Unlocking the Secrets of White Dwarf Stars (Astronomers' Universe)
Language: English
Pages: 324
ISBN: 3319093681
Format: PDF / Kindle (mobi) / ePub
White dwarfs, each containing about as much mass as our Sun but packed into a volume about the size of Earth, are the endpoints of evolution for most stars. Thousands of these faint objects have now been discovered, though only a century ago only three were known. They are among the most common stars in the Milky Way Galaxy, and they have become important tools in understanding the universe. Yet a century ago only three white dwarfs were known.
The existence of these stars completely baffled the scientists of the day, and solving the mysteries of these strange objects required revolutionary advances in science and technology, including the development of quantum physics, the construction and utilization of large telescopes, the invention of the digital computer, and the ability to make astronomical observations from space.
This book tells the story of the growth in our understanding of white dwarf stars, set within the context of the relevant scientific and technological advances. Part popular science, part historical narrative, this book is authored by one of the astrophysicists who participated directly in uncovering some of the secrets of white dwarf stars.
Apollo Expeditions to the Moon
A Concise History of Astronomy
The Planet Observer's Handbook (2nd Edition)
Astronomy: Principles and Practice (4th Edition) (PBK)
Leap of Faith: An Astronaut's Journey Into the Unknown
through relatively easily. The first step in incorporating heat transport by radiation was taken in 1905 by the brilliant German astrophysicist Karl Schwarzschild (1873–1916), who established the concept of radiative equilibrium and applied it to the solar atmosphere.10 Schwarzschild made a number of other profound contributions to physics and astrophysics before his life was cut short during World War I. In contrast to the case of convective equilibrium considered earlier, the condition of
decade earlier, never seeing the final fruition of his great vision. Astronomer Edwin P. Hubble (1889–1953) took the first photographic exposure with the 200-in. telescope in January 1949, and the giant instrument was made available for regular use by Caltech and Carnegie Institution astronomers that October. It remained the largest and arguably the most productive telescope in the world for the next 45 years. Figure 8.3The 200-in. Hale Telescope on Mt. Palomar. Public domain image courtesy
show He II absorption lines. Cooler DO stars (below about 50,000 K) show absorption by both He II and neutral helium (He I). Below 30,000 K, where He I lines dominate, the white dwarfs are classified as DBs. The DB star Feige 4, shown in Figure 8.5, has T eff about 17,000 K and exhibits only strong, very broad absorption lines of neutral helium. When the temperature falls below 11,000 K, the non-DA atmospheres become too cool to display optical He I lines, and if only helium is present, there
the scheme. They worked at night. … As a result, although it took them nine months to do three problems before, we did nine problems in three months, which is nearly ten times as fast.” In the meantime, mathematician John von Neumann (1903–1957)—invariably called “Johnny” by his colleagues—was commuting back and forth between Princeton and Los Alamos, where he also was helping with work on the atomic bomb. According to Rhodes, Lt. Goldstine recalled that sometime in the summer of 1944, “ ‘I was
marked the strongest of these lines with the letters A through H. By mid-century, a number of scientists had recognized that a strong double line in the solar spectrum, which Fraunhofer had labeled “D,” coincided precisely in wavelength with the bright yellow double line in the spectrum of sodium. The obvious conclusion was that sodium is present in the Sun. During the years 1859–1862, physicist Gustav Kirchoff (1824–1887) established three important “laws of radiation”3 that provided a solid
