GLORY OF THE STARS

New Zealand Herald, Volume LXXIV, Issue 22769, 1 July 1937, Page 8

GLORY OF THE STARS

HEAVENS IN JTJLY

DARK NEBULOSITIES

REFLECTION OF STARS* LIGHT

BY CItUX AUSTRALI9

There nre in portions of the sky remarkable starless gaps in the midst of the rich star streams of the Galaxy which have long been objects of beauty and interest to astronomers. It is recorded that the famous Sir "William Herschel, on discovering by chance such a gap in the constellation Scorpio, exclaimed: "Hero is surely a hole.in the heavens! " A similar gap, but on a larger soale, is visible near the famous southern constellation of the Cross, and is popularly known as the Coalsack. It is difficult to decide when astronomers first realised the true nature of these mysterious patches of darkness. Possibly Herschel or Secchi realised the truth, but it was left to Barnard, who is famous for his wonderful photographs of the Galaxy and stellar systems, to announce that these regions were not starless voids, but were caused by large masses of dark matter lying between the earth and the background of the ctars and hiding their light. These regions are now known as dark nebulae, and the great rift in the Galaxy extending from Cygnus to Crux, one-third of the total length of the Galaxy, is a belt of overlapping dark clouds. Star-lit Nebulae A development in the study of dark nebulae occurred in 1912, when Slipher was able to show that bright stars in the neighbourhood of dark nebulae shone on the dark clouds, making them appear faintly luminous, and the spectroscope revealed that the faint light from the nebula was the same as that of the near by star. The best example of this is shown in the Pleiades, the extensive nebulosity of which is illuminated by the seven stars. In 192.':! Hubble showed that every diffuse irregular nebula within the Galaxy was thus lit, and that the amount illuminated depended upon tho brightness of the near by star. A further confirmation could be obtained if it were found that both nebula and star were of the same colour. But colours could be obtained only photographically, and for many years astronomical cameras were not fast enough to photograph these extremely faint nebulae. Newly-found Red Nebula AntareJi, the principal star of Scorpio, is a good object for the purpose of this research, it is a red star in a moving cluster and there is a dark nebulosity near by. Ordinary photographs reveal illumination around two blue stars near by, but only faintly around Antares. Last year, with a remarkably fast camera recently designed, critical photographs in. yellow light revealed the star as the brightest object in the constellation, with a large diamond-shaped nebula more than one degree in length, which cannot be photographed in blue or violet light, while th<2 blue nebulae near by- are much less conspicuous than before. _ Strangely enough, tho new nebula is easily seen in good binoculars provided Antares is hidden behind some convenient obstruction. These researches confirm the conclusion previously arrived at that these great interstellar clouds —dark and light alike—lie at substantially the same distance as the stars in the cluster of Scorpio or a little behind them. Phenomena in July The Sun will be in the constellation Gemini until July 20, when it will pass into Cancer. Its altitude at Auckland increases during the month from 30 degrees to 34J degrees. As the Sun is now entering upon the maximum phase of its l.'l-year cycle of activity, large groups of sunspots can generally be seen upon its surface. The Moon in the course of its monthly circuit of the zodiac will be in conjunction with the various naked-eye planets as follows: —Saturn, Ist, 10.30 p.m.; Venus, sth, 10.30 a.m.; Mars, 18th, 8.30 a.m.; Jupiter, 23rd, 8.30 a.m.; Saturn. 29tli,i 3.30 a.m. Mercury, which Will be in superior conjunction with the Sun on July S, will then enter the evening sky. On the 31st it will be in conjunction with the star Kegulus, being then half a degree north of the star. Venus remains visible 011I3* in the early mornings. Observations of Jupiter Mars remains a prominent object in the evening sky in Libra, but, having passed opposition with the Sun, its distance from us is steadily increasing, making it more difficult to observe satisfactorily in the telescope. Jupiter, in Sagittarius, will be in opposition on July 15, when it will remain visible throughout the night. It is now especially . favourably placed for observation, and even with small telescopes pleasing views can be obtained of . tho cloud belts covering its disc and the movements of its four tiny moons.

The wonderful ringed planet, Saturn, is now becoming better placed for observation, and its ring system is nonwidening out again after the recent opposition, when the rings were placed edgewise to the Earth and therefore were invisible in most telescopes.