UNDISCOVERED WORLDS.

Otago Daily Times, Issue 19965, 6 December 1926, Page 6

UNDISCOVERED WORLDS.

’ SOUGHT BY ASTRONOMERS. BETWEEN MERCURY AND SUN. Is there an undiscovered planet between ; Mercury and the sun? Many astronomers believe there is. Yet it has never been seen. Such a planet, being so close to the sun, would be imperceptible (states J. A. Lloyd, F.R.A.S., in the Daily Mail). Mercury itself is most difficult to see except on rare occasions. Even then we must know where to look. But so sure are some astronomers of the existence of this ! unknown planet that i they have given it - a name. They call it “Vulcan.” There are several ways in which it might be ; discovered. The mathematician, Le Verrier. hoped that a tudy of the movements of Mercury would reveal it. Yet, though ?• he found irregularities in the movements of Mercury which pointed to the disturb- - ing influence of this hypothetical _ planet, he was unabe to lay his hands on it. But a body, revolving between the earth and the sun must sometimes cross the disc of the alter as a dark spit. Mercury and Venus both “transit” in this way, and their times of doing so are known with great accuracy. Le Verrier calculated the probable path of Vulcan and the probable date of its next transit across the sun’s disc. Everyone kept an eye on the sun for the new planet. Nothing, however, J was seen. It is true that clack spots have been observed crossing the sun’s disc on several occasions. Whether one of ' these was Vulcan is not certain. Between the orbits of Mars and Jupiter there is a wide zone occupied by a vast number of minor planets or “asteroids.” ' About 1000 of these little bodies have been found. Since the systematic photographic survey of the heavens by our leading observatories has been in operation, every year has added to the number of asteroids. Yet many more remain to be discovered. Everyone knows that the planet Neptune, which marks the boundary of the solar system as we know it, was discovered by mathematics. Certain irregularities in the movement! of Uranus suggested the existence of an unknown planet influencing it. A careful analysis of these irregularities led to the discovery of Neptune, which was actually found in the exact position in the heavens that the mathematicians had indicated. In the same way irregularities in Neptune’s motion have led many astronomers to suspect the presence of an unknown planet still farthei away. Indeed, there is reason to believe that there are at ’east three undiscovered planets farther off than Neptune.