Observation of Double Stars
Visual double stars are defined as double stars which are visible in an optical telescope. This is the majority of all known double stars. If visual doubles show similar properties, such as similar proper motion through space, trigonometric parallaxes, or radial velocities, this is evidence that they are gravitationally attached and form a binary system; in this case, the visual double star is called a visual binary.
Observation of visual double stars by visual measurement will yield the separation, or angular distance, between the two component stars in the sky and the position angle. The position angle specifies the direction in which the stars are separated and is defined as the bearing from the brighter component to the fainter, where north is 0°. These measurements are called measures. In the measures of a visual binary, the position angle will change progressively and the separation between the two stars will oscillate between maximum and minimum values. Plotting the measures in the plane will produce an ellipse. This is the apparent orbit, the projection of the orbit of the two stars onto the celestial sphere; the true orbit can be computed from it. Although it is expected that the majority of catalogued visual doubles are visual binaries, orbits have been computed for only a few thousand of the over 100,000 known visual double stars.
Read more about this topic: Double Star
Famous quotes containing the words observation of, observation, double and/or stars:
“The Artist is he who detects and applies the law from observation of the works of Genius, whether of man or Nature. The Artisan is he who merely applies the rules which others have detected.”
—Henry David Thoreau (18171862)
“Men look on knowledge which they learnor might learnfrom others as they do on the most beautiful structures which are not their own: in outward objects, they would rather behold their own hogsty than their neighbors palace; and in mental ones, would prefer one grain of knowledge gained by their own observation to all the wisdom of a thousand Solomons.”
—Sarah Fielding (17101768)
“Because I have work to care about, it is possible that I may be less difficult to get along with than other women when the double chins start to form.”
—Gloria Steinem (b. 1934)
“Young men of the fairest promise, who begin life upon our shores, inflated by the mountain winds, shined upon by all the stars of God, find the earth below not in unison with these,but are hindered from action by the disgust which the principles on which business is managed inspire, and turn drudges, or die of disgust,some of them suicides.”
—Ralph Waldo Emerson (18031882)