ASTRONOMICAL NOTES

Evening Star, Issue 21992, 30 March 1935, Page 9

ASTRONOMICAL NOTES

THE SKIES IN APRIL [Written by A. G. C. Crust, M.Sc., for the ‘ Evening Stai;-’j POSITION OF THE STARS Local Sidereal Time. 10b; Latitude, •iGdeg, S. The following star positions hold good locally four minutes earlier each evening, as at midnight on April 3-4, 11 p.m. on April 18, and at 10.24 p.in. on the 27th. After the use of summer time is discontinued the stars must be looked for in these positions at 10.50 p.m. on April 28, and at 10.30 p.m. on May 3. Achernar is now in the S.S.W., at ah altitude of 22deg, while Canopus is B.W. by W., 55deg, and in the W.N.W, Betelgeusq is 14deg above the horizon, Sirius being 26dog higher still, or W.N.W., 40deg. Procyon is N.W., 30deg., Pollux N.W. by N., lOdeg, and due north shines liegulus, 32dcg above the horizon Arcturus his risen and lies N.E. by E, 3deg. while Spica is E.N.E., S6deg, Antares E.S.E., lodeg, and Alpha Centauri S.E., 50deg. 3tie highest bright star is Alpha Crucis, S.E. by S., 65deg. The Moon will pass the planet Saturn on the afternoon of April 1 ,and New Moon occurs at midnight April 3-4. For Mohammedans this is the New Year New Moon, the year 1354 of their «ra beginning on April 5. At midday on the 6th the Moon will pass the planet’ Venus, and first quarter falls on the morning of the 11th, the Moon passing south of the star Pollux at midday. On the evening of the 13th our satellite will be placed N. by W., 32deg, at 11.20 p.m. on the afternoon of tho 14th she will pass liegulus, and at 11 p.m. on the 18th she will be E.N.E., 38deg. Early on the 19th she will pass Spica, full Moon occurring the game forenoon, while on that of the 21st tho Moon will -pass the planet Jupiter. On the afternoon of tho 22nd the Moon will be close to Antares, at 10.40 p.m. on the 23rd she will appear S.B, by E., sdeg, last quarter falls on the afternoon of the 26th, and a second conjunction with Saturn on the morning of tho 29th. The plfi .t Mercury is very close to the Sun, in conjunction with TJranns on the evening of the 25th, and in superior conjunction with the Sun on April 27. The brilliant planet Venus is still in the evening sky, but not visible at our epoch for the positions. She will pass three degrees below the Pleiades on April 15. The bright reddish planet. Mars,, is in the eastern sky at 10b, S.T. He will pass one degree north of the fourth mag. star Theta Virginia on April 4, on the 6th he will be in opposition to the Sun, and on the 24th will be O.Odeg south of the fine binary Gamma Virginia. At lOh, S.T., the position of Mars will change during the month from N.E. by E., 31clcg, to N.E.,35deg. , , . ... - i Tho brightest heavenly body visible l at 10b, S.T., is Jupiter, whoso position changes from B. by 18dcg, to E.,

20deg, during the month. Ho does not pass very near to any bright star this month, but on April 23 Beta Librae (Zubenel Chamali), will be 7.6 deg north of him. Those of our readers who possess small telescopes may be interested in the predictions of his satellites, which we now comhieiice. The epoch of superior conjunction is the time when the satellite is directly beyond Jupiter, and so usually in eclipse. Thus 10 is in superior conjunction lor the first time on April 2, 11.35—i.e., 11.35 a.m. on tho 2nd, and for the seventeenth time on April 30, 18.33 i.e., 0.33 p.m. on the 30tli. To find the mean period for the month divide the difference between the two times quoted by 10. Thus all the epochs of superior conjunction may be located, the period being one-sixteenth of 28: 00: 58, or Id 12h llmin. To find times of inferior conjunction, take the epochs hallway between those of superior conjunction, thus April 3:05:41 is one of these. At inferior conjunction the satellite is in front of Jupiter, and may be seen with rather a large telescope, but at-elongation she will bo as far as possible from the planet, and so most easily visible'. Tho epoch of elongation cast occurs midway • between superior and inferior conjuction, that of elongation west midway between inferior and superior conjunction. Europa perforins eight revolutions ju the month, her first superior conjunction occurring at April 2:08:39, and her ninth on April 30:17:51. Ganymede is in superior conjunction for the first time on April 7:11:41, and for the fourth time on April 28 ;21:43. She reaches her greatest elongation west on Fridays, east on Tuesdays. Calhsto is in superior conjunction twice on April 11:20:07 and 28:10:38. Ail these times are given in summer time. CalJisto is at west elongation on the 7th and 23rd, and at east elongation on April 15. .. From the Queen’s Gardens, Dunedin, at lOhrs S.T., Canopus will appear rather high over High street, Regains moderately low over First Church, Arcturus very low opposite to Canopus, and Spica moderately low over the Early Settlers’ Flail. Mars will be moderately lo w in the same direction as Arcturus, and Jupiter, early in the month, rather low over the seaward end of Rattray street. The Moon, at 11.20 p.m. on the 13th, will shine down Burlington street.

constellations' of the equatorial ZONE SOME SMALL CONSTELLATIONS. In this zone of the heavens there are several constellations which each contain only one star of the fourth magnitude. Readers who are drawing the zone are recommended to insert tlie constellation boundaries in pencil only. Fornax, the Furnace, is represented by Alpha Fornacis, of mag. 4.0 and typo FB, in the square 47,60. It is a close binary, having a companion of mag. 6.9, which is thought to he variable in its brightness. The light from the system takes forty-one years to travel to our eyes, and the colour is white. The brighter star yields 3.8 times the light

of the Sun, the fainter being of one quarter sunpower. The probable ternjieratures are 6,400 deg absolute and 4,ooodeg, and the diameters 1.7 and 1.5 times that of the Sun.

Pyxis Nautica, the Mariner’s Compass, was originally part of the large constellation of Argo, and on some maps bears the name of Mains, the Mast. It is represented by Gamma Pyxidis, of mag. 4.2 and type K2, in the square 132.57, distant 190 light years, and yielding 67 sunpower. It is a yellow giant 43 times as wide as the Sun, with a surface temperature of 3,460 deg. Sextans, tho Sextant, occupies a rather blank space between Leo and Hydra, and its brightest star, 15 Sextautis, just qualifies for a place in the fourth magnitude, being of mag. 4.5 and type AO, in the square 151.30. It is a blue star, 230 light years away, 1.7 times as wide but 74 times as bright as tho Sun, with a temperature of 20,220dcg, Scutum Sohieskii, or Sohieski’s Shield, lying south of Aquila, contains Alpha Scuti, of mag. 4.1 and typo KO, in the square 278.39. Its light takes two centuries to travel to our eyes, its sunpower is 86 and its diameter 47 times that of the Sun, or 41,000,000 miles, with a surface temperature of 3,500d0g. Delphinus, tho Dolphin, an ancient constellation lying east of Aquila, is represented by Alpha Delphini, mag. 3.9 and type 158, a bine star 180 light years away, of sunpower 80, and diameter 2.8 times that of the Sun. The temperature is ll,9oodeg, and the zone in position 309.15. Equuleus, a nearby group, contains Alpha Eqnulei, of mag. 4.1, type FB,A3, in the square 318.26, and distant 37 light years. Its white colour probably results from the combination of the pale yellow of a star of 19 sunpower and temperature s,loodeg, and the blue of a companion of 8.6 sunpower and temperature 9,Boodeg. The diameter of the large star is then 6.6, that of the small one 1.2 times that of the Sun. The name of the constellation means ‘ The Little Florsc.’

Piscis Australis, the Southern Fish, contains the bright star Fomalhaut, but lies mainly in the South Rectangular Zone. In the Equatorial portion is Epsilon P.iscis Australis, of type B 8 and mag 4.2, distant 77 light years according to the Commonwealth Solar Observatory. This 110 sunpower star has a temperature of 13,600 deg, and is 2.9 times as wide as the Sun, its zone position being 339.58.

Of the asterisms mentioned above, only Scutum and Delphinus contain more than one fourth magnitude star. The contracted forms of the names are For., Pyx., Sex., Set., Del., Equ., and Ps A . respecti ve!y.■