Detectors improved and new wavebands opened up, but mass, flexure and thermal inertia proved serious obstacles to larger mirrors.Ī mirror needs to be stiff enough to hold its shape against the wind and (at least in the mid-20 th-century paradigm) against its own weight. device in the 1930s and its commissioning in 1948 after the war, growth in telescopes was put on pause for almost half a century. Following the construction of the 200-in. A brief history of telescopesĪ previous burst of telescope development occurred during the early 20 th century, when George Ellery Hale led efforts that culminated in the 60-in. Direct imaging will one day lead to spectroscopy and the ability to detect oxygen in a planet’s atmosphere, the signature of life. The new generation of telescopes, including the GMT, will be able to image mature planets down to about Jupiter’s size, with orbits as small as Earth’s, as well as smaller Earth-like planets that are young enough to glow in the infrared as their gravitational energy leaks out. Just last year, astronomers reported the first images of several large planets orbiting other stars-planets several times larger than Jupiter with orbits similar to those of Uranus, Neptune and Pluto. Several hundred extrasolar planets have been detected by their star’s tiny oscillation around the common center of mass, or the slight darkening that appears when they pass in front of the star.ĭirect imaging is much more difficult because the planet is so close to the billion-times-brighter star. One quest that demands all of the sensitivity and resolution that can be squeezed out of a telescope is the direct imaging of planets around other stars. Sensitivity scales with area, and resolving power scales with diameter if a coherent wavefront can be maintained. With their unprecedented sensitivity and angular resolution, these telescopes open new windows onto the universe. And slight distortions in the images of distant galaxies can map the distribution of the invisible dark matter that appears to make up over 80 percent of the universe’s mass. A large telescope can capture supernovae (catastrophic explosions of stars that have run out of nuclear fuel) at such great distances that scientists can use the images to trace the expansion and acceleration of the universe. In others, they will study objects to reveal the fundamental structure and evolution of the universe as a whole. In some cases, their goal is to understand the structure and evolution of the objects themselves. Astronomers will use them to study distant planets, stars, galaxies and black holes. The GMT is part of a wave of new, ever-larger telescopes that first came on the astronomical scene in the early 1990s. Today, it’s a piece of the test optic system that is guiding the manufacture of the 25-m primary mirror for the Giant Magellan Telescope (GMT). Twenty years earlier, this mirror could have become the primary mirror for the sixth largest optical telescope in the world. In August 2006, the Steward Observatory Mirror Lab cast a 3.75-m mirror under the stands of the University of Arizona football stadium. The seven primary mirror segments form a single 25-m parent surface, while the seven matching secondary mirror segments form a 3.2-m concave surface. Artist’s concept of the Giant Magellan Telescope.
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