Barnaba Oriani (17 July 1752 – 12 November 1832) was an Italian

priest A priest is a religious leader authorized to perform the sacred rituals of a religion, especially as a mediatory agent between humans and one or more deity, deities. They also have the authority or power to administer religious rites; in parti ...

, geodesist,

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

and

scientist A scientist is a person who Scientific method, researches to advance knowledge in an Branches of science, area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engag ...

Life

Oriani was born in Garegnano (now part of

Milan Milan ( , , ; ) is a city in northern Italy, regional capital of Lombardy, the largest city in Italy by urban area and the List of cities in Italy, second-most-populous city proper in Italy after Rome. The city proper has a population of nea ...

), the son of a mason, and died in Milan. After getting his elementary education in Garegnano, he went on to study at the College of San Alessandro in Milan, under the tutelage and with the support of the Order of Barnabites,Students for the Exploration and Development of Space
/ref> which he later joined. After completing his studies in the

humanities Humanities are academic disciplines that study aspects of human society and culture, including Philosophy, certain fundamental questions asked by humans. During the Renaissance, the term "humanities" referred to the study of classical literature a ...

, physical and

mathematical Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...

sciences,

philosophy Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...

, and

theology Theology is the study of religious belief from a Religion, religious perspective, with a focus on the nature of divinity. It is taught as an Discipline (academia), academic discipline, typically in universities and seminaries. It occupies itse ...

, he was ordained a priest in 1775. When

Napoleon I Napoleon Bonaparte (born Napoleone di Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French general and statesman who rose to prominence during the French Revolution and led Military career ...

established the Republic of Lombardy, Oriani refused to swear an oath against the monarchy, and the new republican government modified the oath of allegiance on his behalf. He was retained in his position at the observatory and was made president of the commission appointed to regulate the new system of

weights and measures A unit of measurement, or unit of measure, is a definite magnitude (mathematics), magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other qua ...

. When the republic became a Napoleonic kingdom, Oriani was awarded the

Iron Crown The Iron Crown (in Italian, Latin, and Lombard: ''Corona Ferrea''; ) is a reliquary votive crown, traditionally considered one of the oldest royal insignia of Christendom. It was made in the Middle Ages, consisting of a circlet of gold and j ...

and the

Legion of Honour The National Order of the Legion of Honour ( ), formerly the Imperial Order of the Legion of Honour (), is the highest and most prestigious French national order of merit, both military and Civil society, civil. Currently consisting of five cl ...

, was made a

count Count (feminine: countess) is a historical title of nobility in certain European countries, varying in relative status, generally of middling rank in the hierarchy of nobility. Pine, L. G. ''Titles: How the King Became His Majesty''. New York: ...

and

senator A senate is a deliberative assembly, often the upper house or Legislative chamber, chamber of a bicameral legislature. The name comes from the Ancient Rome, ancient Roman Senate (Latin: ''Senatus''), so-called as an assembly of the senior ...

, and was appointed to measure the

arc of the meridian In geodesy and navigation, a meridian arc is the curve between two points near the Earth's surface having the same longitude. The term may refer either to a segment of the meridian, or to its length. Both the practical determination of meridian ...

between the zeniths of

Rimini Rimini ( , ; or ; ) is a city in the Emilia-Romagna region of Northern Italy. Sprawling along the Adriatic Sea, Rimini is situated at a strategically-important north-south passage along the coast at the southern tip of the Po Valley. It is ...

and

Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...

. Oriani was a devoted friend of the Theatine monk

Giuseppe Piazzi Giuseppe Piazzi ( , ; 16 July 1746 – 22 July 1826) was an Italian Catholic Church, Catholic priest of the Theatines, Theatine order, mathematician, and astronomer. He established an observatory at Palermo, now the ''Palermo Astronomical Ob ...

, the discoverer of Ceres. Oriani and Piazzi worked together for thirty-seven years, cooperating on many astronomical observations.

Astronomy

Given his strong interest in astronomy, Oriani was appointed on the staff of the Observatory of Brera in Milan in 1776, becoming assistant astronomer in 1778 and director in 1802. In 1778 he began publishing various in-depth dissertations on astronomical objects, the ''Effemeridi di Milano'' ( Ephemerides of Milan). A very capable astronomer, Oriani's work began to attract considerable attention. His research in the areas of astronomic refraction, the

obliquity of the ecliptic In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbital ...

, and orbital theory were of considerable noteworthiness in themselves; but his greatest achievement was his detailed research of the planet

Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a Supercritical fluid, supercritical phase of matter, which astronomy calls "ice" or Volatile ( ...

, which had been discovered by

Sir William Herschel Frederick William Herschel ( ; ; 15 November 1738 – 25 August 1822) was a German-British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline Herschel. Born in the Electorate of Hanover ...

in 1781. Oriani devoted significant time to observations of Uranus, calculating its orbital properties which he published as a booklet of tables in 1793.Alexandro Malaspina Research Centre
After others had shown that Uranus was not on a parabolic orbit but rather in a roughly circular orbit, he calculated the orbit in 1783. In 1789, Oriani improved his calculations by accounting for the gravitational effects of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

and

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

. In addition to his continual contributions to the ''Effemeridi'', he published a series of memoirs on

spherical trigonometry Spherical trigonometry is the branch of spherical geometry that deals with the metrical relationships between the edge (geometry), sides and angles of spherical triangles, traditionally expressed using trigonometric functions. On the sphere, ge ...

: the ''Memorie dell'Istituto Italiano'', 1806–10, and the ''Istruzione suelle misure e sui pesi'', 1831. For his work in astronomy, Oriani was honoured by naming

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

4540 "Oriani". This asteroid had been discovered at the Osservatorio San Vittore in

Bologna, Italy Bologna ( , , ; ; ) is the capital and largest city of the Emilia-Romagna region in northern Italy. It is the List of cities in Italy, seventh most populous city in Italy, with about 400,000 inhabitants and 150 different nationalities. Its M ...

on 6 November 1988.

Oriani's theorem

In ''De refractionibus astronomicis'', Oriani showed that astronomical refraction could be expanded as a series of odd powers of (tan Z), where Z is the observed

zenith distance The zenith (, ) is the imaginary point on the celestial sphere directly "above" a particular location. "Above" means in the vertical direction (plumb line) opposite to the gravity direction at that location (nadir). The zenith is the "highest" p ...

. Such a series had previously been derived by J. H. Lambert, who dropped all but the first term. However, Oriani investigated the higher terms, and he found that neither of the first two terms depended on the structure of the atmosphere. The

series expansion In mathematics, a series expansion is a technique that expresses a Function (mathematics), function as an infinite sum, or Series (mathematics), series, of simpler functions. It is a method for calculating a Function (mathematics), function that ...

he obtained was effective at up to 85 degrees from the zenith. Unlike previous approximations, however, Oriani's two-term expression did not depend on a hypothesis regarding atmospheric temperature or

air density The density of air or atmospheric density, denoted '' ρ'', is the mass per unit volume of Earth's atmosphere at a given point and time. Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmosph ...

in relation to

altitude Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometr ...

. Thus, the effects of atmospheric curvature are only dependent upon the temperature and pressure ''at the location of the observer''. Oriani's theorem explains why Cassini's uniform-density model works well except near the horizon—the atmospheric refraction from the zenith to a zenith distance of 70° is not dependent on the details of the distribution of the gas.

References

Bibliography

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External links