The opposition of Jupiter, 1955–’56

2024 August 9

Richard McKim

During the previous apparition, there was a weak Revival of the South Equatorial Belt. This was followed during 1955–’56 by the recovery of that belt and a slight slowing of the North Equatorial Current. In 1955 September, shortly after solar conjunction, a new South Tropical Disturbance formed, and during early 1956 this expanded to reach a maximum length of 42°. The Red Spot Hollow (which had formed in 1955 as the South Equatorial Belt revived) was still present, but the Great Red Spot had become faintly visible again. As in the previous apparition, the South Temperate Belt between white ovals BC and DE appeared double, with a lighter central region. The northern Equatorial Zone was very active, while large and conspicuous dark spots were present upon the northern edge of the North Equatorial Belt, two of which displayed unusually rapid drifts for the North Tropical Current. Spots upon the North Temperate Belt and in the North Temperate Zone were again observed to move in North Temperate Current A, while drift rates were also established for features upon the NN and NNN Temperature Belts. Accurate photographic belt latitudes, synthetic photographic maps, and a colour photograph are presented. Rare mutual satellite phenomena, including a triple shadow transit, were observed.

Introduction

Jupiter came to opposition on 1956 Feb 16. At declination +14°, it was lower in the sky than in 1955 from Great Britain but was still well placed. Numerous observations were made under the directorship of Dr A. F. O’D. Alexander, by (from the UK unless otherwise stated): L. B. Abbey (Decatur, Georgia, USA), F. M. Bateson (Rarotonga, Cook Islands), J. D. Bestwick, J. H. Botham & I. R. H. Brickett (with J. R. Jooste; Union Observatory, Johannesburg, South Africa), B. Burrell, W. B. Caunter, E. H. Collinson, S. Cortesi (Lugano, Switzerland), A. C. Curtis, U. Dall’Olmo (with L. Baldinelli; Bologna, Italy), H. E. Dall, Miss M. Davies-Scourfield, G. Fielder (with Z. Kopal & J. Ring at Pic du Midi Observatory, France), V. A. Firsoff, A. R. J. Foulger (and Birmingham Astronomy Group), W. E. Fox (Assistant to the Director), M. Gadsden, M. Guest, W. H. Haas (Las Cruces, NM, USA), A. W. Heath, M. B. B. Heath, A. P. Lenham (Dearborn Observatory, USA), R. M. Lippert (San Diego, CA, USA), R. A. McIntosh (Auckland, New Zealand), E. C. Melville (Kingston, Jamaica, West Indies), D. W. Millar, R. Milligan, P. A. Moore, J. Morley, B. M. Peek, L. Pointon, T. W. Rackham, O. C. Ranck (Milton, Pennsylvania, USA), E. J. Reese (Uniontown, Pennsylvania, USA), J. Hedley Robinson, G. Ruggieri (Mestre, Venice, Italy), C. A. Shain (Sydney Observatory, Australia), J. R. Smith, K. S. G. Stocker, H. Sykes (Taiping, Perak, Malaysia), G. Turner, F. Vaughn (Madison, Wisconsin, USA), A. W. Vince, V. Warburton, B. Warner, H. Welsh (Port Elizabeth, South Africa), and J. E. Westfall (Oakland, CA, USA).

Photographs were taken by Botham (with the Union Observatory’s 9-inch (279-mm) OG; Figure 2), Dall, Dall’Olmo, Fielder et al., Gadsden, Rackham (Figure 2), and Shain. Lenham observed with an 18-inch (46-cm) refractor. Very good series of central meridian (CM) transits were made by Bateson, Botham, Burrell, Dall’Olmo, Fox, Haas, Peek, and Reese, yielding the highest total in a decade.

In addition to these substantial records, observations from W. Löbering (Germany) were used, as well as the Pic du Midi photographs available online.¹ Lauren Amundson (Lowell Observatory) provided scans of numerous original plates taken by E. C. Slipher, from which Johan Warell, Emmanuel Kardasis and the author made enhanced stacked images, a composite colour image (Figure 1), and a whole-planet map (Figure 3). The best professional photographs were measured for latitude by the author.

Brief notes on the phenomena of 1955–’56 and 1956–’57 were published by W. E. Fox (1956, 1957),^2,3 while Alexander (1956) discussed possible correlations between Jovian radio emissions and visible features:⁴ an enduring theme of the 1950s decade.⁵ As with the 1953–’54 and 1954–’55 apparitions, no BAA final report for 1955–’56 has been produced until now, but a table of rotation periods appeared in a Memoir:⁶ though reliable, the latter are superseded by the more comprehensive ones published here. Contemporary reports (from small datasets) were published by the Association of Lunar & Planetary Observers (ALPO),⁷ the Société Astronomique de France (SAF),⁸ Baldinelli & Dall’Olmo,⁹ Antonini & Cortesi,¹⁰ and T. Osawa.¹¹

The 1955–’56 apparition linked all the Directors of our Jupiter Section over nine decades: Welsh used the 8-inch (20-cm) refractor formerly on loan from the RAS to the Rev. T. E. R. Phillips (Director, 1901–’34), while B. M. Peek (Director, 1934–’49) and D. W. Millar (1949–’50) made observations; Dr Alexander (Director, 1950–’57) and W. E. Fox (1957–’89) summarised the Section’s work in print.

Observations covered the period 1955 Sep 19 to 1956 Jul 5. Limiting solar conjunctions occurred on 1955 Aug 4 and 1956 Sep 4. This paper, a sequel to the 1954–’55 report,¹² fills another gap in the record.¹³ The appearance of a new South Tropical Disturbance was the highlight of 1955–’56: Peek’s chance discovery of it one morning in 1955 September marked his return to serious observing.¹⁴

The observations

North Polar Region (NPR)

The NPR, as usual, appeared bland and shaded. It was marked at its S. edge by a darker NNN Temperate Belt, though a N⁴TB was occasionally seen within the polar shading. The NNNTB appeared patchy and discontinuous upon the best photographs and in the map in Figure 3, while Botham (Figure 2C) could photograph at least one of the larger spots. Several NNNTB features moved in the NNN Temperate Current, and drift rates were obtained for two of them. More detail was seen in this region and in the NNTB than in 1954–’55.

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