ROUGH ASTRONOMICAL NOTES

Evening Star, Issue 3827, 31 May 1875, Page 3

ROUGH ASTRONOMICAL NOTES

Jdni, 1875. 1. The Sun. During the month of May but few spots have been visible on the Sun’s face. Those that have been seen have been small, and on many drays no sign of solar disturbance has been visible. On Saturday last there was only one minulJe spot: it was near the centre of the disc. Wo are now entering upon one of the giriods of. “minimum frequency of solar spots,” n the 2* 2nd of the month, at about half-past eight in the morning, the Sun enters Gemini, and winter commences. 2. The Moon will be in Perigee on the 3rd at about 5.! 22 in the afternoon, and in Apogee on •?, at 11.22 in the morning. The phases will take place as follows :

New Moon on the 4th, at 9hrs. 43min. a.m. First ‘jnarter „ 11th, at 7hrs. I7min. a.m. Full Moon „ 19th, at llhrs. 18min. a.m. Last ,, 27th, at 2hrs. Imin, a.m. 0n afternoon of the 19th the Moon will oceulfc -Mars. When the Moon rises the ocoultatio.n will be over, but the planet will be seen very dose to the Moon, above and to the Jett of it. Jupiter will be near the Moon at about i oidmght on the 13th. 3. M ercury will be at his greatest eastern dongaiaon—24deg9min— on the 10th; but he wiU be very far north, and it will not be possible to get a satisfactory telescopic view of him, commanding a good horizon, as . fce too low down. Mercury may be i f . or about three-quarters of an hour after t^ d ** re “ north of the Sun’s track. He ados about an hour and a-quarter after the Venus is still a fine object as seen with the naked eye, but not very interesting to the ?}* people observer. She has now a Well-marked t^ ai l d t to ° J ar from the Earth to afford the least chance of any of her peculiar be bSIP'TK diffi . Cult t0 ™ake out) bil “ TS m the constellation -a.t7.es, about half way between the stars Alnha Ar.et.sand Alpha 6eti. She rises™tft JL**? now la the constellation Sagitro^ adin g towards the wSt. t0 gIVO Actions for finding aim, as he is the most striking obiect in tb« *y. Hi, great bright '“JiS th,.ttS.ffo?S d ( ? ,lor - “f®* “f to altaS S'®lfSJ IO S °, f “ost careless star-gazer. Mare rises at about 6.36 p.m., and is visible all j#LS”*’ P^ Bn ?{f the meridian at about naif-past one in the morning This nUnot °& ct th * «<£Ssf At Kfir eter V n *. nearl y 23 seconds! hereMed l l the “°, nfch breadth wm bavo increased to more than 254 seconds Mara will be m opposition to the l?un on the 20th b6 «“ meridiS at “ d brightness of the planet, howdavs a « nU6 slightly for a few mS. aS ® p P°, Bltlon - because the orbits oi Jm2ftbifto Eartha ? a 0 r ?l ated that a t the nWtfJn ll reß P ec tive orbits at which the then be, the inclination of the path f ftl oward « the path of the Earth wilf for a m °re than counterbalance the invS^ Bbetween 8 between the two planets, which S jSJ ?° m the E& rth’s greater velocity concent dleg Wer ® Celling in similar anfl ffif f °PP oßi tions of Mars take w^bv^^™ 13 oiabeut 2* years, but they The most a the same character. coiusTibl^'"fb 16 oppositions take place of “ ¥ If *?■*•* h’*s least Tf 'if ~ , u ’ anc i Mars is at toe eoceiWcity T very considerable ami tu 01 mars „ lß If • the distance from the&rth to Maw whra the opposition takes place near the !£f latter planet’s aphelion and wTior,+?? 0 * be 61,000 000 mil,, bom |La, £ Sj " " wa* « 36,000.000 iShSSSSj

used). At the present opposition Mars will be at no very great distance from perihelion, while the Barth will be nearly as far from the » Q un as it ever is. The distance between the two bodies will be, roughly, 42,000,003 miles. The next opposition, in li>77, will be with regard to the nearness of Mars to tlin perihelion point much more favorable than the present. The planet’s brilliancy will be very much greater than on the present occasion, and he willhave an apparent diameter of more than thirty seconds; but these advantages will be to some extent counterbalanced, as far as Southern observers are concerned, by his attaining a much lower altitude than ho will at the present opposition. This is amatter of nosmall importance, for Mars, though the most interesting, and, to us, the most “ intelligible ” of all the planets, is by no means easy to observe satisfactorily, and unless he is at a very considerable altitude it is almost impossible to see the details of the features on his surface. In a telescope of about eight inches aperture with a power of 200, Mars now has a cucular figure; the color of the planet is for the most part red, though by no means so ruddy is to the naked eye. The more the magnifying power is increased the less marked does the color become. At one part of the edge of the planet (the south at present) and extending for a short distance on to the disc is a sort of cap cf dazzling whiteness; not a trace of red can be seen in it. . At the opposite part of the disc is another white cap, but much smaller and far less distinct than that at the south. Next to this comes a greenish stripe of varying breadth running across the face of the planet, and forming a sort of border to the white cap. Then, running from_ this stripe right down to the north of the disc is a sort of irregular mark something the shape of a boomerang, the convex part being towards the west, also of a greenish color. Besides this there are many other shorter streaks scattered here and there over the of the planet. All around the edge of the disc, the planet is both brighter and whiter than it is towards the centre. As Mars rotates on his axis in 24h. 37m. 225. he does not always present the same appearance, but what has been given above is a pretty accurate description of the appearance that he presented on Saturday evening last at nine o’clock. It may be interesting to some of our readers whose reading has not lain much in this direction to learn what our leading astronomers make of the appearances described. In the first place, then, the red color of the planet is not owing to its atmosphere, but is the prevailing color of its soil. If the atmosphere were red, they say, then the cap at the south might be bright, but it certainly would be red, too—not as it is, dazzling white, without a tinge of red. The greenish streaks they say are seas ; many reasons might be adduced to show that this is probably the case. There is first the analogy derived from ihe only primary planet with which we are very intimately acquainted the Barth. In the next place these markings appear like what we might imagine our own smaller seas to look like at a distance of 40,000,000 miles, They arevery much darker than the rest of the planet: just what masses of fluid absorbent of the Sun’s rays ought to be. Then the polar caps are white, “ snow-colored,” in fact, and just in the place where snow ought to be; and further these caps increase as the martial winter comes on and decrease at the approach of summer, just as our own polar snows do ; but without large bodies of water, by evaporation from which rain and snow could be produced, it would be difficult to imagine ‘how the supply of snow could be kept up. It is now spring in the southern parts of Mars, and consequently the winter s snows should be only just beginning to melt in the polar region; consequently too we should expect, what indeed we see at the present time, viz., that the southern white polar cap should be very large and very distinct. A»aj n the edges of Mars, where it is sunrise or sunset, are nearly always found to be brighter than the middle of the disc on which the Sun has fully risen, as was the case on Saturday. But this is just as it ought to be if it is ?,s a rule cloudier on Mars in the mornings and evenings than at mid-day, as with us; for clouds would reflect more light back to us than the body of the planet would do. Where could these clouds come from if not from seas on Mars, just as our clouds come from our oceans? Finally, the spectroscope shows most unmistakeably that the atmosphere of Mars contains watery vapor. Where does this water come from, if not from the Martial Seas ? On the whole it is extremely hard for those acquainted with the facts to avoid coming to the conclusion that Mars is a world not unlike our own. The principal differeßCo is tlmt whereas the sea-covered surface of the Earth is much greater than that occupied by land, the seas of Mars are much less extensive than the land. In conclusion, it may be mentioned that one reason why Mars is not easy to observe is that the Martial weather is not of the best. It often happens that the observer, who has been fortunate enough to get first rate observing weather as far as the Earth is concerned, finds that owing to cloudy or foggy weather on Mars a considerable portion of the disc of the planet is hazy and indistinct. This alters the whole appearance of Mars so mach that the observer cannot, so to speak, find his way about at all. This is, of course, another proof of the existence of water on Mars, but one that the observer would sometimes gladly with. A small telescope, say of two or three inches aperture, will sometimes, under very favorable circumstances, show some of the more prominent features of Mars. 6, Jupiter is still a fine object. He is in the constellation Virgo, at no great distance from the star Spica. He passes the meridian at a quarter to nine in the evening. 7. Saturn will soon be favorably situated for observation in the evenings. He rises at about a quarter past ten o’clock, to the S. of East, ana passes the meridian at about a quarter past five in the morning. He is in the constellation Aquarius, but very near the borders of Capricomus, into which he will commence to retrograde very shortly. 8, Uranus is getting toe near the Sun to be well observed. 9. Neptune is a morning star.