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  • richardmitnick 4:19 pm on January 15, 2016 Permalink | Reply
    Tags: , , , Gemini Planet Imager, TW Hydrae   

    From AAS NOVA: ” A Gap in TW Hydrae’s Disk” 

    AASNOVA

    American Astronomical Society

    15 January 2016
    Susanna Kohler

    Temp 1
    Observations from the Gemini Planet Imager confirm the presence of a gap in the dusty disk surrounding the nearby star TW Hydrae. Click for a full view! [Adapted from Rapson et al. 2015]

    Located a mere 176 light-years away, TW Hydrae is an 8-million-year-old star surrounded by a nearly face-on disk of gas and dust. Recent observations have confirmed the existence of a gap within that disk — a particularly intriguing find, since gaps can sometimes signal the presence of a planet.

    Gaps and Planets

    Numerical simulations have shown that newly-formed planets orbiting within dusty disks can clear the gas and dust out of their paths. This process results in pressure gradients that can be seen in the density structure of the disk, in the form of visible gaps, rings, or spirals.

    For this reason, finding a gap in a protoplanetary disk can be an exciting discovery. Previous observations of the disk around TW Hydrae had indicated that there might be a gap present, but they were limited in their resolution; despite TW Hydrae’s relative nearness, attempting to observe the dim light scattered off dust particles in a disk surrounding a distant, bright star is difficult!

    But a team led by Valerie Rapson (Rochester Institute of Technology, Dudley Observatory) recently set out to follow up on this discovery using a powerful tool: the Gemini Planet Imager (GPI).

    NOAO Gemini Planet Imager
    Gemini Planet Imager
    Gemini Planet Imager

    Temp 2
    Comparison of the actual image of TW Hydrae’s disk from GPI (right) to a simulated scattered-light image from a model of a ~0.2 Jupiter-mass planet orbiting in the disk at ~21 AU (left) in two different bands (top: J, bottom: K1).[Adapted from Rapson et al. 2015]

    New Observations

    GPI is an instrument on the Gemini South Telescope in Chile.

    Gemini South telescope
    Gemini South

    Its near-infrared imagers, equipped with extreme adaptive optics, allowed it to probe the disk from ~80 AU all the way in to ~10 AU from the central star, with an unprecedented resolution of ~1.5 AU.

    These observations from GPI allowed Rapson and collaborators to unambiguously confirm the presence of a gap in TW Hydrae’s disk. The gap lies at a distance of ~23 AU from the central star (roughly the same distance as Uranus to the Sun), and it’s ~5 AU wide.
    Modeled Possibilities

    There are a number of other potential explanations for this gap — for instance, the inner disk could be casting a shadow on the outer disk, or the gap could be a natural consequence of how grains fragment and evolve within the disk.

    Nevertheless, an orbiting planet embedded in the disk may well be the cause. When Rapson and collaborators ran numerical simulations of a planet orbiting within a disk like TW Hydrae’s, they found that a planet of 0.16 Jupiter masses, orbiting at a distance of 21 AU, reproduces the observations well.

    With any luck, we’ll be able to learn more with additional observations in the future. Deeper images may reveal additional features that point to a planet shaping the disk structure. And if the planet is actively accreting gas in the disk, we may even be able to directly image the planet!
    Citation

    Valerie A. Rapson et al 2015 ApJ 815 L26. doi:10.1088/2041-8205/815/2/L26

    See the full article here .

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  • richardmitnick 6:05 pm on December 23, 2015 Permalink | Reply
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    From Gemini: “Gap in Dusty Disk is Likely Embryonic Sub-Jupiter Mass Planet” 

    NOAO

    Gemini Observatory
    Gemini Observatory

    December 22, 2015
    No writer credit

    1
    Left: GPI J band (top) and K1 band (bottom) polarized intensity (Qr) images of the TW Hya disk. Right: Qr(i; j) scaled by r2(i; j), where r(i; j) is the distance (in pixels) of pixel position (i; j) from the central star, corrected for projection effects. All images are shown on a linear scale. The coronagraph is represented by the black filled circles and images are oriented with north up and east to the left.

    TW Hydrae (TW Hya) is one of the best-studied young stars in the galaxy.At just 180 light years from Earth and a ripe young age of roughly 8 million years, this nearly solar-mass star and its orbiting, circumstellar disk of dust and gas are prime targets to better understand the processes involved in star and planet formation. The most sensitive telescope systems available, accessing wavelengths from radio to X-ray, have observed the TW Hya system. Astronomers have now used the Gemini Planet Imager (GPI) on Gemini South to image infrared light from TW Hya that is scattered off dust grains in its surrounding disk.

    NOAO Gemini Planet Imager
    GPI

    Gemini South telescopeGemini South Interior
    Gemini South

    The new GPI images confirm the presence of a darkened ring or gap in the disk at 23 AU (i.e., 23 times the earth-Sun distance) — and GPI brings this gap into the sharpest focus yet. Comparison with detailed numerical simulations of planets forming in circumstellar disks indicates that the 5-AU-wide gap’s observed structure could be generated by a sub-Jupiter-mass planet orbiting within the disk at a position roughly equivalent to that of Uranus in our solar system. “These GPI data reveal tell-tale disk structure in the giant-planet-forming region around TW Hya at higher resolution than any other measurements to date,” says Dr. Valerie Rapson of Rochester Institute of Technology, who led the research team. “The results will help us piece together the story of how giant planets form around sun-like stars.”

    The paper is published in The Astrophysical Journal.

    We present Gemini Planet Imager (GPI) adaptive optics near-infrared images of the giant-planet-forming regions of the protoplanetary disk orbiting the nearby (D = 54 pc), pre-main-sequence (classical T Tauri) star TW Hydrae. The GPI images, which were obtained in coronagraphic/polarimetric mode, exploit starlight scattered off small dust grains to elucidate the surface density structure of the TW Hya disk from ~80 AU to within ~10 AU of the star at ~1.5 AU resolution. The GPI polarized intensity images unambiguously confirm the presence of a gap in the radial surface brightness distribution of the inner disk. The gap is centered near ~23 AU, with a width of ~5 AU and a depth of ~50%. In the context of recent simulations of giant-planet formation in gaseous, dusty disks orbiting pre-main-sequence stars, these results indicate that at least one young planet with a mass ~0.2 MJ could be present in the TW Hya disk at an orbital semimajor axis similar to that of Uranus. If this (proto)planet is actively accreting gas from the disk, it may be readily detectable by GPI or a similarly sensitive, high-resolution infrared imaging system.

    See the full article here .

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    Gemini North
    Gemini North, Hawai’i

    Gemini South
    Gemini South, Chile
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    Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

    The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

    The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

     
  • richardmitnick 6:34 pm on November 12, 2015 Permalink | Reply
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    From SETI Institute: “Gemini Planet Imager Exoplanet Survey — One Year Into The Survey” 


    SETI Institute

    November 12 2015
    Media Contacts:

    Peter Michaud
    Public Information and Outreach
    Gemini Observatory, Hilo, HI
    Email: pmichaud”at”gemini.edu
    Cell: (808) 936-6643

    Seth Shostak
    SETI Institute
    Email: sshostak”at”seti.org
    Phone: +1-650-960-4530

    Science Contacts:

    Franck Marchis
    SETI Institute
    Email: fmarchis”at”seti.org
    Phone: +1-510-599-0604

    Eric Nielsen
    SETI Institute
    Email: enielsen”at”seti.org
    Phone: +1-408-394-4582

    Li-Wei Hung
    University of California, Los Angeles
    Email: liweih”at”astro.ucla.edu
    Phone: +1 310-794-5582

    The SETI Institute press release.

    1
    Orbital motion of 51 Eri b detected between two H-band observations taken with the Gemini Planet Imager in December 2014 and September 2015. From this motion, and additional observations of the system, the team of astronomers confirmed that this point of light below the star is indeed a planet orbiting 51 Eri and not a brown dwarf passing along our line of sight. (credit: Christian Marois & the GPIES team)

    The Gemini Planet Imager Exoplanet Survey (GPIES) is an ambitious three-year study dedicated to imaging young Jupiters and debris disks around nearby stars using the GPI instrument installed on the Gemini South telescope in Chile.

    Gemini Planet Imager
    GPI

    Gemini South telescope
    Gemini South

    On November 12, at the 47th annual meeting of the AAS’s Division for Planetary Sciences in Washington DC, Franck Marchis, Chair of the Exoplanet Research Thrust of the SETI Institute and a scientist involved in the project since 2004, will report on the status of the survey, emphasizing some discoveries made in its first year.

    Led by Bruce Macintosh from Stanford University, the survey began a year ago and has already been highly successful, with several findings already published in peer-reviewed journals.

    “This very large survey is observing 600 young stars to look for two things: giant planets orbiting them and debris disks. In our first year, we have already found what GPI was designed to discover — a young Jupiter in orbit around a nearby star,” said Marchis. This discovery was announced in an article published in Science on Oct. 2, 2015 [http://www.sciencemag.org/content/350/6256/64], with an impressive list of 88 co-authors from 39 institutions located in North and South America. “This is modern astronomy at its best,” said Marchis. “These large projects gather energy and creativity from many groups of researchers at various institutions, enabling them to consider different strategies to improve the on-sky efficiency of the instrument and its scientific output.”

    The survey was officially launched in November 2014. Eight observing runs allowed the study of approximately 160 targets, or a quarter of the sample. Other parts of the survey are more frustrating, though. Due to the incipient El Nino, weather in Chile is worse than expected, with clouds, rain, snow, and atmospheric turbulence too severe even for GPI to fix. Since late June, out of the last 20 nights that team members have spent at the telescope, they’ve only gotten a few hours of good quality data Despite this loss, over which the team of course had no control, they have already published ten peer-reviewed papers in the last year. Two of the findings are described below.

    GPI data has revealed that 51 Eri b, the recently discovered Jupiter-like exoplanet around the nearby star 51 Eridani [http://www.gemini.edu/node/12403], indeed has an atmosphere of methane and water, and likely has a mass twice that of Jupiter. The team has continued to observe this planetary system, and observations recorded on Sept. 1, 2015, are most consistent with a planet orbiting 51 Eri and not a brown dwarf passing along our line of sight.

    “Thanks to GPI’s incredible precision, we can demonstrate that the odds are vanishingly small that 51 Eri b is actually a brown dwarf that has a chance alignment with this star. In fact it’s five times more likely that I’ll be struck by lightning this year than future data will show this is not a planet orbiting 51 Eri” said Eric Nielsen, a postdoctoral scholar at the SETI Institute and one of the authors of the paper recently accepted for publication in the Astrophysical Journal Letters [http://arxiv.org/abs/1509.07514]. Another author of this study, SETI Research Experience for Undergraduates student Sarah Blunt, analyzed the motion of 51 Eri b and found it to be completely consistent with a planet on an approximately 40-year orbit around its host star.

    The team has also discovered and imaged disks of dusty debris around several stars. Astronomers believe that these are planetary systems that are still forming their planets. Some have complex structures because they host planets and fragments of the asteroidal and cometary materials that formed those planets. One such system is HD 131835: a massive 15 Myr-old star located 400 light-years from Earth. Using GPI’s high-contrast capability, the team imaged this disk for the first time in near-infrared light in May 2015.

    “The disk shows different morphology when observed in different wavelengths. Unlike the extended disk previously imaged in thermal emission, our GPI observations show a disk that has a ring-like structure, indicating that the large grains are distributed differently from the small ones. In addition, we discovered an asymmetry in the disk along its major axis. What causes this disk to be asymmetric is the subject of ongoing investigation, “ said Li-Wei Hung, a graduate student in the UCLA Department of Physics and Astronomy and lead author of the article submitted to the Astrophysical Journal Astrophysical Journal Letters [http://arxiv.org/abs/1502.02035]. As asymmetries like the one seen in the system may be due to the gravitational influence of an unseen planet, more detailed observational study could one day confirm its existence.

    As the GPIES survey enters in its second year, we are collaborating with the Gemini Observatory to continue to improve the instrument. The Gemini South telescope primary mirror was recently re-coated with silver to improve reflectivity, and the GPI instrument was equipped with a new cooling system to optimize performance.

    “Continued collaboration between the Gemini Observatory and the GPIES collaboration has worked really well — we’re learning a lot about how it performs in the field and interacts with the atmosphere, and are working to make GPI an even a better instrument to see even fainter and closer planets,” said Bruce Macintosh, principal investigator of the project and professor at Stanford University.

    See the full article here .

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  • richardmitnick 6:08 pm on September 16, 2015 Permalink | Reply
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    From GPI: “What do we know about planet formation?” 

    GPI bloc

    GPI

    September 16, 2015
    Roman Rafikov

    1
    This artist’s impression shows the formation of a gas giant planet around a young star. Credit: ESO/L. Calçada

    Understanding how planets form in the Universe is one of the main motivations for GPI. Thanks to its advanced design, GPI specializes in finding and studying giant planets that are similar to Jupiter in our solar system. These are the kind of planets whose origin we hope to understand much better after our survey is complete.

    We know that planets form within protoplanetary disks that orbit young stars, and gas giants need to be fully formed within 3-10 million years of the formation of their parent star as the gaseous nebula dissipates past this point. This very important time constraint is based on statistics of observed protoplanetary disks in nearby young stellar associations such as Taurus. At present there are two main rival theories of giant planet formation — core accretion and gravitational instability, which effectively represent the “bottom up” and “top down” routes to planetary genesis.

    Core accretion relies on the formation of a planetary core — a compact, massive object composed of refractory elements, similar to a terrestrial planet like Earth but typically more massive. Cores form by assembly of a large number of planetesimals — smaller asteroid-like bodies composed of rock and ice that collide with each other, merge and grow in size. This process is thought to be rather slow, especially if it happens far from the star, where the characteristic timescales, which are determined by the local orbital period, become very long. As protoplanetary cores increase their mass, their gravitational pull attracts gas from the surrounding nebula, forming atmospheres around them. Atmospheric mass increases quite rapidly, and at some point the whole gaseous envelope becomes self-gravitating. In theoretical models, this transition typically occurs when the core mass exceeds 10-20 Earth masses. Beyond this point rapid gas accretion ensues, turning the core into a giant planet in a relatively short period of time. This process is accompanied by a brief phase of high luminosity as the gravitational energy of accreted gas is radiated away. The final mass of the planet is likely to be set by how much nebular gas is available for accretion, which may be limited by the formation of a gap around the planetary orbit, or by the dispersal of the protoplanetary disk.

    Gravitational instability may operate in cold, massive disks in which random gas overdensities start growing under their own self-gravity, which neither pressure nor rotational support can initially resist. If this collapse of dense regions can continue deeply into the nonlinear regime, and their density come to far exceed the nebula’s, such clumps become self-gravitating objects — and, over time, contract, cool, and look like giant planets. Theoretical arguments and numerical simulations suggest that this is possible only when the collapsing gas is able to cool rapidly. Otherwise, pressure inside the contracting clump would increase so fast that it could stall collapse. Detailed analysis shows that in gravitationally unstable disks, conditions for such rapid cooling are realized only far from the star, beyond approximately 50 AU, which is in the range of separations probed by GPI.

    2
    A schematic illustration of the two main theoretical channels of the giant planet formation: core accretion (on the left) and gravitational instability (on the right). Credit: NASA and A. Feild (STScI)

    Both theories have their own virtues and problems. Core accretion is natural in the sense that it represents a culminating step in the formation of terrestrial planets (or massive cores). It nicely explains the overabundance of refractory elements and the presence of cores for giant planets in the solar system (although the latter is not so obvious in the case of Jupiter). It also naturally accounts for the so-called metallicity correlation — the tendency of more metal-rich stars to host a giant planet: higher abundance of metals in the nebula increases the availability of solids and speeds up core growth, facilitating core accretion. However, formation of the core is the Achilles’ heel of core accretion because it typically takes a long time. Standard theory predicts that far from the star, the core buildup by planetesimal coagulation should take much longer than the lifespan of a protoplanetary disk, which is several million years. This makes it problematic to explain the origin of directly imaged planets by core accretion at tens of AU from their stars. That’s why a number of ideas have been proposed recently for speeding up core formation, by efficient accretion of either cm- or mm-sized “pebbles” early on, or small fragments and debris resulting from planetesimal collisions at later stages.

    Gravitational instability nicely bypasses the nebula-lifetime constraint as it should operate on a relatively short dynamical timescale, which is about thousands of years at 100 AU distances. However, as mentioned above, conditions for this formation channel can exist only far from the star. It also requires very massive protoplanetary disks, typically tens of percent of the stellar mass, which may not be unusual early on but is not very common in later stages. High disk mass raises a number of important issues for gravitational instability. Bound objects produced by gravitational instability are expected to have rather high initial masses (of order 10 Jupiter masses), and can easily grow from planetary mass into the brown dwarf regime by accreting from the surrounding dense nebula. Tidal coupling to a massive disk may also lead to fast migration of forming protoplanets towards the star, where they can be efficiently destroyed.

    3
    A series of snapshots from a simulation of a gravitationally unstable protoplanetary disk. Bright objects seen at late stages are the self-gravitating clumps forming as a result of gravitational instability that may subsequently turn into giant planets. Credit: G. Lufkin et al (University of Washington)

    Discoveries of planets such as 51 Eri b are very important for understanding the efficiency of each of these two channels (their “branching ratios”) in producing the planets we have observed. With its small projected separation of only 13 AU and relatively low mass (possibly as low as two Jupiter masses) this object would have little problem forming by core accretion even at its current location, which is close to the orbit of Saturn in our solar system. At this stage, gravitational instability appears a more unlikely scenario for 51 Eri b. GPI and similar surveys will provide better statistics for directly imaged planets at different separations, and give us a much better understanding of how the majority of giant planets form in the Universe.

    See the full article here .

    Gemini Planet Imager
    GPI

    Gemini South telescope
    Gemini South

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    GPI: A scientific partnership between institutions from the U.S.A., Canada, Australia, Argentina, Brazil and Chile.

     
  • richardmitnick 9:20 am on May 27, 2015 Permalink | Reply
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    From phys.org: “Discovery shows what the solar system looked like as a ‘toddler'” 

    physdotorg
    phys.org

    May 27, 2015
    No Writer Credit

    1
    Left: Image of HD 115600 showing a bright debris ring viewed nearly edge-on and located just beyond a Pluto-like distance to the star. Right: A model of the HD 115600 debris ring on the same scale. Credit: T. Currie

    Astronomers have discovered a disc of planetary debris surrounding a young sun-like star that shares remarkable similarities with the Kuiper Belt that lies beyond Neptune, and may aid in understanding how our solar system developed.

    2
    Kuiper Belt

    An international team of astronomers, including researchers from the University of Cambridge, has identified a young planetary system which may aid in understanding how our own solar system formed and developed billions of years ago.

    Using the Gemini Planet Imager (GPI) at the Gemini South telescope in Chile, the researchers identified a dTisc-shaped bright ring of dust around a star only slightly more massive than the sun, located 360 light years away in the Centaurus constellation.

    Gemini Planet Imager
    GPI

    Gemini South telescope
    Gemini South

    The disc is located between about 37 and 55 Astronomical Units (3.4 – 5.1 billion miles) from its host star, which is almost the same distance as the solar system’s Kuiper Belt is from the sun. The brightness of the disc, which is due to the starlight reflected by it, is also consistent with a wide range of dust compositions including the silicates and ice present in the Kuiper Belt.

    The Kuiper Belt lies just beyond Neptune, and contains thousands of small icy bodies left over from the formation of the solar system more than four billion years ago. These objects range in size from specks of debris dust, all the way up to moon-sized objects like Pluto – which used to be classified as a planet, but has now been reclassified as a dwarf planet.

    The star observed in this new study is a member of the massive 10-20 million year-old Scorpius-Centaurus OB association, a region similar to that in which the sun was formed. The disc is not perfectly centred on the star, which is strong indication that it was likely sculpted by one or more unseen planets. By using models of how planets shape a debris disc, the team found that ‘eccentric’ versions of the giant planets in the outer solar system could explain the observed properties of the ring.

    “It’s almost like looking at the outer solar system when it was a toddler,” said principal investigator Thayne Currie, an astronomer at the Subaru Observatory in Hawaii.

    The current theory on the formation of the solar system holds that it originated within a giant molecular cloud of hydrogen, in which clumps of denser material formed. One of these clumps, rotating and collapsing under its own gravitation, formed a flattened spinning disc known as the solar nebula. The sun formed at the hot and dense centre of this disc, while the planets grew by accretion in the cooler outer regions. The Kuiper Belt is believed to be made up of the remnants of this process, so there is a possibility that once the new system develops, it may look remarkably similar to our solar system.

    “To be able to directly image planetary birth environments around other stars at orbital distances comparable to the solar system is a major advancement,” said Dr Nikku Madhusudhan of Cambridge’s Institute of Astronomy, one of the paper’s co-authors. “Our discovery of a near-twin of the Kuiper Belt provides direct evidence that the planetary birth environment of the solar system may not be uncommon.”

    This is the first discovery with the new cutting-edge Gemini instrument. “In just one of our many 50-second exposures we could see what previous instruments failed to see in more than 50 minutes,” said Currie.

    The star, going by the designation HD 115600, was the first object the research team looked at. “Over the next few years, I’m optimistic that GPI will reveal many more debris discs and young planets. Who knows what strange, new worlds we will find,” Currie added.

    The paper is accepted for publication in The Astrophysical Journal Letters.

    See the full article here.

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 7:40 am on March 7, 2015 Permalink | Reply
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    From GPI: “Debris Disks: Searching for Dust to Find Planets” 

    GPI bloc

    GPI

    March 4, 2015
    Rahul Patel

    1
    A star system where gas and dust have formed into a disk around a newly formed star. The leftover disk will most likely form planets, comets and asteroids. Credit: NASA

    No one is ever excited when the topic of “dust” is brought up. Usually dust is a hindrance – something you sweep away during spring-cleaning, or an annoyance because your allergies can’t handle it. But for astronomers, finding dust around another star – i.e., circumstellar dust – is like finding the next piece of an interstellar puzzle. That’s because circumstellar dust holds clues to understanding not only the origins of planets outside of our solar system, but also gives us a leg up in figuring out our place in the Universe.

    Before we can uncover the secret of how dust and exoplanets are linked, we need to understand what happens after a planetary system forms. Once a star is created, it leaves behind a large disk of gas and dust. The gas and dust start sticking together and coalescing into larger objects such as planets, asteroids and comets. The central star removes the remaining gas and dust either by accreting it, or by throwing it out of the system with its stellar wind and radiation pressure. About 10 million years or so after the star forms, all of the leftover dust and gas have either been ejected out of the system, eaten up by the star, or used to form planets, asteroids and comets. But here’s a mystery: astronomers have found stars much older than 10 million years with circumstellar dust.

    So then where does all this dust come from if we know it shouldn’t be there?

    One word – collisions.

    2

    Large planets will gravitationally tug on smaller bodies such as asteroids and comets as they pass by. And if these asteroids and comets are pulled hard enough, they will eventually collide with one another! This can be catastrophic and destructive, breaking the original asteroid into smaller chunks. These chunks can then collide and become still smaller and smaller and smaller – grinding down the original body into dust. The dust then forms a disk around the star — what astronomers call a “debris disk.”

    3

    Had there not been large planets around these stars, there might not have been any destructive collisions, which in turn would not produce any dust for us to find. In other words, finding dust around a star is like seeing a large signpost saying “PLANETS! Come and get ‘em’!” Of course, initially we don’t actually see the planets. But knowing a debris disk exists around these stars tells us there is a good chance we’ll find them.

    Detecting Dust

    4
    Emission spectrum seen from a star that does and does not have dust around it. A star with dust will have excess infrared radiation compared to the emission from the star. Credit: NASA

    Now, astronomers typically look for debris disks by measuring the infrared light coming from a star. Dust around a star will warm as it soaks up the light from the central star. As it heats up, it will start emitting its own light in the infrared – just like a stove-top coil will begin to feel hot before you see it glow red. The amount of infrared light the dust gives off, combined with what the star produces, will be more than the amount of infrared light produced only by the star. This excess light is what betrays the presence of dust in the system. This dust is usually 10 to 100 microns in size, or roughly the thickness of a human hair.

    Astronomers have found infrared excess emission – most likely caused by debris disks – in over 1,000 star systems, all of which have the potential to host planetary systems.

    But what about planets? How can we confirm that planets are responsible for the creation of the dust we’re seeing?

    5
    Left: Hubble image of the Formalhaut dust ring. Credit: Kalas et al. 2012. Center: Beta pic debris disk by Smith and Terrile. Right: Beta pic b planet over plotted on image of the beta pic debris disk. The stars in each image are blocked out by a coronagraph.

    In some cases, taking an image of a system that has a known debris disk reveals much more than one can discern from just measuring the amount of infrared light produced by a star. In 2005, GPIES’ own Dr. Paul Kalas and his team used the Hubble Space Telescope to image the debris belt of Fomalhaut – a star roughly 16 times brighter and almost four billion years younger than our sun. These images show a sharp, eccentrically misaligned ring, which hints that a large planet might be orbiting inside the ring. Follow-up observations inspired by this suspicion revealed a planet, Fomalhaut b, though not the one thought responsible for the shape of the debris disk.

    NASA Hubble Telescope
    Hubble

    6
    DSS image of Fomalhaut, field of view 2.7×2.9 degrees.
    Credit NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)

    7
    Hubble Space Telescope observation of the debris ring around Fomalhaut. The inner edge of the disk may have been shaped by the orbit of Fomalhaut b, at lower right.

    Another star system whose imaged disk betrays the existence of a planet is “beta Pictoris” – or beta Pic for short. Beta Pic’s debris disc was the first to be imaged. In 1984, Dr. Brad Smith and Dr. Rich Terrile took an image of the beta Pic disk by blocking out the star’s light using a coronagraph, which revealed an edge-on disk. The disk of this 20-million- year-old star – much younger than our sun – is full of warps and substructures. Such structures in the disk led astronomers to believe that a large planet may be influencing its shape.

    And then..

    In 2008, astronomers finally discovered the faint signal of a planet eight times the mass of Jupiter, captured in images taken by the Very Large Telescope in 2003. These two systems are only the tip of the iceberg, as many more such stars have been studied, all of which show a wide variety of disk structures and hint at the presence of planets hidden behind the dust.

    How does this all link back to us here on Earth?

    Although the puzzle of each exosolar system becomes clearer when we study its debris disk, information gleaned from every system can be used to deduce whether a planetary system like ours can form elsewhere in the Universe. This is mainly because the interaction of our solar system’s planets and debris disk – which is made up of the asteroid belt between Mars and Jupiter, and the Kuiper belt way past Neptune – have heavily influenced the current structure of our solar system.

    6

    Roughly 3.7 billion years ago, Jupiter and Saturn began a gravitational dance in which the orbital periods of the titans lined up, and for every orbit around the Sun Jupiter made, Saturn made two. This enhanced gravitational interaction forced Saturn to migrate slowly away from the Sun, pushing Uranus and Neptune further out in the solar system as well. Neptune fatefully crashed into the outer Kuiper belt, sending large ice and rock bodies hurling all over the solar system, and turning its inner region– and Earth – into an interplanetary shooting range. A large amount of dust would have been created during this time period, one quite noticeable to any alien observing our system.

    8
    Known objects in the Kuiper belt beyond the orbit of Neptune (scale in AU; epoch as of January 2015). Source: Minor Planet Center, http://www.cfeps.net and others

    Although this event made the primordial Earth a hellish place to live, there is some good news. Some scientists have theorized that a large portion of Earth’s oceans were fed by the transport of these water-rich comets and asteroids from the Kuiper belt during the “Late Heavy Bombardment.”. And so had it not been for the relationship between our planets and debris belts, Earth would probably not exist as we know it.

    We have seen evidence of similar catastrophic events around the young “eta Corvi” system. Using spectroscopic data obtained in 2010 from the Spitzer Space Telescope, Dr. Carey Lisse’s team discovered that for some reason, large numbers of cometary bodies from the outer regions of this system were colliding with a planetary sized body in the inner regions, and releasing water ice dust whose total mass was about 0.1% of all the water in Earth’s oceans!

    NASA Spitzer Telescope
    Spitzer

    The similarity between eta Corvi and our early solar system is uncanny. Additionally, it’s exciting to think that the events that may have allowed for life to arise on Earth are currently going on around other stars – events that require a symbiotic relationship between planets and the remnant asteroid and comet population.

    Events that we can witness by studying debris disks.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    GPI: A scientific partnership between institutions from the U.S.A., Canada, Australia, Argentina, Brazil and Chile.

     
  • richardmitnick 4:52 pm on January 8, 2015 Permalink | Reply
    Tags: , , , , , Gemini Planet Imager   

    From Gemini Observatory: “THE GEMINI PLANET IMAGER PRODUCES STUNNING OBSERVATIONS IN ITS FIRST YEAR” 

    NOAO

    Gemini Observatory
    Gemini Observatory

    January 6, 2015
    Media Contacts:

    Peter Michaud
    Public Information and Outreach Manager
    Gemini Observatory, Hilo, HI
    Email: pmichaud”at”gemini.edu
    Cell: (808) 936-6643
    Desk: (808) 974-2510

    Science Contacts:

    Marshall Perrin
    STScI
    Email: mperrin”at”stsci.edu
    Phone: (410) 507-5483

    James R. Graham
    University of California Berkeley
    Email: jrg”at”berkeley.edu
    Cell: (510) 926-9820

    Stunning exoplanet images and spectra from the first year of science operations with the Gemini Planet Imager (GPI) were featured today in a press conference at the 225th meeting of the American Astronomical Society (AAS) in Seattle, Washington. The Gemini Planet Imager GPI is an advanced instrument designed to observe the environments close to bright stars to detect and study Jupiter-like exoplanets (planets around other stars) and see protostellar material (disk, rings) that might be lurking next to the star.

    1
    Figure 1. GPI imaging of the planetary system HR 8799 in K band, showing 3 of the 4 planets. (Planet b is outside the field of view shown here, off to the left.) These data were obtained on November 17, 2013 during the first week of operation of GPI and in relatively challenging weather conditions, but with GPI’s advanced adaptive optics system and coronagraph the planets can still be clearly seen and their spectra measured (see Figure 2). Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team.

    2
    Figure 2. GPI spectroscopy of planets c and d in the HR 8799 system. While earlier work showed that the planets have similar overall brightness and colors, these newly-measured spectra show surprisingly large differences. The spectrum of planet d increases smoothly from 1.9-2.2 microns while planet c’s spectrum shows a sharper kink upwards just beyond 2 microns. These new GPI results indicate that these similar-mass and equal-age planets nonetheless have significant differences in atmospheric properties, for in-stance more open spaces between patchy cloud cover on planet c versus uniform cloud cover on planet d, or perhaps differences in atmospheric chemistry. These data are helping refine and improve a new generation of atmospheric models to explain these effects. Image credit: Patrick Ingraham (Stanford University), Mark Marley (NASA Ames), Didier Saumon (Los Alamos National Laboratory) and the GPI Team.

    Marshall Perrin (Space Telescope Science Institute), one of the instrument’s team leaders, presented a pair of recent and promising results at the press conference. He revealed some of the most detailed images and spectra ever of the multiple planet system HR 8799. His presentation also included never-seen details in the dusty ring of the young star HR 4796A. “GPI’s advanced imaging capabilities have delivered exquisite images and data,” said Perrin. “These improved views are helping us piece together what’s going on around these stars, yet also posing many new questions.”

    The GPI spectra obtained for two of the planetary members of the HR 8799 system presents a challenge for astronomers. GPI team member Patrick Ingraham (Stanford University), lead the paper on HR 8799. Ingraham reports that the shape of the spectra for the two planets differ more profoundly than expected based on their similar colors, indicating significant differences between the companions. “Current atmospheric models of exoplanets cannot fully explain the subtle differences in color that GPI has revealed. We infer that it may be differences in the coverage of the clouds or their composition.” Ingraham adds, “The fact that GPI was able to extract new knowledge from these planets on the first commissioning run in such a short amount of time, and in conditions that it was not even designed to work, is a real testament to how revolutionary GPI will be to the field of exoplanets.”

    Perrin, who is working to understand the dusty ring around the young star HR 4796A, said that the new GPI data present an unprecedented level of detail in studies of the ring’s polarized light. “GPI not only sees the disk more clearly than previous instruments, it can also measure how polarized its light appears, which has proven crucial in under-standing its physical properties.” Specifically, the GPI measurements of the ring show it must be partially opaque, implying it is far denser and more tightly compressed than similar dust found in the outskirts of our own Solar System, which is more diffuse. The ring circling HR 4796A is about twice the diameter of the planetary orbits in our Solar System and its star about twice our Sun’s mass. “These data taken during GPI commissioning show how exquisitely well its polarization mode works for studying disks. Such observations are critical in advancing our understanding of all types and sizes of planetary systems – and ultimately how unique our own solar system might be,” said Perrin.

    3
    Figure 3. GPI imaging polarimetry of the circumstellar disk around HR 4796A, a ring of dust and planetesimals similar in some ways to a scaled up version of the solar system’s Kuiper Belt.

    Kuiper Belt
    Kuiper Belt, for illustration of the discussion

    These GPI observations reveal a complex pattern of variations in brightness and polarization around the HR 4796A disk. The western side (tilted closer to the Earth) appears brighter in polarized light, while in total intensity the eastern side appears slightly brighter, particularly just to the east of the widest apparent separation points of the disk. Reconciling this complex and apparently-contradictory pattern of brighter and darker regions required a major overhaul of our understanding of this circumstellar disk. Image credit: Marshall Perrin (Space Telescope Science Institute), Gaspard Duchene (UC Berkeley), Max Millar-Blanchaer (University of Toronto), and the GPI Team.

    4
    Figure 4. Diagram depicting the GPI team’s revised model for the orientation and composition of the HR 4796A ring. To explain the observed polarization levels, the disk must consist of relatively large (> 5 µm) silicate dust particles, which scatter light most strongly and polarize it more for forward scattering. To explain the relative faintness of the east side in total intensity, the disk must be dense enough to be slightly opaque, comparable to Saturn’s optically thick rings, such that on the near side of the disk our view of its brightly illuminated inner portion is partially obscured. This revised model requires the disk to be much narrower and flatter than expected, and poses a new challenge for theories of disk dynamics to explain. GPI’s high contrast imaging and polarimetry capabilities together were essential for this new synthesis. Image credit: Marshall Perrin (Space Telescope Science Institute).

    During the commissioning phase, the GPI team observed a variety of targets, ranging from asteroids in our solar system, to an old star near its death. Other teams of scientists have been using GPI as well and already astronomers around the world have published eight papers in peer-reviewed journals using GPI data. “This might be the most productive new instrument Gemini has ever had,” said Professor James Graham of the University of California, who leads the GPI science team and who will describe the GPI exoplanet survey in a talk scheduled at the AAS meeting on Thursday, January 8th.

    The Gemini Observatory staff integrated the complex instrument into the telescope’s software and helped to characterize GPI’s performance. “Even though it’s so complicated, GPI now operates almost automatically,” said Gemini’s instrument scientist for GPI Fredrik Rantakyro. “This allows us to start routine science operations.” The instrument is now available to astronomers and their proposals are scheduled to start ob-serving in early 2015. In addition, “shared risk” observations are already underway, starting in November 2014.

    The one thing GPI hasn’t done yet is discovered a new planet. “For the early tests, we concentrated on known planets or disks” said GPI PI Bruce Macintosh. Now that GPI is fully operational, the search for new planets has begun. In addition to observations by astronomers world-wide, the Gemini Planet Imager Exoplanet Survey (GPIES) will look at 600 carefully selected stars over the next few years. GPI ‘sees’ planets through the infrared light they emit when they’re young, so the GPIES team has assembled a list of the youngest and closest stars. So far the team has observed 50 stars, and analysis of the data is ongoing. Discovering a planet requires confirmation observations to distinguish a true planet orbiting the target star from a distant star that happens to sneak into GPI’s field of view – a process that could take years with previous instruments. The GPIES team found one such object in their first survey run, but GPI observations were sensitive enough to almost immediately rule it out. Macintosh said, “With GPI, we can tell almost instantly that something isn’t a planet – rather than months of uncertainty, we can get over our disappointment almost immediately. Now it’s time to find some real planets!”

    About GPI/GPIES

    The Gemini Planet Imager (GPI) instrument was constructed by an international collaboration led by Lawrence Livermore National Laboratory under Gemini’s supervision. The GPI Exoplanet Survey (GPIES) is the core science program to be carried out with it. GPIES is led by Bruce Macintosh, now a professor at Stanford University and James Graham, professor at the University of California at Berkeley and is designed to find young, Jupiter-like exoplanets. They survey will observe 600 young nearby stars in 890 hours over three years. Targets have been carefully selected by team members at Arizona State University, the University of Georgia, and UCLA. The core of the data processing architecture is led by Marshall Perrin of the Space Telescope Science Institute, with the core software originally written by University of Montreal, data management infrastructure from UC Berkeley and Cornell University, and contributions from all the other team institutions. The SETI institute located in California manages GPIES’s communications and public out-reach. Several teams located at the Dunlap Institute, the University of Western Ontario, the University of Chicago, the Lowell Observatory, NASA Ames, the American Museum of Natural History, University of Arizona and the University of California at San Diego and at Santa Cruz also contribute to the survey. The GPI Exoplanet Survey is supported by the NASA Origins Program NNX14AG80, the NSF AAG pro-gram, and grants from other institutions including the University of California Office of the President. Dropbox Inc. has generously provided storage space for the entire survey’s archive.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Gemini North
    Gemini North, Hawai’i

    Gemini South
    Gemini South, Chile
    AURA Icon

    The Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on two of the best observing sites on the planet. From their locations on mountains in Hawai‘i and Chile, Gemini Observatory’s telescopes can collectively access the entire sky.
    Gemini was built and is operated by a partnership of six countries including the United States, Canada, Chile, Australia, Brazil and Argentina. Any astronomer in these countries can apply for time on Gemini, which is allocated in proportion to each partner’s financial stake.

     
  • richardmitnick 4:12 pm on May 20, 2014 Permalink | Reply
    Tags: , , , , , Gemini Planet Imager   

    From Gemini Observatory: “Tour of the Telescope” 

    NOAO

    Gemini Observatory
    Gemini Observatory

    gpi

    May 15, 2014
    Jason Wang

    Yesterday, we had a chance to see the telescope in all of its glory. And it is HUGE!

    scope
    The Gemini South Telescope with the dome lights on.

    It really makes you appreciate the amount of equipment you need to directly image these faint extrasolar planets that are orbiting other stars. Andrew, the telescope operator, then pointed the telescope down so that we could get some nice photographs with the 8-meter mirror. Here’s my telescope selfie:

    j
    Telescope selfie!

    The 8 meter mirror is so big it’s hard to fit into one single shot. This was the best I could do. Although some others are a bit more serious about their photography…

    men
    Markus sprawling out to get a nice shot of Lee, a journalist visiting us, with the telescope.

    Before the sun fully set, I ran outside to grab this image of the telescope dome open.

    g2
    The telescope dome open at sunset .

    Now back to observing!

    About Jason Wang
    Jason is a graduate student at the University of California, Berkeley. He is currently working with Professor James Graham on the Gemini Planet Imager (GPI). He works on GPI astrometry, the image reduction pipeline, and high contrast imaging techniques.

    See the full article here.

    Gemini North
    Gemini North, Hawai’i

    Gemini South
    Gemini South, Chile
    AURA Icon

    The Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on two of the best observing sites on the planet. From their locations on mountains in Hawai‘i and Chile, Gemini Observatory’s telescopes can collectively access the entire sky.
    Gemini was built and is operated by a partnership of six countries including the United States, Canada, Chile, Australia, Brazil and Argentina. Any astronomer in these countries can apply for time on Gemini, which is allocated in proportion to each partner’s financial stake.


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