitions that are equally important, however, a fact that tends to be overlooked in these discussions).

    How many dwarf planets are there? Ceres is the only asteroid that is known to be round.

    2
    Ceres

    After that it gets complicated. All of the rest of the new dwarf planets are in the distant region of the Kuiper belt, where we can’t actually see them well enough to know for sure if they are round or not.

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    While we can’t see most of the objects in the Kuiper belt well enough to determine whether they are round or not, we can estimate how big an object has to be before it becomes round and therefore how many objects in the Kuiper belt are likely round. In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round, so somewhere around 900 km is a good cutoff for rocky bodies like asteroids. Most Kuiper belt objects have a lot of ice in their interiors, though. Ice is not as hard as rock, so it less easily withstands the force of gravity, and it takes less force to make an ice ball round. The best estimate for how big an icy body needs to be to become round comes from looking at icy satellites of the giant planets. The smallest body that is generally round is Saturn’s satellite Mimas, which has a diameter of about 400 km.

    4
    Mimas

    Several satellites which have diameters around 200 km are not round. So somewhere between 200 and 400 km an icy body becomes round. Objects with more ice will become round at smaller sizes while those with less rock might be bigger. We will take 400 km as a reasonable lower limit and assume that anything larger than 400 km in the Kuiper belt is round, and thus a dwarf planet.

    How many objects do we know in the Kuiper belt that are 400 km or larger? That question is harder to answer, because we don’t actually know how big most of the objects in the Kuiper belt are. While we can see how bright there are, we don’t know if they are bright because they are larger or are highly reflective. In the past, we had to just throw our hands up in the air and say we don’t know enough to even make reasonable guesses. But in the past few years, systematic measurements of the sizes of objects from the Spitzer Space Telescope and now the Herschel Space Telescope have taught us enought that we can make some reasonable estimates of how reflective objects are.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    ESA/Herschel
    ESA/Herschel

    (It’s complicated: read the details here ) These reasonable estimates, combined with all available actually measurements, give us the list of the largest Kuiper belt objects, sorted by diameter, below. Carefully note the lack of any error bars. Every single measurement or estimate below is uncertain to some extent or another. I don’t include the individual uncertainties in the table, but instead use the ensemble uncertainties to inform classification below. In other words: take the sizes of specific objects with bigger or smaller grains of salt.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 12:05 pm on August 17, 2016 Permalink | Reply
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    From Eos: “Six Things Dwarf Planets Have Taught Us About the Solar System” 

    Eos news bloc

    Eos

    8.17.16
    JoAnna Wendel

    1
    On 14 July 2015, NASA’s New Horizons probe snapped the first ever close-up images of Pluto. Scientists continue to be stunned by its unexpectedly complex surface features. Credit: NASA/JHUAPL/SRI

    Classrooms across the world received some bad news on 24 August 2006. Pluto—the celestial body discovered in 1930 and named by an 11-year-old girl, the “pizzas” in the planet mnemonic “My very educated mother just served us nine pizzas”—had been officially stricken from the solar system’s family of planets and reclassified as a “dwarf planet.”

    The discovery of the slightly more massive object Eris inspired the International Astronomical Union’s (IAU) decision. Proponents of the change insisted that if Pluto got to keep the label “planet,” so too should similarly sized objects—like Ceres, for instance, which was then considered a large asteroid.

    A dwarf planet, by IAU’s new definition, must directly orbit the Sun. It must be massive enough for gravity to pull it into a roughly spherical shape. But unlike regular planets, dwarf planets haven’t cleared other smaller celestial debris out of its orbital path.

    As more objects got discovered, Pluto’s new label “dwarf planet” stuck. Then the jokes began.

    Facebook group pages popped up, with snarky titles of “When I was your age, Pluto was a planet!” Angry Pluto enthusiasts wrote hate mail to astronomer Mike “Pluto Killer” Brown, one of the scientists who found Eris. Astrophysicist Neil deGrasse Tyson, a strong proponent of the dwarf planet label, received his own stream of hate mail from crushed 6-year-olds; Twitter users still hurl insults at him occasionally.

    Although some consider the reclassification a “demotion,” Pluto and its cousins Ceres, Makemake, Eris, Haumea, and others continue to dazzle scientists with their strange features and surprising geology. But perhaps more critically, these dwarf planets also trace a trail of scientific breadcrumbs that scientists can follow back in time to understand the origins of the solar system.

    “I like to think of Pluto being the dwarf planet that showed us how the solar system’s architecture came to be,” said Renu Malhotra, a planetary scientist at University of Arizona’s Lunar and Planetary Laboratory.

    Here are six such revelations about the solar system that we gained from studying dwarf planets.

    1. Dwarf Planets Are as Complex as Regular Planets

    When the New Horizons probe passed by Pluto more than a year ago, scientists found a complex system with areas of geologically young surface and evidence of active geology.

    NASA/New Horizons spacecraft
    NASA/New Horizons spacecraft

    Pluto, the images revealed, wasn’t just a chunk of rock orbiting in space. “Even I underestimated what we would find,” said Alan Stern, principal investigator of the New Horizons mission.

    2
    A mosaic of Pluto’s complex surface taken by the New Horizons probe from about 15,000 kilometers away as it approached Pluto on 14 July 2015. Scientists are working to understand the origins of these unexpectedly diverse features. Credit: NASA/JHUAPL/SwRI

    Pluto continues to stun scientists with its unexpected surface features, but its newly revealed complexity is just the beginning.

    Makemake has no atmosphere. Haumea spins faster than any other known large object in the solar system. Eris might have a thin, icy surface. Ceres hosts mysterious bright spots.

    “The fact that these objects can be every bit as complicated as terrestrial planets is a headline,” Stern said. “It should be written in as big a point size as we can write it, because it was completely unexpected.”

    2. Dwarf Planets Reveal Neptune’s Orbital Origins

    3
    Scientists calculated that in the early solar system, Neptune migrated out to its current position and nudged Pluto into a resonance orbit. Although Pluto sometimes crosses Neptune’s orbital path, the resonance protects the two planets from colliding. Credit: NASA/JPL

    By studying the particular orbital relationship between Pluto and Neptune, scientists figured out how Neptune got to its current position in the solar system. The two bodies are inextricably locked in an orbital resonance: Every time Neptune orbits the Sun three times, Pluto orbits twice, which means that even though Pluto may occasionally cross Neptune’s orbital path, they will never meet.

    Scientists have always known about this resonance, but it was Malhotra who realized its significance. In a 1995 paper, Malhotra calculated that the only way Neptune and Pluto could have ended up in this resonance was if they both had formed closer to the Sun, then migrated out.

    Scientists theorize that in the early days of the solar system, the gas giants, Jupiter, Saturn, Neptune, and Uranus, migrated inward toward the Sun and knocked out leftover debris. This gravitational push on planetary debris ended up changing the planets’ orbits as well, sending Neptune farther out. Neptune’s gravitational force encountered Pluto’s, and the two bodies pushed and pulled at each other until they fell into a resonance orbit. Astronomers detected the same effect in other bodies, including a new dwarf planet announced to the world this year.

    3. Dwarf Planets Give Us a Peek into the Early Solar System

    Dwarf planets are handy guides to the ancient solar system. For instance, all the Kuiper belt dwarf planets—Pluto, Haumea, Makemake, and Eris—have moons that scientists suspect formed from high-impact collisions, said Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington, D. C. Haumea in particular is the only known Kuiper belt object to have a “family” that orbits along with Haumea and its moons, meaning that the debris kicked off by an impact long ago didn’t have enough energy to escape Haumea’s gravitational pull.

    The presence of such moons is further evidence of an early period of “late heavy bombardment” of objects in the solar system. Scientists think that during this time, about 3.8–4 billion years ago, gravitational interactions between Jupiter, Saturn, and Neptune sent comets and asteroids sprawling across the solar system to collide with planets.

    In the last 2 years, Ceres has also provided various windows into the past. In 2015, NASA’s Dawn probe headed to the dwarf planet after visiting the asteroid Vesta. There, scientists detected ammonia-rich clays in Ceres’s surface.

    Ammonia itself isn’t stable at the temperatures found on Ceres (130–200 kelvins), but it is plentiful in the outer solar system. So how did the molecule get there? Scientists have formulated different hypotheses, said Carol Raymond, deputy principal investigator for Dawn. Either Ceres formed in the outer solar system, during its early days, and got kicked inward by a chaotic migration of the gas giants, or Ceres formed in the asteroid belt, and somehow ammonia-rich material from the outer solar system made its way inward.

    Further study of Ceres will help clarify details of solar system formation, Raymond said.

    4. Dwarf Planet Candidates Helped Scientists “Find” Planet 9

    Thanks to a handful of debris orbiting farther away than Pluto, scientists this year found evidence that a rocky, Neptune-sized planet may lurk beyond the gaze of even our most powerful telescopes.

    The story began in 2003, when Brown and his team at the California Institute of Technology (Caltech) discovered Sedna, a dwarf planet candidate that orbits far beyond the Kuiper belt, Pluto’s neighborhood of large, icy bodies 30 astronomical units (AU) away.

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Sedna maintains a steady orbit and comes within only 76 AU of the Sun at its closest approach.

    4
    The orbits of Planet 9 and the dwarf planets it supposedly influences. Scientists calculated that only a Neptune-sized planet could keep these objects in their peculiar, angled orbit. The diagram was created using WorldWide Telescope. Credit: Caltech/R. Hurt

    Since then, scientists have spotted several more objects near Sedna, including 2012 VP113, found by Sheppard and colleague Chad Trujillo of Hawaii’s Gemini Observatory.

    5
    This orbit diagram shows the paths of Oort cloud objects 2012 VP113 (red) and Sedna (orange), which circle the Kuiper belt (blue) at the Solar System’s edge. Scott S. Sheppard/Carnegie Institution for Science

    Gemini/North telescope at Manua Kea, Hawaii, USA
    Gemini North Interior
    Gemini/North telescope at Manua Kea, Hawaii, USA

    The pair noticed that their new object and the rest of these far-away objects had similar, steady orbits.

    Back at Caltech, after reading Sheppard’s and Trujillo’s work, Brown and his colleagues set out to find the cause of such clustering, and after many hours of poring over models and simulations, they officially proposed that only a planet-sized body could exert enough gravitational pull to keep the far-away cluster of dwarf-planet-sized objects in steady orbits. This hypothesized planet was deemed Planet 9 (sometimes called Planet X).

    “Right now we’re doing surveys trying to find more dwarf planets,” Sheppard said. “If we find more and more of these, they can lead us to the much bigger, major Planet X.”

    5. Ceres (We Hope) Will Help Us Understand Icy Ocean Moons

    Kuiper belt dwarf planets aren’t the only thing keeping scientists busy. Dawn mission scientists recently discovered that regions of Ceres contain higher concentrations of carbonate minerals than anywhere outside of the Earth’s ocean floor. These minerals reveal that Ceres is like a “fossilized” ocean world, Raymond explained. They could be the remnants of a vast ocean that once existed on the dwarf planet.

    In Ceres’s geologically young Occator crater, scientists figured out that mysterious bright patches come from sodium carbonate, a highly reflective mineral found in hydrothermal environments under Earth’s oceans. This means that at some point in Ceres’s history, hydrothermal processes must have pushed this material to the surface, Raymond said.

    6
    Scientists found evidence of carbonate minerals in the bright spots of dwarf planet Ceres’s Occator crater. Stripes on the inset represent where the spectrometer frames lie, whereas red signifies a high abundance of carbonates and gray indicates a low abundance. These carbonate minerals mean that Ceres may have been covered once by an ocean. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/ASI/INAF

    If hydrothermal processes are confirmed, Ceres’s surface may be analogous to the current seafloors underneath the solar system’s ice-covered moons. Astrobiologists yearn to peek below the icy shells of Jupiter’s and Saturn’s moons Europa and Enceladus because there are vast oceans underneath, and life needs water to proliferate.

    Ceres is similar to these moons because 25% of the dwarf planet is water ice. Plus, its seafloor-type conditions are “where all of the elements necessary for habitability occur together,” Raymond said.

    6. Dwarf Planets Are Prolific

    Pluto holds a special place in the Internet’s collective heart but may not be so special in the solar system. Currently, there are six dwarf planets officially designated by the IAU: Pluto, Ceres, Eris, Makemake, Haumea, and 2015 RR245, discovered in July. Since scientists started looking deeper into the Kuiper belt, they have found at least 20 more similarly sized objects, Sheppard said.

    7
    There may be only six officially designated dwarf planets (missing from the image is 2015 RR245, announced this year), but many more dwarf-planet-sized objects exist. They may even be the dominant class of objects in the solar system. Credit: Konkoly Observatory/András Pál, Hungarian Astronomical Association/Iván Éder, NASA/JHUAPL/SwRI

    And there may be dozens more out there. “We discovered that dwarf planets are the most populous class in the solar system,” Stern said. Other galaxies may be like ours, too, he added.

    This population revelation, along with the surprising geological and atmospheric complexity found on dwarf planets, means that the field could be “at the very beginning of a paradigm shift and a revolution,” Stern said. Perhaps, he continued, it’s the classic large planets that are the “oddballs” of planetary formation.

    He wonders, “Who’s the misfit now?”

    See the full article here .

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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

     
  • richardmitnick 11:05 am on May 27, 2016 Permalink | Reply
    Tags: , , , Kuiper belt objects, , Object 1994 JR1   

    From Astronomy: “New Horizons collects first science on a Kuiper Belt object past Pluto” 

    Astronomy magazine

    Astronomy Magazine

    May 18, 2016
    NASA

    The spacecraft has now twice observed 1994 JR1, a Kuiper Belt object orbiting more than 3 billion miles from the Sun.

    NASA/New Horizons spacecraft
    NASA/New Horizons spacecraft

    1
    New Horizons scientists used light curve data – the variations in the brightness of light reflected from the object’s surface – to determine JR1’s rotation period of 5.4 hours. NASA/JHUAPL/SwRI

    Warming up for a possible extended mission as it speeds through deep space, NASA’s New Horizons spacecraft has now twice observed 1994 JR1, a 90-mile-wide (145 kilometers) Kuiper Belt object (KBO) orbiting more than 3 billion miles (5 billion km) from the Sun. Science team members have used these observations to reveal new facts about this distant remnant of the early solar system.

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Taken with the spacecraft’s Long Range Reconnaissance Imager (LORRI) on April 7-8 from a distance of about 69 million miles (111 million km), the images follow on observations from November 2015, when New Horizons detected JR1 from 170 million miles (280 million km) away.

    NASA New Horizons LORRI Camera
    NASA New Horizons LORRI Camera

    Simon Porter, a New Horizons science team member from the Southwest Research Institute (SwRI) in Boulder, Colorado, said the observations contain several valuable findings. “Combining the November 2015 and April 2016 observations allows us to pinpoint the location of JR1 to within 600 miles (1,000km), far better than any small KBO,” he said, adding that the more accurate orbit also allows the science team to dispel a theory, suggested several years ago, that JR1 is a quasi-satellite of Pluto.

    From the closer vantage point of the April 2016 observations, the team also determined the object’s rotation period, observing the changes in light reflected from JR1’s surface to determine that it rotates once every 5.4 hours (or a JR1 day). “That’s relatively fast for a KBO,” said John Spencer from SwRI. “This is all part of the excitement of exploring new places and seeing things never seen before.”

    Spencer added that these observations are great practice for possible close-up looks at about 20 more ancient Kuiper Belt objects that may come in the next few years, should NASA approve an extended mission. New Horizons flew through the Pluto system on July 14, 2015, making the first close-up observations of Pluto and its family of five moons. The spacecraft is on course for an ultra-close flyby of another Kuiper Belt object, 2014 MU69, on January 1, 2019.

    See the full article here .

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  • richardmitnick 5:43 pm on March 3, 2016 Permalink | Reply
    Tags: , , CHIMERA camera on Caltech Palomar 200 inch Hale Telescope, Kuiper belt objects,   

    From JPL: “Versatile Instrument to Scout for Kuiper Belt Objects” 

    NASA JPL Banner

    JPL-Caltech

    March 3, 2016
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    Elizabeth.Landau@jpl.nasa.gov

    At the Palomar Observatory near San Diego, astronomers are busy tinkering with a high-tech instrument that could discover a variety of objects both far from Earth and closer to home.

    Caltech Palomar 200 inch Hale Telescope
    Caltech Palomar 200 inch Hale Telescope interior
    Caltech Palomar 200 inch Hale Telescope

    The Caltech HIgh-speed Multi-color camERA (CHIMERA) system is looking for objects in the Kuiper Belt, the band of icy bodies beyond the orbit of Neptune that includes Pluto.

    Caltech Palomar CHIMERA camera on 200 inch Hale telescope
    Caltech Palomar CHIMERA camera on 200 inch Hale telescope

    Kuiper Belt
    Known objects in the Kuiper belt beyond the orbit of Neptune. (Scale in AU; epoch as of January 2015.)

    It can also detect near-Earth asteroids and exotic forms of stars. Scientists at NASA’s Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, are collaborating on this instrument.

    “The Kuiper Belt is a pristine remnant of the formation of our solar system,” said Gregg Hallinan, CHIMERA principal investigator at Caltech. “By studying it, we can learn a large amount about how our solar system formed and how it’s continuing to evolve.”

    The wide-field telescope camera system allows scientists to monitor thousands of stars simultaneously to see if a Kuiper Belt object passes in front [transits] of any of them. Such an object would diminish a star’s light for only one-tenth of a second while traveling by, meaning a camera has to be fast in order to capture it.

    “Each of CHIMERA’s cameras will be taking 40 frames per second, allowing us to measure the distinct diffraction pattern in the wavelengths of light to which they are sensitive,” said Leon Harding, CHIMERA instrument scientist at JPL. “This high-speed imaging technique will enable us to find new Kuiper Belt objects far less massive in size than any other ground-based survey to date.”

    Hallinan’s CHIMERA team at Caltech and JPL published a paper led by Harding describing the instrument this week in the Monthly Notices of the Royal Astronomical Society.

    Astronomers are particularly interested in finding Kuiper Belt objects smaller than 0.6 miles (1 kilometer) in diameter. Since so few such objects have ever been found, scientists want to figure out how common they are, what they are made of and how they collide with other objects. The CHIMERA astronomers estimate that in the first 100 hours of CHIMERA data, they could find dozens of these small, distant objects.

    Another scientific focus for CHIMERA is near-Earth asteroids, which the instrument can detect even if they are only about 30 feet (10 meters) across. Mike Shao of JPL, who leads the CHIMERA group’s near-Earth asteroid research effort, predicts that by using CHIMERA on the Hale telescope at Palomar, they could find several near-Earth objects per night of telescope observation.

    Transient or pulsing objects such as binary star systems, pulsing white dwarfs and brown dwarfs can also be seen with CHIMERA.

    “What makes CHIMERA unique is that it does high-speed, wide-field, multicolor imaging from the ground, and can be used for a wide variety of scientific purposes,” Hallinan said. “It’s the most sensitive instrument of its kind.”

    CHIMERA uses detectors called electron multiplying charged-coupled devices (EMCCDs), making for an extremely high-sensitivity, low-noise camera system. One of the EMCCDs picks up near-infrared light, while the other picks up green and blue wavelengths, and the combination allows for a robust system of scanning perturbations in starlight. The detectors are capable of running at minus 148 degrees Fahrenheit (minus 100 degrees Celsius) in order to avoid noise when imaging fast objects.

    “Not only can we image over a wide field, but in other modes we can also image objects rotating hundreds of times per second,” Harding said.

    One of the objects the CHIMERA team used in testing the instrument’s imaging and timing abilities was the Crab Pulsar. This pulsar is the end result of a star whose mass collapsed at the end of its life. It weighs as much as our sun, but spins 32 times per second. The instrument focused on the pulsar for a 300-second exposure to produce a color image.

    “Our camera can image the entire field of view at 40 frames per second,” Hallinan said. “We zoomed in on the pulsar and imaged it very fast, then imaged the rest of the scene slowly to create an aesthetically-pleasing image.”

    Highlighting CHIMERA’s versatility, the instrument also imaged the globular cluster M22, located in the constellation Sagittarius toward the busy center of our galaxy. A single 25-millisecond image captured more than 1,000 stars. The team will be observing M22, and other fields like it, for 50 nights over three years, to look for signatures of Kuiper Belt objects.

    See the full article here .

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  • richardmitnick 2:53 pm on January 20, 2016 Permalink | Reply
    Tags: , , , , Kuiper belt objects   

    From AAS NOVA: “A Ninth Planet in Our Solar System?” 

    AASNOVA

    American Astronomical Society

    20 January 2016
    Susanna Kohler

    Temp 1
    Artist’s illustration of a possible ninth planet in our solar system. A recent study has revealed that the unexpected behavior of some Kuiper belt objects could be explained by the presence of a distant, planet-sized object yet undetected in our solar system. [Caltech/Robert Hurt]

    The recent discovery that the orbits of some Kuiper belt objects (KBOs) share properties has proved puzzling. A pair of scientists have now proposed a bold explanation: there may be a planet-sized object yet undetected in our solar system.

    Temp 6
    Objects of the Kuiper belt (blue). Plot displays the known positions of objects in the outer Solar System within 60 astronomical units (AU) from the Sun. Epoch as of January 1, 2015.

    Mysterious Clustering

    KBOs, the population of mainly small objects beyond Neptune, have proven an especially interesting subject of study in the last decade as many small, distant bodies (such as Eris, the object that led to the demotion of Pluto to dwarf planet) have been discovered.

    Previous studies have recently discovered that some especially distant KBOs — those that orbit with semimajor axes of a > 150 AU, nearly four times that of Pluto — all cross the ecliptic at a similar phase in their elliptical trajectories. This is unexpected, since gravitational tugs from the giant planets should have randomized this parameter over our solar system’s multi-billion-year lifespan.

    Temp 2
    Physical alignment of the orbits of Kuiper belt objects with a > 250 AU (and two objects with a > 150 AU that are dynamically stable). [Batygin & Brown 2016]

    Two scientists at California Institute of Technology, Konstantin Batygin and Michael Brown (you might recognize Brown as the man who “killed Pluto”) have now increased the mystery. In a recently published a study, they demonstrate that for KBOs that have orbits with a > 250 AU, the orbits are actually physically aligned.

    To explain this unexpected alignment — which Batygin and Brown calculate has only a 0.007% probability of having occurred by chance — the authors ask an exciting question: could this be caused by the presence of an unseen, large, perturbing body further out in the solar system?

    Simulating a Ninth Planet

    The authors test this hypothesis by carrying out both analytical calculations and numerical N-body simulations designed to determine if the gravitational influence of a distant, planetary-mass companion can explain the behavior we observe from the large-orbit KBOs.

    Temp 3
    Simulation of the effect of a distant planet (M = 10 M⊕, a = 700 AU, and e = 0.6) on KBOs; click for a better look! The perihelion position of KBOs with a > 250 AU clusters around 180° from the perihelion position of the perturbing planet. More-transparent points are less observable. [Batygin & Brown 2016]

    The result? It turns out that such a distant planet can cause the orbits of KBOs with a > 250 AU to all align in the opposite direction of the orbit of the planet. What’s more, the gravitational pull of this planet can also explain other unresolved puzzles about the Kuiper belt, such as the presence of high-perihelion Sedna-like objects, as well as a population of KBOs we’ve observed that have misaligned orbits.

    Unfortunately, Batygin and Brown found it isn’t possible to exactly determine the properties of the possible planet, since multiple combinations of its mass, eccentricity, and semimajor axis can create the same observational results. That said, they believe the distant perturber’s orbit is highly eccentric, its orbital inclination is low, and it’s fairly massive (since anything less than an Earth-mass won’t create the observed clustering of KBO orbits within the age of the solar system).

    As an example, one possible set of parameters that approximately reproduces the observed KBO orbits is the following:

    planet mass of 10 Earth-masses
    semi-major axis of a = 700 AU
    eccentricity of e = 0.6

    This would correspond to a perihelion distance of 280 AU and an aphelion distance of 1,120 AU.

    The authors speculate such a planet might have been formed closer in to the Sun, but it was ejected later on during our solar system’s evolution. Interactions with the Sun’s birth cluster could have then caused the planet to be retained in a bound orbit.

    Temp 4
    Our solar system on a logarithmic scale (click for the full view). KBOs with a semimajor axis of a > 250 AU may be being aligned by a planetary-mass body with an even more distant orbit. [NASA]

    Future Tests

    How can we test this hypothesis of a ninth planet? Obviously, directly observing the planet would confirm its presence. But the authors’ model has an additional testable hypothesis: if it’s correct, there should be a population of high-perihelion Kuiper belt objects that don’t exhibit the same alignment of their orbits as the KBOs we know about, but instead have opposite-aligned orbits. If we discover such a collection of objects, that would be an excellent confirmation of this model.

    The authors caution that their work is preliminary, and additional investigation will be required to better understand the possibilities presented here. But with any luck, future theoretical work, as well as observational tests of this model’s predictions, will help us determine whether there might be a distant ninth planet in our solar system!

    [See the original article for a video which walks us first through a view of the six aligned KBO orbits, then shows a possible orbit for the hypothesized planet, and then shows an additional population of already-discovered objects (also predicted by the model) that have orbits perpendicular both to the plane of the solar system and to the planet’s orbit. (Caltech/Robert Hurt)]

    Citation

    Konstantin Batygin and Michael E. Brown 2016 AJ 151 22. doi:10.3847/0004-6256/151/2/22

    See the full article here .

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