The Comet of 1729, also known as C/1729 P1 or Comet Sarabat, was an assumed parabolic comet with an absolute magnitude of −3, possibly the brightest ever observed for a comet; it is therefore considered to be potentially the largest comet ever seen. 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 warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

was discovered in the constellation of

Equuleus Equuleus is a faint constellation located just north of the celestial equator. Its name is Latin for "little horse", a foal. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern const ...

by Father Nicolas Sarabat, a professor of mathematics, at

Nîmes Nîmes ( , ; ; Latin: ''Nemausus'') is the Prefectures in France, prefecture of the Gard Departments of France, department in the Occitania (administrative region), Occitanie Regions of France, region of Southern France. Located between the Med ...

in the early morning of August 1, 1729. At the time of discovery the comet was making its closest approach to Earth at a distance of and had a solar elongation 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 or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. 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. 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. He was known as Cassini II. Biography Cassini was born at the Paris Observatory. He was first admitted ...

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

. 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 Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

3–4, about the brightness of the

Andromeda Galaxy The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a Galaxy#Isophotal diameter, D25 isop ...

Orbit

The comet's orbit, later computed by John Russell Hind, showed a

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

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 Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

. 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 absolute magnitude 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, formerly 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 ...

on the order of in diameter. 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 b ...

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

References

Notes

Citations

External links

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