Galileo Encyclopedia Articles

Galileo observations of Jovian satellites When the Galileo spacecraft arrived at Jupiter on December 7, 1995, it first dropped a probe through the planet's atmospheric clouds. Data were relayed to Earth via the Galileo Orbiter, sweeping past Jupiter before going into orbit. When the Galileo Orbiter flew just 835 km (519 mi) above Ganymede's surface on June 27, 1996, it began devoting much of its resources (its on-board tape recorder and its radio downlink to Earth) to studying Jupiter's four large galilean satellites, discovered by Galileo Galilei with his primitive telescope nearly four centuries ago... Hubble Space Telescope The Hubble Space Telescope is the largest visible-light observatory ever placed into space. Hubble's orbit, some 612 km (380 mi) above Earth's surface (Fig. 1), keeps it above almost all of Earth's atmosphere, at a location where its view of the heavens is much clearer than that of ground-based telescopes. The superior view afforded by Hubble's orbit has made the telescope a unique resource for astronomers worldwide and has led to fundamental discoveries about the size and age of the universe, the birth and death of stars,... Telescope An instrument used to collect, measure, or analyze electromagnetic radiation from distant objects. A telescope overcomes the limitations of the eye by increasing the ability to see faint objects and discern fine details. In addition, when used in conjunction with modern detectors, a telescope can "see" light that is otherwise invisible. The wavelength of the light of interest can have a profound effect on the design of a telescope. See also: Electromagnetic radiation; Light... Twinkling stars A phenomenon by which light from the stars, as it passes through fluctuations in the Earth's atmosphere, is rapidly modulated and redirected to make the starlight appear to flicker. Although it is familiar to those who have looked with the unaided eye at the night sky, the twinkling phenomenon affects all wavelengths that manage to penetrate the Earth's atmosphere, from the visible to the radio wavelengths. At visible wavelengths, atmospheric fluctuations are caused predominantly by temperature irregularities along the line of sight. Minor contributions are made by irregularities in atmospheric density and in water vapor content. All such irregularities introduce slight changes in the index of refraction of air, and these changes affect light... Use of optics by Renaissance artists An extensive visual investigation by the artist David Hockney, supported by optical evidence detailed in subsequent technical papers, shows that important artists began using optical devices as aids for creating their work early in the Renaissance, approximately 175 years before the time of Galileo. These discoveries show there has been a continuous use of optics for artistic purposes continuing until today, that started about 1425 with Jan van Eyck and Robert Campin in Flanders, followed by such well-known artists as Bartholomé Bermejo in Spain about 1474, Hans Holbein in England about 1530, and Caravaggio in Italy about 1600. Before the optical evidence in representative Renaissance paintings is described, the state of optical... Articles courtesy of Access Science http://www.AccessScience.com Copyright McGraw-Hill, all rights reserved. Back Spotlight Home Page