. Elements of theoretical and descriptive astronomy, for the use of colleges and academies. our own equator rotates with a velocity of only about 24,000miles a day. 211. Satellites— Jupiter is attended by five satellites ormoons, revolving about it from west to east. Tour are dis-tinguished from each other by the numbers L, II., III., andIV., the first satellite being the nearest to Jupiter. Thesecond satellite is about as large as our moon, and the othersare somewhat larger. They are not usually visible to thenaked eye, though a few instances to the contrary are onrecord. The distance of the
. Elements of theoretical and descriptive astronomy, for the use of colleges and academies. our own equator rotates with a velocity of only about 24,000miles a day. 211. Satellites— Jupiter is attended by five satellites ormoons, revolving about it from west to east. Tour are dis-tinguished from each other by the numbers L, II., III., andIV., the first satellite being the nearest to Jupiter. Thesecond satellite is about as large as our moon, and the othersare somewhat larger. They are not usually visible to thenaked eye, though a few instances to the contrary are onrecord. The distance of the first satellite from Jupiter is 174 SATELLITES OF JUPITER. 270,000 miles, and that of the fourth is 1,200,000 miles. Thefirst revolves about Jupiter in a period of 42 hours, and thefourth in a period of 16d. 17h. [See Note J, page 270.] 212. Phenomena Presented by the Satellites.—The satellites, inthe course of their revolution about their primary, present fourdistinct classes of phenomena, which are shown in Fig. 70. Inthis figure let S be the disc of the sun, and EEEE the orbit is. Fig. 70. of the earth. Let J be Jupiter, and ABD O the orbit of one ofits satellites. Since the planes of all the orbits very nearlycoincide with the plane of the ecliptic, we may consider ABD Oto lie in that plane. Suppose the earth to be at E, and, in orderto simplify the case, suppose it also to remain at that pointduring the short time required by the satellite to revolve aboutJupiter. An eelipse of the satellite will occur when it passes throughthe arc MN} since it is then within the shadow formed by linesdrawn tangent to the disc of the sun and that of Jupiter. It mayreadily be calculated that the length of the shadow, from J to C,is about 55,000,000 miles, so that the shadow extends far beyondthe orbit of the fourth satellite. In extremely rare cases thissatellite, owing to the inclination of its orbit to the ecliptic, mayfail to be eclipsed. An oceultation of the satellite will occur wh
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