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The strength of seeing is often characterized by the angular diameter of the long-exposure image of a star (seeing disk) or by the Fried parameter r 0. The diameter of the seeing disk is the full width at half maximum of its optical intensity. An exposure time of several tens of milliseconds can be considered long in this context. The Fried ...
Astrophysical fluid dynamics is a branch of modern astronomy which deals with the motion of fluids in outer space using fluid mechanics, such as those that make up the Sun and other stars. [1] The subject covers the fundamentals of fluid mechanics using various equations , such as continuity equations , the Navier–Stokes equations , and Euler ...
The scale is a five-point system, with 1 being the best seeing conditions and 5 being the worst. The actual definitions are as follows: (I.) Perfect seeing, without a quiver. (II.) Slight quivering of the image with moments of calm lasting several seconds. (III.) Moderate seeing with larger air tremors that blur the image. (IV.)
Reynolds Experiment (1883). Osborne Reynolds standing beside his apparatus. In 1883, scientist Osborne Reynolds conducted a fluid dynamics experiment involving water and dye, where he adjusted the velocities of the fluids and observed the transition from laminar to turbulent flow, characterized by the formation of eddies and vortices. [5]
A simple argument can be based on consideration of net effects. To create the magnetic field, the net electric current must wrap around the axis of rotation of the planet. In that case, for the term to be positive, the net flow of conducting matter must be towards the axis of rotation. The diagram only shows a net flow from the poles to the ...
From planetary meet-ups to the first total lunar eclipse in three years, here are the top astronomy events to look for throughout 2025: Stellar views of Mars will greet stargazers in January as ...
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a ...
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. [1] [2] As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space—what they are, rather than where they are", [3] which is studied ...