Abstract
ON December 22 at 18h. the sun enters the sign Capricornus (the winter solstice). In the latitude of London, the night then lasts for 16¼ hours. The moon is new on December 10 and full on December 16. Lunar conjunctions with the planets occur as follows: on December 9d. 10h. with Mercury; 13d. 1h. with Venus; 18d. 10h. with Mars; 19d. 8h. with Jupiter; and on 21d. 8h. with Saturn. The geocentric distance between moon and Mercury at conjunction on December 9 is only 0·23°. Mars, Jupiter and Saturn south at about 17½h., 18½h. and 20h. respectively in mid-December and are therefore well placed for observation in the evening sky. Venus is also coming into visibility as an evening star and may be seen low in the south-west after sunset. Mercury is at greatest elongation (21° W.) on December 17, and it may then be seen low down in the south-east before sunrise. In the late evenings of this month, there is a fine array of stars between the eastern horizon and the meridian. The variable star, Algol (β Persei), souths at about 2l½h. in mid-December. Its change of light is most easily noticeable about 1½ hours before and after the following epochs: December 4d. 4·8h.; 7d. l·7h.; 9d. 22·5h.; 12d. 19·3h.; 15d. 16·1h.; 27d. 3·4h. and 30d. 0·2h. To the east of Algol, spread over an area of about 2° in diameter, is a cluster of about five hundred remote stellar systems. A member of another cluster in Gemini, for which a spectrogram was secured at the Mt. Wilson Observatory, shows a redward shift of the spectral lines equivalent to a speed of recession from the solar system of more than 14,000 miles per second and indicating a distance of 135 million light years. The Geminid meteors, with their greatest frequency about December 10–12, have a radiant point a few degrees preceding Castor. At midnight on December 31, the brightest star, Sirius (mag. —1·6), is 4½ min. past the southern meridian.
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The Night Sky in December. Nature 144, 938 (1939). https://doi.org/10.1038/144938c0
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DOI: https://doi.org/10.1038/144938c0