The Comet of 1729, also known as C/1729 P1 or Comet Sarabat, was an assumed parabolic comet with an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of −3, the brightest ever observed for a comet;'' Comet Caesar'' (C/-43 K1) has, however, been calculated to have possibly had the brightest

in recorded history: −3.3 at the time of discovery and −4.0 during a later flare-up; cp. John T. Ramsey & A. Lewis Licht, ''The Comet of 44 B.C. and Caesar's Funeral Games'', Atlanta, 1997, . it is therefore considered to be potentially the largest comet ever seen.Moore, P. ''The Data Book of Astronomy'', CRC, 2000, p.232 With an assumed eccentricity of 1, it is unknown if this comet will return in a hundred thousand years or be ejected from the Solar System.

Discovery

The

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

was discovered in the constellation of

Equuleus Equuleus ( ) is a constellation of stars that are visible in the night sky. Its name is Latin for "little horse", a foal. Located just north of the celestial equator, it was one of the 48 constellations listed by the 2nd century astronomer Ptolem ...

by Father

Nicolas Sarabat Fr. Nicolas Sarrabat or Sarabat (February 7, 1698 – April 27, 1739), also known as Nicolas Sarrabat de la Baisse, was an eighteenth-century France, French mathematician and scientist. He was born in Lyon, the son of the painter Daniel Sarrabat (1 ...

, a professor of mathematics, at

Nîmes Nîmes ( , ; oc, Nimes ; Latin: ''Nemausus'') is the prefecture of the Gard department in the Occitanie region of Southern France. Located between the Mediterranean Sea and Cévennes, the commune of Nîmes has an estimated population of 148,5 ...

in the early morning of August 1, 1729. At the time of discovery the comet was making its closest approach to Earth of and had a

solar elongation In astronomy, a planet's elongation is the angular separation between the Sun and the planet, with Earth as the reference point. The greatest elongation of a given inferior planet occurs when this planet's position, in its orbital path around t ...

of 155 degrees. Observing with the naked eye, he saw an object resembling a faint, nebulous star: he was at first unsure if it was a comet or part of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

. Moonlight interfered with Sarabat's observations until August 9, but after recovering the object and attempting to detect its motion without the aid of any measuring instruments, he became convinced that he had found a new comet.Kronk, G. W. ''Cometography: A Catalog of Comets'', Cambridge University Press, 1999
pg 394
/ref> News of the discovery was passed to

Jacques Cassini Jacques Cassini (18 February 1677 – 16 April 1756) was a French astronomer, son of the famous Italian astronomer Giovanni Domenico Cassini. Cassini was born at the Paris Observatory. Admitted at the age of seventeen to membership of the French ...

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. S ...

. He was able to confirm the comet's position, though with extreme surprise at how little it had moved since the first observation nearly a month previously. Cassini was able to continue observation until 18 January 1730, by which time the comet was located in

Vulpecula Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is commonly known simply as the fox. It was identified in the seventeenth century, and is located in the middle of the Summer Triangle (an ...

. This was an extraordinarily long period for observation of a comet, though it never rose above

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

3–4, about the brightness of the

Andromeda Galaxy The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The gala ...

Orbit

The comet's orbit, later computed by

John Russell Hind John Russell Hind FRS FRSE LLD (12 May 1823 – 23 December 1895) was an English astronomer. Life and work John Russell Hind was born in 1823 in Nottingham, the son of lace manufacturer John Hind and Elizabeth Russell, and was educated at ...

, showed a

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

distance (closest approach to the Sun) of 4.05 AU which is just within the orbit 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 mass more than two and a half times that of all the other planets in the Solar System combined, but ...

. However, despite this it became visible, although faintly, to the naked eye, and indeed remained visible for six months in total. This suggests that its

or intrinsic brightness was unusually high, possibly as high as −3.0. It is therefore likely that the Comet of 1729 was an exceptionally large object, with a

cometary nucleus The nucleus is the solid, central part of a comet, once termed a ''dirty snowball'' or an ''icy dirtball''. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublime and produce an atmosphere su ...

of the order of 100 km in diameter. Sagan, Carl and Druyan, Ann ''Comet'', Ballantine, 199
pg137
/ref> The JPL small-body database only uses three observations, a two-body model, and an assumed

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

to compute the orbit of this assumed parabolic comet. With such a limited dataset, undefined uncertainties, and an assumed eccentricity of 1, (that is, a parabolic trajectory) it is unknown if the comet will return

on the order of An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic dis ...

100,000 years or be ejected from the Solar System.

References

External links

Orbital simulation
from JPL (Java)
Horizons Ephemeris

C/1729 P1 (Sarabat) at CometBase database by Neil Norman
{{DEFAULTSORT:1729 P1 Non-periodic comets 17290801