Book contents
- Frontmatter
- EDITOR'S PREFACE
- PREFACE
- Contents
- LIST OF ILLUSTRATIONS
- CHAPTER I BELIEFS AND SUPERSTITIONS RELATIVE TO COMETS
- CHAPTER II COMETARY ASTRONOMY UP TO THE TIME OF NEWTON
- CHAPTER III THE MOTIONS AND ORBITS OF COMETS
- CHAPTER IV PERIODICAL COMETS
- CHAPTER V PERIODICAL COMETS
- CHAPTER VI THE WORLD OF COMETS AND COMETARY SYSTEMS
- CHAPTER VII PHYSICAL AND CHEMICAL CONSTITUTION OF COMETS
- SECTION I COMETS PHYSICALLY CONSIDERED
- SECTION II COMETARY NUCLEI, TAILS, AND COMÆ
- SECTION III COMETS DEVOID OF NUCLEUS AND TAIL
- SECTION IV DIRECTION OF THE TAILS OF COMETS
- SECTION V NUMBER OF TAILS
- SECTION VI DIFFERENT FORMS OF TAILS
- SECTION VII LENGTH OF TAILS
- SECTION VIII FORMATION AND DEVELOPMENT OF TAILS
- SECTION IX BRILLIANCY OF COMETS
- SECTION X DIMENSIONS OF NUCLEI AND TAILS
- CHAPTER VIII PHYSICAL TRANSFORMATIONS OF COMETS
- CHAPTER IX MASS AND DENSITY OF COMETS
- CHAPTER X THE LIGHT OF COMETS
- CHAPTER XI THEORY OF COMETARY PHENOMENA
- CHAPTER XII COMETS AND SHOOTING STARS
- CHAPTER XIII COMETS AND THE EARTH
- CHAPTER XIV PHYSICAL INFLUENCES OF COMETS
- CHAPTER XV SOME QUESTIONS ABOUT COMETS
- I ELLIPTIC ELEMENTS OF THE RECOGNISED PERIODICAL COMETS OF THE SOLAR SYSTEM
- II GENERAL CATALOGUE OF THE ORBITS OF COMETS
- Plate section
SECTION X - DIMENSIONS OF NUCLEI AND TAILS
Published online by Cambridge University Press: 05 March 2012
- Frontmatter
- EDITOR'S PREFACE
- PREFACE
- Contents
- LIST OF ILLUSTRATIONS
- CHAPTER I BELIEFS AND SUPERSTITIONS RELATIVE TO COMETS
- CHAPTER II COMETARY ASTRONOMY UP TO THE TIME OF NEWTON
- CHAPTER III THE MOTIONS AND ORBITS OF COMETS
- CHAPTER IV PERIODICAL COMETS
- CHAPTER V PERIODICAL COMETS
- CHAPTER VI THE WORLD OF COMETS AND COMETARY SYSTEMS
- CHAPTER VII PHYSICAL AND CHEMICAL CONSTITUTION OF COMETS
- SECTION I COMETS PHYSICALLY CONSIDERED
- SECTION II COMETARY NUCLEI, TAILS, AND COMÆ
- SECTION III COMETS DEVOID OF NUCLEUS AND TAIL
- SECTION IV DIRECTION OF THE TAILS OF COMETS
- SECTION V NUMBER OF TAILS
- SECTION VI DIFFERENT FORMS OF TAILS
- SECTION VII LENGTH OF TAILS
- SECTION VIII FORMATION AND DEVELOPMENT OF TAILS
- SECTION IX BRILLIANCY OF COMETS
- SECTION X DIMENSIONS OF NUCLEI AND TAILS
- CHAPTER VIII PHYSICAL TRANSFORMATIONS OF COMETS
- CHAPTER IX MASS AND DENSITY OF COMETS
- CHAPTER X THE LIGHT OF COMETS
- CHAPTER XI THEORY OF COMETARY PHENOMENA
- CHAPTER XII COMETS AND SHOOTING STARS
- CHAPTER XIII COMETS AND THE EARTH
- CHAPTER XIV PHYSICAL INFLUENCES OF COMETS
- CHAPTER XV SOME QUESTIONS ABOUT COMETS
- I ELLIPTIC ELEMENTS OF THE RECOGNISED PERIODICAL COMETS OF THE SOLAR SYSTEM
- II GENERAL CATALOGUE OF THE ORBITS OF COMETS
- Plate section
Summary
Real dimensions of the nuclei and atmospheres of various comets–Uncertainty of these elements; variations of the nucleus of Lonali's comet–Observations of Hevelius upon the variations of the comet of 1652–Do cometary nebulosities diminish in size when their distance from the sun decreases?–Encke's comet considered in regard to this question at its apparitions in 1828 and 1838.
The observations that we have just recorded give an idea of the brightness of cometary light, and the intensity to which that brightness may attain ; but they afford no certain indication concerning the dimensions of cometary nuclei or atmospheres. Upon this point we are about to give the result of a few measurements ; but these measurements, it must be understood, are not so exact as those of the bodies of the solar system, the planets, the moon, and sun. The uncertainty we speak of does not arise from the difficulties experienced in the determination of the measures themselves, although they contribute to it, cometary nuclei being often as deficient in a clear and well-defined outline as the nebulosities; but what more especially prevents us from regarding the numbers we now give as constant, and therefore characteristic elements of the comets to which they belong, is the continual variation to which the different parts of the head are subject during the time of the comet's apparition.
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- The World of Comets , pp. 238 - 244Publisher: Cambridge University PressPrint publication year: 2010First published in: 1877