This month, Jupiter was generally quiet and no significant change was observed. RS was seen as definite elliptical oval with dark core on its center. No dusky feature like arch was seen around it. Its longitude was at II:100.9 deg. (Jan. 27, measured by Miyazaki). Observer who keep on watching Jupiter many years must be filled with deep emotion to find that RS finally reaches beyond II:100 deg., more than 30 years after it crossed the meridian.

SEB generally calmed down, showing weak activity in post-RS disturbance, which extended to II:140 deg., without prominent spots. On the other hand, numerous projections and dark rings were seen on SEBs edge, particularly preceding RS where large ones projected into STrZ. Many of these were rapidly retrograding with SEBs jetstream speed, and if these collide with RS, dark arch would develop along south edge of RS. But interestingly, those not far from RS were almost stationary relative to II, as images taken in January always showed one large dark ring at around II:60 deg., and two smaller ones on its both side. Therefore, retrograding spots may disappear or slow down before reaching RS. This could be the reason why RS was prominent in spite that SEBs was very active.

BA was at II:6.4 deg. (Jan. 24, measured by Miyazaki), and easily seen as prominent oval even through small telescope. It grew longitudinally in second half of January, that is, it became 12.2 deg. in longitude on Jan. 24, nearly three degrees longer than that on Jan. 2, when it had been 9.3 deg. (both measured by Miyazaki). Of the two small white spots following BA in previous month, southerly one in STZ had passed just south of BA in January. Miyazaki pointed out that longitudinal extension of BA might be caused by effect of this passage.

In broadened NEB, white spots and streaks involved by rift activity were seen in some places, though no violent activity such as disturbed white clouds extended from a prominent spot were observed. Northern area of the belt included 4 barges and 5 portholes, which increased by twos each this month.

NTB was substantially invisible in all longitude, and no sign of expected jetstream outbreak was found. NNTB was seen as narrow belt segment in a sector ranging from II:180 deg. to 300 deg., and there was a dark fragment of some 15 deg. long at about II:10 deg. In NNTZ following above fragment, somewhat large prominent white oval was observed at II:35.3 deg. (Jan. 17, measured from Einaga's image).

(2) Saturn

Saturn passed the opposition on Jan. 13. This month, we have received observations listed below. Also, 10 GIF animations, in which rotation of Saturn could be seen, were sent by Yunoki.

This month, Yunoki's images taken on Jan. 9 and 13 showed white spot in SEB at about III:200 deg. Though it was indistinct due to low contrast in single image, his GIF animation presented it moving with Saturn's rotation. Also, he captured disturbed region in SEB between III:75 and 90 deg. on Jan. 28. As faint shadings in SEB could be seen in other images, it seemed to suggest that SEB was active.

The 'opposition effect' of Saturnian ring was reported by Yunoki. The opposition effect is phenomenon found in 19th century that ring become bright near opposition, when shadows of ring particles are obscured by themselves. But it has been suspected to be an illusion for long time. This year, opposition effect was especially emphasized by straight arrangement of Sun-Earth-Saturn, because opposition of this apparition came just after Saturn passed the ascending node. The brightness of the ring was also pointed out by Pellier, and could be seen in other images. To be easily confirmed such a suspected phenomenon might be because of a multiplier effect of excellent opportunity described above and propagation of CCD imaging in recent years.

(February 9, K. Horikawa)

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