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  • richardmitnick 11:24 am on March 1, 2019 Permalink | Reply
    Tags: "Exiled planet linked to stellar flyby 3 million years ago", , , , Binary stars, , KIPAC- Kavli Institute for Particle Astrophysics and Cosmology, The planet dubbed HD 106906 b, The star HD 106906,   

    From UC Berkeley: “Exiled planet linked to stellar flyby 3 million years ago” 

    From UC Berkeley

    February 28, 2019
    Robert Sanders
    rlsanders@berkeley.edu

    1
    Simulation of a binary star flyby of a young planetary system. UC Berkeley and Stanford astronomers suspect that such a flyby altered the orbit of a planet (in blue) around the star HD 106906 so that it remained bound to the system in an oblique orbit similar to that of a proposed Planet Nine attached to our own solar system. (Paul Kalas animation)

    Some of the peculiar aspects of our solar system — an enveloping cloud of comets, dwarf planets in weird orbits and, if it truly exists, a possible Planet Nine far from the sun — have been linked to the close approach of another star in our system’s infancy that flung things helter-skelter.

    But are stellar flybys really capable of knocking planets, comets and asteroids askew, reshaping entire planetary systems?

    UC Berkeley and Stanford University astronomers think they have now found a smoking gun.


    A planet orbiting a young binary star may have been perturbed by another pair of stars that skated too close to the system between 2 and 3 million years ago, soon after the planet formed from a swirling disk of dust and gas.

    If confirmed, this bolsters arguments that close stellar misses help sculpt planetary systems and may determine whether or not they harbor planets with stable orbits.

    “One of the mysteries arising from the study of exoplanets is that we see systems where the planets are misaligned, even though they are born in a flat, circular disk,” said Paul Kalas, a UC Berkeley adjunct professor of astronomy. “Maybe a cosmic tsunami hit these systems and rearranged everything about them, but we haven’t had proof. Our paper gives rare observational evidence for one of these flybys gently influencing one of the planetary systems in the galaxy.”

    2
    Two binary stars, now far apart, skated by one another 2-3 million years ago, leaving a smoking gun: a disordered planetary system (left).

    Astronomers are already searching for a stellar flyby in our solar system’s past, but since that likely happened 4.6 billion years ago, most of the evidence has gone cold. The star system that the astronomers studied, identified only by the number HD 106906 and located about 300 light years from Earth in the direction of the constellation Crux, is very young, only about 15 million years old.

    Kalas and Robert De Rosa, a former UC Berkeley postdoc who is now a research scientist at Stanford’s Kavli Institute for Particle Astrophysics and Cosmology, describe their findings in a paper accepted for publication in The Astronomical Journal.

    Rogue stars

    Kalas, who studies young, newly formed planetary systems to try to understand what happened in the early years of our own solar system, first focused on HD 106906 in 2015 after it was found to have a massive planet in a highly unusual orbit. The planet, dubbed HD 106906 b, has a mass of about 11 Jupiters, and it orbits HD 106906 — recently revealed to be a binary star — in an orbit tipped about 21 degrees from the plane of the disk that contains all the other material around the star. Its current location is at least 738 times farther from its star than Earth is from the sun, or about 18 times farther from its star than Pluto is from the sun.


    Some 2 to 3 million years ago, in a young, newly formed planetary system, a planet was in danger of being kicked out of the system because of gravitaional interactions with the central, binary star (left panel). A close pass by another binary star (not shown) within the same cluster gave the planet an extra kick that stabilized the orbit and rescued it from certain ejection (right panel). (Video by Paul Kalas)

    Kalas used both the Gemini Planet Imager on the Gemini Telescope in the Chilean Andes and the Hubble Space Telescope to look more closely at HD 106906 and discovered that the star has a lopsided comet belt, as well. The planet’s strange orbit and the fact that the dust disk itself is asymmetrical indicated that something had disrupted the young system.

    NOAO Gemini Planet Imager on Gemini South


    Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    NASA/ESA Hubble Telescope

    Kalas and his colleagues, including De Rosa, proposed that the planet had been kicked out of its solar system by interactions with another as-yet-unseen planet in the system or by a passing star. Kalas and De Rosa now believe that both happened: The planet was kicked into an eccentric orbit when it came dangerously close to the central binary star, a scenario proposed in 2017 by theorist Laetitia Rodet and her collaborators from the Grenoble Observatory in France. Repeated gravitational kicks from the binary would have quickly ejected the planet into interstellar space, but the passing stars rescued the planet by nudging its orbit to a safer distance from the binary.

    The Gaia space observatory gave them the data they needed to test their hypothesis. Gaia, launched in 2012 by the European Space Agency, collects precise measurements of distance, position and motion for 1.3 billion stars in the Milky Way Galaxy, a catalog 10,000 times larger than Gaia’s predecessor, Hipparcos.

    ESA/GAIA satellite

    Kalas and De Rosa gathered Gaia information on 461 stars in the same cluster as HD 106906 and calculated their positions backward in time—reversed the cosmic clock, so to speak—and discovered that another binary star system may have approached close enough 3 million years ago to alter the planetary system.

    “What we have done here is actually find the stars that could have given HD 106906 b the extra gravitational kick, a second kick so that it became long-lived, just like a hypothetical Planet Nine would be in our solar system,” Kalas said.

    They also found also that the binary star came in on a trajectory that was within about 5 degrees of the system’s disk, making it even more likely that the encounter had a strong and lasting impact on HD 106906.

    Such double kicks may be important to stabilizing planets, asteroids and comets around stars, Kalas said.

    “Studying the HD 106906 planetary system is like going back in time to watch the Oort cloud of comets forming around our young sun,” he said. “Our own giant planets gravitationally kicked countless comets outward to large distances. Many were ejected completely, becoming interstellar objects like ʻOumuamua, but others were influenced by passing stars. That second kick by a stellar flyby can detach a comet’s orbit from any further encounters with the planets, saving it from the prospect of ejection. This chain of events preserved the most primitive solar system material in a deep freeze far from the sun for billions of years.”

    Kalas hopes that future observations, such as an updated catalog of Gaia measurements, will clarify the significance of the flyby on HD 106906.

    “We started with 461 suspects and discovered two that were at the scene of the crime,” he said. “Their exact role will be revealed as we gather more evidence.”

    The work was supported by the National Science Foundation (AST-1518332), National Aeronautics and Space Administration (NNX15AC89G) and Nexus for Exoplanet System Science (NExSS), a research coordination network sponsored by NASA’s Science Mission Directorate (NNX15AD95G).

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

    UC Berkeley Seal

     
  • richardmitnick 4:58 pm on October 15, 2018 Permalink | Reply
    Tags: , , , , , , , KIPAC- Kavli Institute for Particle Astrophysics and Cosmology,   

    From SLAC National Accelerator Lab: “Missing gamma-ray blobs shed new light on dark matter, cosmic magnetism” 

    From SLAC National Accelerator Lab

    October 15, 2018
    Manuel Gnida

    Astrophysicists use a catalog of extended gamma-ray sources spotted by Fermi spacecraft to home in on mysterious properties of deep space.

    1
    Extended gamma-ray sources (circled areas) identified in data taken with the Large Area Telescope on NASA’s Fermi spacecraft. (Matthew Wood/Fermi-LAT collaboration)

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    When astrophysicists look at the gamma-ray glow from a galaxy outside our own, all they typically see is a small spot because the galaxy is extremely far away. So, when a galaxy appears as an extended blob, something extraordinary must be going on that could help researchers better understand the properties of deep space.

    Now, scientists, including researchers from the Department of Energy’s SLAC National Accelerator Laboratory, have compiled the most detailed catalog of such blobs using eight years of data collected with the Large Area Telescope (LAT) on NASA’s Fermi Gamma-Ray Space Telescope. The blobs, including 19 gamma-ray sources that weren’t known to be extended before, provide crucial information on how stars are born, how they die, and how galaxies spew out matter trillions of miles into space.

    Intriguingly, though, it was the cosmic regions where they didn’t find blobs that shed new light on two particularly mysterious ingredients of the universe: dark matter – an invisible form of matter six times more prevalent than regular matter – and the magnetic field that pervades the space between galaxies and whose origin is unknown.

    “These data are very exciting because they allow us to study some of the most fundamental processes in the universe, and they could potentially lead us to discover completely new physics,” says NASA scientist Regina Caputo, one of the leaders of the recent study by the international Fermi-LAT collaboration, which was published in The Astrophysical Journal.

    One of the things the researchers looked for were gamma-ray blobs associated with companion galaxies orbiting our Milky Way.

    2
    Researchers have discovered a set of possible dwarf satellite galaxies orbiting the Milky Way. The new objects (red dots) were detected in the new sky area (gray transparent area) covered by the Dark Energy Survey. Scientists have seen about two dozen dwarf galaxies (blue dots) before. They are the smallest known galaxy structures and may hold the key to understanding unseen dark matter, which accounts for about 85 percent of all matter in the universe but whose nature is unknown. The zoom-in region shows an image of the stars that likely belong to one of the dwarf galaxy candidates. (Kavli Institute for Particle Astrophysics and Cosmology/SLAC National Accelerator Laboratory/Fermi National Accelerator Laboratory/Dark Energy Survey/Infrared Processing and Analysis Center/California Institute of Technology/University of Massachusetts)

    Since the faintest of these satellites contain very few stars, they are thought to be held together by dark matter.

    Scientists believe dark matter could be made of particles called WIMPs, which would emit gamma rays when they collide and destroy each other. A gamma-ray blob signal coming from an ultrafaint satellite galaxy would be a strong hint that WIMPS exist.

    “Our simulations of galaxy formation predict that there should be more satellite galaxies than those we’ve been able to detect in optical surveys,” Caputo says. “Some of them could be so faint that we might only be able to see them if they produced gamma rays due to dark matter annihilation.”

    In the new study, the Fermi-LAT researchers searched for gamma-ray blobs associated with those predicted satellite galaxies. They didn’t find any. But even the fact that they came up empty-handed is an important result: It will allow them, in future studies, to define the distribution of dark matter in Milky Way satellites and the likelihood that WIMPs produce gamma rays. It also provides new input for models of galaxy evolution.

    3
    The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy orbiting our Milky Way. The image superimposes a photograph of the SMC with one-half of a model of its dark matter. Lighter colors indicate greater density and show a strong concentration of dark matter toward the SMC’s center. (Regina Caputo/NASA; Axel Mellinger/Central Michigan University)

    Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

    Faint cosmic magnetism

    The researchers also used their data to obtain more information on the strength of the magnetic field between galaxies, which they hope will be an important puzzle piece in determining the origin of the field.

    For this part of the study, the team looked at blazars – active galaxies that spit high-speed jets of plasma far into space. The Fermi spacecraft can detect gamma rays associated with jets that point in the direction of the Earth.

    Blazars appear as point-like sources, but a mechanism involving the intergalactic magnetic field could potentially make them look like extended sources, says Manuel Meyer, a Humboldt fellow at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) and another lead author of the study.


    Manuel Meyer, Humboldt fellow at the Kavli Institute for Particle Astrophysics and Cosmology, explains a process involving the intergalactic magnetic field that could potentially make active galaxies known as blazars appear as extended gamma-ray sources in data taken with the Large Area Telescope onboard NASA’s Fermi mission. (Manuel Meyer/Kavli Institute for Particle Astrophysics and Cosmology)

    The researchers didn’t find any blobs associated with blazars. Again, this no-show was valuable information: It allowed the team to calculate that the magnetic field is at least a tenth of a millionth billionth as strong as Earth’s magnetic field. The magnetic field’s upper limit – a billion times weaker than Earth’s field – was already known.

    The intergalactic field is stronger than the researchers had expected, Meyer says, and this new information might help them find out whether it stems from material spilled into space in recent times or whether it was created in processes that occurred in earlier cosmic history.

    The cosmic magnetism could also have ties to dark matter. In an alternative to the WIMP model, dark matter is proposed to be made of lighter particles called axions that could emerge from gamma rays (and convert back into them) in the presence of a magnetic field. “For that to occur, the field strength would need to be closer to its upper limit, though,” Meyer says. “It’s definitely interesting to take this mechanism into account in our dark matter studies, and we’re doing this right now within the Fermi-LAT collaboration.”

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy Office of Science and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States. The Fermi mission recently celebrated its 10th anniversary. A number of SLAC researchers are members of the international Fermi-LAT collaboration. SLAC assembled the LAT and hosts the operations center that processes LAT data. The new analysis benefitted from a data analysis package, initially developed by KIPAC researcher Matthew Wood, that automates common analysis tasks. KIPAC is a joint institute of SLAC and Stanford University.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
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