Results 61 to 70 of about 951 (180)

Connecting VLBI and Gaia celestial reference frames

Frontiers in Astronomy and Space Sciences, 2016
The current state of the link problem between radio and optical celestial reference frames is considered.The main objectives of the investigations in this direction during the next few years are the preparation of a comparisonand the mutual orientation ...
Zinovy Malkin
doaj   +1 more source

Globally Critical Infrastructure: The Unique Risks and Challenges

Risk Analysis, Volume 45, Issue 12, Page 4804-4817, December 2025.
ABSTRACT Critical infrastructure is typically identified at the national level. However, disruption to certain infrastructure systems, facilities, and assets can have negative consequences for global societies. Such globally critical infrastructure entails a distinct risk profile for both countries dependent on the infrastructure, and countries that ...
Zachary Kallenborn, Henry H. Willis
wiley   +1 more source

Constraining the size, shape, and albedo of the large trans-Neptunian object (28978) Ixion with multi-chord stellar occultations

Astronomy & Astrophysics
Context. Trans-Neptunian objects (TNOs) are among the most primitive remnants of the early Solar System. Determining their sizes, shapes, albedos, and surface properties is essential for understanding their origin and evolution.
Kilic Y., Braga-Ribas F., Pereira C. L., Ortiz J. L., Sicardy B., Santos-Sanz P., Erece O., Rizos J. L., Gómez-Limón J. M., Margoti G., Souami D., Morgado B., Gomes-Junior A., Catani L. M., Desmars J., Kretlow M., Rommel F., Duffard R., Alvarez-Candal A., Camargo J. I. B., Kaplan M., Morales N., Herald D., Assafin M., Benedetti-Rossi G., Sfair R., Savalle R., Arcas-Silva J., Bernasconi L., Blank T., Bonavita M., Carlson N., Christophe B., Colesanti C. A., Collins M., Columba G., Dunford R., Dunham D. W., Dunham J., Emilio M., Ferrante W. G., George T., Hanna W., Isopi G., Jones R., Kenyon D. A., Kerr S., Kouprianov V., Maley P. D., Mallia F., Mattei J., Meunier M., Napoleao T., Peixoto V. F., Pollock J., Snodgrass C., Stechina A., Thomas W., Venable R., Viscome G. R., Zapparata A., Bardecker J., Castro N., Cebral C., Chapman A., Gao C., Green K., Guimaraes A., Jacques C., Jehin E., Konishi M., Leiva R., Liberato L., Magliano C., Mammana L. A., Melita M., Moura V., Olivera-Cuello Y., Peiro L., Spagnotto J., Stuart P. C., Vanzi L., Wilberger A., Malacarne M.   +83 more
doaj   +1 more source

Precision astrometry with adaptive optics [PDF]

SPIE Proceedings, 2008
We investigate the limits of ground-based astrometry with adaptive optics using the core of the Galactic globular cluster M5. Adaptive optics systems provide near diffraction-limit imaging with the world's largest telescopes. The substantial improvement in both resolution and signal-to-noise ratio enables high-precision astrometry from the ground.
Cameron, P. B., Britton, M. C., Kulkarni, S. R.   +2 more
openaire   +5 more sources

JWST Imaging of the Closest Globular Clusters—VI. The Lowest‐Mass Objects in M 4 and the Galactic Bulge

Astronomische Nachrichten, Volume 346, Issue 9, November 2025.
ABSTRACT We present James Webb Space Telescope observations of M 4—the closest globular cluster—that probe the lower Main Sequence down to the hydrogen‐burning limit. The unveiled stellar sequence reaches much fainter luminosities than previously possible, revealing a few extremely red objects that are consistent with brown dwarfs as cool as Teff∼1000K$
L. R. Bedin, R. Gerasimov, A. Calamida, M. Libralato, M. Scalco, D. Nardiello, M. Griggio, D. Apai, J. Anderson, A. Bellini, A. Burgasser   +10 more
wiley   +1 more source

Measuring Titan’s rapid orbital expansion combining Cassini radio science normal points and astrometry

Astronomy & Astrophysics
Recent analyses of Titan’s orbital migration have yielded conflicting results regarding Saturn’s tidal dissipation (Q) at Titan’s frequency. While some studies reported a low Q consistent with resonance locking using independent radio science and ...
Magnanini Andrea, Lainey Valery, Gomez Casajus Luis, Zannoni Marco, Tortora Paolo   +4 more
doaj   +1 more source

Integration of Statistical Models and Deep Learning: A CEEMDAN‐Based Hybrid Framework for Frequency‐Domain Prediction of Polar Motion

Earth and Space Science, Volume 12, Issue 10, October 2025.
Abstract High‐precision Earth Rotation Parameter (ERP) products often experience delays that range from several days to weeks. The use of precise forecasting models can effectively compensate for the impact of such delays. Based on a systematic analysis of the forecasting capabilities of the traditional harmonic least squares fitting and autoregressive
Chen Ren, Chen Wang, Zhenhong Li, Haoran Gong, Jialiang Liu   +4 more
wiley   +1 more source

Astrometric microlensing probes of the isolated neutron star population with Roman

Astronomy & Astrophysics
Context. Notoriously hard to detect and study, isolated neutron stars (NSs) might provide valuable answers to fundamental questions about stellar evolution and explosion physics.
Kaczmarek Z., Halasi-Kun A., McGill P., Perkins S. E., Dawson W. A.   +4 more
doaj   +1 more source

Astrometry And Data Centers [PDF]

Symposium - International Astronomical Union, 1988
SummaryThe paper tries to provide some background to answer the problem if old astrometric data should be stored. The cases of the AC and the CdC are examined, as well as the storage of some more recent catalogues on optical disc. Finally the necessity of producing general catalogues (of the SAO type) for non-astrometrists is underlined, to satisfy the
openaire   +1 more source

Reassessing the Relationship Between Meteor Radio Afterglows and Optical Persistent Trains

Journal of Geophysical Research: Space Physics, Volume 130, Issue 9, September 2025.
Abstract Meteor radio afterglows (MRAs) and optical persistent trains (PTs) are two types of long‐lived phenomena which are occasionally observed following the occurrence of a meteor. Both phenomena are thought to be produced by intrinsic emission mechanisms; PTs have been associated with chemiluminescent reactions between meteoric metals and ...
L. E. Cordonnier, K. S. Obenberger, G. B. Taylor, J. M. Holmes, J. Dowell, D. Vida   +5 more
wiley   +1 more source