Visible astronomy

Identification of molecules in space, even small molecules, by IR astronomy requires a rotational progression in the spectrum to be measured and resolved by the telescopes. For the transitions in the simpler molecules such as CO the telescope must be capable of aresolution of 2150/1.93 1114, which is within the resolution limit of the UK Infrared Telescope (3000-5000). However, the rotational constant for CO is rather large and many molecules, especially polyatomic species, will have a rotation constant ten times smaller than this, placing the observation of a resolved rotational progression beyond the resolution of the telescopes. Confidence in the identification of the molecule is then severely dented. The problem is worse for visible astronomy. 

Visible astronomy does, however, provide most of the atomic and black body spectra of stars and astronomical objects and is of course appealing to us because the human eye is uniquely adapted to detection in the wavelength range 300-800 nm. The appeal of colour pictures has lead to the development of false colour scales used routinely by astronomers to visualise the intensity of radiation at other wavelengths. The concepts of temperature and colour are linked by the black body radiation and it... 

During the past decades infrared detectors have been developed in array format, with thousands or millions of detector elements arranged in two-dimensional configurations. Applications of arrays have allowed significant advances in infrared astronomy similar to those experienced in visible astronomy when Charge Coupled Devices (CCD) in array format were introduced. Infrared arrays of InSb, HgCdTe, Si As, and other materials are available in a variety of formats ranging from 128 x 128 up to 2048 x 2048 elements. Individual elements are typically tens of micrometers in size. 

Laboratory measurements of the vibrational spectra of C3, C5 and C7 show transitions that lie in the spectral region 2300-1700 cm-1 or 4.35-5.88 p,m, but again the usual caveat about the resolution of the IR instrument and the precise identification of molecules still applies. Infrared astronomy is still best at identifying families of molecules containing C-H or C-C stretch, whether aromatic or aliphatic. Laboratory measurements are, however, possible for these species both in the IR and in the visible, and the positive identification of C2 emission in the Red Rectangle is without question, as in the identification of long chains up to HCm . 

Then suddenly, against her will but in all lucidity, Urania the ancient Greek muse of astronomy was compelled to admit that what is visible is only the froth of existence. She even came to give precedence to what cannot be seen, to what neither shines nor absorbs light. Astronomical observation and theoretical reasoning suggest that most of matter is actually invisible. 

From the birth of the gods to the advent of dark matter, the visible sky has barely changed. It is not therefore the sky that changes, but our ideas about it. Each new cosmology opens up a new era of human experience. The truly universal matter which governs the future of the Universe, determining whether it is open or closed, may still be unknown to us, but at least we are now convinced of its existence. It is unknown, but not unknowable. Let us venture that by the tenth year of this millennium, it will have revealed its true identity. The discovery of dark matter will be a major scientific event. It remains to wonder whether it will come to us from the sky via astronomy, or from the Earth through the mediation of the particle accelerator. 

Light is a conscientious messenger. It carries messages diligently from one point of the atomic universe to another, for it is the very expression of its finer features. Atoms in stars speak the language of the visible to atoms in eyes. No more is needed for a whole astronomy of light and shade, of stars and clouds to blossom forth. 

Astronomy is infinitely subdivided. There are as many astronomies as colours in the visible and invisible spectra, and even more if we include the study of non-electromagnetic signals like neutrinos and gravitational waves. 

American astronomy holds several trump cards. Until recently, its great optical telescopes, the HST and the twin telescopes Keck I and II set up on Manna Kea in Hawaii, reigned imperially over the visible and near UV sky. Although the European VET has largely counterbalanced this domination, the USA is ready to step into the lead once more. 

Optimised for the 1-5 pm wavelength range with extensions into the visible (0.5 pm) and infrared (30 pm), this great winged giant should restore supremacy to the astronomy of the new continent. It is wise to accept the fact and encourage transatlantic cooperation. 

Today, particle accelerators and computers are as much apart of astronomy as telescopes intent on spying out the visible and the invisible. In their accelerators, high-energy physicists are able to reproduce conditions in the Big Bang and in the stellar core. Then, taking over from them, numerical simulation by computer can write the story of matter through its various cycles of concentration, nucleosynthesis and dispersion. 

Chemistry at the beginning of the nineteenth century was in a position analogous to Ptolemaic astronomy. Around 100 C.E., Ptolemy created his astronomical system, which could be used to accurately chart the movement of all the visible planets, the sun, and the moon. His system worked perfectly well for navigation, time keeping, and all the other activities for which knowing the place of celestial objects was needed. Yet, Ptolemy s system had a philosophical problem. Each of the planets had its own system of movement, and the laws of planetary motion were different from those that governed motion on the Earth. Newton s astronomy and physics put all the planets, the stars, and motion here on Earth into a single system. 

Absorption spectroscopy in the visible and near-ultraviolet region of the spectrum dominated molecular astronomy in the three decades from 1937 to 1968. The species CH, CH+, and CN, observed by using bright hot stars as light sources, were seen in the spectra of many stars. The spectra of these species, as shown in Figure 17.1, establish that the population in the quantum levels is strongly biased toward the lowest levels. The population distributions are fit by a temperature of 2.73 K (Bortolot et al., 1969). ... 

Tycho s devotion to astronomy was stimulated first by the prediction of a solar eclipse and secured by his personal observation of the famous new star (nova) of 1572 in Cassiopeia. He managed to demonstrate that the shining object, brighter than Venus and visible in broad daylight, was one of the fixed stars in the process of disintegration. This observation was a serious blow to the Aristotelian concept of the immutability of the heavens. 

The most important result of radio astronomy, to date, has been the identification of quasi-stellar objects, to be discussed next. In addition countless radio galaxies and blank radio fields have been identified. The blank fields are good radio sources without visible counterparts. It is not clear whether the blank fields contain radio galaxies or quasi-stellar objects. 

A Hybrid Detector Phoswich detectors are used extensively in hard x-ray/ gamma ray astronomy, but suffer from poor performance at low energies due to the small number of visible photons produced by the Nal crystal. The hybrid instrument [14, optically couples a 40 cm x 40 cm phoswich, currently... 

Radio Astronomy. Most radio astronomy applications operate in the microwave spectrum. Usually, naturally occurring microwave radiation is observed however, radio astronomy has been used to measure distances precisely within the solar system. Radio astronomy has also been employed to map the surface of Venus, which is not visible via optical telescopes because of its dense cloud cover. The technology has expanded astronomical knowledge and has led to the discovery of new objects, including radio galaxies, pulsars, and quasars. Radio astronomy allows objects that are not detectable with an optical telescope to be seen. These objects are some of the most extreme and... 

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