An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

300 VIXE:l)D S1TA1S.
Icershel,.'T'he grleat: llssia astronomer, Stl.ruve, by a comparisonl of the best observGations, finds the exact point toward
-which the solar system is moving is in a line wich joins the
two stars lC anid pt Iterculis,'- -..a 1)poinlt whlich can be easily found
oni tlhe celestial globe, and fllence transferred. to the heavens.
(.tig'ht Rascunsion'2590, declination 3441~.) Thle researchels of
tle younger Stlruve haveY conducted him to the veloeity witht
wthltichl the solar system is moving in space. Iorl havinlg founll
tllat thie are traversed by the sun in a )year is 0".3392, if viewe(t
at the mean distance of the stars of the first magnitudeC, andt
halving previously ascertained that the mean parallax of the
stars of this class Allloults to 0".209, lie infers tlhat the space
throtiugt which tle sutl moves annually is 1t5,:,000,000 ltiles.
Grcata as thlitis space is, yet it malay be remarked that it is only
ab)oult onc-urth tlat traversed by the earthI in its revolhition
around thle sun. Within tlhe comparatively short perio
during whiclt tlhese observ<ations on tthe solar motion have lbeen
continued, the directiont ap)pears rcetilinear; b1)ut all analogy
leads to the belief that it is in fact a motion of revolution, altlhough on account of the immenllse size of tlhe orbit, and, consequently, its small curvature many lll years will be requisite in
ordler to determine the deviation friom tlte line of the tanlgent.''
43:,,. When -we reflect on tlhe immense distance of the:stars, w\e may readily believe that they may be in fact int rpid.
motion, and yet lappelar qulliescont; as a distant ship, tunder full
sail, al)pears at rest, although actually 1moving at thlCe ato of
tell knots an hIour. lThus \e hlave see above that a motion of
the sun in space, as seen fiom the nearest fixed stars, would
make it describe an are of only about one-tlirdl of a second
anltnually, althoughl travelsing a space of 15.t milliols of miles.
lBut a small chan gee in tlle place of a star in a single year tmay,
in a long series of years, accumulate to a very sensible amomnt.
FIor example, tlhe latitudes of the three briglht sta3rs, Sirius,.Arcturus, and Aldeblaran, were determinedt by'[iipparch us 130
years before the Christian era, andl thleir assigneld places are
transmlitte d to us in the Almnagest of ]Ptolemy. About the
yea r 1.7[00, Dr. IlHalley found that these stars had, (luring thoe
* t~tudels d'Astron. Stelltire, p. 108. f Grant's list. Phys. Ast., p. 657.