“HOLES IN THE SKY”

Evening Star, Issue 18809, 6 December 1924, Page 3

“HOLES IN THE SKY”

MYSTERY OE DARK SPOTS. Some celestial bodies shine by Ibeir own light, as (he sun: others, like our earth, are dark. The conception of vast masses of nun-hnninons material, however, so great as to cut oil the starlight from whole regions of the sky, and In modify the apparent shapes of luminous regions dno fo nebular or star clusters, is comparatively new to astronomy. The existence of dark spots in the heavens, or “holes in the sky,” has been supposed In show the absence of matter in those regions, instead of the presence of a great obscuring mass. In an article on ‘ Occulting Matter in Space,’ contributed to ‘ Popular’ Astronomy,’ Elliott Smith assembles lire evidence for celestial dark matter, and concludes that its existence is now well established, and that it affects the wljoln study of the limiting distance at which stars may be observed from the earth. He writes: “ How much starlight is by non-luminous matter in space! The planets and satellites arc familiar examples of non-lumimms bodies which at limes cut, off' our view. Meteors are other wellknown bodies whose occulting properties should be taken into consideration. Comets, also, should bo considered in Ibis connection. “ It is evident that planets, satellites, and asteroids hud intimately related origins within the solar system. Comets, until recently, were supposed to be of interstellar origin. Whether their origin be. solar or interstellar, the fact that their orbits show, in general, no definite relation one to the other, nor to the plane of the ecliptic, indicafes that their distribution about the sun is spherical. “ That the sun is surrounded by a spherical shell many astronomical units in diameter, in which there is a distnbution of meteoric bodies which have Hie property of cutting off the light which the sun would otherwise radiate into space, seems to be of significance in its relation to occulting matter beyond our solar system. The stars are suns which differ from each other because of their varying physical conditions. The spherical shell of meteoric bodies, corresponding to that which surrounds the solar system, might be of such density in a distant stellar as to decrease effectively the light emanating from it. “It was not recognised until_ recent years that noii-luinmons matter existed in the sky in any conspicuous quantity. In writiim of the dark configurations on his photographs of the Milky Way as late as 1905 Professor Barnard spoke of them as vacancies, ~ “ In 1919 Professor Barnard published a ‘ Catalogue of 182 Dark Markings of the Sky.’ In (he introduction ho says; ‘lt would be unwise to assume that all dark places shown on photographs of the sky are duo to intervening opaque masses between us and the stars. In a considerable number of cases no other conclusion seems pO . S . S j>PQf eS i- or Barnard further emphasises the fact that masses of obscuring matter are found in other parts of the sky than the Milky Way.” . , ' “ The dark areas found in definite outline in such irregular nebulae as the Trifid grp believed to he due to daik mattei which cuts off our view of the nebula beyond. The structural detail of the light 'and dark areas observed in the Orion nebula their sharp boundary lines and distinctive forms, give every indication of the presence of occulting matter in space.