Chemical Factories in Space

The existence of interstellar molecules is recognized because, just like the hydrogen atom, they emit radio waves in the form of spectral lines. Today over 140 molecular species have been identified in interstellar space. This number compares with 27 in the 1973 edition of this book, and 64 in the 1987 edition. Another 500 or so lines have been observed but not identified. Most of these species are detected at very high frequencies, about 5,000 MHz (short wavelengths, below 6 cm and down to a...

A2L Wavelength and Frequency

Electromagnetic waves have a wavelength and a frequency which are related in a simple manner. Consider waves crashing into the seashore or lapping the edge of a lake. You may notice that the waves strike the shore at a certain rate, or frequency. Along the California coast a typical interval between waves is 10 s, which indicates a frequency of 6 waves per minute. The frequency at which the water waves break is related to their speed. The faster they travel the greater their frequency. There is...

A22 The Wavelength Range of the Electromagnetic Spectrum

Radio waves are at the long-wavelength end of the electromagnetic spectrum, as long as hundreds of meters down to a millimeter and well-known microwaves have wavelengths of around a few centimeters. As wavelength decreases we find infrared (1R) radiation, commonly experienced as heat, then light waves which range from 70 millionths of a centimeter (7 x 10-5 cm) for the long wavelength red light down to 40 millionths of a centimeter (4 x 105 cm) tor violet light. The colors of the rainbow fall...

J ALMAThe Atacama Large Mil lime te rSubm il timet er Array

In the quest to better understand the nature of molecular clouds and what drives the chemistry of the universe, an array of 64 dishes, each 12 m in diameter capable of operating from 30 to 1,950 MHz (wavelength range from 9.6 to 0.3 mm) is to be constructed at the heady altitude of 5,100 m (16,500 ft) on the Chajnan-tor plain of the Chilean Andes in the District of San Pedro de Atacama. Figure 15.4 shows an artist's impression of what it will look like. At that altitude there is little water...

Radio Waves from the Milky

A Steady Hiss Type Static of Unknown Origin By J 933 Jansky had concluded that the source of the steady hiss he had detected with his antenna must be somewhere outside the earth since it seemed to move through the sky along with the stars in a manner consistent with its being of an extraterrestrial nature. He established an approximate direction for the source as IK h right ascension and 10 declination. (Right ascension and declination are coordinates astronomers generally use to locate...

The Birth of Radio Astronomy

Karl Guthe Jansky, the father of radio astronomy, was employed at Bell Laboratories, which, in 1927, introduced the first transatlantic radiotelephone. For a mere 75 one could speak for three minutes between New York and London, but the radio links were terribly susceptible to electrical interference. The hrst system operated at the extraordinarily low frequency of 60 kHz that is, at the very long wavelength of 5 km and in 1929 a change was made to short waves whose frequencies were in the...