ii6 



KNOWLEDGE & SCIENTIFIC NEWS. 



[May, 1905. 



The Face of the Sky for May. 



By \V. Shackleton, F.R.A.S. 



The Son. — On the ist the Sun rises at 4.36, and sets at 

 7.20 ; on the 31st he rises .at 3.52, and sets at S.3. 



Sunspots and faculjE may be observed on the solar 

 disc on any clear day, whilst spectroscopic observations 

 usually show conspicuous prominences on the limb. For 

 locating the positions of spots, &c., with respect to the 

 Sun's axis, the required data is as follows : — 



OccuLTATioNs. — The following occultations of the 

 brighter stars are visible at Greenwich 



The Planets. — Mercury is a morning star in Aries, 

 and is at greatest westerly elongation of 25" 26' on the 

 2ist, when he rises at 3.26 a.m. 



\'enus is also a morning star in Aries, rising about 

 3 a.m. near the middle of the month. 



Mars is a conspicuous object in the evening sky, look- 

 ing S.E. and rather low down. The planet is now at a 

 favourable point for observation, as he is in opposition to 

 the Sun on the 8th. 



IB90- _ . 



0|. position of Maij \'K)b 



The present opposition is more favourable than that of 

 1903, in that we approach nearer the planet by some 

 9 millions of miles, the apparent diameter of the planet 

 now being 1 7"- 2, as compared with i4"-6 in 1903. The 

 position of the planet in the sky, however, is more 

 unfavourable for these latitudes, since the meridian alti- 

 tude is 17° lower than at the last opposition. .\s will be 

 seen from the appended diagram, the present opposition 

 is not the most favourable since the distance of the planet 

 from the Earth is 50 millions of miles, whilst under the 

 best conditions the distance is only 35 million miles. 



The latitude of the centre of the planet's disc is + 15°. 

 Thus the northern hemisphere is presented to us. The 

 season on Mars corresponds to our .\ugust. On the ist 

 the planet rises at 8.3 p.m. and on the 31st at 5.15 p.m. 



It is interesting to note that the Earth and NIoon as 

 seen from Mars will appear to transit across the Sun's 

 disc on May S, since the planet happens to be near the 

 descending node. The last two transits occurred in 1879 

 and 1800 at the other node. The next will be in 1984. 



According to Mr. Crommelin the diagram below re- 

 presents the transit of the Earth and Moon as seen from 

 Mars, across the Solar disc. 



The beginning and end of the liarlh's transit across 

 the Sun's disc will be 4.10 p.m. on the 8th and 0.52 a.m. 

 on the 9th respecti\ely, hence owing to the absolute 

 symmetry of the illumination of the planet between these 

 times, it will be a favourable opportunity for measuring 

 the diameter and polar compression of Mars. 



Jupiter is invisible, being in conjunction with the Sun 

 on the 4th. 



Saturn is a morning star in y\quarius, rising about 

 2 a.m. near the middle of the inonth. 



Uranus is situated in Sagittarius, and rises about 

 1 1 p.m. on the 15th. 



Neptune appears in proximity to the staryaGeminorum, 

 but it is now getting well to the west, and sets about 

 1 1 p.m. near the middle of the month. 



MiniioRs. — The principal shower during May is the 

 i\quarids. This may be looked for between May 1-6; 

 the radiant being in R.A. 22 h. 32 m. Dec. S. 2°., near 

 the star Aquarii. 



