C/1785 A1 (Messier–Méchain)
Faint parabolic comet discovered by Messier and Méchain in 1785.
C/1785 A1, also known as Comet Messier–Méchain, is a faint parabolic comet discovered independently by French astronomers Charles Messier and Pierre Méchain in January 1785. It is notable for being observed only with telescopes and for never becoming visible to the naked eye, as well as for its later orbital similarity to a modern comet that was determined to be coincidental.
Quick Facts
- Discovery Ref
- Messier_1811
- Discoverer
- Charles Messier / Pierre Méchain
- Discovery Site
- Paris, France
- Discovery Date
- 7 January 1785
- Designations
- 1785 IICQ1
- Orbit Ref
- jpl
- Epoch
- 27 January 1785 (JD 2373045.325)
- Observation Arc
- 32 days
- Obs
- 9
- Perihelion
- 1.143 AU
- Eccentricity
- ~1.000
- Inclination
- 70.238°
Facts from the source article.
Lore & Background
Charles Messier discovered this comet using a small refractor following an observation of Uranus on the night of 7 January 1785. Approximately 40 minutes later, Pierre Méchain also discovered the same comet from the Paris Observatory. At the time, the comet was located within the constellation Cetus. Messier described the comet as a faint object surrounded by a 'central condensation' around it, and noted that it became brighter on 9 January than it was two days earlier, but it never became visible to the naked eye. He continued to observe the comet until 17 January 1785, when it was no longer visible near the star ε Cet. The only known orbital calculations of the comet were written by Méchain in 1788, where he determined a parabolic trajectory that indicated the comet had reached perihelion on 27 January, while making its closest approach to Earth a day later at a distance of 0.417 AU.
Reader's Guide
The significance of C/1785 A1 lies in its discovery by two prominent French astronomers within a short time of each other, and in its status as a faint telescopic comet that never reached naked-eye visibility. Its orbital calculations, performed by Méchain in 1788, established a parabolic path with a perihelion on 27 January 1785 and a close approach to Earth on 28 January at 0.417 AU. In 2012, Maik Meyer noted that the preliminary orbital calculations for comet C/2012 L2 (LINEAR) were strikingly similar to those of Messier–Méchain, but he concluded that this is only a coincidence rather than a return of C/1785 A1 itself. This highlights the challenge of linking historical comets to modern ones, and underscores the importance of precise orbital data. The comet's legacy is thus tied to its careful observation and documentation by Messier and Méchain, and to the later cautionary tale of apparent orbital matches that prove coincidental.
Did You Know?
- Charles Messier discovered the comet using a small refractor after observing Uranus on 7 January 1785.
- Pierre Méchain independently discovered the same comet about 40 minutes later from the Paris Observatory.
- The comet never became visible to the naked eye, even at its brightest on 9 January 1785.
- In 2012, Maik Meyer noted that the orbit of C/2012 L2 (LINEAR) was strikingly similar to that of Messier–Méchain, but concluded it was a coincidence.
Frequently Asked Questions
Who discovered C/1785 A1 (Messier–Méchain)?
French astronomers Charles Messier and Pierre Méchain independently spotted this faint parabolic comet on 7 January 1785 while working at the Paris Observatory. At the time of its sighting it was located in the constellation Cetus.
Why is C/1785 A1 (Messier–Méchain) considered notable?
It is remembered as a strictly telescopic object that never brightened enough to be seen with the naked eye, distinguishing it from the brighter comets of the era. Its parabolic orbit also set it apart from the more common elliptical comets catalogued in the 18th century.
What happened to C/1785 A1 (Messier–Méchain) after its discovery?
The comet followed a parabolic trajectory and was never observed again, effectively lost to the outer solar system. A later orbital resemblance between it and a modern comet was investigated but ultimately ruled to be purely coincidental.
Where and when was C/1785 A1 (Messier–Méchain) found?
It was detected on 7 January 1785 at the Paris Observatory, with Messier and Méchain each identifying it independently. The object was catalogued in the constellation Cetus at the time of discovery.
Why does C/1785 A1 (Messier–Méchain) matter in comet history?
As one of the earlier comets known to be visible only through a telescope, it helped broaden what astronomers expected a cometary object to look like. Its dual discovery by two of France's most prominent observers also highlighted the collaborative nature of 18th-century sky surveys.
More in Named Comets, Part 2 1-24
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