CONJUNCTION. In astronomy, one of the aspects (q.v.) of the planets. Two heavenly bodies are in conjunction when they have the same longitude—that is, when the same per pendienlar to the ecliptic passes through both. If they have, at the same time, the same latitude —that is, if they are both equally far north or south of the eeliptic—they appear from the earth to be in the same spot of the heavens, and to cover one another. This phenomenon is called an eclipse in the ease of the sun and moon, and In occultation in the ease of the moon and a star. The sun and moon are in conjunction at the period of new moon. In the ease of inferior planets. like Mercury and Venus, which revolve in orbits interior to that of the earth, there is an inferior conjunction when the planet is between the earth and the sun, and a superior when the sun is between the earth and the planet. In general, a heavenly body is in con junction with the sun when it is on the same side of the earth and in a line with the sun; and it is in opposition to the sun when it is on the opposite side of the earth, the earth being in a line between it and the sun. Planets are invisible
when in conjunction with the sun, except in rare cases when an inferior planet passes over the sun's disk, and may be seen as a speck on its surface. The foregoing has reference to geocen tric conjunctions, or such as are soon from the earth. Helioerntrie conjunctions are analogous planetary arrangements, such as could be seen by a supposed observer on the sun. In observing a conjunction, eclipse, or occultation. front the earth's surface, it is usual to reduce the observa tion to what it would be if made from the earth's centre. By this means, the exact times of con junction are more accurately fixed, and the observations of one astronomer made available to every other, wherever he may be on the earth's surface. Orem/. conjuuctions, in astrology, are those where several stars or planets are found together. Chinese history records one in the reign of the Emperor Tehuenhiu (B.C. 2514-2436), which astronomers calculate to have actually taken place.