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WITH THE PLANETS
by
Geoffrey Gaherty, Jr.

JUPITER: Surface Features, cont. Jupiter was rather inactive during the 1959 apparition and devoid of prominent features. The Red Spot was missing and the Red Spot Hollow was very inconspicuous. The most active region was along the S edge of the NEBs with many projections, bays, and white spots being recorded. There was an extremely dark spot in the NEBn which might be related to the dark marking seen in this latitude last year (May-August 1959 Strolling Astronomer p.63). Of great interest was a small dark spot in the STrZ, joined to the SEBn by a thin grey wisp. Similar objects have heralded major outbursts of activity in the SEB in the past, but this one seemed to change little during the period it was under observation (June 5 - August 14).

Rotation Periods. Only one observer, the writer, contributed transits this year. When the 149 transits observed are plotted on graph paper, 40 of them produce "drifts" for 12 Jovian marks. Because of the small number of observations and the inexperience of the observer, the derived rotation periods should be taken with a grain of salt.

In the table, the columns give respectively: an identifying number; whether the object was dark (D) or bright (W) and whether the preceding (p) or following (f) and, or the centre (c) of the spot was observed; the first and last dates of observation; the longitudes on those dates; the longitude extrapolated to opposition; the number of transits; the drift in 30 days; and the rotation period.

No Mark Limiting Dates Limiting L. L. Transits Drift Period
North Equatorial Current (S edge NEB, N part EZ), System I:
1 Dp Jul. 15 - Jul. 29 101° - 102° 96° 3 2°.6 9 50 34
2 Dc Jul. 15 - Jul. 29 111 - 106 126 3 -9.0 9 50 18
3 Df Jul. 15 - Jul. 29 117 - 112 132 3 -9.4 9 50 17
4 Dp Jul. 22 - Aug. 14 125 - 123 132 3 -2.8 9 50 26
5 Dc Jul. 20 - Aug. 14 132 - 127 141 4 -4.7 9 50 24
6 Df Jul. 20 - Aug. 14 135 - 134 136 4 -0.9 9 50 29
7 Dc Jul. 4 - Aug. 12 159 - 161 158 5 0.6 9 50 31
8 Df Jul. 4 - Jul. 29 169 - 166 174 3 -3.4 9 50 25
9 Wc Jul. 4 - Jul. 29 175 - 173 180 3 -2.8 9 50 26
        Mean Rotation Period (without nos 2, 3): 9h 50m 28s
 
North Tropical Current (N edge NEB, NTrZ), System II:
1 Dp Jul. 17 - Aug. 8 129°-123° 145° 3 -7°.9 9 55 30
2 Dc Jul. 17 - Aug. 8 132 - 127 144 3 -6.0 9 55 32
3 Df Jul. 17 - Aug. 8 136 - 131 150 3 -6.9 9 55 31
        Mean Rotation Period: 9h 55m 31s

Satellite Phenomena. The following table gives the times of satellite phenomena observed during 1959. All times are in U.T. Abbreviations used are: To - observed time (mean of 1st and 2nd contacts); Tc - time predeicted in Nautical Almanac; Tr.c. - Transit commences; E.f. - Eclipse finishes; and Im. - Occultation immersion. In the July 29 observation, To was obtained by adding half the mean interval between contacts to the time of 1st contact.

Date Phenomena 1-Contact 2-Contact To Tc To-Tc Observer
 
July 28 II. Tr.c. 01:56 02:07 02:01.5 02:00 1.5 Gaherty
July 29 III. E.f. 00:49.5 ------- 00:53.0 00:53.7 -0.7 Gaherty
Aug. 2 I. Im. 01:52 01:54 01:53.0 01:59 -6.0 Williamson
Aug. 12 III. Im. 01:05 01:13 01:09.0 01:19 -10.0 Gaherty