Mem. S.A.It. Suppl. Vol. 9, 28c© SAIt 2006

Memorie della

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Pietro Tacchini (1838-1905), a key-figure in thepost-Unitarian Italian astronomy

I. Chinnici

INAF, Osservatorio Astronomico di Palermo Giuseppe S. Vaiana, Piazza del Parlamento 1,I-90134 Palermo, Italye-mail: chinnici@astropa.unipa.it

Abstract. A short scientific profile of the astronomer Pietro Tacchini is drafted in thispaper, paying special attention to his contribution in the field of solar physics and his lead-ing role in the establishment of the Societa degli Spettroscopisti Italiani, forerunner of theSocieta Astronomica Italiana.

Key words. History, Sun, astrophysics, Italy

Pietro Tacchini (1838-1905) is one of themost important but less known figures in thecontext of the Italian XIX century science, af-ter the political Unity of the nation. His activityconcerned not only astronomy but also manyother scientific disciplines, such as meteorol-ogy, seismology, etc. A complete and detaileddescription of his scientific works is out of theaim of this paper, whose main purpose is todraft his contribution to astronomy and espe-cially to the development of solar physics, afield in which he played an important role inItaly.

Born in Modena on March 21st, 1838,he studied at first as engineer in the na-tive town and then went to Padua to prac-tice astronomy, as requested by GiuseppeBianchi (1791-1866), Director of the smallModena Observatory, who needed him as as-sistant. Tacchini spent two years at the PaduaObservatory under the direction of GiovanniSantini (1787-1877) and then he come back to

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Modena, where the situation was changed inthe meantime: Bianchi has resigned as a conse-quence of the establishment of a revolutionarygovernment and Tacchini applied for the po-sition of director of the Modena Observatory- and obtained it. At that time, he was only21 years-old and his activity at the ModenaObservatory was no more than a continuationof his training in practical astronomy: actually,he published only a few works about positionalastronomy and meteorology - the only kind ofresearch he could carry out with the small in-struments installed at the Modena Observatory.

An important opportunity was offeredto Tacchini in 1863 by Giovanni VirginioSchiaparelli (1787-1877). The famous as-tronomer had been contacted by MicheleAmari (1806-1889), Minister of the PublicInstruction, who asked his advice about the sit-uation of the Palermo Observatory, where ”anassistant acting as a Director” was requested.The Palermo Observatory was a prestigiousinstitution, thanks to the scientific activity ofits first Director, Giuseppe Piazzi (1746-1826),

Chinnici: Pietro Tacchini 29

Fig. 1. Pietro Tacchini (1838-1905).

whose main works were the discovery of thefirst asteroid, Ceres, and the publication of astellar catalogue in 1803, re-edited in 1814.Moreover, at that time it was equipped withvery good instruments, such as a MeridianCircle by Pistor & Martins and a 25-cm aper-ture Merz equatorial, the latter unfortunatelystill laying in the packing cases. The direc-tor Gaetano Cacciatore (1814-1889), an ac-tive supporter of the anti-borbonic party, bet-ter known for his political engagement than forhis scientific activity, did not appear in a con-dition to manage properly the research at theObservatory. For this reason, it was decided toappoint a smart assistant who could give a newimpulse to the scientific activity of the estab-lishment.

Schiaparelli wrote to Tacchini asking himto accept the position of adjoint astronomer atthe Palermo Observatory, explaining him allthe advantages of this choice:

... Il Ministro della Pubblica Istruzione miordina di farle privatamente la seguente do-manda: = Accetterebbe V. S. di andare 2◦Astronomo all’Osservatorio di Palermo con unassegno annuo di L. 4000, e senz’altro ob-bligo che quello di attendere con zelo alle os-servazioni astronomiche? = Mi premerebbe diavere una risposta pronta e decisiva. [...] Ionon conosco altri che meglio di V. S. possariempire questo ufficio. E d’altra parte preme,che i buoni strumenti, di cui in Italia non v’etroppa abbondanza, siano degnamente impie-gati. Sono gli strumenti in parte forse nuoviper Lei; ma Ella non avra difficolta a render-seli famigliari: circa poi all’uso dei medesimi,norma eccellente avra dal suo egregio mae-stro Santini; io pure mi prestero per via epis-tolare a servirla in tutto quello di cui sonocapace [...] Ella stessa vedra quali saranno igrandi lavori da intraprendersi con strumentisı belli. [...] Non devo dimenticare di farle cog-nito, che a Palermo il vivere e a molto buonmercato; che la sua abitazione sara gratuita,sotto l’Osservatorio, ampia, e bellissima; checoi Siciliani si puo vivere molto bene; checon Cacciatore se l’intendera facilmente; cheil clima Palermitano e temperato in ogni sta-gione, e forse il piu sano d’Italia; che le donnePalermitane infine sono belle oltre ogni dire.1

Tacchini consulted Santini in Padua andwas encouraged by him to accept:

Palermo deve essere una bella, grande, ericca citta; [...] lo stipendio di Fr. 4000, ilnome dell’Osservatorio di Palermo, di Piazzi;non che i lavori gia illustri ... degli altri as-tronomi che vi figurarono, parmi che gius-tifichino la vostra disposizione ad accettare;ed io pure accetterei la esibizione, che viviene fatta se fossi nella vostra posizione. [...]Costı in fine siete quasi solo, ed isolato inAstronomia, e cola avreste [...] occasioni dipoter[v]i distinguere in un osservatorio benmontato, e gia conosciuto.2

1 Schiaparelli to Tacchini, Milan, 19-08-1863; in:Lugli, 2001, pp. 225-6.

2 Santini to Tacchini, Padua, 22-08-1863(Archives Ufficio Centrale di Ecologia Agraria,Fondo Tacchini).

30 Chinnici: Pietro Tacchini

Fig. 2. The Merz telescope installed by Tacchini atthe Palermo Observatory in 1865; he used it to startsolar physics research in Palermo.

In October 1863 Tacchini therefore arrivedin Palermo and immediately worked at the in-stallation of the Merz Equatorial, last legacy ofthe Borbonic Government before its fall. Onceset the instrument, he paid special attention tothe solar observations. In those years, somecontroversies had arisen about the solar pho-tospheric features; important contributions onthis subject had been given by Angelo SecchiS. J. (1818-1878) in Rome, who used a Merzequatorial identical to the one in Palermo. Ofcourse, it was very interesting for Tacchini tocheck Secchi’s observations with his own in-strument.

Tacchini started also spectroscopic obser-vations of the solar limb in 1871, when he ob-tained a good spectroscope acquired for ob-serving the total solar eclipse of 1870, visiblefrom Sicily: he had been the most active orga-nizer of the Italian expedition and the Editor ofthe Report of the Italian Committee.

Thanks to his excellent ability in observingand drawing, Tacchini drafted one of the firstclassifications of the solar prominences:

Fin dalle prime osservazioni da me fattenel marzo 1871 io fui subito condotto alladistinzione generale delle protuberanze in duegrandi categorie, cioe nebulose e filamentose... e notai inoltre diversi casi di forma radiatea punte dritte distintissime.3

Tacchini and Secchi shared the same con-viction that the future of astronomy was inastrophysics, a borning discipline which ap-plied spectral analysis to starlight. Many as-tronomers did not accept this view and pre-ferred to confine astronomy simply in the rangeof celestial mechanics, showing a sort of hos-tility towards astrophysics, as Tacchini wroteto Secchi:

... in tutti gli uomini avvezzi alle for-mole si trova una ripugnanza eccessiva perl’astronomia fisica: mentre per la scienza ame pare che sia di eguale interesse l’arrivarea conoscere la composizione di una protuber-anza come l’orbita di un pianeta o di una stella...4

Because of the same scientific interests,Tacchini’s contacts with Secchi became moreand more frequent; the two astronomers starteda fruitful cooperation which led to the birthof a scientific society, especially devoted tothe spectroscopic observations of the Sun. TheSocieta degli Spettroscopisti Italiani was estab-lished in October 1871 by Secchi and Tacchiniwith the aim to coordinate the solar spectro-scopic research in Italy:

... il Secchi mi comunicava l’idea di for-mare una societa di Spettroscopisti Italiani,i quali lavorando di comune accordo e sec-ondo un programma stabilito, avrebbero datoin poco tempo la richiesta serie di regolari econtinue osservazioni per la sicura ed accel-erata soluzione di importanti problemi relativialla fisica solare. 5

They involved in their programme otherItalian astronomers working in the field of so-lar spectroscopy, such as Giuseppe Lorenzoni(1843-1914) in Padua and Lorenzo Respighi

3 Tacchini, 1871, pp. 93-94.4 Tacchini to Secchi, 08-02-1873 (Archives P.

Universit Gregoriana, Fondo Angelo Secchi S. J.,20, 88).

5 Tacchini, 1872, p. 3.

Chinnici: Pietro Tacchini 31

Fig. 3. Solar prominences observed by Tacchini in 1871.

(1824-1889) in Rome. Tacchini became editorof the journal of the Society, the Memorie dellaSocieta degli Spettroscopisti Italiani (see pa-per by S. Serio) which can be rightfully con-sidered the first astrophysical journal and hadso a good welcome from the international as-tronomical community that they were awardedwith a medal and a diploma in 1873 at theUniversal Exhibition in Vienna.

In 1874 Tacchini was the promoter ofan Italian scientific expedition to Bengala forobserving the transit of Venus. Because ofthe scarce financial support received from theGovernment, the aim of the expedition wasnot to measure the solar parallax, as thiswould need many distant stations, but to de-termine the best method for observing the con-tacts - spectroscopic or visual. The expedition,headed by Tacchini himself, found a differ-ence between the size of the solar disk ob-served with the visual method and that ob-served with the spectroscope; moreover, some

spectral lines were found confirming the exis-tence of Venus’atmosphere.

On that occasion, Tacchini had the op-portunity to establish an astrophysical obser-vatory in Calcutta, with the aim to have awinter station for the solar spectroscopic ob-servations. The Observatory was located inthe St. Xavier’s College and was directed bythe jesuit Eugene Lafont (1837-1908), whohas been invited to join the Italian expedi-tion for the transit of Venus. Unfortunately,the Observatory never gave a regular contribu-tion to the programme of solar observations be-cause of Lafont’s health problems.

Before his departure for India, Tacchinipublished a report on the conditions ofthe Italian astronomical observatories.The Government had maintained all theObservatories existing in the pre-unitaryStates; Tacchini’s analysis compared thebudget of the Italian Observatories with that ofthe main foreign Observatories and concluded:

32 Chinnici: Pietro Tacchini

... la somma spesa per l’intero manteni-mento delle dieci specole in Italia non valequanto la spesa di mantenimento di un soloOsservatorio estero. 6

He therefore proposed to divide the ob-servatories into two classes: the first one, thatof the research observatories, included thoseof Milan, Florence, Naples and Palermo; thesecond one included the University observato-ries, namely those of Padua, Turin and Rome -the other small observatories, such as Bologna,Parma and Modena, would be declassed to me-teorological observatories. Tacchini’s projectwas accepted by the Government (except forthe Bologna Observatory, which was includedamong the University observatories) but un-fortunately the decree signed in 1876 by theMinister Ruggiero Bonghi (1828-1895) wasnever applied because of a political changein the Government which actually stopped theprocedure of the law.

Tacchini’s activity as a promoter of the as-trophysical research led also to the establish-ment of the Catania Observatory (see paper byC. Blanco) for solar observations on the MountAetna.

In 1879 Tacchini was appointed Directorof the new Ufficio Centrale di Meteorologia inRome with the task to coordinate the Italianmeteorological network; he chose the buildingof the Collegio Romano to establish the Ufficioin order to preserve the Collegio RomanoObservatory from shutting down - actually, af-ter Secchi’s death, the Observatory had beenconfiscated by the Italian Government whichcould not maintain it. Tacchini annexed theObservatory to the Ufficio: in his opinion, infact, solar activity could influence terrestrialmeteorology, as fra noi ed il sole vi e una co-municazione continua ... sole e terra non sonone piu ne meno che una macchina elettrica e unelettroscopio a piccola distanza nel gabinettodi un professore di fisica.7

Thanks to Tacchini’s support, another as-tronomical and meteorological observatorywas built in 1883 on the Mount Cimone in

6 Tacchini, 1875, p. 7.7 Rivista Sicula vol. V, 1871, p. 420.

Fig. 4. Frontpage of the first volume of theMemorie della Societa degli Spettroscopisti Italiani(1872), edited by Tacchini; it contained the report ofthe first coordinated observation of the solar limb.

the Appennino Emiliano, but it never becamea real astronomical observatory.

Tacchini was well-known abroad and of-ten invited by foreign astronomical societiesto join their scientific expeditions. In 1875he joined the English expedition headed byNorman J. Lockyer (1836-1920) to observethe total solar eclipse visible from the NicobarIsles; in 1882 he went to Egypt, to observe an-other solar total eclipse, invited by the Directorof the Cairo Observatory; in 1883 he joined theFrench expedition headed by Jules C. Janssen(1824-1907) to observe a total solar eclipsevisible from Micronesia and in 1886 was in-vited by the Royal Astronomical Society to ob-serve a total solar eclipse at the Antilles. In1887 Tacchini went to Russia with his col-league Annibale Ricco (1844-1919) to observe

Chinnici: Pietro Tacchini 33

Fig. 5. Tacchini’s book on eclipses (1888), whichcontains most reports and travel books of the scien-tific expeditions in which Tacchini took part.

a total solar eclipse at Surwiskaja and in 1900,with Ricco again, he went to Algeria for ob-serving another total solar eclipse. Most re-ports and travel books of these expeditionswere collected and published by Tacchini in1888 in a volume, Eclissi totali di Sole; thebook is full of remarks about ethnography,botanics, geology, etc. of the several regionsvisited and shows clearly the variety of inter-ests and the scientific curiosity which markedTacchini’s activity.

Tacchini’s reputation is confirmed also byhis participation in many scientific interna-tional commissions; in particular, he was anactive member of the Carte du Ciel ExecutiveCommittee, established in Paris in 1887 withthe aim to produce a map and a catalogue

of the whole sky by photographic means andheobtained that a part of the work was as-signed to the Catania Observatory. Because ofHis renowned scientific activity, especially inthe field of solar physics, in 1888 Tacchiniwas awarded by the Royal Society of Londonwith the Rumford Medal and in 1892 by theAcademie des Sciences of Paris with the PrixJanssen;it is interesting to read the reason ofthe first prestigious award, as it describes verywell Tacchini’s stature: The Rumford Medalhas been awarded to Professor Pietro Tacchinifor important and long-continued investiga-tions, which have largely advanced our knowl-edge of the physics of the sun. ProfessorTacchini occupies a foremost place amongthose who have paid special attention to thephysics of the sun. Since 1870 he has unceas-ingly observed, first at Palermo, and after-wards at Rome, the solar prominences. The in-formation at our disposal at the present time,both as regards their distribution, their spec-tra, and the changes which take place in them,and their connexion with other solar phenom-ena, rests to a large extent upon his individualefforts. His memoirs on this subject are verynumerous. He has been engaged in the obser-vation of four total solar eclipses, and fromsome of the phenomena therein observed hasdrawn the important conclusion that many ofthe so-called prominences are really descend-ing currents.8 It is to mention that, in the lastyears of his career, Tacchini paid attention alsoto seismology, establishing in 1895 the SocietaSismologica Italiana and being the editor ofthe bulletin of the society; actually, in 1887the Ufficio Centrale di Meteorologia directedby Tacchini had become Ufficio Centrale diMeteorologia e Geodinamica, in order to co-ordinate also the national network of seismicstations.

Tacchini was planning to observe anothertotal solar eclipse in 1905 when he died sud-denly on March 24th in Spilamberto, in his na-tive land. He had retired from his position atthe Ufficio Centrale in 1899 and then, in 1902,he had left the Collegio Romano Observatory,

8 Proceedings of the Royal Society, vol. XLV, p.55.

34 Chinnici: Pietro Tacchini

maybe deceived by the Italian policy of sci-ence, which did not give adequate support tothe astrophysical research; as a consequence,Italian astronomy withdrew the spectroscopicstudies and come back to the celestial me-chanics - the golden era of the Italian spectro-scopists, opened by Tacchini, was ended.

References

Fodera Serio G., Chinnici I. 1997,L’Osservatorio Astronomico di Palermo,Flaccovio Editore, Palermo

Lugli, M. U. 2001, Pietro Tacchini, Edizioni IlFiorino, Modena

Tacchini, P. 1871, Bullettino Meteorologicodel R. Osservatorio di Palermo, vol. VII, 49-62; 69-75; 85-99; 111-113; 121-132

Tacchini, P. 1872, Memorie della Societa degliSpettroscopisti Italiani, vol. I, 3-6

Tacchini, P. 1875, Memorie della Societa degliSpettroscopisti Italiani, Appendice al vol.IV, 1-20

Tacchini, P. 1888, Eclissi totali di sole deldicembre 1870, del maggio 1882 e 1883, edell’agosto 1886 e 1887, Roma, TipografiaEredi Botta