Shapley And Star Clusters (Major Trends In The History of Astronomy)

Progress on the nebulae in the early twentieth century was stim lated by the construction of large telescopes in good climates and the regular use of permanent records such as photographic plates and spectrograms. The Harvard telescope in Peru, the Crossley 1-m reflector at the Lick Observatory and the Mount… Read more“Shapley And Star Clusters (Major Trends In The History of Astronomy)”

Nineteenth-Century Research On Nebulae ( Major Trends In The History of Astronomy)

Herschel’s discovery of stars embedded in nebulosity, the so-called planetary nebulae, reinforced a possible interpretation of the nebulae as planetary systems in the making. Such an interpretation correlated very well with the accepted theory of the origin of the Solar System developed by Pierre Simon de Laplace towards the end… Read more“Nineteenth-Century Research On Nebulae ( Major Trends In The History of Astronomy)”

Stellar Astrophysics After 1900 ( Major Trends In The History of Astronomy)

The Draper catalogues provided astrophysicists with the massive numbers of spectra needed for statistical studies of the distribution of stellar types, which in turn might provide clues on stellar evolution. Two independent studies of particular interest, one by E.Hertzsprung, a Danish astronomer, the other by the American astronomer H.N.Russell, resulted… Read more“Stellar Astrophysics After 1900 ( Major Trends In The History of Astronomy)”

Stellar Studies From 1850 To 1900 ( Major Trends In The History of Astronomy)

In the mid-nineteenth century, very little was known about stars other than positions, apparent magnitudes, and, in a few cases distances. The method of determining distance, by trigonometrical parallax, was limited to those stars within a hundred parsecs of the Sun ; thus, even by 1890 fewer than 100 stars… Read more“Stellar Studies From 1850 To 1900 ( Major Trends In The History of Astronomy)”

The First Distance To The Stars (Major Trends In The History of Astronomy)

Vital step were taken towards the detection of stellar parallax during the eighteenth century through the collection of extensive and precise stellar catalogues. In addition, more precise instruments, impossible for the crude technologies of earlier times, were being constructed. Both these factors contributed to many false alarms until the actual… Read more“The First Distance To The Stars (Major Trends In The History of Astronomy)”

X-rays And Gamma Rays From Supernova Remnants (Clouds ,Nebulae Star Births And Deaths)

X-rays have been detected from several supernova remnants by the use of satellite-borne telescopes. The case of the Crab Nebula has already been mentioned; here the X-rays are almost certainly due to synchrotron radiation. Most SNRs, however, do not contain a pulsar that can maintain the supply of the ultra-relativistic… Read more“X-rays And Gamma Rays From Supernova Remnants (Clouds ,Nebulae Star Births And Deaths)”

Radio Emission From Supernova Remnants (Clouds ,Nebulae Star Births And Deaths)

There are about a hundred known supernova remnants in Galaxy. Although visible, X-ray and gamma radiation have been detected from a few of these, most are seen only at radio wave¬lengths. The radio emission is caused by high-speed electrons, produced within the supernova, spiralling around magnetic field lines. This process,… Read more“Radio Emission From Supernova Remnants (Clouds ,Nebulae Star Births And Deaths)”