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Astronomy Reference Libraries

Page 8 of about 165 Articles
Light Pollution
2004-10-19 04:45:43

Light Pollution -- Light pollution refers to excess light, created by human activities, that brightens the night sky enough to hide many stars from observers. For the average person, light pollution means that even on a clear, moonless night, only a few stars may be visible. When a city grows up near an astronomical observatory, light pollution can make the observatory effectively useless....

Interferometry
2004-10-19 04:45:43

Interferometry -- Interferometry is the applied science of combining two or more input points of a data type, such as optical, and combine these data to form a greater picture based on the combination of the two sources. This technique is the basis for proposed radio telescope arrays, which spread out upon a wide area of hundreds of miles, can together produce a picture with resolution...

Hertzsprung-Russell Diagram
2004-10-19 04:45:43

Hertzsprung-Russell Diagram -- In stellar astronomy, the Hertzsprung-Russell diagram (H-R diagram) shows the relation between the absolute magnitude and the spectral types of stars. It was invented around 1910 by Ejnar Hertzsprung and Henry Norris Russell. There are two equivalent forms. One is the observer's form which plots the color of the star on one axis and the absolute magnitude on...

Gamma-Ray Astronomy
2004-10-19 04:45:43

Gamma-Ray Astronomy -- Gamma-ray astronomy is the astronomical study of gamma rays. Long before experiments could detect gamma rays emitted by cosmic sources, scientists had known that the universe should be producing these photons. Work by Feenberg and Primakoff in 1948, Hayakawa and Hutchinson in 1952, and, especially, Morrison in 1958 had led scientists to believe that a number of...

Amateur Astronomy
2004-10-19 04:45:43

Amateur Astronomy -- Amateur astronomy, also called backyard astronomy, is a hobby whose participants enjoy watching the night sky (and the day sky too, for sunspots, eclipses, etc.), and the plethora of objects found in it, mainly with portable telescopes and binoculars. Even though scientific research is not their main goal, many amateur astronomers make a contribution to astronomy by...

Adaptive Optics
2004-10-19 04:45:43

Adaptive Optics -- Adaptive optics is a technology to improve the performance of Earth-based telescopes, reversing the effect of atmospheric distortions. When light from a star or another astronomical object enters the Earth's atmosphere, the different temperature layers and different wind speeds distort and move the image in various ways (see seeing for a proper discussion). The net...

Active Optics
2004-10-19 04:45:43

Active Optics -- Active optics is a relatively new technology for astronomic telescopes. Most modern telescopes are reflectors, with the primary element being a very large mirror. Historically, a fixed weight-to-diameter relation was used to build these mirrors, limiting their maximum diameter to 5 or 6 meters (200 or 230 inches), like in the Palomar Observatory. A new generation of...

X-ray Pulsar
2004-10-19 04:45:43

X-ray Pulsar -- This dramatic artist's vision shows a city-sized neutron star centered in a disk of hot plasma drawn from its enfeebled red companion star. Ravenously accreting material from the disk, the neutron star spins faster and faster emitting powerful particle beams and pulses of X-rays as it rotates 400 times a second. Could such a bizarre and inhospitable star system really exist...

X-ray Burster
2004-10-19 04:45:43

X-ray Burster -- X-ray bursters are a class of binary stars which are luminous in X-rays. They contain a neutron star and a low-mass companion star. The companion fills its Roche lobe and therefore the neutron star is accreting matter from it. The inflowing gas forms an accretion disk around the neutron star. Sometimes X-ray bursters show a sudden increase in their X-ray luminosity, called...

X-ray Binaries
2004-10-19 04:45:43

X-ray Binaries -- X-ray binaries are a class of binary stars that are very luminous in X-rays. The X-rays are produced by matter falling from one component (usually a relatively normal star) to the other component, which is a neutron star or a black hole. The infalling matter releases gravitational potential energy, up to several tens of per cent of its rest mass as X-rays. (Hydrogen...

Word of the Day
omadhaun
  • A fool; a simpleton: a term of abuse common in Ireland and to a less extent in the Gaelic-speaking parts of Scotland.
This word is partly Irish in origin.