Having now reached the limit of discovery with his present instrument, he makes another of still greater power, and points it to the planet Jupiter. On the 7th of January, 1610, he observes three little stars near the body of the planet, all in a straight line and parallel to the ecliptic, two on the east and one on the west of Jupiter. On the next observation he finds that they have changed places, and are all on the west of Jupiter; and the next time he observes them they have changed again. He also discovers that there are four of these little stars revolving round the planet. What is the explanation of this singular phenomenon? They cannot be fixed stars, or planets; they must then be moons. Jupiter is attended with satellites like the earth, but has four instead of one! The importance of this last discovery was of supreme value, for it confirmed the heliocentric theory. Old Kepler is filled with agitations of joy; all the friends of Galileo extol his genius; his fame spreads far and near; he is regarded as the ablest scientific man in Europe. His enemies are now dismayed and perplexed. The principal professor of philosophy at Padua would not even look through the wonderful instrument. Sissi of Florence ridicules the discovery. "As," said he, "there are only seven apertures of the head,--two eyes, two ears, two nostrils, and one mouth,--and as there are only seven days in the week and seven metals, how can there be seven planets?" But science, discarded by the schools, fortunately finds a refuge among princes. Cosimo de' Medici prefers the testimony of his senses to the voice of authority. He observes the new satellites with Galileo at Pisa, makes him a present of one thousand florins, and gives him a mere nominal office,--that of lecturing occasionally to princes, on a salary of one thousand florins for life. He is now the chosen companion of the great, and the admiration of Italy. He has rendered an immense service to astronomy. "His discovery of the satellites of Jupiter," says Herschel, "gave the holding turn to the opinion of mankind respecting the Copernican system, and pointed out a connection between speculative astronomy and practical utility." But this did not complete the catalogue of his discoveries. In 1610 he perceived that Saturn appeared to be triple, and excited the curiosity of astronomers by the publication of his first "Enigma,"--_Altissimam planetam tergeminam observavi_. He could not then perceive the rings; the planet seemed through his telescope to have the form of three concentric O's. Soon after, in examining Venus, he saw her in the form of a crescent: _Cynthioe figuras oemulatur mater amorum_,--"Venus rivals the phases of the moon." At last he discovers the spots upon the sun's disk, and that they all revolve with the sun, and therefore that the sun has a revolution in about twenty-eight days, and may be moving on in a larger circle, with all its attendant planets, around some distant centre.