Point Source: An idealized discrete source of radiation that subtends an infinitesimally small angle.
Polarization: The action or process of affecting radiation and especially light so that the vibrations of the wave assume a definite form.
Point Source
(a) A source whose angular extent cannot be measured (< 0".05).
(b) A source of exactly spherical wave fronts. All sources can be considered to be point-like if viewed from a large enough distance.
Point sourcePoint source mutationsPoint Stadium
Point State ParkPoint systemPoint targets
Point TheatrePoint to point racingPoint Township, Pennsylvania ...
"The point sources we saw in the galactic plane were actually active galaxies with bright cores millions of light years behind our galaxy," said Ebisawa.
When a point source, such as a star, is observed through a telescope with a circular aperture, the image is not a point source - it is a disk surrounded by a number of very faint rings.
Imagine a point source of light of luminosity L that radiates equally in all directions. A hollow sphere centered on the point would have its entire interior surface illuminated.
All Sky Map of IRAS Point Sources
The plane of our galaxy runs horizontally across the image
Exploring the Hidden Universe ...
calcium Fraunhofer region (NASA SP-7, 1965) That region of the field in which the energy flow from an antenna proceeds essentially as though coming from a point source located in the vicinity of the antenna.
Two different surveys at 20 cm (the NVSS and FIRST projects) have been carried out with the VLA, covering most of the accessible sky to flux limits typically a few mJy for point sources.
They confirmed the earlier findings of the gamma-ray background, produced the first detailed map of the sky at gamma-ray wavelengths, and detected a number of point sources.
SAS-2 and COS-B confirmed the earlier findings of gamma-ray background radiation and also detected a number of point sources, ...
Stars as point sources: The vast distance to stars means we cannot resolve them as disks, instead we see the light from a point source. Our eyes are relatively insensitive to colour from point sources.
Because OSSE was able to slew its four detectors in almost any direction and it had a small field of view, it was primarily used to observe point sources like neutron stars, x-ray binaries, AGN, and quasars.
Even with Hubble, taking a picture would likely be out of the question, for a typical Kuiper Belt object at that distance would appear as little more than a point source.
point source) although many have had their "host galaxies" identified. The galaxies themselves are often too dim to be seen with all but the largest telescopes.
He also managed to make out individual point sources in some of these nebulae, lending credence to Kant's earlier conjecture.
This is a traditional criterion for image quality and is the ratio of maximum intensity of the point spread to that of a theoretically perfect point source image (Airy disk). A perfect (no distortion) diffraction limited image would have R = 1.0.
Large magnifications are very useful for observing the Moon and the planets; however, since stars appear as point sources owing to their great distances, magnification provides no additional advantage when viewing them.
Interferometry has many uses, and one of the most intriguing is its ability to cancel out the light from a point source such as a star by superimposing the images in such a way that the oscillations in light intensity from one image are the reverse ...
The stars we see in the night sky are so far away that they are essentially point sources.
An unresolved infrared point source (color temperature about 600 K) in the Orion Nebula. It is the brightest infrared object known at . Discovered in 1966. (also known as the BN Object ) [H76]
Becquerel (Bq) ...
" Within this extended radio patch is a point source, "Sagittarius A*," which is without much question the true center of the Galaxy itself.
In optics, a bright spot that appears in the center of the shadow of a circular disk illuminated by a point source, caused by diffraction.
Also on this site: ...
Typically, deep sky objects that present themselves as point sources of light, as opposed to diffuse and extended sources of light, will be affected by light pollution the least.
Integrated Magnitude The magnitude which would apply if all the light energy from an extended object was coming from a point source.
J ...
That takes less time than it takes for the center of the Sun to pass from A to B (top drawing) which would be the duration of the eclipse if the Sun were a tiny point source, located at its middle.
Gamma ray pulsars are quite rare, and most are young neutron stars with strong magnetic fields. A few of these are also visible as radio and optical pulsars. At gamma ray wavelengths near 100 MeV, the Vela pulsar is the strongest point source in ...
So if light is a wave phenomenon, then two light sources produce waves that in some places produce large amplitudes and other places produce zero. When to point sources of light are projected onto a screen this wave interference effect produces ...
Also present is information that can be mathematically assembled into 'radio pictures' of these cosmic objects. Some signals arrive from finely defined sources that can be, by and large, considered as point sources (quasars and pulsars for example).
In an optical system, a result of spherical aberration in which a point source of light, not on the axis, has a blurred, comet-shaped image. Coma Berenices (NASA SP-7, 1965) (abbr Com, Coma)
See constellation.
 See also: Light, Sky, Field, Earth, Universe
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