OBSERVATIONS OF EROS

Nelson Evening Mail, Volume LXIV, 14 January 1931, Page 10

OBSERVATIONS OF EROS

WORK AT OBSERVATORY The planet Eros, which was discovered in 1898 by G. Witt in Berlin, is oile of thousands of small planets revolving around the sun between (be orbits of Mars and Jupiter. These bodies are generally known under the name of minor planets. The fact that Eros has an orbit with a high eccentricity, which causes it at times to approach closely to the earth, led astronomers in 1900-1901 lo observe the __ opposition with very great care. F rom the material they then obtained, it was found that the distance of the earth from the sun was something like 92,875,000 miles. This value is of extreme importance in astronomy, and is often spoken of as the astronomer’s measuring unit because the of ail distances and sizes in tbe Solar System depend on tbe correct value cf the distance between the earth *od the sun. During the first three months of 1931, Eros is making an even closer approach to tlie earth than in 1900. It will be closest on 30th January, when its distance will be only 16 million miles. This is far closer than Mars approached the earth in 1924, and it will surprise many to learn that although this body is so close it will not be visible to the naked eye. Small telescopes, however, should render it easily visible. The present time, therefore, is an excellent opportunity for astronomers to revise their “measuring unit by observing Eros. In fact, a world-wide attack is being made on Hie problem. Altogether, 64 observatories, scattered in all quarters of the globe, will be taking as many photographs as, possible in order to determine with extreme accuracy tbe exact place of Eros among the stars. Of these 64 observatories, 50 are situated in the Northern Hemisphere and 14 in the Southern Hemisphere. Among the latter tho Dominion Observatory at Kelburn is co-oper-ating with the observatories at Cordoba and La Plata, in South America. For this work the nine-inch photovisual refracting telescope at the Wellington City Observatory is being used reports “The Post.” A camera has replaced the usual eye-piece on the telescope and many minor adjustments have been made in order to make it useful as a photographic telescope. Preliminary , work was commenced last Thursday night under the direction of the Dominion Astronomer, Dr. C. E. Adams. Several plates were exposed to determine the best focus of the lens, and also to find the correct exposure time for stars of faint magnitude. The time of exposure for photographs of Eros will have to be very short on account of the rapid motion of tho planet. Perhaps three minutes will be sufficient to obtain clear images of the comparison stars. At present Eros is rising very late at night—about 11.30—and it is necessary to wait until about 2 or 3 o’clock in the morning before a photograph can be taken.

Another interesting tiling about this planet is that the light coming from it is found to undergo variations. The period from maximum to maximum in light intensity is about two and a half hours, and astronomers think that possibly this is due to Eros not being quite spherical. This is quite probable •since it is considered to be not more than 15 miles in diameter. A study of this light variation is to be made in New Zealand by amateur astronomers under the direction of the Variable Star Section of the New Zealand Astronomical Society. The combined results of the work to be done in New Zealand should be of great value to the Northern Hemisphere astronomers.