File:The American Museum journal (c1900-(1918)) (17537932714).jpg

Title: The American Museum journal
Identifier: americanmuseumjo15amer (find matches)
Year: c1900-(1918) (c190s)
Authors: American Museum of Natural History
Subjects: Natural history
Publisher: New York : American Museum of Natural History
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

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THE PHOTOGRAPH IN ASTRONOMY 213 detail from which it could be deduced, until photographs of its spectrum made at Flagstaff in 1910 and 1911 revealed for it a retrograde rotation which it accomplishes in a day of about ten and three-fourths hours. It is from a similar analysis of their light that the motions of stars and nebulse are found. The incandescent condition of these bodies makes it possible to ascertain the identity of the substances of which they consist; and by a com- parison of their spectra with that of our sun, some knowledge is obtained of their state of evolution. Many startling dis- coveries result from these investigations, especially in case of some of the nebulie whose velocities of approach or recession are so great as almost to defy belief, reaching in several instances, one thou- sand kilometers per second. In one case at least, that of the nebula in Virgo, Dr. V. M. Slipher has detected the rotation of this great mass by the inclined lines of its spectrum. Another interesting and unique spectrographic discovery is that the wisplike nebula in the Pleiades in all probability shines by reflected light received from relatively near by stars. This is the only known example of a nebula that shines by any but its own light. Direct photographs of the great Hal- ley's Comet and Comet a 1910 show remarkable structural details and the great length of their tails which stretch from thirty to fifty degrees or more across the sky. The cloudlike streamers in the tails of these comets indicate something of the rapid flow away from the head of the mingled meteoric and gaseous material, and
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Photo by C. O. Lampland Jupiter, August 11, 1913. In order to secure the best Images of a planet photographically, it is advisable, since our air is never at its best for long, to make many exposures consecutively, moving the plate first laterally and then up and down. We thus get a chance at a good photograph and further- more one photograph corroborates another

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