As early as 1573, Thomas Digges had suggested that this theory should necessitate a parallactic shifting of the stars, and, consequently, if such stellar parallaxes existed, then the Copernican theory would receive additional confirmation.
Now it is necessary to bear in mind that all observed motions are relative; and, especially in dealing with stellar motions, it is arbitrary what shall be considered at rest, and used as a standard to which to refer their movements.
His experiments, in the same year, on the photographic registration of stellar spectra, marked an innovation of a momentous character.
In 1876 he successfully applied photography to the study of the ultra-violet region of stellar spectra.
But, whilst recognizing the existence of local drifts and systems, and admitting the possibility of relative motion between the nearer and more distant, or other classes of stars, it is;only recently that astronomers have seriously doubted the correctness of the hypothesis of random distribution of stellar motions as at least a rough representation of the truth.
When James Bradley and Samuel Molyneux entered this sphere of astronomical research in 1725, there consequently prevailed much uncertainty as to whether stellar parallaxes had been observed or not; and it was with the intention of definitely answering this question that these astronomers erected a large telescope at the house of the latter at Kew.
== be applied to the sun and other stellar bodies.
In 1882 Pritchard commenced a systematic study of stellar photometry.
In the formation of the constellations of the zodiac little regard was paid to stellar configurations.
Various considerations tend to show that this apparent crowding does not imply a really greater density or clustering of the stars in space, but is due to the fact that in these directions we look through a greater depth of stars before coming to the boundary of the stellar system.
If the stellar spectrograph is viewed in the focus of 0 2 and the converging rays are reflected by the prism P2 to P4, no image would be seen in the eyepiece, for the rays would pass out directly through the parallel glass plate which is formed by the cementing together of the prisms P 3 and P 4.
He did much to advance stellar photography and its use in cataloguing the stars, and he was responsible for the geodetic surveys of Natal and Cape Colony, British Bechuanaland, German S.-W.
The average speed is obtained very accurately from solar and stellar observations for the position of the ship. The difference between the speed of the ship and the rate of paying out gives the amount of.
But if it be possible to mount a fixed telescope by which a solar or stellar image can be formed within a laboratory we give the following advantages: - (1) There is no mechanical limit to the length of the telescope; (2) the clockwork and other appliances to move the mirror, which reflects the starlight along the axis, are much lighter and smaller than those required to move a large telescope; (3) the observer remains in a fixed position, and spectroscopes of any weight can be used on piers within the laboratory; and (4) the angular value of any linear distance on a photographic plate can be determined by direct measurement of the distance of the photographic plate from the optical centre of the object-glass.
In 1868 he proved incandescent carbon-vapours to be the main source of cometary light; and on the 23rd of April in the same year applied Doppler's principle to the detection and measurement of stellar velocities in the line of sight.
The moon was the earliest " measurer " both of time and space; but its services can scarcely have been rendered available until stellar " milestones " were established at suitable points along its path.
The small stellar groups characterizing the Arab " mansions of the moon " (manazil alkamar) were more equably distributed than either the Hindu or Chinese series.
In 1886 the widow of Henry Draper, one of the pioneers of stellar spectroscopy, made a liberal provision for carrying on spectroscopic investigations at Harvard College in memory of her husband.
Edward C. Pickering carried on his study of stellar spectra with the funds of the Henry Draper Memorial at Harvard, endowed by his widow (née Mary Anna Palmer) .
When spectroscopes are used for stellar purposes further considerations have to be taken account of in their construction; and these are discussed in a paper by H.
The mirrors of Lindemann's equatorial coude reflecting light downwards upon the mirror R would furnish an ideal siderostat for stellar spectroscopy in conjunction with a fixed horizontal telescope.
The agreement is too close to be dismissed as a mere coincidence, and it is confirmed by a corresponding agreement of their radial motions determined by the spectroscope; and yet, seeing that a and Ursae Majoris are 19° apart, these two stars must be distant from each other at least one-third of the distance of each from the sun; thus the members of this singular group are separated by the ordinary stellar distances, and probably each has neighbours, not belonging to the system, which are closer to it than the other four stars of the group. Further, E.
The determination of stellar parallaxes is a matter of great difficulty on account of the minuteness of the angle to be measured, for in no case does the parallax amount to I"; moreover, there is always an added difficulty in determining an annual change of position, for seasonal instrumental changes are liable to give rise to a spurious effect which will also have an annual period.
A unit of length, which is often used in measuring stellar distances, is the light year or distance that light travels in a year; it is rather less than six billion miles.
But the two theories lead to a very different statistical distribution of the stellar motions.
The application of photography to exact astronomy has created the necessity for new forms of apparatus to measure the relative positions of stellar and planetary images on photographic plates, and the relative positions of lines in photographic spectra.
For accurate measurement of the displacements of lines of stellar spectra which are produced by the relative motion of star and observer in the line of sight, a very beautiful instrument has been devised by Dr J.
Then the lines of the stellar spectrogram would be seen in focus of the eyepiece and the image of the solar spectrograph would be obliterated.
25 shows the stellar and solar lines of the two spectrographs in coincidence, whilst the metallic lines of comparison are non-coincident.
26 shows the metallic lines of comparison in coincidence whilst the solar and stellar lines are non-coincident.
He now resolved to try the experiment of applying photography to the determination of stellar parallax.
He was elected a fellow of the Royal Society in 1840, and in 1892 was awarded one of the royal medals for his work on photometry and stellar parallax.
But this explanation cannot be accepted as it stands, being open to the same objection as Arago's theory of stellar scintillation.'
In determinations of stellar or solar parallax, comparison stars, symmetrically situated with respect to the object whose parallax is sought, should be employed, in which case the instantaneous scale-value may be regarded as an unknown quantity which can be derived in the process of the computation of the results.
Data of this kind, which are by other means inaccessible to the astronomer, are obviously indispensable to any adequate conception of the stellar system as a whole or in its parts.
From Professor Hale's The Study of Stellar Evolution, by permission of the University of Chicago Press.
Of the magnificent Atlas of Representative Stellar Spectra, published in 1899, by Sir William and Lady Huggins conjointly, for which they were adjudged the Actonian prize of the Royal Institution.
Of Atlas of Stellar Spectra, containing a history of the Tulse Hill observatory; Sir W.
Such were the Hindu nakshatras, a word originally signifying stars in general, but appropriated to designate certain small stellar groups marking the divisions of the lunar track.
The Greek signs of the zodiac, including Libra, are obvious upon both these monuments, which have thrown useful light upon the calendar system and method of stellar grouping of the ancient Egyptians.16 Planispheres.
Shrewd sense and considerable knowledge of the world came to the aid of stellar lore in the preparation of "prognostics" which, not unfrequently hitting off the event, earned him as much credit with the vulgar as his cosmical speculations with the learned.
Stellar spectroscopy dates from 1862, when Sir William Huggins (with a small slit-spectroscope attached to an 8-in.
The first determination of a stellar parallax was made by F.
Fraunhofer is especially known for the researches, published in the Denkschriften der Miinchener Akademie for 1814-1815, by which he laid the foundation of solar and stellar chemistry.
For stellar parallaxes see Star; the solar parallax is discussed below.
Examples of this mode of procedure will be found, in the case of stellar parallax in the Mem.
Their presence indicates the characteristic difference between the spark and the arc. The name is due to Sir Norman Lockyer, who has studied these lines and drawn the attention of astronomers to their importance in interpreting stellar spectra.
From Professor Hale's The Study of Stellar Evolution, by permission of the University of Chicago Press.
For details of the coelostat applied to the Snow telescope - the most perfect installation for spectroheliograph and bolometer work yet erected - see The Study of Stellar Evolution by Prof. G.
The divergences depend mainly on the different views taken by their authors as to the order of stellar evolution.
Although the parallaxes hitherto measured have added greatly to our general knowledge of stellar distances and absolute luminosities of stars, a collection of results derived by various observers choosing specially selected stars is not suitable for statistical discussion.
There is another method of determining stellar distances, which is applicable to a few double stars.
Raucous Stellar Jays squawked their encouragement while buzzards circling overhead seemed to keep out a careful eye for fallen bikers.
The method originally used by Huggins, who first conceived and proved the possibility of measuring stellar velocities in the line of sight, was to measure with a filar micrometer the displacement of some well-known line in a stellar spectrum relative to the corresponding line of a terrestrial spectrum.