ASTRONOMICAL NOTES FOR JUNE.

Lyttelton Times, Volume XCVI, Issue 14386, 31 May 1907, Page 6

ASTRONOMICAL NOTES FOR JUNE.

The- sun comes to its northern solstice on June 23 at 1.58 a.m. The word solstice* translated literally means the fffcatioiiairy point of the sun, and is a term that has been used by astronomers since the primitive days, when the length of a shadow was- measured to determine the progress of the year. At the beginning of June the sun's; daily motion in declination is eight minutes, which makes each day in these latitudes eighty seconds shorter than the previous clay. But the motion becomes slower as the solstice is approached, so that on June 21 it only amounts to forty seconds of arc making a difference of seven seconds of time in the length, of the day. The same may be said of the southward motion after the shortest day. At first tho mm moves very slowly im. declination, but his motion becomes more rapid daily. It is quickest at tho time of the equinoxes, when it amounts to twenty-three minutes of aire, making the length of the day alter three minutes of time daily. On June 6 the earth will be moving directly towards tho planet Mars, so that tihe pLaaiet will appear to be etationaay in right ascension. After that tOi© earth will be overtaking and passing the planet, sso that for some time Mars will appear to move retrograde. All this time he will be moving in declination, at first to the south and afterwards to the north, and his apparent path marked on a map can only be described by comparing it to a rather broad number 6. It must be remembered that o-n stair maps the right hand side is the west. The second magnitude star, Sigma- Sagiterii is in tho upper part of the 6, and the fourth magnitude, Tau Sagitaiii is within ihe enclosed space. Consequently Mars circles round the ' smaller stair, and crosses his own path again on September 22 at the same place which he occupies on June 13. On April 28 Mare was l at the top of the 6. Ho was then in conjunction with Sigma Sagitarii and 2deg 29. min north of it. On July 15 his retrograde motion again brings him into conjunction with this star, but he is then at the bottom of the 6 and passes 2deg 9min south of the star. The third conjunction is on September 2, when, he is at the top of the enclosed space, and is tilieu. onlj- 1 deg 11 min south of the star. Retrograde motions such as these are seen at the opposition of amy planet, but they are most consmcuous in tho case of Mars, because the proper motion of Mara is faster than that of any other exterior planet, eo that it takes longer for the earth to overtake him. The retrograde motion is fastest at the time of the opposition, when Mais and the earth are alongside one aaiother and moving in nearly the same direction.

Jupiter will Boon be in. conjunction, with tii© sun, and, consequently, _he sets soon after the sun. The Nautical Almanac does not give the phenomena. of the satellites from June 17 to August 14, because during that time the planet is too near the sun for the satellites to bo seen. On June 12 their© _is a very close conjunction of Jupiter with *t!ho moon. In till© south of New Zealand the planet will be occulted by the moon, but at Christchurch there will be a space of about two minutes between, them. The time of nearest approach is 6.17 p.m., and the moon gets three minutes later. On the evening of June 16 Jupiter and Mercury will be in conjunction, Mercury being ldeg 41min north. Mercury may also be gieen on June 11 in close conjunction with the star Epsilon Geminorunn The least distance between them is about twenty : seconds, but they will set before they are as close together as this. Mercury is at his greatest eastern elongation on June 27, when his sotting will be delayed until 6.32 p.m., the sun having set at 4.29 p.m. Venus and Saturn are both visible in the morning, rising about two hours before the sun. On June 26 the moon will be full, and will also be almost at her nearest to the earth and at her farthest south. These three favourable circumstances combine to produce an exceptionally brilliant moonlight night. When the moon is at her nearest to the earth—that is, in perigee—her diameter is greater than when in. apogee in the ratio of eight to seven. The. apparent surface is therefore increased in the ratio of sixty-four to forty-nine. Being' in declination 21 south, her altitude above the horizon is considerable, so that the apparent diameter is " augmented." Consequently some full moons give quite a quarter more light than others.

Tie long dark evenings at the beginning of June are very favourable for the observation of star-clusters and nebulas. On© of the richest portions of the Milky Way is that between Scorpio and Sagittarius, a position which is easily recognised at present as just above the planet Mars, and here any small telescope shows numbers of dene© clusters of stars: The Southern Cross is at, its greatest altitude between 8 and 9 p.m. About half a degree east of the farthest east of the four bright stars a email fifth-magnitude star is visible. Hero tho telescope shows a beautiful cluster of coloured stars, sometimes called the Jewel Cluster, owing to Hers dial having compared its colours to “a superb piece of fancy jewellery.There are eight fairly bright stars, of which two are blue, two red, three green, and one white, and there are more than a hundred fainter ones, some of which seem to ho coloured also. Alpha Crucis, the first-magni-tude star in the Cross, is a triple star consisting of two yellow eacond-magni-tude stars five seconds apart, and a blue sixth-magnitude star about Imin south. Tlie following occultation© of stars by tho moon are calculated for Christchurch :

ReJune. oppearanoe. appearance. 6 33 Ceti . . . 6 22 a.in. invisible. 24 B.A.C. 5579 . . 7.17 p.m. 7.49 p.m. £6 BA.C. 6093 . . 3.2S a.m. -t.27 a.m. £6 33 S fritarii . 8-13 p.m. 9.36 p.m. 26 X.I. Fagiiarii . . 10. 4 p.m. 10.43 p.m. 27 Pi Sagitsrii . . 1. 3 a.m. 4.53 a.m. 24 B.D. 17, 6218 . 2.23 a.m. 3.25 a.m. 30 15 Aquarii . 5. C a.m. 6.14 a.m.