The spectra of stars of the tenth magnitude, or fainter, can be photographed well enough to be measured in this way, so that the relative distances of nearly a million stars could be thus determined.
When we consider the attention the photography of stellar spectra is receiving at the present time, in nearly all the great observatories in the world, it may well be regarded as the third great advance in astronomy.
The third great advance in astronomy is in photographing thespectra of the stars.
The remarkable progress made in all spectroscopic research dates from the investigations made by Kirchhoff (1859) on the relation between absorption spectraand the spectra of luminous incandescent gases.
There is no reason for supposing that the spectrum of a compound is equal to the sum of the spectra of its elements--that is, every compound which is not decomposed by heat has its own proper spectrum.
This is especially the case with gases whose spectra are obtained by an electric discharge in tubes.
The construction of spectroscopes destined for special purposes (for example, for investigating the light of stars, or for determining the absorption spectra in microscopic preparations, &c.
In the majority of cases the spectra of compounds are composed of indistinct luminous lines and complete bright bands, whilst metallic elements generally give a few clearly-defined spectral lines.
Their spectra consist of a few bright lines revealing the presence of hydrogen, nitrogen, and other gaseous elements.
Hydrogen does not predominate so much in these as in the Sirian stars, and their spectra resemble closely the solar spectrum, indicating that they are composed of elements similar to those which exist in the Sun.
Their spectra present a banded or columnar appearance, and there is greater absorption, especially of the blue rays of light.
Upon the screen are photographs taken by Mr. Briscoe, a student in the laboratory at South Kensington, of the spectra of some of these fibers at different angles of incidence.
The banded spectra are then visible, and it is the work of a moment to pick out one with the number of bands that has been found to be given by a fiber of the desired size.
In the plano-concave lens the triangular prisms may be considered as placed with their apices towards each other, and so would tend to disperse the coloured rays in the opposite direction, to form spectra at t t.
The memory size is totally inadequate for multiple users because of the large amount of data space needed for the high-resolution spectra now obtainable with Ge(Li) detectors.
The radiation spectra of persons of the same age but different diet habits were compared, and correlation was found between their cesium-137 content and the amount of dairy products they ate.
The two isotopes, however, were separated chemically, and whole body spectra were prepared from samples of the pure elements.
One slit is a little below the other, the rays being reflected to the collimating lens L, by means of two right-angled prisms P, and two spectra are formed, one above the other.
The method that would be first thought of would be to use two spectra, from two sources of light; but should we adopt that plan there would be no guarantee that the spectra would not vary in intensity from time to time.
The point then that had to be aimed at was to form two spectra from the same source of light, and with the same beam that passes through the slit of the collimator.
The problem to solve is how to utilize these two spectra now we have got them.
It should be noted that as the two spectra are formed by the identical quality of light, this same ratio will hold good throughout their length.
Instead of the small slit with a right-angled prism in front to deflect the beam from the top spectrum, where two spectra are produced (see Fig.
Examination of the absorption spectra of coloured compounds shows that certain groupings displace the absorption bands in one direction, and other groupings in the other.
Miller on the spectra of nebulæ where one of the lines of nitrogen was found alone; and that this suggested to them that the line might have been produced by one of the elements of nitrogen; and that nitrogen may therefore be compound.
Miller on spectra of nebulæ with one nitrogen line, 84 Hull, Prof.
Mr. Huggins on spectra of nebulæ with one nitrogen line, 84 Mills, Dr.
For certain purposes the Royal Observatory at Greenwich is in requisition, and there are three observatories at different places in India at which photographs of the sun-spots and solar spectra are taken regularly.
Subsequently Adams, who had thus become familiar with these lines and their variability, studied them extensively in the spectra of other stars.
The publication of the new Henry Draper Catalogue of Stellar Spectra is in progress, a work of vast magnitude.
The first observers of stellar spectra placed the spectroscope beyond the focus of the telescope with which it was used, thereby limiting the examination to but one star at a time.
These stars are somewhat yellowish in tinge like the sun, and from this similarity of spectra they are called "solars.
Attention was first directed toward lines of this character in 1906, when it was inferred that the weakening of some lines in the spectra of sun spots and the strengthening of others was the result of reduced temperature of the spot vapors.
The spectra of all the Algol variables are of the first or Sirian type.
By prolonged and minute comparison of the solar spectrum with spectra of terrestrial elements, something like forty elemental substances are now known to exist in the sun.
Their spectra show a complexity of helium and hydrogen bands.
Vogel has ascertained by a special system of photography in relation to the spectra of stars, that Rigel has a velocity away from the earth of nearly 39 miles per sec.
The fact that the spectra of the nebulae are continuous, revealing no dark lines, seems to indicate the purity of some of the nebulae, and that therefore they are free from all known elements.
Thus high atomicity corresponds to complicated atomic arrangement, and we should expect to find the spectra of bodies of low atomicity much simpler than those of high.
At this temperature it is possible for the more refractory chemical compounds to form, the oxides and the hydrides, and the spectra of sun-spots reveal the presence of titanium oxide and magnesium and calcium hydride.
If then the spectroscopists, without knowing it, have caught the spectra of the hearts of cyclones, we can conceive them to be right, otherwise no.
Should the difference we expect be found, the experiment might be extended by spectra being taken at different degrees of exhaustion, from which some useful information might be derived.
Tacchini devoted his attention to the spectra of the prominences, and showed that their upper portions contained no hydrogen lines, but only the H and K lines of calcium.
Frost also photographed the combined bright-and dark-line spectraof the solar cusps at the instants before and after totality.
In this connection, more accurate results are obtained by measuring the photographs of stellar spectra than by measuring the spectra themselves.
It has been known since the early days of the spectroscope that the major planets exhibit in their spectra bands produced by absorption by the gases of their atmospheres, and that these bands are strongest in the outer planets.
A tube 45 meters long, containing methane at 40 atmospheres pressure, produces bands comparable to those in the spectra of Saturn.
By employing higher dispersion, spectra were secured which permitted the measurement of radial velocity.
Hartmann, in 1904, had observed a similar line in the spectra of Delta Orionis, and suggested that it was absorbed in a cloud of gas somewhere between the sun and the star.
By this process the rotations of planets were determined; and the spectra of the major ones—often reproduced in astronomical works—have been a puzzle to astrophysicists until their interpretation in very recent years.
With the new spectrograph, beautiful spectra were obtained, showing numerous dark lines, of just the character that might have been expected from vast clouds of stars of all spectral types.
Their spectra are continuous and so faint that previous instruments brought out only tantalizing suggestions of dark lines.
Water vapor has been identified in the atmosphere of cool red stars and an analysis of the Martian spectra showed a greater abundance of carbon dioxide than had previously been believed.
Martian infraredspectra and those of D2O-HDO-H2O mixtures and, particularly, of HDO.
May 6 Periodical changes in spectra of sun-spots announced by Lockyer.
Their spectra are quite closely similar to that of sunlight, in being ruled throughout by innumerable fine dark lines; and they share its yellowish tinge.
Fraunhofer's device of using a cylindrical lens for the purpose of giving a second dimension to stellar spectra was adopted by all, and was, indeed, indispensable.
Had simple incandescence by heat been in question, the effect would have been different; the two spectra would have been superposed without prejudice to either.
No sooner had Kirchhoff supplied the key to the hidden meaning of those ciphered characters than it was eagerly turned to the interpretation of the dim scrolls unfolded in the spectra of the stars.
It was replaced by one founded on certain periodical changes on the spectraof sun-spots.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "spectra" in a variety of sentences. We hope that you will now be able to make sentences using this word.
