Galileo and 400 Years of Telescopic Astronomy (Astronomers' Universe)
Peter Grego, David Mannion
Format: PDF / Kindle (mobi) / ePub
In 1609 Galileo first used his telescope to kick start the science of observational astronomy - an event that proved to be of enormous historic, scientific, and cultural importance. Galileo and 400 Years of Telescopic Astronomy will feature the life and achievements of Galileo, around which has pivoted the story of four centuries of telescopic astronomy. The book will detail how astronomy has progressed through four centuries and contain glimpses of future space research and astronomy goals. Uniquely, interwoven with the text will be a range of practical projects for backyard astronomers in which to participate, projects that serve to illustrate many of Galileo's scientific discoveries.
From time to time at inferior conjunction Mercury moves directly between the Sun and Earth, appearing as a small black spot that slowly moves across the solar disk. Since Kepler’s time it has been possible to predict the occurrence of these transits; the first one ever to have been observed took place on November 7, 1631, and was viewed by Pierre Gassendi (1592–1655) from Paris, who wrote about the event in his Mercurius in sole visus. Transit of Mercury observed by Doppelmayer in 1710 Future transits of Mercury Date Time (UT, mid-transit) Duration 2016 May 09 14:57 07 h 30 m 2019 Nov 11 15:20 05 h 29 m 2032 Nov 13 08:58 04 h 26 m The transit of Mercury on May 7, 2003, observed (Credit: Peter Grego) It was to be quite a while before telescopes became powerful enough for astronomers to discern markings on the tiny disk of the innermost planet.
News of the marvelous invention quickly spread around Europe, and first reached the ears of Galileo in May 1609. By July of that year Galileo, working without any special knowledge of Lippershey’s invention, had figured out what kinds of lenses were required and built his first refracting telescope. Consisting of a pair of lenses in an adjustable tube – an objective lens to collect and focus the light and an ocular lens to magnify the focused image – Galileo’s first telescope only magnified about three times.
Dubhe and Merak, the “pointer” stars in Ursa Major which indicate the direction of the north celestial pole, are separated by 5°, or the width of the three middle fingers. From northern Italy, the midwinter Sun rises to an altitude of around 20°, which equates to the distance between the tip of the thumb and little finger in an outstretched hand; on the same date in Fairbanks, Alaska, the Sun heaves itself to just under 2° above the southern horizon, about the width of a thumb. Carefully constructed instruments will of course enable more accurate measurements to be made.
More accurate spectrographs were developed when photography was applied to spectroscopy, with notable pioneering work at Harvard College Observatory by Edward Pickering (1846–1919), where great leaps forward were made in understanding stellar spectra. Pickering recruited many women to work for him, including Annie Jump Cannon (1863–1941), who developed a system of classifying stellar spectra. This has become the well-known series: W O B A F G K M L T, in order of decreasing surface temperature. You might see in some older books spectral types R, N, and S after type M.
The Orion Molecular Cloud 1,500 light years from Earth is the nearest star formation region. SupernovaA cataclysmic explosion at the end of a star’s life, which can release as much energy per second as the output of a whole galaxy, i. e. 100 billion stars. There have been six observed supernovae by the naked eye in the last 2,000 years. Synchrotron radiationWhen charged particles traveling close to the speed of light are accelerated in magnetic fields, then synchrotron radiation is released. The radiation was first postulated by I.