Elements of AstronomyLongmans, Green and Company, 1880 - 459 páginas |
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Términos y frases comunes
actual angle apparent diameter appears ascertained astronomical axis binary star body brilliancy Cassini Cél celestial sphere centre changes circle circular clock comet cone culmination declination determined direction diurnal motion double stars earth earth's orbit eccentricity ecliptic epoch equal equator equinox fixed stars greatest elongation Greenwich heavens heliometer Herschel horizon inclination interval Jupiter Kepler's known Laplace latitude length Leverrier light Longitude magnitude Mars mass mean distance measured Méc Mém Mercury meridian micrometric miles moon moon's move movement nebulæ nutation object glass observations orbit parallax parallel Paris passes pendulum perihelion period perturbations planet Pole Star position precession proper motions radius rays refraction revolution right ascension rotation round the sun satellite Saturn seen shooting stars sidereal Sirius solar solstice spot Struve subtends sun's suppose surface telescope tion transit of Venus velocity Venus vernal equinox visible zenith distance
Pasajes populares
Página 323 - It would be a vain task to attempt to count the stars in one of these globular clusters. They are not to be reckoned by hundreds ; and on a rough calculation, grounded on the apparent intervals between them at the borders...
Página 324 - ... thousand stars, compacted and wedged together in a round space, whose angular diameter does not exceed eight or ten minutes; that is to say, in an area not more than a tenth part of that covered by the moon.
Página 274 - Mystery,' according to which Euclid's five regular solids do not allow more than six planets round the sun. * * * I am so far from disbelieving the existence of the four circumjovial planets, that I long for a telescope, to anticipate you, if possible, in discovering two round Mars, as the proportion seems to require, six or eight round Saturn, and perhaps one each round Mercury and Venus.
Página 284 - ... that the squares of the periodic times are proportional to the cubes of the mean distances of the planets from the Sun.
Página 338 - Resolvable nebulae, or such as excite a suspicion that they consist of stars, and which any increase of the optical power of the telescope may be expected to resolve into distinct stars; 3d...
Página 273 - Still, for several days the inner moon was a puzzle. It would appear on different sides of the planet in the same night, and at first I thought there were two or three inner moons, since it seemed to me at that time very improbable that a satellite should revolve around its primary in less time than that in which the primary rotates.
Página 273 - I thought there were two or three inner moons, since it seemed to me at that time very improbable that a satellite should revolve around its primary in less time than that in which the primary rotates. To decide this point I watched this moon throughout the nights of August 20 and 21 and saw that there was in fact but one inner moon, which made its revolution around the primary in less than one-third the time of the primary's rotation, a case unique in our solar system.
Página 50 - ... centre of the sphere it cuts the sphere in a circle which is called a great circle. A plane which cuts the sphere, but which does not pass through the centre, has also a circle for the line along which it intersects the sphere ; this is called a small circle. The radius of a great circle is of course equal to the radius of the sphere. The radius of a small circle may be of any length less than the radius of the sphere. We may suppose that a sphere is produced by the revolution of a circle about...
Página 137 - The plane of the ecliptic is inclined to the plane of the equinoctial at an angle of about 23° 27'.
Página 253 - The squares of the periods of revolution of any two planets are in the same ratio as the cubes of their mean distances from the sun.