EROS APPROACHES.

Otago Daily Times, Issue 21264, 19 February 1931, Page 16

EROS APPROACHES.

YARDSTICK OF UNIVERSE. A familiar planet will swim into their ken, and astronomers the world over have been eagerly awaiting the near approach of Eros to the earth (says the Sun-News Pictorial). The campaign began in Melbourne some time ago. At the observatory photographs are being taken for determination of our visitor. Eros will serve as the yardstick of the universe! Never before have astronomers had such a fine opportunity of measuring exactly the distance of a planetary body from the earth as Bros will afford them this month. For years they have been preparing for the great event. A minor planet or asteroid, Eros —only at its brightest, of the seventh magnitude—has become vastly important. On January 30 it was within 16,000,000 miles of the earth, a closer approach than any planet has hitherto made since man began his records of the heavens.

Invisible to the naked eye, Eros is revealed in the telescope as a beautiful stellar image, astronomers assure us. Hundreds of telescopes will be sweeping the sky to “ pick up ” the planet. It has been coming nearer every day, and at last is within an astronomical cooee of earth, or about one-third of the distance of Mars when in opposition to the sun. Hundreds of photographs will be taken. An international committee probably will make arrangements for the collation of results from all parts of the world. Australia is well situated for the event, and photographs made by our astronomers will, be compared with those taken at observatories in Europe and North America. Eros, usually more remote from our planet than is Mars, has remarkably large eccentricity. Thus its travels are bringing it so close as to make it earth’s nearest neighbour for a while. During the present month this minor planet’s motion in declination will be very rapid (a Melbourne astronomer states). On January 10 Eros was 19 degrees to _ the north of the celestial equator, which it crossed on January 25. On March 1 it will be 24 degrees south of tho equator. During this period the motion in right ascension ' will be only about 10 degrees. Between January 10 and February 20 the stellar magnitude of Eros is the seventh, so that it can easily be detected hy means of a telescope of two inches aperture. The image of Eros will be so plain on a photograph as to be measurable with accuracy. But it brightness is variable. , , Our system will upset Eros during its near approach; or, in astronomical terms, the asteroid -will “suffer large perturbations.” These will be of service to science; from them astronomers will be able to gain better knowledge of the mass of our own planet, and also of the moon. Eros, the asteroid, is a tiny world witn a diameter of, apparently, only some 30 miles. It was discovered by Witt, of Berlin, in 1898, and became notable owing to the eccentricity of its orbit. But Eros is not the smallest known world. An asteroid discovered in 1918 has a diameter not exceeding four miles, while one measured at Mount Wilson Observatory is only three miles in diameter. Asteroids may be classed as meteoric bodies rather than as minor planets.