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  • richardmitnick 8:17 am on October 24, 2014 Permalink | Reply
    Tags: Astronomy, , , , , ,   

    From SPACE.com:”Saturn’s ‘Death Star’ Moon Mimas Is Weird Inside” 

    space-dot-com logo

    SPACE.com

    October 16, 2014
    Kelly Dickerson

    There’s something strange going on below the surface of Saturn’s Death Star-looking moon Mimas, a new study suggests.

    star

    Mimas’ rotation and its orbit around Saturn make the moon look like it’s rocking and back forth and oscillating similar to the way a pendulum swings. The rocking motion is called libration, and it’s commonly observed in moons that are influenced by the gravity from neighboring planets. However, using images of the moon captured by the Cassini spacecraft, Radwan Tajeddine, a research associate at Cornell University, discovered that the satellite’s libration was much more exaggerated in one spot than predicted. He expects it must be caused by the moon’s weird interior.

    NASA Cassini Spacecraft
    NASA/ Cassini

    “We’re very excited about this measurement because it may indicate much about the satellite’s insides,” Tajeddine said in a statement. “Nature is essentially allowing us to do the same thing that a child does when she shakes a wrapped gift in hopes of figuring out what’s hidden inside.”

    Feel the libration

    Astronomers have long been using the rotation and orbit of celestial bodies to guess what their interiors might be like. Most of the rocking is explained by the interacting forces from Mimas’ rotation and orbit, but one libration was much larger than expected.

    Tajeddine and the team tested five different models of what Mimas might look like below the surface to see which one could explain the exaggerated rocking. They quickly ruled out the possibility that Mimas has a uniform interior, an interior with two different layers or an abnormal mass under the moon’s 88-mile-long (142 kilometers) crater that makes it look like the Death Star from the “Star Wars” franchise.

    However, the last two models could both explain Mimas’ extreme libration. One idea is that the moon has an elongated, oval-shaped core. This elongation might have happened as the moon formed under the push and pull of Saturn’s rings. The teeter tottering could also come from a subsurface ocean, similar to the one on Jupiter’s moon Europa.

    While it’s still a possibility, Tajeddine thinks the subsurface ocean is an unlikely explanation. Astronomers have not observed any evidence of liquid water on Mimas, unlike some of Saturn’s other moons. The heat radiating from the core escapes through the moon’s ice-covered shell and would cause any subsurface ocean that existed to quickly freeze.

    3D Mimas map

    Mimas is the smallest and closest of Saturn’s main eight moons. Its giant crater covers almost one-third of the moon’s icy surface.

    For the past 10 years,the Cassini space probe has been collecting data on Mimas, Saturn and the ringed wonder’s other natural satellites. The Imaging Science Subsystem (ISS) onboard Cassini is a two-camera system that captures ultraviolet and infrared images of Saturn and its moons.

    Tajeddine and a team of researchers sifted through dozens of images captured by ISS and created a 3D map of the moon from the photos to study how Mimas spins and orbits Saturn.

    The new research was published this week in the journal Science.

    See the full article here.

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  • richardmitnick 8:01 am on October 24, 2014 Permalink | Reply
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    From SETI: “New Insights on the Origin of the triple asteroid system (87) Sylvia” 


    SETI Institute

    Oct 24, 2014
    Franck Marchis, Senior Research Scientist

    Combining observations from the world’s largest telescopes with those from smaller instruments used by amateur astronomers, a team of scientists has discovered that the large main-belt asteroid (87) Sylvia has a complex interior. This has been deduced by using the motions of the two moons orbiting the main asteroid as probes of the object’s density distribution. The complex structure is probably linked to the way the multiple system was formed.

    two
    Description Discovery of the two moons Romulus and Remus of the asteroid (87) Sylvia
    Date 24 January 2007
    Adaptive Optics observations of (87) Sylvia, showing its two satellites, Remus and Romulus

    The findings were announced last year at the 45th annual Division of Planetary Sciences meeting in Denver, Colorado and were published last month in the journal Icarus.

    The asteroid (87) Sylvia is the first known to have two moons. One moon was discovered in 2001, and the second was found in 2005 by a team led by Franck Marchis, senior research scientist at the Carl Sagan Center of the SETI Institute. Since then, the team has continued to make new observations of the system using 8 to 10 m-class telescopes, including those at the Keck Observatory, the European Southern Observatory, and Gemini North.

    Keck Observatory
    Keck Observatory Interior
    Keck

    ESO VLT Interferometer
    ESO VLT Interior
    ESO VLT

    Gemini North telescope
    Gemini North Interior
    Gemini North

    syl
    (credit: Danielle Futselaar/SETI Institute).
    An artist’s rendition of the triple system showing the large 270-km asteroid Sylvia surrounded by its two moons – Romulus and Remus – gives a pictorial representation of this intriguing triple system.

    The differentiated interior of the asteroid is shown in a cutaway diagram. The primary asteroid may have a dense, regularly-shaped core, surrounding by fluffy or fractured material. The outer moon, named Romulus, is known to be strongly elongated, possibly having two lobes, as suggested by a recently observed occultation recorded by amateur astronomers.

    “Combined observations from small and large telescopes provide a unique opportunity to understand the nature of this complex and enigmatic triple asteroid system,” Marchis said. “Thanks to the presence of these moons, we can constrain the density and interior structure of an asteroid, without the need for a spacecraft’s visit. Knowledge of the internal structure of asteroids is key to understanding how the planets of our solar system formed.”

    The article Physical and dynamical properties of the main belt triple Asteroid (87) Sylvia, published last month in Icarus, is co-authored by J. Berthier, F. Vachier, B. Carry from IMCCE-Obs de Paris, J. Durech from Charles University, Prague, and F. Marchis from the SETI Institute and Obs. de Paris.

    Reference
    Berthier, J., F. Vachier, F. Marchis, J. Ďurech, and B. Carry. 2014. Physical and Dynamical Properties of the Main Belt Triple Asteroid (87) Sylvia. Icarus 239 (September): 118–30. doi:10.1016/j.icarus.2014.05.046.

    Abstract
    We present the analysis of high angular resolution observations of the triple Asteroid (87) Sylvia collected with three 8-10 m class telescopes (Keck, VLT, Gemini North) and the Hubble Space Telescope. The moons’ mutual orbits were derived individually using a purely Keplerian model. We computed the position of Romulus, the outer moon of the system, at the epoch of a recent stellar occultation which was successfully observed at less than 15 km from our predicted position, within the uncertainty of our model. The occultation data revealed that the Moon, with a surface-area equivalent diameter Ds=23.1±0.7km, is strongly elongated (axes ratio of 2.7±0.32.7±0.3), significantly more than single asteroids of similar size in the main-belt. We concluded that its shape is probably affected by the tides from the primary. A new shape model of the primary was calculated combining adaptive-optics observations with this occultation and 40 archived light-curves recorded since 1978. The difference between the J2=0.024-0.009+0.016 derived from the 3-D shape model assuming an homogeneous distribution of mass for the volume equivalent diameter Dv=273±10km primary and the null J2 implied by the Keplerian orbits suggests a non-homogeneous mass distribution in the asteroid’s interior.

    See the full article here.

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  • richardmitnick 8:09 pm on October 23, 2014 Permalink | Reply
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    From Frontier Fields: “Recent Guide Star Loss with Abell 2744″ 

    Frontier Fields
    Frontier Fields

    May 30, 2014
    Patricia Royle – Frontier Fields Program Coordinator

    We have just experienced our first non-acquisition of a guide star during Frontier Fields observations. This occurred while in the midst of Abell 2744 observations.

    bel
    Abell 2744, nicknamed Pandora’s Cluster. The galaxies in the cluster make up less than five percent of its mass. The gas (around 20 percent) is so hot that it shines only in X-rays (coloured red in this image). The distribution of invisible dark matter (making up around 75 percent of the cluster’s mass) is coloured here in blue.

    Since HST is in constant motion, pointing is maintained by a set of three Fine Guidance Sensors (FGS) which find and lock on to a pair of guide stars, or a single guide star if pairs are not available. These guide stars are selected by software based on several criteria, including magnitude, relative position to other similar stars, position within the FGS “pickles” (Fields of View) and any pointing constraints on the observation such as ORIENT or POS TARGs within the Phase 2 program. Selected guide stars need to stay within the FGS pickles for the entire orbit, including all pointing changes due to POS TARGs or PATTERNs. If an observation spans more than one visibility interval, the guide stars are reacquired after each interruption either from occultation or SAA passages. A pair of guide stars provides the most accurate and stable pointing since they act as sort of handles for HST to focus on. If two stars are used in two separate FGS pickles, then HST is able to maintain almost perfect pointing throughout the observations. If only one star is used, HST may show some drift around the single star since there is not a second star to keep the telescope from rotating. More information about the accuracy of each type of guiding can be found online at http://www.stsci.edu/hst/acs/faqs/guide_star.html.

    In some cases, a guide star may fail to acquire or it might successfully acquire but can not be maintained. Sometimes this is a result of a telescope problem, but more often, it turns out that a selected guide star fails to meet one of the criteria it initially appeared to pass. This can happen in the case of a variable star, a multi-star system that previously appeared as a single star, or with the presence of a similar star (called a spoiler) nearby that confuses the FGS. When PAIRs are used, it is possible to fail to acquire one star, but succeed with the other, resulting in observations taken with single star guiding which is often good enough for most science. There may also be situations when a star is acquired initially but fails to re-acquire in a subsequent orbit, or lock may be lost on one star during an orbit. This is usually due to the star itself being at the very edge of usability and violating one of the limits set by the telescope to help ensure HST knows where it is pointing. With guide star pairs, science can usually continue as long as one of the stars is acquired. If both stars fail (very unusual) or an observation using single star guiding fails to acquire its one star, the observations default to gyro control. This is often problematic to the science as the observations are likely to show significant drift and rotation, or may be far enough off that the target is completely missed.

    During the first Frontier Fields visit observing Abell 2744 on May 14, one of the two selected guide stars failed to acquire, resulting in the observations continuing on single star guiding instead. As with all failures, the failed star was investigated and was found to be a bad star. It was flagged in the database within 24 hours of the failure, such that future observations would not attempt to use the same bad star. The second Frontier Fields visit of Abell 2744 on May 15 also failed, as it was already on the telescope and set to use the same guide star pair. Several other visits that were scheduled to execute on the telescope the following week, with the same guide star pair, were quickly reworked by the calendar-building team at STScI to use a different guide star pair. The remaining visits in the epoch not yet put on a calendar are unaffected, since the bad star is no longer an option for our software when selecting from available guide star pairs.

    fs
    Figure 1: The HST Field of View of Abell 2744, with Fine Guidance Sensors Fields of View indicated by the large, gray arcs.

    The green boxes in Figure 1 identify potential guide stars. To use guide star pairs, two stars must fall into separate FGS pickles and remain there throughout any shifts in pointing during the visit. If two similar guide stars are too close to each other, neither can be used since the FGS could lock onto the wrong star. Because of the multiple criteria involved and the need for precision, not all guide stars can be used for a given observation, even if the Field of View seems to show stars that could be used.

    The Frontier Fields data products team carried out a detailed examination of all the data from the two visits that were affected by these guidestar issues. For the first visit (number 37), only one of the guidestars was lost, while the other star was successfully acquired and the observations were able to continue in single guide star mode. Analysis of the resulting images showed no measurable impact on the pointing or the PSF quality (consistent with our knowledge that HST is able to perform successfully with a single guide star, when necessary), and all the data from this visit were included in the mosaics.

    For the second visit (number 81), the failure mode was somewhat different. The guide stars were fine during the first two orbits of this 4-orbit visit, but began to show problems during the third orbit and failed the reacquisition for the fourth orbit. Consequently, the ACS shutter was closed at the start of the fourth orbit and the fourth exposure for each filter was not obtained. As a result, we include only the first two exposures for each filter in our fast-turnaround v0.5 products, although we may include the third exposure in future versions. For WFC3/IR, all the exposures were obtained, and analysis revealed that the last exposure was offset by no more than a few tenths of an arcsecond compared to its expected location. Thus, there was no significant evidence of drift during the exposures, indicating that the telescope was able to track successfully in gyro mode during these exposures.

    So, it makes no difference. Two, one, or zero guide stars – we can do great science in any case!

    See the full article here.

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

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  • richardmitnick 3:48 pm on October 22, 2014 Permalink | Reply
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    From NASA/Spitzer: “Galactic Wheel of Life Shines in Infrared” 



    Spitzer

    10.22.14
    No Writer Credit

    It might look like a spoked wheel or even a “Chakram” weapon wielded by warriors like “Xena,” from the fictional TV show, but this ringed galaxy is actually a vast place of stellar life. A newly released image from NASA’s Spitzer Space Telescope shows the galaxy NGC 1291. Though the galaxy is quite old, roughly 12 billion years, it is marked by an unusual ring where newborn stars are igniting.

    “The rest of the galaxy is done maturing,” said Kartik Sheth of the National Radio Astronomy Observatory of Charlottesville, Virginia. “But the outer ring is just now starting to light up with stars.”

    NGC 1291 is located about 33 million light-years away in the constellation Eridanus. It is what’s known as a barred galaxy, because its central region is dominated by a long bar of stars (in the new image, the bar is within the blue circle and looks like the letter “S”).

    The bar formed early in the history of the galaxy. It churns material around, forcing stars and gas from their original circular orbits into large, non-circular, radial orbits. This creates resonances — areas where gas is compressed and triggered to form new stars. Our own Milky Way galaxy has a bar, though not as prominent as the one in NGC 1291.

    Sheth and his colleagues are busy trying to better understand how bars of stars like these shape the destinies of galaxies. In a program called Spitzer Survey of Stellar Structure in Galaxies, or S4G, Sheth and his team of scientists are analyzing the structures of more than 3,000 galaxies in our local neighborhood. The farthest galaxy of the bunch lies about 120 million light-years away — practically a stone’s throw in comparison to the vastness of space.

    lg
    Local Group

    The astronomers are documenting structural features, including bars. They want to know how many of the local galaxies have bars, as well as the environmental conditions in a galaxy that might influence the formation and structure of bars.

    “Now, with Spitzer we can measure the precise shape and distribution of matter within the bar structures,” said Sheth. “The bars are a natural product of cosmic evolution, and they are part of the galaxies’ endoskeleton. Examining this endoskeleton for the fossilized clues to their past gives us a unique view of their evolution.”

    In the Spitzer image, shorter-wavelength infrared light has been assigned the color blue, and longer-wavelength light, red. The stars that appear blue in the central, bulge region of the galaxy are older; most of the gas, or star-making fuel, there was previously used up by earlier generations of stars. When galaxies are young and gas-rich, stellar bars drive gas toward the center, feeding star formation.

    ngc

    Over time, as the fuel runs out, the central regions become quiescent and star-formation activity shifts to the outskirts of a galaxy. There, spiral density waves and resonances induced by the central bar help convert gas to stars. The outer ring, seen here in red, is one such resonance area, where gas has been trapped and ignited into star-forming frenzy.

    See the full article here.

    Another view of NGC 1291
    ngc1291
    This composite image of NGC 1291 is processed primarily from data collected by NASA’s Galaxy Evolution Explorer in December 2003. The blue in this image is ultraviolet light captured by GALEX’s long wavelength detector, the green is ultraviolet light detected by its short wavelength detector, and the red in the image is visible light courtesy of data from the Cerro Tololo Inter-American Observatory in Chile

    NASA Galex telescope
    NASA GALEX

    The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory located on the campus of the California Institute of Technology and part of NASA’s Infrared Processing and Analysis Center.
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  • richardmitnick 3:20 pm on October 22, 2014 Permalink | Reply
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    From Hubble: Hubblecast #78 Part 1 

    NASA Hubble Telescope

    Hubble

    October 22, 2014

    Dr J answers questions about Hubble

    Last month we asked the public to send us their Hubble- and astronomy-related questions, and the response was incredible! In this episode Dr J answers a selection of the questions that were specifically about Hubble itself. These range from where Hubble is and how it avoids crashing into space debris, to what the future holds for Hubble, how its life will end, and what will take its place. Watch out for the next episode in which the more science-related questions will get their turn.

    Watch, enjoy, learn.

    See the video here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 2:20 pm on October 22, 2014 Permalink | Reply
    Tags: Astronomy, , , , Human Space Flight, ,   

    From LLNL: “NASA taps Livermore photon scientists for heat-shield research” 


    Lawrence Livermore National Laboratory

    10/22/2014
    Breanna Bishop, LLNL, (925) 423-9802, bishop33@llnl.gov

    Researchers in Lawrence Livermore National Laboratory’s NIF & Photon Science Directorate are working with NASA Ames Research Center at Moffet Field, California on the development of technology to simulate re-entry effects on the heat shield for the Orion spacecraft, NASA’s next crewed spaceship. Orion is designed to carry astronauts beyond low Earth orbit to deep-space destinations such as an asteroid and, eventually, Mars.

    NASA Orion Spacecraft
    NASA/Orion

    The Orion heat shield will have to withstand re-entry temperatures that are too severe for existing reusable thermal protection systems, such as those used on the space shuttles. NASA’s development and characterization of a more robust shield requires that radiant heating capability be added to the Arc Jet Complex at NASA Ames, which develops thermal protection materials and systems in support of the Orion Program Office at NASA Johnson Space Center in Houston and the NASA Human Exploration and Operations Mission Directorate at NASA headquarters in Washington, DC.

    NASA Ames currently owns two 50 kilowatt (kW) commercial fiber laser systems and needs to augment the optical power into the Arc Jet chamber by another 100 to 200 kW. The team at Ames recently approached LLNL to explore an option of using commercially available radiance-conditioned laser diode arrays for this task, similar to the diodes used in the Laboratory’s Diode-Pumped Alkali Laser (DPAL) and E-23/HAPLS laser projects. Their aim is to assess whether such systems can better meet the technical objectives for survival testing. If successful, such diode arrays would offer a dramatically lower-cost solution.

    shield
    Technicians install a protective shell onto the Orion crew module for its first test flight this December. Credit: Dimitri Gerondidaki/NASA

    To perform these tests, LLNL is collaborating with Ames on diode array characterizations using an existing diode system developed for LLNL’s laser programs. These tests will allow NASA Ames to assess whether their optical output can meet in-chamber target illumination requirements, and thus inform their choice for a future system.

    While the space shuttles traveled at 17,000 miles per hour, Orion will be re-entering Earth’s atmosphere at 20,000 miles per hour on its first flight test in December. The faster a spacecraft travels through the atmosphere, the more heat it generates. The hottest the space shuttle tiles got was about 2,300 degrees Fahrenheit; the Orion back shell could get as hot as 4,000 degrees. For more about Orion, see the NASA video.

    See the full article here.

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  • richardmitnick 1:30 pm on October 22, 2014 Permalink | Reply
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    From ESO: “Two Families of Comets Found Around Nearby Star” 


    European Southern Observatory

    22 October 2014
    Contacts

    Alain Lecavelier des Etangs
    Institut d’astrophysique de Paris (IAP)/CNRS/UPMC
    France
    Tel: +33-1-44-32-80-77
    Cell: +33 6 21 75 12 03
    Email: lecaveli@iap.fr

    Flavien Kiefer
    Institut d’astrophysique de Paris (IAP)/CNRS/UPMC and School of Physics and Astronomy, Tel Aviv University
    France / Israel
    Tel: +972-502-838-163
    Email: kiefer@iap.fr

    Richard Hook
    ESO education and Public Outreach Department
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.

    ESO HARPS
    ESO HARPS at La Silla

    ESO LaSilla Long View
    La Silla

    comets

    Beta Pictoris is a young star located about 63 light-years from the Sun. It is only about 20 million years old and is surrounded by a huge disc of material — a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.

    Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”

    For almost 30 years astronomers have seen subtle changes in the light from Beta Pictoris that were thought to be caused by the passage of comets in front of the star itself. Comets are small bodies of a few kilometres in size, but they are rich in ices, which evaporate when they approach their star, producing gigantic tails of gas and dust that can absorb some of the light passing through them. The dim light from the exocomets is swamped by the light of the brilliant star so they cannot be imaged directly from Earth.

    To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

    ESO 3.6m telescope & HARPS at LaSilla
    ESO 3.6 metre telescope with HARPS

    The researchers selected a sample of 493 different exocomets. Some exocomets were observed several times and for a few hours. Careful analysis provided measurements of the speed and the size of the gas clouds. Some of the orbital properties of each of these exocomets, such as the shape and the orientation of the orbit and the distance to the star, could also be deduced.

    This analysis of several hundreds of exocomets in a single exo-planetary system is unique. It revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet [1], and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in the Solar System.

    The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris [2].

    The exocomets of the second family are much more active and are also on nearly identical orbits [3]. This suggests that the members of the second family all arise from the same origin: probably the breakdown of a larger object whose fragments are on an orbit grazing the star Beta Pictoris.

    Flavien Kiefer concludes: “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”
    Notes

    [1] A giant planet, Beta Pictoris b, has also been discovered in orbit at about a billion kilometres from the star and studied using high resolution images obtained with adaptive optics.

    [2] Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped in orbital resonance with a massive planet. The properties of the comets of the first family show that this planet in resonance must be at about 700 million kilometres from the star — close to where the planet Beta Pictoris b was discovered.

    [3] This makes them similar to the comets of the Kreutz family in the Solar System, or the fragments of Comet Shoemaker-Levy 9, which impacted Jupiter in July 1994.
    More information

    This research was presented in a paper entitled Two families of exocomets in the Beta Pictoris system which will be published in the journal Nature on 23 October 2014.

    The team is composed of F. Kiefer (Institut d’astrophysique de Paris [IAP], CNRS, Université Pierre & Marie Curie-Paris 6, Paris, France), A. Lecavelier des Etangs (IAP), J. Boissier (Institut de radioastronomie millimétrique, Saint Martin d’Hères, France), A. Vidal-Madjar (IAP), H. Beust (Institut de planétologie et d’astrophysique de Grenoble [IPAG], CNRS, Université Joseph Fourier-Grenoble 1, Grenoble, France), A.-M. Lagrange (IPAG), G. Hébrard (IAP) and R. Ferlet (IAP).

    See the full article here.

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  • richardmitnick 1:26 pm on October 22, 2014 Permalink | Reply
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    From NASA Goddard: “NASA-led Study Sees Titan Glowing at Dusk and Dawn” 

    NASA Goddard Banner

    October 22, 2014
    Nancy Neal-Jones 301-286-0039
    nancy.n.jones@nasa.gov
    Elizabeth Zubritsky 301-614-5438
    Goddard Space Flight Center, Greenbelt, Md.
    elizabeth.a.zubritsky@nasa.gov

    New maps of Saturn’s moon Titan reveal large patches of trace gases shining brightly near the north and south poles. These regions are curiously shifted off the poles, to the east or west, so that dawn is breaking over the southern region while dusk is falling over the northern one.

    two
    High in the atmosphere of Titan, large patches of two trace gases glow near the north pole, on the dusk side of the moon, and near the south pole, on the dawn side. Brighter colors indicate stronger signals from the two gases, HNC (left) and HC3N (right); red hues indicate less pronounced signals.
    Image Credit: NRAO/AUI/NSF

    The pair of patches was spotted by a NASA-led international team of researchers investigating the chemical make-up of Titan’s atmosphere.

    “This is an unexpected and potentially groundbreaking discovery,” said Martin Cordiner, an astrochemist working at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the lead author of the study. “These kinds of east-to-west variations have never been seen before in Titan’s atmospheric gases. Explaining their origin presents us with a fascinating new problem.”

    The mapping comes from observations made by the Atacama Large Millimeter/submillimeter Array (ALMA), a network of high-precision antennas in Chile. At the wavelengths used by these antennas, the gas-rich areas in Titan’s atmosphere glowed brightly. And because of ALMA’s sensitivity, the researchers were able to obtain spatial maps of chemicals in Titan’s atmosphere from a “snapshot” observation that lasted less than three minutes.

    ALMA Array
    ALMA Array

    Titan’s atmosphere has long been of interest because it acts as a chemical factory, using energy from the sun and Saturn’s magnetic field to produce a wide range of organic, or carbon-based, molecules. Studying this complex chemistry may provide insights into the properties of Earth’s very early atmosphere, which may have shared many chemical characteristics with present-day Titan.

    In this study, the researchers focused on two organic molecules, hydrogen isocyanide (HNC) and cyanoacetylene (HC3N), that are formed in Titan’s atmosphere. At lower altitudes, the two molecules appear concentrated above Titan’s north and south poles. These findings are consistent with observations made by NASA’s Cassini spacecraft, which has found a cloud cap and high concentrations of some gases over whichever pole is experiencing winter on Titan.

    NASA Cassini Spacecraft
    NASA/Cassini

    The surprise came when the researchers compared the gas concentrations at different levels in the atmosphere. At the highest altitudes, the gas pockets appeared to be shifted away from the poles. These off-pole locations are unexpected because the fast-moving winds in Titan’s middle atmosphere move in an east–west direction, forming zones similar to Jupiter’s bands, though much less pronounced. Within each zone, the atmospheric gases should, for the most part, be thoroughly mixed.

    The researchers do not have an obvious explanation for these findings yet.

    “It seems incredible that chemical mechanisms could be operating on rapid enough timescales to cause enhanced ‘pocket’’ in the observed molecules,” said Conor Nixon, a planetary scientist at Goddard and a coauthor of the paper, published online today in the Astrophysical Journal Letters. “We would expect the molecules to be quickly mixed around the globe by Titan’s winds.”

    At the moment, the scientists are considering a number of potential explanations, including thermal effects, previously unknown patterns of atmospheric circulation, or the influence of Saturn’s powerful magnetic field, which extends far enough to engulf Titan.

    Further observations are expected to improve the understanding of the atmosphere and ongoing processes on Titan and other objects throughout the solar system.

    NASA’s Astrobiology Program supported this work through a grant to the Goddard Center for Astrobiology, a part of the NASA Astrobiology Institute. Additional funding came from NASA’s Planetary Atmospheres and Planetary Astronomy programs. ALMA, an international astronomy facility, is funded in Europe by the European Southern Observatory, in North America by the U.S. National Science Foundation in cooperation with the National Research Council of Canada and the National Science Council of Taiwan, and in East Asia by the National Institutes of Natural Sciences of Japan in cooperation with the Academia Sinica in Taiwan.

    See the full article here.

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

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  • richardmitnick 7:12 pm on October 21, 2014 Permalink | Reply
    Tags: Astronomy, , , , , POLARBEAR Experiment   

    From Daily Galaxy: “Astrophysicists Using Big Bang’s Primordial Light to Probe Largest Structures in the Universe” 

    Daily Galaxy
    The Daily Galaxy

    October 21, 2014
    The Daily Galaxy via University of California – Berkeley

    An international team of physicists has measured a subtle characteristic in the polarization of the cosmic microwave background radiation that will allow them to map the large-scale structure of the universe, determine the masses of neutrinos and perhaps uncover some of the mysteries of dark matter and dark energy. The POLARBEAR team is measuring the polarization of light that dates from an era 380,000 years after the Big Bang, when the early universe was a high-energy laboratory, a lot hotter and denser than now, with an energy density a trillion times higher than what they are producing at the CERN collider.

    Cosmic Background Radiation Planck
    CMB per Planck

    The Large Hadron Collider near Geneva is trying to simulate that early era by slamming together beams of protons to create a hot dense soup from which researchers hope new particles will emerge, such as the newly discovered Higgs boson. But observing the early universe, as the POLARBEAR group does may also yield evidence that new physics and new particles exist at ultra-high energies.

    The team uses these primordial photon’s light to probe large-scale gravitational structures in the universe, such as clusters or walls of galaxies that have grown from what initially were tiny fluctuations in the density of the universe. These structures bend the trajectories of microwave background photons through gravitational lensing, distorting its polarization and converting E-modes into B-modes. POLARBEAR images the lensing-generated B-modes to shed light on the intervening universe.

    In a paper published this week in the Astrophysical Journal, the POLARBEAR consortium, led by University of California, Berkeley, physicist Adrian Lee, describes the first successful isolation of a “B-mode” produced by gravitational lensing in the polarization of the cosmic microwave background radiation.

    Polarization is the orientation of the microwave’s electric field, which can be twisted into a “B-mode” pattern as the light passes through the gravitational fields of massive objects, such as clusters of galaxies.

    lens

    “We made the first demonstration that you can isolate a pure gravitational lensing B-mode on the sky,” said Lee, POLARBEAR principal investigator, UC Berkeley professor of physics and faculty scientist at Lawrence Berkeley National Laboratory (LBNL). “Also, we have shown you can measure the basic signal that will enable very sensitive searches for neutrino mass and the evolution of dark energy.”

    The POLARBEAR team, which uses microwave detectors mounted on the Huan Tran Telescope in Chile’s Atacama Desert, consists of more than 70 researchers from around the world. They submitted their new paper to the journal one week before the surprising March 17 announcement by a rival group, the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) experiment, that they had found the holy grail of microwave background research. That team reported finding the signature of cosmic inflation – a rapid ballooning of the universe when it was a fraction of a fraction of a second old – in the polarization pattern of the microwave background radiation.

    Huan Tran Telescope
    Huan Tran Telescope (Kavli IPMU)

    BICEP 2
    BICEP2 with South Pole Telescope

    Subsequent observations, such as those announced last month by the Planck satellite, have since thrown cold water on the BICEP2 results, suggesting that they did not detect what they claimed to detect.

    While POLARBEAR may eventually confirm or refute the BICEP2 results, so far it has focused on interpreting the polarization pattern of the microwave background to map the distribution of matter back in time to the universe’s inflationary period, 380,000 years after the Big Bang.

    POLARBEAR’s approach, which is different from that used by BICEP2, may allow the group to determine when dark energy, the mysterious force accelerating the expansion of the universe, began to dominate and overwhelm gravity, which throughout most of cosmic history slowed the expansion.

    BICEP2 and POLARBEAR both were designed to measure the pattern of B-mode polarization, that is, the angle of polarization at each point in an area of sky. BICEP2, based at the South Pole, can only measure variation over large angular scales, which is where theorists predicted they would find the signature of gravitational waves created during the universe’s infancy. Gravitational waves could only have been created by a brief and very rapid expansion, or inflation, of the universe 10-34 seconds after the Big Bang.

    In contrast, POLARBEAR was designed to measure the polarization at both large and small angular scales. Since first taking data in 2012, the team focused on small angular scales, and their new paper shows that they can measure B-mode polarization and use it to reconstruct the total mass lying along the line of sight of each photon.

    The polarization of the microwave background records minute density differences from that early era. After the Big Bang, 13.8 billion years ago, the universe was so hot and dense that light bounced endlessly from one particle to another, scattering from and ionizing any atoms that formed. Only when the universe was 380,000 years old was it sufficiently cool to allow an electron and a proton to form a stable hydrogen atom without being immediately broken apart. Suddenly, all the light particles – called photons – were set free.

    “The photons go from bouncing around like balls in a pinball machine to flying straight and basically allowing us to take a picture of the universe from only 380,000 years after the Big Bang,” Lee said. “The universe was a lot simpler then: mainly hydrogen plasma and dark matter.”

    These photons, which, today, have cooled to a mere 3 degrees Kelvin above absolute zero, still retain information about their last interaction with matter. Specifically, the flow of matter due to density fluctuations where the photon last scattered gave that photon a certain polarization (called E-mode polarization).

    “Think of it like this: the photons are bouncing off the electrons, and there is basically a last kiss, they touch the last electron and then they go for 14 billion years until they get to telescopes on the ground,” Lee said. “That last kiss is polarizing.”

    While E-mode polarization contains some information, B-mode polarization contains more, because photons carry this only if matter around the last point of scattering was unevenly or asymmetrically distributed. Specifically, the gravitational waves created during inflation squeezed space and imparted a B-mode polarization that BICEP2 may have detected. POLARBEAR, on the other hand, has detected B-modes that are produced by distortion of the E-modes by gravitational lensing.

    While many scientists suspected that the gravitational-wave B-mode polarization might be too faint to detect easily, the BICEP2 team, led by astronomers at Harvard University’s Center for Astrophysics, reported a large signal that fit predictions of gravitational waves. Current doubt about this result centers on whether or not they took into account the emission of dust from the galaxy that would alter the polarization pattern.

    In addition, BICEP2’s ability to measure inflation at smaller angular scales is contaminated by the gravitational lensing B-mode signal.

    “POLARBEAR’s strong suit is that it also has high angular resolution where we can image this lensing and subtract it out of the inflationary signal to clean it up,” Lee said.

    Two other papers describing related results from POLARBEAR were accepted in the spring by Physical Review Letters.

    One of those papers is about correlating E-mode polarization with B-mode polarization, which “is the most sensitive channel to cosmology; that’s how you can measure neutrino masses, how you might look for early behavior of dark energy,” Lee said.

    The [basically blue] image [above] shows the scale of a large quasar group” (LQG), the largest structure ever seen in the entire universe that runs counter to our current understanding of the scale of the universe. Even traveling at the speed of light, it would take 4 billion years to cross. This is significant not just because of its size but also because it challenges the Cosmological Principle, which has been widely accepted since [Albert] Einstein, the assumption that the universe, when viewed at a sufficiently large scale, looks the same no matter where you are observing it from.

    See the full article here.

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  • richardmitnick 3:29 pm on October 20, 2014 Permalink | Reply
    Tags: , , Astronomy, , , ,   

    From astrobio.net: ” Exomoons Could Be Abundant Sources Of Habitability” 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 20, 2014
    Elizabeth Howell

    With about 4,000 planet candidates from the Kepler Space Telescope data to analyze so far, astronomers are busy trying to figure out questions about habitability. What size planet could host life? How far from its star does it need to be? What would its atmosphere need to be made of?

    NASA Kepler Telescope
    NASA/Kepler

    Look at our own solar system, however, and there’s a big gap in the information we need. Most of the planets have moons, so surely at least some of the Kepler finds would have them as well. Tracking down these tiny worlds, however, is a challenge.

    europa
    Europa is one of the moons in our solar system that could host life. What about beyond the solar system? Credit: NASA/JPL/Ted Stryk

    A new paper in the journal Astrobiology, called Formation, Habitability, and Detection of Extrasolar Moons, goes over this mostly unexplored field of extrasolar research. The scientists do an extensive literature review of what is supposed about moons beyond the Solar System, and they add intriguing new results.

    A wealth of moons exist in our own solar system that could host life. Icy Europa, which is circling Jupiter, was recently discovered to have plumes of water erupting from its surface. Titan, in orbit around Saturn, is the only known moon with an atmosphere, and could have the precursor elements to life in its hydrocarbon seas that are warmed by Saturn’s heat. Other candidates for extraterrestrial hosts include Jupiter’s moons Callisto and Ganymede, as well as Saturn’s satellite Enceladus.

    Lead author René Heller, an astrophysicist at the Origins Institute at McMaster University, in Ontario, Canada, said some exomoons could be even better candidates for life than many exoplanets.

    “Moons have separate energy sources,” he said. “While the habitability of terrestrial planets is mostly determined by stellar illumination, moons also receive reflected stellar light from the planet as well as thermal emission from the planet itself.”

    Moreover, a planet like Jupiter — which hosts most of the moons in the Solar System that could support life — provides even more potential energy sources, he added. The planet is still shrinking and thereby converts gravitational energy into heat, so that it actually emits more light than it receives from the Sun, providing yet more illumination. Besides that, moons orbiting close to a gas giant are flexed by the planet’s gravity, providing potential tidal heating as an internal, geological heat source.

    tri
    Triton’s odd, melted appearance hint that the moon was captured and altered by Neptune. Credit: NASA

    Finding the first exomoon

    The first challenge in studying exomoons outside our Solar System is to actually find one. Earlier this year, NASA-funded researchers reported the possible discovery of such a moon, but this claim was ambiguous and can never be confirmed. That’s because it appeared as a one-time event, when one star passed in front of another, acting as a sort of gravitational lens that amplified the background star. Two objects popped out in the gravitational lens in the foreground — either a planet and a star, or a planet and an extremely heavy exomoon.

    For his part, Heller is convinced that exomoons are lurking in the Kepler data, but they have not been discovered yet. Only one project right now is dedicated to searching for exomoons, and is led by David Kipping at the Canadian Space Agency. His group has published several papers investigating 20 Kepler planets and candidates in total. The big restriction to their efforts is computational power, as their simulations require supercomputers.

    Another limiting factor is the number of observatories that can search for exomoons. To detect them, at least a handful of transits of the planet-moon system across their common host star would be required to absolutely make sure that the companion is a moon, Heller said. Also, the planet with the moon would have to be fairly far from its star, and decidedly not those close-in hot Jupiters that take only a few days to make an orbit. In that zone, the gravitational drag of the star would fatally perturb any moon’s orbit.

    Heller estimates that a telescope would need to stare constantly at the same patch of sky for several hundred days, minimum, to pick up an exomoon. Kepler fulfilled that obligation in spades with its four years of data gazing at the same spot in the sky, but astronomers will have to wait again for that opportunity.

    Because two of Kepler’s gyroscopes (pointing devices) have failed, Kepler’s new mission will use the pressure of the Sun to keep it steady. But it can only now point to the same region of the sky for about 80 days at at time because the telescope will periodically need to be moved so as not to risk placing its optics too close to the Sun.

    NASA’s forthcoming Transiting Exoplanet Survey Satellite [TESS} is only expected to look at a given field for 70 days. Further into the future, the European Space Agency’s PLAnetary Transits and Oscillations of stars (PLATO) will launch in 2024 for what is a planned six-year mission looking at several spots in the sky.

    NASA TESS
    NASA/TESS

    ESA PLATO
    ESA PLATO

    “PLATO is the next step, with a comparable accuracy to Kepler but a much larger field of view and hopefully a longer field of view coverage,” Heller said.

    Clues in our solar system

    pla
    Thousands of exoplanets and exoplanet candidates have been discovered, but astronomers are still searching for exomoons. Credit: ESA – C. Carreau

    Heller characterizes moons as an under-appreciated feature of extrasolar planetary systems. Just by looking around us in the Solar System, he says, astronomers have been able to make crucial explanations about how the moons must have formed and evolved together with their planets. Moons thus carry information about the substructure of planet evolution, which is not accessible by planet observations alone.

    The Earth’s moon, for example, was likely formed when a Mars-sized object collided with the proto-Earth and produced a debris disk. Over time, that debris coalesced into our moon.

    While Heller says the literature mostly focuses on collision scenarios between an Earth-sized object and a Mars-sized object, he doesn’t see any reason why crashes on a bigger scale might not happen. Perhaps an Earth-sized object crashed into an object that was five times the mass of Earth, producing an extrasolar Earth-Earth binary planet system, he suggests.

    Another collision scenario likely took place at Uranus. The gas giant’s rotation is tilted about 90 degrees in its orbit around the Sun. In other words, it is rolling on its side. More intriguing, its two dozen moons follow Uranus’ rotational equator, and they do not orbit in the same plane as Uranus’ track around the Sun. This scenario suggests that Uranus was hit multiple times by huge objects instead of just once, Heller said.

    Examining mighty Jupiter’s moons gives astronomers a sense of how high temperatures were in the disk that formed the gas giant and its satellites, Heller added. Ganymede, for example, is an icy moon. Models indicate that beyond Ganymede’s orbit (at about 15 Jupiter radii) it is sufficiently cold for water to pass from the gas to the solid (ice) stage, so the regular moons in these regions are very water-rich compared to the inner, mostly rocky moons Io and Europa.

    “It sounds a bit technical, but we couldn’t have this information about planetary accretion if we did not have the moons today to observe,” Heller said.

    Some moons could also have been captured, such as Neptune’s large moon, Triton. The moon orbits in a direction opposite to other moons in Neptune‘s system (and in fact, opposite to the direction of other large moons in the Solar System.) Plus, its odd terrain suggests that it used to be a free-floating object that was captured by Neptune’s gravity. Neptune is so huge that it raised tides within the moon, reforming its surface.

    Even comparing the different types of moons around planets in the Solar System reveals different timescales of formation. Jupiter includes four moons similar in size to Earth’s moon (Europa, Callisto, Ganymede and Io), while the next largest planet in our solar system, Saturn, only has one large moon called Titan. Astronomers believe Saturn has only one large moon because the gas that formed objects in our solar system was more plentiful in Jupiter’s system to provide material for the moons to form.

    The gas abundance happened as a consequence of the huge gas giant creating a void in the material surrounding our young Sun, pulling the material in for its moons. Saturn was not quite large enough to do this, resulting in fewer large moons.

    More strange situations could exist beyond our solar system’s boundaries, but it will take a dedicated search to find exomoons. Once they are discovered, however, they will allow planet formation and evolution studies on a completely new level.

    This research was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Center for Exoplanets and Habitable Worlds, which is supported by the Pennsylvania State University, the Pennsylvania Space Grant Consortium, the National Science Foundation (NSF) the NASA Astrobiology Institute.

    See the full article here.

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