Sirius: the Brightest Diamond in the Night Sky



Sky & Telescope December 2007



Dog-Star Science


Many Bad Jokes and puns came to mind as I prepared to peruse Sirius: Brightest Diamond in the Night Sky.  The author, Jay Holberg, has probably heard them all, given that he has spend much of the past 20 years studying the Dog Star and its nearby Pup.  Fortunately, Holberg has turned all that experience in a tale that's a pleasure to read.

            The book opens with an in-depth discussion of Egyptian, Greek and Roman mythology surrounding Sirius.  Part 2 ("The Nature of Stars" starts with this comment: "The long intellectual journey from viewing Sirius and other stars as the heavenly counter part of myth and superstition, to the realization that the stars are actual material objects governed by physical laws, spanned nearly 25 centuries."

            "AhA!" I thought.  That's how the author turned musing on one object - Sirius - into a 265-page book: by expanding the topic's boundaries.  For instance, this second part includes the discovery of planetary motion, the misconception of "fixed" stars, stellar parallax, and Newton's laws of gravitation.

            Holberg, isn't contend to merely summarize how astronomers determined that the pup (Sirius B) is a white dwarf.  Instead, Part 3, "The Physics of Stars", opens with an account of the first visual observation of the Pup in 1862 and then traces a century of work by astronomers, physicists, chemists and mathematicians that eventually leads to an understanding of stars in general, and white dwarfs in particular.  All the while the story of Sirius, and the prominent part it played in these discoveries, is woven throughout the narrative.

            From ancient mythology through centuries of science the book explores long-standing controversies (including the alleged connection between Sirius and the Dogon tribe) and closes with modern research.  In between is a well-written tale that’s ostensibly about the brightest star in the nighttime sky but which is actually a marvelous dissertation that reveals how science advances.


Contributing editor Paul Deans took this review seriously and kept the jokes to himself.




Journal for the History of Astronomy - August 2007 (Vol. 38 p386)




The story of Sirius epitomizes much of astronomical history.  As such, Sirius is the only star (well, other than our Sun) that can support a whole book.  The first book in Sirius (by Holberg) is a history book, not an astrophysical treatise.  Many fun stories are told, the writing is engaging, and the historical analyses are insightful, I especially appreciate the in-depth and original research.

            Holberg tells this story of Sirius as a connected whole.  We have the astrometry reported in the Almagest, followed by its use by Halley to deduce the proper motion of the star.  Then, small variations on this motion led to the discovery by Bessel that Sirius was orbited by a dark star.  This companion was discovered in 1862 by the Clarks trying out a new lens, with rapid confirmation by Bond and Struve.  Adams, Russell, and Eddington were all involved in the realization that Sirius B is not a normal star, but what we now call a white dwarf that has very low luminosity and very high density.   Fowler and Chandrasekhar took this result and explained it with the new quantum and relativistic physics, despite Eddington's famously disputing the mass limit for white dwarfs.  This situation was turned around with Adam's spectroscopic measures of Sirius B that confirmed Einstein's prediction of gravitational redshift from General Relativity.    The situation was turned around again with spacecraft observations that use the modern physics to derive incredibly accurate properties for the Pup Star, for example with the Hubble Space Telescope's returning an orbit that gives a mass of 1.00 ± 0.01 solar mass.

            This basic story from Ptolemy to HST is further extended both to ancient times and into the future.  Holberg starts the book with how the early Egyptians worshipped Sirius and used it as the basis for their calendar.  He also covers the legendary Sirius in Greco-Roman society as well as briefly in other cultures around the world.  Holberg also extends the history of Sirius into the future, where he describes the certain and inevitable history of the system until its ultimate demise as a wide binary star composed of two 'cold' white dwarfs.  So the book covers from 2276 B.C. until A.D. 10,000,0002,000.

            Sirius has spawned several 'mysteries', including why Ptolemy called it 'red', why the Dogon tribe in Africa is reported to know about Sirius B, whether there is a third star in the Sirius system, and why a New Age cult committed mass 'suicide' to travel to Sirius.  I am impressed with the way Holberg handles these topics.  For example, the treatment of the Dogon traditions is different from all other treatment that I have seen in that he looks closely at the primary data.  Thus, Holberg has extensive interviews with two anthropologists who where there at the time and place that the lore was collected, he airs a debate on the original lore collector hidden from us in the anthropological literature, he quashes the idea that Benjamin Bannekar had Dogon heritage, tells of his own relevant experience in remotest Africa, and refutes various astrophysics points claimed to be in the Dogon tradition.

            Jay Holberg is a classical stellar astrophysicist based at the University of Arizona.  He specializes in white dwarfs as viewed from ground-based and space-based telescopes (including HST, EUVE, Voyager, IUE, and FUSE).  Sirius is a focal point of his astrophysics.  His intimate knowledge is apparent in the last two chapters, devoted to the history of modern space observations of Sirius and to the future history of the star system.  For three decades, I have been following the unfolding story of Sirius, and I see his account as a good history (with perspective balance and details).

            The book has no foot notes, but instead has an extensive list of 280 references separated by chapter in the back.  I count 150 of these are primary source material, often from private letters, musty archives, or unpublished papers.

            This book is for historians, with the broad insights supported by original source material.  The book is also for teachers who might base an entire astronomy history class around the theme of Sirius from ancient to modern times.  And this book is also for the amateur and professional astronomers who appreciate the good stories skillfully woven together. I think that this book is itself a new gem in our night sky.


Louisiana State University                                                             Bradley E. Schaefer




BBC Sky at Night - July 2007 (#26 p102)




< A full account of the brightest star in the sky



To write a complete book about a single star might sound like a daunting task, but Jay Holberg, a senior research scientist at the lunar and planetary laboratory in Arizona, has done so with success.


            The Brightest Diamond in the Night Sky, Sirius is certainly an exceptional star, at least from our point of view.  At a mere 8.6 lightyears from us it is also one of closest neighbors.  Among the 20 most brilliant stars in our sky, only Alpha Centauri is closer.  Every nation has legends about it and in historic times it was important to the Egyptians because its times of rising with Sun could be used to predict the annual flooding of the Nile, which was vital to the whole economy of their civilization.


            There are several mysteries associated with Sirius.  For example, why did some ancient stargazers call it red?  Much more recently it has been linked with strange and pseudo-religious cults, one of which ended in tragedy.  And there is of course the Companion, the nearest white dwarf star and certainly the most famous.  Less than a century ago, the nature of this star was a complete puzzle even to the world's leading astronomers.


            Jay Holberg deals with all of these topics, not forgetting to give an excellent description of the history and future of the Sirius sytem.  The book is meticulously researched and isn't marred by a few tiny and unimportant historical slips.  It's a fascinating read and will appeal equally to the newcomer to astronomy and the serious student.  This is recommended without the slightest hesitation.


*****    Patrick Moore





Southern Stars - June 2007 (Vol.46, no 2, p25)


Review by William Tobin


Jay Holberg has chosen Sirius as the subject of this charming and well-written book which covers both the lore and the physics of the brightest star in the sky.


Though a southern object, at declination - 17° Sirius is well-known in both hemispheres.  Holberg begins with its importance to the Egyptians five millennia ago under the name Sophet.   Its heliacal rising (the first visibility in the dawn sky as Sirius escapes westwards from its annual 70-day invisibility in the glare of the Sun) occurred just prior to the flooding of the Nile, so it is not surprising that the Egyptians linked the star with Isis, the goddess of fertility and the fecundity of nature.  The early Greeks were one of many cultures that associated Sirius with dogs and wolves, and for them its heliacal rising announced the sweltering heat or 'dog days' of late summer.   The heliacal rising occurs in cooler weather south of the equator, where we find that the Maori word 'takurua' is synonymous with both Sirius and winter.


Holberg next reviews the rise of heliocentrism and the idea, to quote a charming drawing that he reproduces from the 16th century, that space outside the solar system is "foelicitye garnished with perpetuall shinnge glorious lights innumerable".  Attempts to set up a reference frame for measuring the celestial coordinates of these 'shininge lightes' foundered on Procyon and especially Sirius, which did not have uniform proper motions.  In 1844 the German astronomer Bessel suggested gravitational perturbations by unseen massive companions as the cause, noting perceptively that "light is no real property of mass.  The existence of numberless visible stars can prove nothing against the existence of numberless invisible ones".  This was the "foundation of an Astronomy of the Invisible".  (Johan Mädler, 1867) that was soon to lead to the discovery of Neptune and which is still with us today with black holes, MACHOs and dark matter.   Theoretical analyses by Safford in America and Auwers in Europe (both in their twenties) coincided with the discovery in 1862 of Sirius B by Alvan Clark and his son Alvin Graham Clark in Cambridge, Massachusetts.  The Clarks used their just-completed 18 ½-inch 'object glass', which can be seen today in Chicago's Adler Planetarium.


It was four years later that Otto Struve in Russia realized that the 10-magnitdue brightness differences between Sirius A and Sirius B implied that the latter was of a very different physical constitution.  In a particularly masterful section of his book, Holberg goes on to outline the recognition of the existence of giant and dwarf stars in the first decades of the 20th century, and the realization by Britain's foremost astrophysicist, Arthur Eddington, that Sirius B (and 40 Eridani B) had to be much dwarfer than dwarf.  The snappy term 'white dwarf' coined by the Dutch astronomer Willem Luyten is thus a misnomer.   White dwarfs such as Sirius B are incredibly compact and dense, "made of a material 2000 times denser than platinum", as Eddington put it.   The application of the new theory of quantum mechanics showed that such densities were possible if the atoms were completely ionized.  But when the Indian physicist Subramanyan Chandrasekhar added in special relativity, he obtained the surprising result that increasing mass made a white dwarf smaller, with the radius shrinking to zero for a white dwarf of about 1.4 solar masses.  The clash with Eddington, who refused to accept the reality of the 'Chandrasekhar limit' is the stuff of legend; but suffice it to say that this limit was the work cited when Chandrasekhar shared the Nobel Prize in Physics in 1983.


Eddington nevertheless accepted the compact ness of Sirius B should result in a large gravitational redshift in the object's spectrum - and an observational test of general relativity - but it was only in 1971 that a convincing measurement was finally obtained by the Americans Greenstein, Oke and Shipman, It is now recognized that the gravitational redshift is not so much a test of general relativity as of the more primitive concept of the equivalence between gravitational and inertial mass.


Taking a different tact, Holberg moves on to some mysteries associated with Sirius such as the redness claimed by Ptolemy and its binary nature supposedly known to the Dogon tribe in West Africa.  (To your reviewer, information from missionaries and linguistic misunderstanding seem the almost-certain explanation of the Dogon story.)  In the 1990s the Sirius-inspired Order of the Solar Temple scam-cum-sect culminated in 174 deaths in Canada and Europe.


In the final chapters Holberg explains how the uncertainties in the measured physical properties of Sirius A and B have been reduced to the present percent level.  (Much of this work has been done by Holberg himself, who is a researcher at the Lunar and Planetary Laboratory in Tucson.)   Finally the future evolution of the Sirius system is outlined with its ultimate fate as a pair of ever-cooling white dwarfs.


I thoroughly recommend this book as an instructive and entertaining read (Holberg is good at the apposite analogy), and as one that discusses the early 20th-century advances in astrophysics, which are often ignored in popular books, but underlie our modern understanding of stars.


6 rue Saint Louis, 56000 Vannes, France 

Southern Arizona Authors

The Arizona Daily Star - Aug. 2, 2007

By J. C. Martin


Jay Holberg, senior research scientist as the University of Arizona's Lunar and Planetary Laboratory, has spent the last 20 years making room in his life for a white dwarf star known as Sirius, the Dog Star.

            "Sirius: Brightest Diamond in the Night Sky" (Springer/Praxis, $29.95) is a compilation of Holberg's remarkable findings.  His persistent investigation follows the star's saga from its earliest importance in ancient Egypt, through Greece and Rome, to a small remote present-day African tribe in Mali.  Sirius, a scant 8.6 light-years from Earth, becomes visible again in Tucson in time for the Dog Days of August (a Roman concept).  It can be seen in the very early mornings in the south east sky.  It's bright enough to be visible just before sunrise.   By late November, it will be shrinking in the night sky.



Choice Reviews 2007 September   (Choice Magazine)


Sirius, the brightest star in the night sky, has been of human interest at least since early Egyptian priests watched for its heliacal rising as a sign that the Nile would soon flood and fertilize the fields. Holberg, a scientist at the Lunar and Planetary Laboratory at the Univ. of Arizona, Tucson, begins with the ancient mythology and lore of Sirius, the Dog Star, and continues through the history of stellar astronomy using the search for understanding Sirius as a guide. He thoroughly explores stories that have turned out to be ill founded, such as that Sirius was red in olden times. A modern cult's unfortunate belief that their group suicide would send them to a blissful existence in the Sirius system did indeed lead to mass suicide and murder. About 160 years ago, a binary partner to Sirius A was predicted from its motion and found to be a dimly seen white dwarf, Sirius B. The last chapters focus on the immense increase in scientific understanding of the Sirius binary system that has been achieved by using spacecraft and orbiting telescopes. Ample bibliography for further investigation. Summing Up: Recommended. General readers; lower-division undergraduates through faculty.

Copyright 2007 American Library Association.





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