C/1729 P1 (Sarabat)

Lore & Background

The comet was discovered in the early morning of August 1, 1729, by Father Nicolas Sarabat, a professor of mathematics, in the constellation Equuleus. At discovery, it was at its closest approach to Earth at 3.1 AU and had a solar elongation of 155 degrees. Sarabat initially saw a faint, nebulous star-like object and was unsure if it was a comet or part of the Milky Way; moonlight interfered with his observations until August 9. After recovering the object and detecting its motion without instruments, he became convinced it was a new comet. News reached Jacques Cassini in Paris, who confirmed the position with extreme surprise at how little the comet had moved in nearly a month. Cassini continued observations until January 18, 1730, when the comet was in Vulpecula, an extraordinarily long observation period for a comet, though it never rose above apparent magnitude 3–4, about the brightness of the Andromeda Galaxy.

Reader's Guide

The Comet of 1729 is significant primarily for its extraordinary intrinsic brightness. Despite a perihelion distance of 4.05 AU—just within Jupiter's orbit—it remained visible to the naked eye for six months, suggesting an absolute magnitude as high as −3.0. This implies a cometary nucleus on the order of 100 km in diameter, making it potentially the largest comet ever seen. Its orbit, computed by John Russell Hind, is based on only three observations and a two-body model with an assumed eccentricity of 1 (parabolic). Due to the limited dataset and undefined uncertainties, it is unknown whether the comet will return on the order of 100,000 years or be ejected from the Solar System. The comet's legacy lies in its record-setting brightness and size, though its ultimate fate remains uncertain.

Did You Know?

• The comet was discovered in the constellation Equuleus by Father Nicolas Sarabat on August 1, 1729.
• Its absolute magnitude of −3 is possibly the brightest ever observed for a comet.
• The comet's nucleus is estimated to be about 100 km in diameter.
• It was observed for an extraordinarily long period, from August 1, 1729 to January 18, 1730.