In some cases a pair or small group of stars failed to get clear of one another's gravitational attractions and remain describing orbits about one another as wide binaries or multiple stars.
Spectroscopic binaries form one of the special fields of research with this powerful instrument, and many new binaries have already been detected.
For the spectroscopic binaries the masses are much greater.
Spectroscopic binaries have relatively short periods, one of the shortest known being only 35 hours in length.
The history of the spectroscopic binaries is one of the most interesting chapters in astronomy, and affords a marvelous confirmation of the prediction of Bessel who first wrote of "the astronomy of the invisible.
Unlike the visual binary systems whose periods are years in length, the spectroscopic binaries have short periods, reckoned in some cases in days, or hours even.
The catalogue of spectroscopic binaries is constantly enlarging; but thousands doubtless exist that can never be discovered by this method, as is evident if their orbits are perpendicular to the line of sight or nearly so.
Most of the spectroscopic binaries appear to be upon a smaller scale than the telescopic ones.
In observations of spectroscopic binaries we do not always get a double spectrum.
In the case of some of these binaries the parallax has been measured, from which it appears that in four of the surest cases the orbits are about the size of the orbit of Uranus, these being probably among the smallest stellar orbits.
Great numbers of binaries of this type have since then been discovered, all of short period.
Among the extremely hot and brilliant helium and hydrogen stars, spectroscopic binaries exist in great numbers.
The telescopic binaries which have been observed for a sufficient time to determine their orbits, range from periods of about eleven years as a minimum up to hundreds and even more than a thousand years.
But the spectroscope reveals the fact that the many thousands of telescopic binaries form only a very small part of the binary systems in existence.
This was, accordingly, one of the chief criteria employed by Struve to distinguish true binariesfrom merely optical couples.
In general, the most recent measurements obtainable in 1900 are given in the text, but the observer who wishes to study close and rapid binaries will do well to revise his information about them as frequently as possible.
The assemblage of close binaries in this neighborhood is very curious.
Similarly, the eccentricities of the orbits of the binaries increase as we proceed in the same direction.
Spectroscopic binaries agree with ordinary double stars in having masses rather greater than that of the sun, but there is as yet no assured case of a mass ten times as great as that of the sun.
It must not be supposed that all variable stars are binaries which eclipse each other.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "binaries" in a variety of sentences. We hope that you will now be able to make sentences using this word.
