ASTRONOMICAL NOTES FOR JULY.

Lyttelton Times, Volume CXXIII, Issue 15968, 29 June 1912, Page 10

ASTRONOMICAL NOTES FOR JULY.

Jupiter is still shining brightly. in the cast during the evenings, and hi* satellites can be seen readily with • small telescope or pair of fceld-glassee, The plaiiet is moving retrograde,' will continue to do so all July, but will turn eastward again at the beginning of August. This motion backward and forward will be evident to anyone who notices Jupiter's position with re* ferenco to Antares and Beta Scorpii, for he will move into line between these two stars, and then turn back again. About a week ago the planet passed rather close to the star Omega Uphiu-. elii, which then appeared in the sama field, of view in the telescope. The star is of magnitude 4.7, and is easily visible to the unaided eye an a rule, but at present the brilliancy of the planet overpowers it. The contrast between the telescopic appearance of this star and of Jupiter's moons has been very striking. The star is fully three times as bright as any of the satellites, but yet it is very much, smaller; in fact, the star is a mora point or light, while the satellites look like coarse dots. The satellites really measure various amounts exceeding one second in diameter, and axe of appreciable size when viewed witli a suitable magnifying power, but apparently only the opportunity of comparing them with a star can make 6Uoh small discs obvious. Jupiter will pas? close to this star again in September. There seems to be a good chance of seeing Mercury with the unaided ©ya in the evenings a few days before and after July 25. The planet is at his greatest elongation 27 degrees east of the sun, and at the same time 10 degrees farther south. These two cirouastances combine to retard his time of setting until 7.14 p.m., and at this time of year the skv is quite dark enoughto show up the planet before 6 p.m. The position of Mercury is about a degree south of the star Regulus of magnitude 1.3, and this affords the opportunity of estimating the apparent magnitude of the planet, which a n» bably much brighter than that of the star.

The planet Uranus is in opposition to the sun on July 24, but it is only a famt object of tho sixth magnitude a httle south of the star Omicron Capricorm. It may be mentioned here ttiat Professor Lowell claims to havo discovered the time in which Uranus rotates on its axis, which he states to be 10i hours. Professor Lowell was w i Lngland in May, and communicated this result to the Royal Astronomical Society, at their meeting on May 10, when he also exhibited a number of Ins latest successes in planetary phoAt tho date of writing there is a spot on the sun, not a large one, it is true, but the interest lies in it beinAt there at all. The present time is th« sun spot minimum, and for a considerable time the sun has been almost quit* clear. I am informed that during th« last eight months only two extremely small spots have been seen. The sunspot period from one minimum to another is about eleven years, but if the spots be recorded according to their distribution as well as their numbers, the period is probably thirteen or fourteen years. When a series begins, the first spots appear near heliocentric latitudes 25 or 30 north and south, ana as time passes they draw nearer tm the sun's equator. The maximum occurs about five years after the minimum, when the spots are usually not more than 16 degrees on either side of the sun's equator, and the next minimum comes six years later, when spots are found only about 5 or 6 degrees north and south. But about this time there is a certain amount of overlapping of the periods, for a new series begins in high latitudes before the old one has quite died out near the equator. This is really what is taking place at present. Mr Maunder 6tates that a very small spot was seen last December in latitude 25 north, which is evidently the first arrival of tho new series, but the present spot belongs to the old series, tor according to a photograph obtained here on Juno 21 it is in latitude 7 south.

Professor Bickerton has been studying the spectra of the recent temporary star in Gemini, of which photographs were placed at his disposal by Professor Fowler and the Astronomer-Royal, He has published an interesting explanation of the peculiar and rapid changes of these spectra based on nia own theory of the formation and dispersal of a "third body," But his article has come to hand too late to be described in these notes, and will ba summarised next month. Our fellow-amateurs on the othe* side of the world seem to have had a most enjoyable experience in observing the recent eclipse of the sun. From every station "come enthusiastic reports of cloudless skies and successful work, so that it is a pity that the eclipse was not really total. As explained in these notes for April, it was an annulur eclipse, but the moon s diameter was so large that near the middle of its track the augmentation was just sufficient to produce totality for a fraction of a second. According to the " Nautical Almanac/' this mere instant of totality could be expected between longitudes 14 degrees and 6 degrees west, and a good many observers went to Portugal" to reach this portion of tho central line. But the majoritv of them went to St. Germain and other places within a few miles of Paris, as this part of the track was very easilv reached. Here the eclipse was not total, aild yet it was not exactly annular, for so narrow was the ring of the sun left uncovered that the mountains on the moon's edge cut » up into small beads ail round. M. Flainmarion's description is that tt annulus so slender could only have been complete if the moon were as smooth as a billiprd ball. There were a number of professional astronomers here observing for thoir own amusement and some of them were men of long experience and yet had never witnessed a central eclipse of the sun. A large party of French astronomers, including both amateurs and professionals, "had agreed to photograph the sun from various places north and south of the predicted line of central eclipse, in order to ascertain the exact position of this line. M. Flammariou states that it was onlv about one kilometro (1100yds) north of the line predieted by the Connaissauce des TempsTho American Nautical Almanac laid down the line with greater accuracy than anv European publication. The British 'Nautical Almanac was not among tho prophets, as it did not publish this portion of the shadow-track with fine precision. M. Flammanon also writes that the results will give useful information as to the true value of the moon's diameter, but there dees not seem to be much correction required as far as the British Nautical Almanac is concerned, for it predicted the mere instant of totality in Portugal and the narrow annulus in France exactly as they have been reported. On the contrary the Berliner .Tahrbuch. publisher! in Germany, predicted eight seconds o! totality, which shows considerable room for improvement. In Paris itself the eclipse was only partial, but lesa thsa >

I per cent of the sun remained visible* so llt was a thrilling sight in a Urge, ! crowded city. Few eclipses have passed •within view of millions of observers as itbia one did. Two aeroplanes/and a dirigible were hovering overhead, tryiing to soe the moon's shadow J" 1 *' 16 iliround, and they seem to havp added to enjoyment of the spectators. Ine street lamps were lighted,, but* were found to be quite unnecessary; so brilliant is sunshine that the J6ss of 99 per bent of it did not amount to darkness. In England the weather >vas as clear as in France, and those wha had stayed at kom© saw the partial phase very well, it Greenwich t> per cent of the sun reMined uncovered. >One of the most beautiful photographs published was taken by M. QUemsset at Juvisf. This oliservatory Stbout ten mile* south of Pans, and WW far outside tl's limits of annulanty, but the northw*rd displacement of the JOipon was j ust.sufficient to overlap the tipper limb of the sun. The lower portions of the *late is fogged by the sunIjgK, but tie upper half might belong to ft picture of a real total eclipse, for it lias a dirtinct impression of the inner corona ard one very conspicous promiaen**.