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  • richardmitnick 3:34 pm on September 14, 2018 Permalink | Reply
    Tags: Asteroid named Palma, , , , , In a process called diffraction waves bent around the asteroid and interacted to form a pattern of bright and dark circles, NRAO VLBA, , , VLBA Measures Asteroid’s Characteristics   

    From Astrobiology Magazine: “VLBA Measures Asteroid’s Characteristics” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Sep 14, 2018
    No writer credit

    In an unusual observation, astronomers used the National Science Foundation’s Very Long Baseline Array (VLBA) to study the effects on radio waves coming from a distant radio galaxy when an asteroid in our Solar System passed in front of the galaxy.

    NRAO/VLBA


    NRAO/VLBA

    The observation allowed them to measure the size of the asteroid, gain new information about its shape, and greatly improve the accuracy with which its orbital path can be calculated.

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    Radio waves from a distant galaxy were blocked from view by an asteroid in our Solar System. However, in a process called diffraction, waves bent around the asteroid and interacted to form a pattern of bright and dark circles. Astronomers analyzed this pattern to learn new details about the asteroid’s. size, shape, and orbit. Credit: Bill Saxton, NRAO/AUI/NSF

    When the asteroid passed in front of the galaxy, radio waves coming from the galaxy were slightly bent around the asteroid’s edge, in a process called diffraction. As these waves interacted with each other, they produced a circular pattern of stronger and weaker waves, similar to the patterns of bright and dark circles produced in terrestrial laboratory experiments with light waves.

    “By analyzing the patterns of the diffracted radio waves during this event, we were able to learn much about the asteroid, including its size and precise position, and to get some valuable clues about its shape,” said Jorma Harju, of the University of Helsinki in Finland.

    The asteroid, named Palma, is in the main asteroid belt between Mars and Jupiter. Discovered in 1893 by French astronomer Auguste Charlois, Palma completes an orbit around the Sun every 5.59 years. On May 15, 2017, it obscured the radio waves from a galaxy called 0141+268 with the radio shadow tracing a path running roughly southwest to northeast, crossing the VLBA station at Brewster, Washington. The shadow sped across the Earth’s surface at 32 miles per second.

    In addition to the VLBA’s Brewster antenna, the astronomers also used VLBA antennas in California, Texas, Arizona, and New Mexico. The passage of the asteroid in front of the radio galaxy, an event called an occultation, affected the characteristics of the signals received at Brewster when combined with those from each of the other antennas.

    Extensive analysis of these effects allowed the astronomers to draw conclusions about the nature of the asteroid. In close agreement with earlier observations, they measured the diameter of the asteroid as 192 kilometers. They also learned that Palma, like most other asteroids, differs significantly from a perfect circle, with one edge probably hollowed out. The shape determination, the astronomers said, can be further improved by combining the radio data with previous optical observations of the asteroid.

    Astronomers, both amateur and professional, commonly observe asteroid occultations of stars, and record the change in brightness, or intensity, of the star’s light as the asteroid passes in front of it. The VLBA observation is unique because it also allowed the astronomers to measure the amount by which the peaks of the waves were displaced by the diffraction, an effect called a phase shift.

    “This allowed us to constrain the shape of Palma with a single, short measurement,” said Leonid Petrov, affiliated with the Geodesy and Geophysics Lab, NASA Goddard Space Flight Center.

    “Observing an asteroid occultation using the VLBA turned out to be an extremely powerful method for asteroid sizing. In addition, such radio data would immediately reveal peculiar shapes or binary companions. That means that these techniques will undoubtedly be used for future asteroid studies,” said Kimmo Lehtinen, of the Finnish Geospatial Research Institute, in Masala, Finland.

    One major result from the observation was to improve the precision with which the asteroid’s orbit can be calculated.

    “Although Palma’s position has been measured more than 1,600 times over the past 120 years, this one VLBA measurement reduced the uncertainty in the calculated orbit by a factor of 10,” said Mikael Granvik, of Lulea University of Technology in Sweden and the University of Helsinki, Finland.

    “This is a rather unusual use for the VLBA, and it demonstrates that the VLBA’s excellent technical capabilities, along with its great flexibility as a research tool, can contribute in even some unexpected ways to many fields of astronomy,” said Jonathan Romney of the Long Baseline Observatory, which operates the VLBA.

    See the full article here .


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  • richardmitnick 5:58 pm on June 28, 2017 Permalink | Reply
    Tags: , , , , , , NRAO VLBA, ,   

    From Stanford and Kavli: “Stanford Research Reveals Extremely Fine Measurements of Motion in Orbiting Supermassive Black Holes” 

    Stanford University Name
    Stanford University

    KavliFoundation

    The Kavli Foundation

    1
    Observations from radio telescopes like this one appear to indicate that two black holes are orbiting each other, 750 million light years from Earth. (Credit: National Radio Astronomy Observatory)

    Approximately 750 million light years from Earth lies a gigantic, bulging galaxy with two supermassive black holes at its center. These are among the largest black holes ever found, with a combined mass 15 billion times that of the sun. New research from Stanford University, published today (June 27) in Astrophysical Journal, has used long-term observation to show that one of the black holes seems to be orbiting around the other.

    If confirmed, this is the first duo of black holes ever shown to be moving in relation to each other. It is also, potentially, the smallest ever recorded movement of an object across the sky, also known as angular motion.

    “If you imagine a snail on the recently discovered Earth-like planet orbiting Proxima Centauri – a bit over four light years away – moving at one centimeter a second, that’s the angular motion we’re resolving here,” said co-author of the paper, Roger W. Romani, professor of physics at Stanford and a member of the Kavli Insititute for Particle Astrophysics and Cosmology. The team also included researchers from the University of New Mexico, the National Radio Observatory and the United States Naval Observatory.

    The technical achievements of this measurement alone are reason for celebration. But the researchers also hope this impressive finding will offer insight into how black holes merge, how these mergers affect the evolution of the galaxies around them and ways to find other binary black-hole systems.

    Miniscule movement

    Over the past 12 years, scientists, led by Greg Taylor, a professor of physics and astronomy at the University of New Mexico, have taken snapshots of the galaxy containing these black holes – called radio galaxy 0402+379 – with a system of ten radio telescopes that stretch from the U.S. Virgin Islands to Hawaii and New Mexico to Alaska.

    NRAO VLBA


    NRAO VLBA

    The galaxy was officially discovered back in 1995. In 2006, scientists confirmed it as a supermassive black-hole binary system with an unusual configuration.

    “The black holes are at a separation of about seven parsecs, which is the closest together that two supermassive black holes have ever been seen before,” said Karishma Bansal, a graduate student in Taylor’s lab and lead author of the paper.

    With this most recent paper, the team reports that one of the black holes moved at a rate of just over one micro-arcsecond per year, an angle about 1 billion times smaller than the smallest thing visible with the naked eye. Based on this movement, the researchers hypothesize that one black hole may be orbiting around the other over a period of 30,000 years.
    Two holes in ancient galaxy

    Although directly measuring the black hole’s orbital motion may be a first, this is not the only supermassive black-hole binary ever found. Still, the researchers believe that 0402+379 likely has a special history.

    “We’ve argued it’s a fossil cluster,” Romani said. “It’s as though several galaxies coalesced to become one giant elliptical galaxy with an enormous halo of X-rays around it.”

    Researchers believe that large galaxies often have large black holes at their centers and, if large galaxies combine, their black holes eventually follow suit. It’s possible that the apparent orbit of the black hole in 0402+379 is an intermediary stage in this process.

    “For a long time, we’ve been looking into space to try and find a pair of these supermassive black holes orbiting as a result of two galaxies merging,” Taylor said. “Even though we’ve theorized that this should be happening, nobody had ever seen it, until now.”

    A combination of the two black holes in 0402+379 would create a burst of gravitational radiation, like the famous bursts recently discovered by the Laser Interferometer Gravitational-Wave Observatory, but scaled up by a factor of a billion.


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project


    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    It would be the most powerful gravitational burst in the universe, Romani said. This kind of radiation burst happens to be what he wrote his first-ever paper on when he was an undergraduate.

    Very slow dance

    This theorized convergence between the black holes of 0402+379, however, may never occur. Given how slowly the pair is orbiting, the scientists think the black holes are too far apart to come together within the estimated remaining age of the universe, unless there is an added source of friction. By studying what makes this stalled pair unique, the scientists said they may be able to better understand the conditions under which black holes normally merge.

    Romani hopes this work could be just the beginning of heightening interest in unusual black-hole systems.

    “My personal hope is that this discovery inspires people to go out and find other systems that are even closer together and, hence, maybe do their motion on a more human timescale,” Romani said. “I would sure be happy if we could find a system that completed orbit within a few decades so you could really see the details of the black holes’ trajectories.”

    Additional co-authors on this paper are A.B. Peck, Gemini Observatory (formerly of the National Radio Astronomy Observatory); and R.T. Zavala, U.S. Naval Observatory.

    This work was funded by NASA and the National Radio Astronomical Observatory.

    See the full Stanford article here .
    See the Full Kavli Foundation article here.

    Please help promote STEM in your local schools.
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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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