Comet of 1729

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C/1729 P1
Discovered by Fr. Nicolas Sarabat
Discovery date August 1, 1729
C/1729 P1, 1729,
Comet of 1729
Orbital characteristics A
Epoch 2352731.148
(June 16, 1729)
Perihelion 4.05054 AU[1]
Eccentricity 1.0 (assumed)[1]
Inclination 77.095°[1]
Last perihelion June 16, 1729[1]
Next perihelion unknown

The Comet of 1729, also known as C/1729 P1 or Comet Sarabat, was a non-periodic comet with an absolute magnitude of −3,[2] the brightest ever observed for a comet;[3] it is therefore considered to be potentially the largest comet ever seen.[4]


The comet was discovered in the constellation of Equuleus by Father Nicolas Sarabat, a professor of mathematics, at Nîmes in the early morning of August 1, 1729.[5]

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. 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.[6]

News of the discovery was passed to Jacques Cassini in Paris. 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. This was an extraordinarily long period for observation of a comet, though it never rose above apparent magnitude 3–4.


The comet's orbit, later computed by John Russell Hind, showed a perihelion distance (closest approach to the Sun) of 4.05 AU[1] which is just within the orbit of Jupiter. 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.[2] It is therefore likely that the Comet of 1729 was an exceptionally large object, with a cometary nucleus of the order of 100 km in diameter.[7] The JPL small-body database only uses three observations, a two-body model, and an assumed epoch to compute the orbit of this parabolic comet.[1]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 "JPL Small-Body Database Browser: C/1729 P1". Jet Propulsion Laboratory. Retrieved 2011-07-26.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles> last observation: 1730-01-16 (only 3 observations using a two-body model; very poorly determined)
  2. 2.0 2.1 Kidger, M. 'Comet Hale-Bopp Light Curve', NASA JPL, accessed 24-Nov-2008
  3. Comet Caesar (C/-43 K1) has, however, been calculated to have possibly had the brightest absolute magnitude 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, ISBN 0-7885-0273-5.
  4. Moore, P. The Data Book of Astronomy, CRC, 2000, p.232
  5. Lynn, W. T. 'Sarrabat and the comet of 1729', The Observatory, Vol. 19, p. 239–240 (1896). Sarabat (1698–1737), also known as "de la Baisse", a Jesuit and professor at Marseilles university, himself spelt his name "Sarrabat", but Cassini's spelling is generally used in reference to this comet.
  6. Kronk, G. W. Cometography: A Catalog of Comets, Cambridge University Press, 1999, p.394
  7. Sagan, C. and Druyan, A. Comet, Ballantine, 1997

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