As early as 1900. a British physicist, Sir Oliver Lodge, attempted to detect radio waves from the Sun. His failure to do HO can be attributed mainly to the primitive equipment then available. Marconi, in 191(5, and various radio enthusiasts thereafter, surmised that the static disturbances might be of solar or cosmic origin. Military investigations […]
Brilliant Hashes of light in the solar atmosphere, lasting less than an hour, or even perhaps only a few seconds, are named SOLAR. FLARES. The brightest are visible in white light, but they are easier to see in the light of hydrogen or calcium lines. A flare is a highly concentrated, explosive release of energy, […]
An active region on the Sun (one is shown in figure 8.23) includes not only sunspots but related phenomena: plages, prominences, faculae, and flares, to name but a few. One feature common to all these natural phenomena is the strong magnetic field. PLAGES are highly disturbed zones in the chromospheres. They usually appear before the […]
SUNSPOTS are the sole sign of solar activity that is occasionally detectable to the eye. Known since antiquity, according to Greek sources, they were rediscovered by Europeans in 1611, after Galileo’s epochal application of the telescope to astronomical investigations. Despite the Greek knowledge, the European school of natural philosophy steadfastly held the Sun to be […]
Solar weather and magnetic field So far in this chapter the Sun has been considered as a static ball of hot gas: energy is created in the core, and streams out to space through the convection zone, photosphere, and solar atmosphere. We might expect that the release of energy from the surface regions should be […]
Radiation from the photosphere produces a continuous spectrum without emission or absorption lines. Above the photosphere is a layer of gas about 500 km thick, within which the effective temperature declines steadily from about 6000 to 4000K. Consequently, solar radiation has to traverse a layer of relatively cooler gas, and this absorbs radiation at wavelengths […]
The highly luminous surface of the Sun is called the PHOTOSPHERE. The photosphere is the sharp disc as observed with the eye or a small telescope. Larger telescopes used under excellent observing conditions show that the photosphere is not uniformly bright, but has a mottled texture termed GRANULATION. (Graduations in this structure exist, but the […]
Inside The Sun The Sun condensed about 5 000 million years ago from a pocket of interstellar gas that contracted under the attractive forces of its own gravity. An important property of the Sun is its mass (330000 times the Earth’s mass), which results in a pressure and temperature at the centre of the Sun […]
The Sun is a typical star, but is unique as far as we are concerned because of its proximity to Earth; it is about 150 million km away. A summary of basic solar properties is given in table 8.1. Solar energy provides virtually all the heat and light which our planet receives, and it therefore […]
Nucleosynthesis is closely linked with cosmology. The present composition of the Galaxy has arisen because the history of the Universe took the course it did. Some early theories investigated single processes in the early Universe that might have resulted in the present abundances. One of these was the ALPHA-BETA-GAMMA THEORY, so-called because it was proposed […]