Astrophysics Of The Diffuse Universe

The reference work on astrophysics to provide a comprehensive introduction to the physics of Interstellar Matter. The objective of the book is to show how physics can be applied to the understanding and diagnosis of the phase structure, the physical conditions and the chemical make-up and evolution of the interstellar medium. Unlike other textbooks in the field, here a more systematic approach has been adopted based on the authors' lecture course experience. It is aimed primarily at those undertaking post-graduate courses, or those doing advanced projects as part of honours undergraduate courses in physics or astrophysics.

What if one of the most thrilling stories in the history of science turned out to be wrong? Can urban legends creep into the hallowed grounds of scientific history? As incredible as it may sound, the story of one of the most important elements in modern times – helium - has been often misrepresented in books, encyclopedias, and online sources, despite the fact that archival materials tell a different story. Open the entry for Helium in any encyclopaedia and you will read a false story that has been repeated over the years. ‘Encyclopaedia Britannica’, for example, says that helium was discovered by the French astronomer Pierre Janssen while observing a total solar eclipse from India in 1868. Apparently he noticed something new in the spectrum of the sun, which he thought was the signature of an undiscovered element. The truth is that Janssen never saw any sign of a new element during his observations in India. His reports and letters do not mention any such claim. Other sources would have you believe that helium was jointly discovered by Janssen and Norman Lockyer, a British scientist, and that their discovery letters reached Paris the same day, one sent from India, and the other from England. Again, the truth is completely different. Two letters from Lockyer and Janssen did reach Paris the same day in 1868, but their letters did not mention any new element. What they had discovered was a new way of observing the Sun without a solar eclipse. This would ultimately lead to the discovery of helium, in which Lockyer would play a prominent role, but not Janssen. At the same time, Norman Robert Pogson, a disgruntled British astronomer stationed in India did notice something peculiar during the eclipse. He was the first one to notice something odd about the spectrum of the Sun that day, and his observations would prove crucial to Lockyer’s own investigations of helium. But Pogson’s report was never published in any peer reviewed journal and it languished on the desk of a local British officer in colonial India. This book tells the real story behind the discovery of helium, along with biographical sketches of the scientists and descriptions of the milieu in which they worked. It will convey the excitement, confusion, and passion of nineteenth century scientists, using their own words, from their letters and reports. “The Story of Helium and the Birth of Astrophysics” chronicles one of the most exciting discoveries ever made and explains why it also marked the birth of a new branch of science called ‘astrophysics.’

The study of dust in the universe is an exciting area in current astronomy. Dust formed during an earlier epoch could be different from that formed at a later time, but the nature and composition of dust is not presently understood in its entirety. The comprehensive study presented in this book provides a much needed critical analysis of different types of dust in the universe. The information derived from presolar grains from comets, meteorites and interplanetary dust particles as well as the relevant laboratory studies are discussed. This should help in our goal of understanding the evolution of dust with cosmic time.

Carl Sagan once noted that there is only one generation that gets to see things for the first time. We are in the midst of such a time right now, standing on the threshold of discovery in the young and remarkable field of X-ray astronomy. In The Restless Universe, astronomer Eric Schlegel offers readers an informative survey of this cutting-edge science. Two major space observatories launched in the last few years--NASA's Chandra and the European Newton--are now orbiting the Earth, sending back a gold mine of data on the X-ray universe. Schlegel, who has worked on the Chandra project for seven years, describes the building and launching of this space-based X-ray observatory. But the book goes far beyond the story of Chandra. What Schlegel provides here is the background a nonscientist would need to grasp the present and follow the future of X-ray astronomy. He looks at the relatively brief history of the field, the hardware used to detect X-rays, the satellites--past, present, and future--that have been or will be flown to collect the data, the way astronomers interpret this data, and, perhaps most important, the insights we have already learned as well as speculations about what we may soon discover. And throughout the book, Schlegel conveys the excitement of looking at the universe from the perspective brought by these new observatories and the sharper view they deliver. Drawing on observations obtained from Chandra, Newton, and previous X-ray observatories, The Restless Universe gives a first look at an exciting field which significantly enriches our understanding of the universe.