JUPITER
Will be evening star throughout the month, and continue his retrograde motion from a point about twenty minutes west of Præsepe on the 1st, to 7 hours 48 minutes 35 seconds right ascension on the 29th. He will rise on the 1st at 3:56; on the 15th at 2:53; and on the 29th at 1:52 p. m., and will set on the 2d at 6:30; on the 16th at 5:29; and on March 1st at 4:30 a. m. On the 9th, at 5:39 a. m., he will be 5° 45′ north of the moon. Of the four satellites, or moons, revolving around Jupiter, three are so near as to be eclipsed by him at each revolution. Roemer, a Danish astronomer, observed, however, that when the earth and Jupiter were on opposite sides of the sun, these eclipses occurred, as he estimated, about twenty-two minutes later than the time predicted by the tables. As the earth in this position was some one hundred and eighty-six millions of miles farther away from Jupiter than when Jupiter and the earth were on the same side of the sun, the discovery was made that the discrepancy in time was occasioned by the fact that light must have time to travel; and later and more accurate investigations afford us the truth that it takes light sixteen minutes and forty seconds to cross the earth’s orbit, or eight minutes and twenty seconds to come from the sun to the earth; and hence, that it travels about 180,000 miles per second. These eclipses occur frequently every month, and can be observed with telescopes of quite moderate power.