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1I a e ote rn i fe u i : g s fh t s oV n sn m at 16 b C als re a d a e 7 9 y h r G e n n Jm s e C o ,h wn te lsi lbak o kso ig h c s a"lc ac do " h n me o (AS rhv) rp p e o n n R aci . e

2I a e f aun y aiSe at2 Jn ay 0 4 3I a e f aun y ak n Ng l t n e1 : g oS tr b D v tw r(4 a u r 2 0 ) : g oS tr b M r a d i Sr g ( m d m eo 7 so ig h bak rp f ca te ln t sa o h wn te lc do ef tsh pa e' h d w e s D cmb r 0 2so ig h bak rp f ca te ee e 2 0 )h wn te lc do ef tsh e jstuh sh e g ote ig ytm. uto ce te d e fh r sse n pa e'sa o jstuh sh C siiis n ln t h d w uto ce te as d io . s n vi

T e"lc do "p e o e o h bak rp h n m n n o sre d r g ln tr t n bevd ui pa eay r n a s s o lh v te a e xl a i cud aeh sm epa t n t na as i r f c se o i s i l ef t e n n o ma e S tr,a ME ae, Se at aunsy B iyD tw r l a d Srn e n M t g. o Recent transits of Mercury (15 November 19 9 9 ) and V enus (8 J une 2004 ) have led to new interest in the origin and ex planation of the famous " black drop" phenomenon (e.g. Schaefer 2001, Schneider, P asachoff and Golub 2004 , Sheehan and W estfall 2004 , and references therein). It appears that the effect is an optical phenomenon produced by convolution of the instrumental point-spread function, including " seeing", with the sharp, dark edge of a planetary disc and a sharply cutoff or limb-darkened background source of illumination. There may also be a minor contribution due to the diffraction of light around the dark edge of the occulting disc. O bservations of the phenomenon (e.g. Green and C ook 17 7 1; see fig-

black drop ex tension in both cases (figures 2 and 3). In fact, many drawings and photographs of Saturn show the phenomenon, which (like the black drop) has often been attributed to atmospheric seeing or to some kind of optical illusion or anomaly. Alex ander (19 6 2) B l oe te l e' a n tsh pa t l ns provides many illustrations of the sao pee ta o a u effect, the earliest ex ample being a h dw rsns n m l s o faue ta ma b a etrsh t y e n drawing by W illiam Herschel in o taiui pi l ls n clo 17 8 0. Similarly, Ball (18 8 6 ) shows the effect in his plate I (drawn in late In principle, the shadow of the summer 18 7 2 by L Trouvelot), notplanet falls either on the edge of the ing (p28 2­ 28 3) that the planet's ring system or on the C assini division black shadow presents a number of eight times every Saturnian orbital anomalous features that to some period. The events occur in two ex tent may be an optical illusion. groups of four close to or around the Flammarion (19 00) even notes that times of widest ring opening. As seen his observations display " an interestfrom Earth, the optical circumstances ing `black drop' appearance...". (a sharp, dark shadow lying almost W e propose that the cause of the tangent to a sharply cut-off back- effect in Saturn is the same as for the g r o u n d s o u r c e ) a r e e s s e n t i a l l y t h e classical black drop seen in the case same as those in the classical black of the transit of V enus. Furthermore, drop. Recent high-q uality amateur because the viewing geometry varies images of Saturn show the same so much more slowly in the case of

ure 1) are difficult to obtain under controlled conditions owing to the infreq uency of planetary transits in front of the Sun, and their relatively short duration. Here, we draw attention to a similar black drop seen in the case of Saturn.

Saturn, future observational studies of the " Saturnian black drop" may yield additional insight into the wider black drop phenomenon.
M E Bailey, Armagh Observatory; D Stewart, I rish Astron omic al Assoc iation ; M Stron ge, East An trim Astron omic al Soc iety. T he au thors than k D Asher, A C hristou , K Doyle, J Mc C on n ell an d T Moseley f or help f u l c ommen ts an d su ggestion s. T his work was su p p orted by the N orthern I relan d Dep artmen t of C u ltu re, Arts an d L eisu re.
R frne eee cs Al a d r F ' 162 The Planet Saturn: e n e A OD 9 x A ioy fbervti ,heoy nd i oHs r oO s a o T r a Ds v t n c eryFaber an Faber,on on ( d Ld) . B l S 86 The Stoy f e H avns a R 18 l r oth e e (asell &C .,on on Cs oLd) . Fa mai C 90 M R S 6 441442 l m r n 10 N A 0 ­ o an p t1. d la e 2 Gre C n C o J 71 hispi l e n a d ok 17 P looh c a Transcos oal Soiy 1 9­21 a ti R y c t 6 374 . n e Sh ee B 2001 Hs Atro.2 cafr E J i.s n 3 t 35­3. 2 36 S ehn ad et l 2004 The Transs hea W n W s a J fl i t fe (r h ,m e t e o ) , . oVnusPometeusA hrs N wYrk Sh e e G,aah f Ma d ou L cn i r P scof d J n G lb 2004 I rus 6 249256. c 18 ­ a

B Ase s ep o ln e p yi e uai G e k h l t pa g o hs s d ct n c o
Af b K a ,o b h l o te t a h n n e af f h B is Ge p yi l soi i , ri t h o h s a A sc t n c ao w nse d ak n h fr cma tfe b c o te ot o h i R v wo Ge p yi E ua n ei f o hs s d cg e c t ni teU , n w ns t t i n h K a d a t ia a o d csi me t gn pi i us n ei iA r. s o n l As part of its role in promoting the awareness of geophysics in schools and colleges, and the teaching, learning and career development of geophysicsts, the British Geophysical Association (a joint association of the RAS and the Geological Society of L ondon) is carrying out a Review of Geophysics Education in the U K and plans to report by the summer of
A&G · February 2005 · Vol. 46

2005. Notices about the Review have already appeared in the O ctober 2004 issues of A& G and G eosc ien tist. In view of the wide range of issues to be covered and the need for the widest possible consultation, the Association will be hosting an open meeting at the Geological Society from 2 p.m. on Friday 22 April 2005 to discuss the preliminary findings and recommendations of the Review. As the Review will guide future policy on geophysics education in the U K , the Association invites anyone with an interest in this subject to attend. It is particularly important to

have good representation from the staff and students from universities that run undergraduate and postgraduate courses; school science teachers; employers from the oil, mining, engineering, water and other industries; commerce; relevant research establishments; and the public sector. Tea will be served from 3.30­ 4 p.m. The discussion will be followed by a wine reception at 5 p.m. It would be helpful if attendees could inform the BGA Education Secretary, Dr C hristine Thomas, U niversity of L iverpool, tine@ liverpool.ac.uk in advance.

H ma sae u n p cfg tei l h rv w i e
T e ASicne ig cmmi h R s o vnn a o s s n t rp r o tecs fr i o e ot n h ae o o saerp r S e o l . p c,e ot u B we s r Following the decision that the U K will provide seedcorn money for the Aurora project, the RAS has formed a commission to gather evidence on the scientific case for humans in space, from the astronomical and geophysics perspective. P rof. Frank C lose will chair the commission, which will produce its report by late 2005, before the U K decision on participation in the nex t level of Aurora.

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