Where results make sense

About us   |   Why use us?   |   Reviews   |   PR   |   Contact us

Precision CCD Astrometry   (Site not responding. Last check: 2007-11-02) Indications are that, with 1-2 milliarcsecond measuring accuracy, proper motions should be detectable within 4-5 years of the first epoch. It was useful to use a bin width of 615 milliarcseconds to further examine the precision of the various centering options. A proper motion of 1.4 milliarcseconds was computed using the brightest galaxy in the field as the reference. cse.ssl.berkeley.edu /bmendez/html/figures.html   (2418 words)

Diameters of stars For the Keck telescope, 10 meters in diameter, the resolution at wavelengths used by the human eye is only 20 milliarcsecond (0.02 arcseconds). For reference, a person standing on the moon would have an angular height of 1.0 milliarcseconds. The largest star shown, Hamal, also known as alpha Cassiopeiae, is 6.88 milliarcseconds in diameter. www.nofs.navy.mil /projects/npoi/science/diam.htm   (993 words)

Distance Scale   (Site not responding. Last check: 2007-11-02) Distances, starting with the nearest stars and progressing to the most distant galaxies and quasars, form the basis for converting observed properties of objects (apparent magnitude, angular motions) into real physical properties (luminosities, velocities in km/sec). Until the advent of milliarcsecond parallaxes, accurate knowledge of distances of stars was limited to 10 to 20 parsecs. With current ground-based techniques, relatively few milliarcsecond parallaxes are measured routinely. www.ess.sunysb.edu /simswg/siswg/node20.html   (618 words)

ICRS Narrative   (Site not responding. Last check: 2007-11-02) The formal uncertainties in the star positions of the FK5 at the time of its (somewhat delayed) publication in 1988 were about 30-40 milliarcseconds over most of the sky, but the errors are considerably worse when systematic trends are taken into account. Typical position uncertainties for the defining sources are of order 0.5 milliarcsecond; the orientation of the axes is defined from the ensemble to an accuracy of about 0.02 milliarcseconds. At its General Assembly in 2000 [8] the IAU defined a system of space-time coordinates for (1) the solar system, and (2) the Earth, within the framework of General Relativity, by specifying the form of the metric tensors for each and the 4-dimensional space-time transformation between them. aa.usno.navy.mil /faq/docs/ICRS_doc.html   (4516 words)

New X-ray Telescope Technology Propels Virtual Journey to Black Hole Cash and his colleagues have achieved 100 milliarcsecond resolution (similar to Hubble) in the laboratory with their X-ray interferometer. This is a five-fold improvement over the best conventional X-ray telescopes, which achieve 500 milliarcsecond resolution. This interferometry design is currently under study at Goddard Space Flight Center in Greenbelt, Md., for two proposed NASA missions with the ultimate goal of imaging a fl hole. www.spacedaily.com /news/blackhole-00d.html   (834 words)

Brandeis University Radio Astronomy We are particularly interested in cores of "active galaxies" or "blazars" - powerful radio galaxies, quasars, BL Lacertae objects, and Seyfert galaxies. Our group has pioneered the techniques of making linear polarization images at milliarcsecond resolution using VLBI. Recently, we have extended our techniques to measure the circularly polarized signals that originate from compact radio sources. pc.astro.brandeis.edu   (221 words)

Apparent superluminal motion The tick marks on the axes are in units of two milliarcseconds (1 milliarcsecond = 1 degree / (3.6 x 10 The figure shows how a component in the jet of this quasar moves away from the quasar core at a rate of about three quarters of a milliarcsecond per year. A path at this distance that extends over three quarters of a milliarcsecond in the sky, is more than nine light years long. www.spacetimetravel.org /bewegung/bewegung4.html   (597 words)

Lensing Dictionary Stellar Einstein radii have typical values of microarcseconds while dark matter substructures are typically on milliarcsecond scales. Although resolution on microarcsecond scales is not possible, certain stellar configurations give rise to magnifications that differ substantially from values predicted by a macromodel. Strong lensing in which image separations are on milliarcsecond scales. www.physics.rutgers.edu /~acongdon/lens_dictionary.html   (578 words)

On the Milliarcsecond Scale Structural Properties of Low and High Redshift Quasars (ResearchIndex) On the milliarcsecond scale structural properties of low and high redshift quasars Abstract: Introduction Recently several attempts have been made to use milliarcsecond scale VLBI structures of compact active galactic nuclei (AGN) as "standard" objects for cosmological tests. The "apparent angular size -- redshift" ("` \Gamma z") relation for different samples of AGN shows a non-Euclidean behavior [6,3] suggesting the possibility of constraining the numerical value of some cosmological model parameters like the deceleration parameter (q 0) and the cosmological constant () [8]. citeseer.ist.psu.edu /228812.html   (360 words)

CDDIS | VLBI Summary Using large numbers of time difference measurements from many quasars observed with a global network of antennas, VLBI determines the inertial reference frame defined by the quasars and simultaneously the precise positions of the antennas. Because the time difference measurements are precise to a few picoseconds, VLBI determines the relative positions of the antennas to a few millimeters and the quasar positions to fractions of a milliarcsecond. Since the antennas are fixed to the Earth, their locations track the instantaneous orientation of the Earth in the inertial reference frame. cddis.gsfc.nasa.gov /vlbi_summary.html   (437 words)

MIT Haystack Observatory: Astronomy Wideband VLBI   (Site not responding. Last check: 2007-11-02) The technique of very long baseline interferometry (VLBI) depends on faithfully recording the fluctuations of electric field caused by incoming radio waves from astronomical sources, as captured by the receiving system of an antenna. These recordings must be played back in precise time synchrony at a central location in order to combine signals from multiple antennas, and perform the interferometry, thereby achieving the characteristic and scientifically powerful milliarcsecond resolutions of the VLBI technique. Since the early days of VLBI, recording systems have imposed limits on the performance of VLBI arrays. hyp.haystack.edu /ast/uvlbi/index.html   (369 words)

NOVAS   (Site not responding. Last check: 2007-11-02) At a lower level, NOVAS also provides general astrometric utility transformations, such as those for precession, nutation, aberration, parallax, and the gravitational deflection of light. The computations are precise to better than one milliarcsecond. The NOVAS package is an easy-to-use facility that can be incorporated into data reduction programs, telescope control systems, and simulations. aa.usno.navy.mil /software/novas/novas_info.html   (548 words)

The Second Annual Lowell Observatory Fall Workshop   (Site not responding. Last check: 2007-11-02) I don't really have an answer for that yet, but I have a paper on this in preparation. Another possiblity was that if HIPPARCOS is wrong by just about exactly one millarcsecond, that is, change the HIPPARCOS Pleiades parallax by one milliarcsecond then the Pleiades are bang on, the distance modulus is 5.6, and everybody's happy. Curiously, the Hyades, which is in the same general part of the sky, is also ``off'' by about one milliarcsecond compared to the distance you would have thought prevailed the ground-based observations. www.lowell.edu /users/jch/workshop/drs/drs-d.html   (545 words)

Milliarcsecond Scale Compactness Of Extragalactic Radio Sources At Cosmological Distances (ResearchIndex) Milliarcsecond Scale Compactness Of Extragalactic Radio Sources At Cosmological Distances Abstract: A combination of VSOP pre--launch survey data and our own observations of extremely high redshift quasars provides a data base for studying structural properties of radio--loud quasars as a class of objects. We concentrate our attention on analyzing the compactness of the sources as a function of their redshift (and therefore the emitting frequency) as a precursor to the use of milliarcsecond scale structures of AGN as a cosmological standard rod. citeseer.ist.psu.edu /288207.html   (226 words)

SPIE Proceedings Vol. 2200b Abstract: The Mark III Interferometer on Mt. Wilson, a long-baseline optical interferometer, was in daily operation for more that seven years. During that time it achieved milliarcsecond angular resolution for binary star astronomy, with submilliarcsecond accuracy. For the first time many spectroscopic binaries have been resolved, including binaries in which the companion cannot be detected with spectroscopy. www.spie.org /web/abstracts/2200/2200b.html   (4939 words)

Infrared Absorption-Line Spectroscopy This provides a crucial test of innumerable millimeter-wave CO and continuum measurements made during the past 30 years. Because an entire CO ro-vibrational spectrum can be obtained in a single integration, and all observations correspond to the same milliarcsecond pencil-beam column of molecular gas, derived physical conditions and abundances are more accurate than those typically derived from single-dish radio observations. can be observed, and the abundances and excitation conditions can be cleanly referred to the same milliarcsecond absorbing column of gas. loke.as.arizona.edu /~ckulesa/research/infraredH2.html   (988 words)

Direct 75 Milliarcsecond Images from the Multiple Mirror Telescope with Adaptive Optics (ResearchIndex)   (Site not responding. Last check: 2007-11-02) Direct 75 Milliarcsecond Images from the Multiple Mirror Telescope with Adaptive Optics (ResearchIndex) Direct 75 Milliarcsecond Images from the Multiple Mirror Telescope with Adaptive Optics Design of the 6.5 m MMT adaptive optics system, and results.. citeseer.ist.psu.edu /116925.html   (222 words)

[78.11] The AGN Content of the NOAO Deep Wide Field Survey at Milliarcsecond Resolution   (Site not responding. Last check: 2007-11-02) We are using the NRAO Very Long Baseline Array (VLBA) at 5 GHz to observe compact FIRST sources stronger than 10 mJy in the NOAO Deep Wide-Field Survey (NDWFS). Our study of 206 sources at milliarcsecond resolution overcomes two limitations of past VLBI surveys for active galactic nuclei (AGN), namely biases introduced by targeting flat-spectrum sources stronger than 200 mJy, plus the difficulty of obtaining deep optical identifications and redshifts. Half of the VLBA survey is complete, with almost one in three sources being detected above a typical threshold of 1.5~mJy~beam www.aas.org /publications/baas/v34n4/aas201/693.htm   (289 words)

John D. Monnier Home Page Advances in detectors, optics, and photonics have fueled progress in the field of Optical Interferometry, allowing stars and their surroundings to be probed with unprecedented spatial resolution. Research in my group is focused on visible and infrared imaging with milliarcsecond resolution, developing the precision-calibration techniques necessary to directly detect extra-solar planets, and building the novel instrumentation to make these experiments possible. In addition, we are pursuing other high-resolution projects using large ground-based telescopes, such as adaptive optics, aperture masking, and speckle interferometry. www.astro.lsa.umich.edu /~monnier   (183 words)

Benjamin Lackey   (Site not responding. Last check: 2007-11-02) However, direct detection of extrasolar planets is one of the most promising reasons to build an ELT. Such detections will require milliarcsecond resolution to distinguish the planet from its star, and are not possible even with the small diffraction limited[4] space based telescopes that can fit in existing launch vehicles (Gilmozzi, 2000). Achieving near-diffraction limited optics is the most fundamental scientific requirement of an ELT. www.personal.psu.edu /bdl142/writingsample.html   (1421 words)

VLBI Observations of Nine ESE Sources: Milliarcsecond Scale Structure   (Site not responding. Last check: 2007-11-02) VLBI Observations of Nine ESE Sources: Milliarcsecond Scale Structure Extreme Scattering Events (ESEs) are a recently discovered form of extreme variation in the gigahertz light curves of a number of extragalactic sources. A comparison between the milliarcsecond scale intrinsic structure of these sources and their ESE radio light curves is made in the context of the Fiedler et al. www.aas.org /publications/baas/v27n2/aas186/abs/S3607.html   (183 words)

Amazon.com: Astronomical and Astrophysical Objectives of Sub-Milliarcsecond Optical Astrometry (International ...   (Site not responding. Last check: 2007-11-02) The results of space missions in astrometry, Hipparcos and some results from the Hubble Space telescope are presented for the first time. Combined with ground based results, this provides astrometry results at milliarcsecond resolution. At the same time, the extragalactic reference frame, based on very long baseline interferometry radio positions, is being introduced as the fundamental reference frame. www.amazon.com /Astronomical-Astrophysical-Objectives-Sub-Milliarcsecond-International/dp/0792334426   (690 words)

Amazon.com: "milliarcsecond accuracies": Key Phrase page   (Site not responding. Last check: 2007-11-02) See all pages with references to milliarcsecond accuracies. During the last two decades ofthe century, however, new technologies routinely achieved milliarcsecond accuracies (an improvement by a factor of a million over the ancient Greeks), and technologies for microarcsecond accuracies were being developed. The Hipparcos satellite has provided milliarcsecond accuracies for optical sources. www.amazon.com /phrase/milliarcsecond-accuracies   (406 words)

UK Physics & Astronomy Colloquium   (Site not responding. Last check: 2007-11-02) The technique of Very Long Baseline Interferometry (VLBI) offers the opportunity to study maser component properties at milliarcsecond angular resolution. Recent technical developments in VLBI allow the imaging of maser emission in all Stokes parameters from centimeter to millimeter wavelengths, opening up important new observational frontiers in this field. Results are presented concerning the milliarcsecond VLBI polarization properties of OH and SiO masers towards several late-type stars, and the implications of these observations for maser proper motions, polarization and direct imaging of the circumstellar magnetic field. www.pa.uky.edu /~gardner/colloq/Links/kemball.html   (195 words)

Origins: Library Studying structure of planetary dust disks using starllight nulling imaging Very high resolution (10 milliarcsecond) imaging of broad range of astrophysical phenomena SIM will be the world's first spaceborne operational long- baseline optical interferometer origins.jpl.nasa.gov /library/ipff/ipff14.html   (151 words)

Try your search on: Qwika (all wikis)

About us   |   Why use us?   |   Reviews   |   Press   |   Contact us   Copyright © 2005-2007 www.factbites.com Usage implies agreement with terms.