It has a wealth of diagrams matched with clear. Another worthwhile site is The Art of Renaissance Science: Galileo and Perspective.It is also the source for the image of Galileo at the top of this page. It is hosted by Rice University and includes his writings, details on his experiments and observations and links. An excellent online source for all things related to Galileo is: The Galileo Project.More stars are resolved in this drawing by Galileo of the Pleiades than are visible to the unaided eye. This posed the question as to why there were invisible objects in the night sky? On turning his telescope to the band of the Milky Way Galileo saw it resolved into thousands of hitherto unseen stars. This then eased the problem posed by the failure of astronomers to detect stellar parallax that was a consequence of Copernicus' model. Galileo suggested that this was due to their immense distance from Earth. Stars in the Milky WayĮven through a telescope the stars still appeared as points of light. It was not until 1656 that the Dutch scientist, Christiaan Huygens correctly described them as rings. Galileo noted two appendages from the sides of Saturn. Its blemishes and imperfections again undermined the Aristotelian ideal of a perfect cosmos. Galileo, in his Letters on Sunspots supported the sunspot interpretation and used it to show that the Sun was rotating. Debate centered on whether these were satellites of the Sun or actual spots on its surface. SunspotsĪlong with contemporaries such as Thomas Harriot, David Frabicius and Christoph Scheiner, Galileo observed dark regions that appeared to move across the surface of the Sun. Galileo rejected Tycho's model as an unnecessary hybrid and used the discovery to consolidate his support of the Copernican model. This could not be explained in the Ptolemaic model but could be accounted for by either the Sun-centered Copernican model or the Earth-centered Tychonic model that had the other planets orbiting the Sun as it orbited the Earth. Venus was observed to go through a sequence of phases similar to the Moon. Instead, astrophysicists use special detectors to observe gamma rays and to figure out where they come from in the sky.Galileo's drawings of the moons of Jupiter of successive nights The Phases of Venus They go straight through optics used for other wavelengths, making them impossible to reflect or refract. Gamma rays are the universe’s most energetic form of light. Engineers at NASA’s Goddard and Marshall Space Flight Centers have designed mirrors like these for missions like the X-ray Imaging and Spectroscopy Mission (XRISM) and the Imaging X-ray Polarimetry Explorer (IXPE). Since there’s a lot of empty space in the middle of a single paraboloid, X-ray mirrors incorporate multiple mirrors as nested onion-like shells. This is called a grazing incidence mirror. To detect them, engineers turn the mirrors on their sides so the X-rays can skip off the surface. X-rays can simply pass through the atoms that make up most telescope mirrors. X-ray mirrors use the slightly angled side of the paraboloid. The Webb mirror, for example, is coated with a thin layer of gold so that it can reflect infrared light. Telescope mirrors are coated with different materials depending on the color of the light they need to reflect. (Backyard telescopes can also have mirrors, too.)Īn X-ray Mirror Assembly built for the X-ray Imaging and Spectroscopy Mission consists of a primary and secondary mirror, each containing 812 nested foil mirror segments. Large mirrors can be made thinner and lighter than lenses of the same size, which makes reflecting scopes ideal for sending to space. Reflecting telescopesĪ telescope that uses a mirror as its primary optical element is called a reflecting telescope. The first telescopes, developed in the 1600s, were refractors, as are many backyard telescopes today.īut very large lenses make refracting telescopes large and heavy, which makes them difficult to use in space. Like eyeglasses, the lenses bend, or refract, light passing through them. Refracting telescopesĪ telescope using a lens for its main optical element is called a refracting telescope. The larger a mirror or lens, the more light it collects, and the better its ability to detect fainter objects. The size of the main mirror or lens determines how well a telescope can collect light. Astronomers observe distant cosmic objects using telescopes that employ mirrors and lenses to gather and focus light.
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