Mem. S.A.It. Suppl. Vol. 9, 35c© SAIt 2006

Memorie della

Supplementi

Tacchini and Astrophysics at Catania

C. Blanco

Dipartimento di Fisica e Astronomia dell’Universita di Catania, Italyemailcblanco@ct.astro.it

Abstract. The birth of astrophysics at Catania, as both observational research activity anduniversity teaching, was due to Pietro Tacchini. Matured the idea that by a considerablereduction in the atmospheric absorption it would have been possible trarre vantaggio intutte le ricerche fisiche che riguardano il Sole, la sua atmosfera e gli astri tutti dal nostrosistema alle piu remote stelle e nebulose, at the end of 1800, he proposed and brought toan end the construction of an astronomical observatory in the upper part of Mount Etna.Conscious that the hard travel connections would have made him act only during thesummer, at the same time Tacchini exerted himself to realize a succursale cittadina havingthe dome over the circular antirefectory of the Benedettini Monastery and equipped itwith a telescope analogous to the Etna one, in order to use the same 34-cm aperture Merzobjective. The very good obervational results obtained in this last Station helped Tacchini toobtain the participation of Catania Astrophysical Observatory in the initiative promoted, in1886, by the France Academy to realize the Carte du Ciel, the first photographic Catalogueand Atlas of the entire heaven vault. The undertaking was realized using an astrograph,installed in the garden near the Monastery and having a Steinheil 33-cm aperture objectiveand a Salmoiraghi mounting. Essendosi reso evidente che l’Osservatorio Etneo e quellodi Catania, trovandosi in condizioni eccezionalmente favorevoli agli studi della fisicadegli astri, dovevano essere destinati all’astronomia fisica, piuttosto che all’astronomiadi posizione (Favaro 1923), Tacchini promoted the institution, at Catania University, of anastrophysics chair, unica in Italia.

Key words. Astronomy and astrophysics - atmospheric absorption - observatory building -telescopes - Carte du Ciel

Until a couple of centuries ago the peoplethat attended to heaven bodies, whether theystudied their position and their movementsor estimated their brightness, were namedastronomers and their scientific culture wasprincipally based on mathematics. When thetechnological development and in particularthe coming of spectroscopy, allowed them

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deeper and deeper researches on the physicalcharacteristics of nebulae, stars and planets,astronomy was more and more replaced byastrophysics. The birth, at the end of 1880, ofthe first Astrophysical Observatory in Cataniaand the institution of the first university chairof astrophysics, were a clear example, as itappears from Giorgio Abetti’s lecture duringthe Inaugural session of the CXXXI activityyear of the Gioenia Academy. E interessante

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Fig. 1. The Vincenzo Bellini Observatory built near the Etna central crater at 2941-m a.s.l.. The maintelescope of the new Observatory was a Merz refractor having a 34-cm aperture objective, 5570-mm focallength and an equatorial mounting by Cavignato of Padova, with iron pipe. The dome was ordered fromOretea factory of Palermo.

notare, per quanto proprio qui all’AccademiaGioenia questi fatti sieno ben noti, che lafondazione dell’osservatorio astrofisico e laistituzione della prima cattedra di astrofisicaabbiano avuto origine (as Annibale Ricco saidin the opening lecture Sole, during the solemnInauguration of the 1894 academic year ofCatania University) dalla proposta di Tacchiniin una pubblica riunione solenne di questaAccademia del 1876, di istituire a Cataniaalmeno una stazione astronomica e meteoro-logica sull’Etna. The proposal was consentedto con plauso dall’Accademia, con entusiasmodai catanesi (these are again Ricco’s words).Essendosi reso evidente che l’OsservatorioEtneo e quello di Catania, trovandosi incondizioni eccezionalmente favorevoli aglistudi della fisica degli astri, dovevano es-

sere destinati all’astronomia fisica, piuttostoche all’astronomia di posizione, fu istituitanell’Universita di Catania una cattedra diastrofisica (these are always Ricco’s words)(Abetti et al. 1955), unica in Italia, chiamataper l’art. 69 della legge Casati in seguito aproposta redatta dallo Schiaparelli (Favaro1923).Pietro Tacchini, since 1863 appointed asastronomer to the Palermo AstronomicalObservatory, acquired a noteworthy masteryof astrophysical research, but his observationswere almost completely restricted to the Sunstudy. The observatios of the 1868 total solareclipse had increased his knowledge of theSun physical constitution, mostly thanksto the spectroscopic analysis. L’osservare idetti spettri non e sempre facile cosa ed anzi

Blanco: Tacchini and Astrophysics at Catania 37

Fig. 2. The dome of the sede cittadina built over the circular antirefector of the Benedettini Monastery,rising over a peripheral elevation of Catania town.

avviene che per talune parti dell’atmosferasolare dotate di debole luce, le righe spettralicorrispondenti non si vedano nelle ordinariecondizioni in causa della gran luce diffusao riflessa nella nostra atmosfera (Tacchini

1878). By knowing il clima cosı propizioa queste ricerche come quello di Sicilia ...incoraggiato sempre dai miei colleghi Secchi,Lorenzoni, Serpieri ed altri (Tacchini 1876)matured the idea of building an observatory onthe Etna upper part, to considerably reduce theatmospheric absorption and trarre vantaggioin tutte le ricerche fisiche che riguardanoil Sole, la sua atmosfera e gli astri tuttidal nostro sistema alle piu remote stelle enebulose (Tacchini 1876). These few wordssynthetically sum up Astrophysics basic lines.Secchi, writing to him that sull’Etna il cieloe di una purezza ammirevole, quello di Romasembra, al confronto, sudicio e nebbioso, said

that he was ready to make a survey on thevolcano. Sino dal 18 giugno 1871 fu da meinviato al Ministero della P. Istruzione unrapporto nel quale dopo di avere esposto irisultati avuti in Palermo sulle osservazionidi Sole, dimostravasi che per riuscire comple-tamente era necessario portare gl’istrumentiad una grande elevazione, e percio chiedevai mezzi onde potere salire sull’Etna pereseguirvi osservazioni spettroscopiche epossibilmente anche fotografie solari. Larisposta del Ministro sebbene ripiena di belleparole corrispondeva ad una negativa. Intantoun astronomo americano, il signor Young,concepı piu tardi la stessa idea, e nel lugliodel 1872, cioe un anno dopo egli saliva sulSherman a 2800 metri di quota ... per eseguireuna serie completa di spettrali osservazionisulla cromosfera e sulle macchie del Sole... i brillanti risultati da esso ottenuti, che

38 Blanco: Tacchini and Astrophysics at Catania

Fig. 3. Vincenzo Bellini Observatory surrounded by the 1971 lava flows, few days before its completecoperture. It is possible to note the skylight built to replace the dome when the astrophysical observatorybecame a volcanological one.

Fig. 4. Pietro Tacchini on the Collegio Romanoroof

Fig. 5. Memorial-tablet placed in the entrance ofVincenzo Bellini Observatory that, in addition to theobservational functions, inherited, from Casa degliInglesi the role of mountain refuge.

vennero a confermare le mie previsioni nonsolo, ma anche talune osservazioni da me fatte

Blanco: Tacchini and Astrophysics at Catania 39

Fig. 6. Catania Observatory telescope, equippedwith the same objective and same mounting of theEtnean Observatory, but with a wood pipe.

a Palermo (Tacchini 1876)).

Tacchini, having a thorough knowledgeof the unsuccessful attempt by Gambini(Reina 1839) and Zurria (Rapisardi 1902)to build an observatory in Catania to farstudiare ai loro allievi in via d’osservazionegli astri, reproposed its construction on22 september 1876 during the AccademiaGioenia solemn meeting, called to honour thecatanese musician Vincenzo Bellini, whoseremains were trasported to Catania fromthe parisian Pere Lachaise cemetery to beburied in the Cathedral. In occasione dellefeste di Catania pel trasporto delle ceneridel Bellini essendo stato invitato a leggerequalche mia memoria nella seduta solennetenuta dall’Accademia catanese delle scienze,io pensai che ad onorare la memoria di quelgrande genio, anziche presentare un miomeschino lavoro valeva meglio risollevare laquestione dello impianto di un osservatoriosull’Etna (Tacchini 1876). Tacchini did not

go up the Etna but, beside being a man withenterprise, he had a very careful character equindi prima di leggere all’Accademia stabiliidi salire sul vulcano, affine di verificareanch’io la localita e le condizioni di quelcielo. Al 13 settembre ... in meno di 10 oreeravamo giunti alla Casina degli Inglesi.A Catania lasciammo una temperatura di+28◦ e lassu trovammo quella di -5◦, con unadiminiuzione di pressione di 190 millimetri:il cielo era vario e tendente piu al cattivoche al buono (Tacchini 1876). The quickvariability is a meteorological characteristic ofmount Etna, the sole substantial elevation inthe middle of the Mediterranean sea; infact theatmospheric disturbances, at the Etna latitude,mostly coming from west-northwest, pass veryfast while local condensations, connected toascensional currents of air, depend on dailyatmospheric temperature variations. Il cielosempre vario, e il vento forte m’impedironodi eseguire tutte le osservazioni, che mi eraproposto di fare ... nel mattino del 16 cesso ilpassaggio dei cirri, e solo vedevansi in bassosui paesi circostanti dei cumuli staccati, chesembravano aerostati ... il blu del cielo era piucupo che a Palermo ed a Catania ... la luce delSole aveva un carattere speciale, sembravapiu bianca e quieta, quasi si direbbe artificialeilluminazione a magnesio ... guardato il Solerapidamente ad occhio nudo, lo si vedevacome un disco nero contornato da un’aureolalimitata proiettantesi sul fondo blu del cielo... col mezzo di un debolissimo elioscopio,l’aureola si vedeva molto meglio, il bordo delSole era nettissimo, e il contorno dell’aureolairregolare (Tacchini 1876). Ended the vi-sual observations they mounted the modesttelescopes that carried behind. Riconobbesubito le granulazioni ... potei disegnare unamacchia con alcuni piccoli fori e facole ...nella penombra si distinguevano perfino lesottili correnti fotosferiche. But suddenly thelocal condensations took place ... arrivaronodelle basse nebbie poco dense, che passavanoavanti con una grande velocita ed a brevissimiintervalli ... al loro passaggio formavasi unastupenda serie di anelli colorati attorno alSole, contenenti tutte le gradazioni dei coloridello spettro, e un simile fenomeno non l’aveva

40 Blanco: Tacchini and Astrophysics at Catania

mai veduto. Verso le 3 p.m. si ebbe di nuovoun cielo purissimo ... ed incominciai l’esamedello spettro solare. Subito mi sorprese lagrande nettezza delle righe ed i vivissimi inter-valli colorati, che separano le piu vicine ... lacromosfera presentavasi brillante, ma appenane ebbi incominciato lo studio ritornaronole nubi (Tacchini 1876). Not less stirringwas the nightly sky view ... lo spettacolodel cielo stellato era incantevole e nuovo:le stelle erano quiete e tanto, che quelle diprima grandezza sembravano pianeti, il Sirioquasi si scambiava con Venere: le piu bellecostellazioni acquistano un carattere tuttospeciale, stupende le nebulose e la Via Lattea(Tacchini 1876). The night passed betweenflashes of clear and cloudy sky, early in themorning ... in basso vi erano grandi nebbie, ilcratere era tutto scoperto ... il Sole si scoprıa un 10◦ sopra l’orizzonte: subito dirigemmosu di lui il cannocchiale munito del grandespettroscopio, e notammo anche cosı in bassola solita magnifica distinzione delle righenello spettro ... La cromosfera era magnificae dettagliata abbastanza tenendo conto dellapiccolezza del cannocchiale, ed ottenni subitol’inversione del magnesio e della 1474 K.,cio che non si ebbe a Palermo con lo stessocannocchiale (Tacchini 1876). Suddenly theexpedition broke off because l’Etna incom-incio a cacciar fuori delle sbuffate di vaporacqueo misto a vapori solforosi, che invaseroanche la Casina elevando la temperatura edeponendo goccie di acqua (Tacchini 1876).These last phenomena are an inkling of whatwill hinder the normal running of the futureObservatory.After few days, con maggiore sicurezza,Tacchini went to the Accademia Gioeniainaugural session and presented the plan forthe realization of an annex to be added toCasa degli Inglesi, built in successive stagesby the Gemmellaro brothers on the Etna upperzone at 2941-m a. s. l.. The initiative had agood outcome and to realize the works a con-vention between the Ministeri dell’Istruzione,Agricoltura Industria e Commercio and theProvincia di Catania was stipulated. Theperson in charge of the works was Tacchiniand the Observatory, completed in 1882, was

given il nome del grande Bellini, che primaancora di dare alle scene il suo capolavoro,la Norma, volle in omaggio alla scienza degliastri, suonare all’osservatorio di Palermola celeste melodia della preghiera alla castaDiva (Tacchini 1878). The main telescopeof the new Observatory was a Merz refractorhaving a 34-cm aperture objective, 5570-mmfocal length and an equatorial mounting byCavignato of Padova, with iron pipe. Thedome was ordered from Oretea factory ofPalermo.Conscious that the hard travel connectionswould have made the Station run only duringthe summer, at the same time Tacchini ex-erted himself to build a succursale cittadinaequipped with a mounting telescope analogousto the Etna one, but with a wood pipe. Sifarebbero due montature, una da stabilirsiin Catania e l’altra sull’Etna, in modo chedurante l’inverno le osservazioni si farebberoa Catania stessa, e nell’estate all’OsservatorioEtneo col vantaggio di portare lassu il soloobiettivo, gli oculari e gli altri accessori(Tacchini 1876). In 1885 the Comune diCatania, by supporting the initiative, madeover a great part of the Benedettini Monasteryand the dome was built on its circular antire-fectory.

Due to the working difficulties of VincenzoBellini Observatory, the sede cittadina, pro-vided with a greater instrumental equipment(such as a 15-cm aperture and a 2230-mm fo-cal length Cooke equatorial refractor, a 13-cmaperture Secreten Cassegrain refractor, a 9-cmmeridian circle) became the main station, alsothanks to longer observational times for thegood weather conditions during the winter inCatania. On the contrary the difficult connec-tions and the proximity to the central crater,which turned out to be a bad choice, slowly ledthe Etnean Observatory activity to diminishuntil its closure. The dome was trasformedinto a kind of skylight, the astrophysicalobservatory became a volcanological one, upto 1971 when it was completely covered bylava flows.The town Observatory, on the contrary, metwith a better future. The Monastery rose on an

Blanco: Tacchini and Astrophysics at Catania 41

Fig. 7. An old stamp of Luigi Taffara’s that represents the pavillions built in the garden near the BenedettiniMonastery. On the left the dome of the 15-cm aperture and 2230-mm focal length Cooke equatorial refrac-tor, the 33-cm aperture and 3341-mm focal length astrograph (manufactured by Steinheil of Bayern Munichand with an equatorial mounting realized by Salmoiraghi factory of Milano) and the 9-cm aperture merid-ian circle; on the right the tower of the Merz dome. The Carte du Ciel, the first photographic Catalogueand Atlas of the entire heaven vault, promoted by the France Academy was realized using the Steinheilastrograph.

elevation on the outckirts of Catania, mostlysorrounded by the deserted sciare of the 1642flow, therefore nightly observations were notdisturbed by artificial light, rather scarce at thattime. Thanks to the very good observationalresults Tacchini proposed the participationof Catania Astrophysical Observatory in theinitiative promoted in 1886 by the FranceAcademy to realize the Carte du Ciel, the firstphotographic Catalogue and Atlas of the entireheaven vault. Also this proposal was acceptedand the Italian Government engaged to givethe funds necessary to buy an astrograph witha 33-cm aperture objective and 3341-mm focallength, manufactured by Steinheil of BayernMunich and with an equatorial mountingrealized by Salmoiraghi factory of Milano.The telescope was installed in a pavilion builtin the garden near the Benedettini Monastery(where Vittorio Emanuele hospital lies) andit had an 8-m diameter girante dome ordered

from Audisio factory of Torino. Tacchini’sinitiative turned over a new leaf of Astronomyin Catania, not only for the available instru-mental equipment and the scientific contentof the research programs, but above all forthe School of origin of Catania Universityastronomy teachers that, at the same time,took up the Direction of Catania AstrophysicalObservatory. Gambini and Zurria, the lastuniversity teachers that hold university coursesof Astronomy, came from the school of math-ematics of Catania (Reina 1839; Rapisardi

1902). In 1890 Annibale Ricco was thefirst of many astronomy teachers who werenot educated at Catania to hold the Chair ofAstrofisica ed ad assumere la direzione delReale Osservatorio Astrofisico e l’incaricodella direzione del locale OsservatorioMeteorico e Geodinamico (Favaro 1923).Native of Modena, like Tacchini, and workingat Palermo Observatory, he had a professional

42 Blanco: Tacchini and Astrophysics at Catania

background in observational astrophysics evenif, like all the researchers of the time, he wasinterested in many natural phenomena. In fact,Ricco, continuously in touch with Tacchini(from 1890 in charge of the Collegio Romanoand from 1904 retired in Spilamberto), reallyestablished Catania Astrophysical Observatoryand organized the undertaking of the Cartedu Ciel that took up much of the Observatoryactivity until almost the last half century.

Acknowledgements. I wish to thank the AccademiaGioenia, for the historical citations and LuigiaSantagati for the english revision.

References

Abetti G., Annibale Ricco, l’AccademiaGioenia e l’Osservatorio Astrofisico di

Catania. Boll. Atti Acc. Gioenia, Serie IV,Vol. 3, fasc. 1, 13-25, 1955

Favaro G.A., Cenno necrologico di AnnibaleRicco. Annuario Regia Universita di Catania1922-23, 63-74, 1923

Rapisardi F., Memorie bibliografiche diGiuseppe Zurria. Atti Acc. Gioenia, SerieIV, Vol. 15, 1-19, 1902

Reina E., Elogio del Prof. Francesco Gambini.Atti Acc. Gioenia, Serie II, Vol. 13, 247-250,1839

Tacchini P., Una gita sull’Etna. Memorie Soc.Spettr. Ital. Vol. 5, 151, 1876

Tacchini P., Della convenienza ed utilita dierigere sull’Etna una Stazione astronomica-meteorologica. Atti Acc. Gioenia, Ser. III,Vol. 12, 7, 1878