D/1766 G1 (Helfenzrieder)
Lost Jupiter-family comet with highest Earth impact probability.
D/1766 G1 (Helfenzrieder) is a Jupiter-family comet first observed between April and May 1766. It was never recovered on subsequent apparitions and is considered lost, but it is notable for having the highest probability of impacting Earth among near-Earth comets, though its current existence is uncertain.
Quick Facts
- Discoverer
- Johann E. Helfenzrieder
- Discovery Site
- Dillingen, Germany
- Discovery Date
- 1 April 1766
- Designations
- 1766 IIICQ1
- Orbit Ref
- jpldata
- Epoch
- 3 May 1766 (JD 2366200.5)
- Observation Arc
- 24 days
- Obs
- 22
- Perihelion
- 0.406 AU
- Aphelion
- 4.923 AU
- Semimajor
- 2.665 AU
- Period
- ~4.35 years
Facts from the source article.
Lore & Background
Comet Helfenzrieder was first seen between April and May 1766. Uncertainties in orbital calculations prevented its recovery on later apparitions, leading to its classification as a lost comet. Between 1766 and 1773, Alexandre Guy Pingré computed parabolic orbits, giving a perihelion date of 17 April 1766 at 0.637 AU, though he considered this uncertain. He revised his calculations in 1784, suggesting perihelion on 23 April 1766 at 0.33 AU. In 1821, Johann Karl Burckhardt first determined the comet has a short-period elliptical orbit with a period of 5.02 years. In 1915, Carl Wilhelm Wirtz noted that the comet had a close encounter with Jupiter on 11 November 1763 at a distance of 0.03 AU. The comet is likely a member of the Hephaistos group, a subset of the Taurid complex that also includes 2P/Encke, 169P/NEAT, and P/2003 T12 (SOHO). Of all near-Earth comets, Helfenzrieder has the highest probability of impacting Earth, though it is not clear if the comet still exists. In March 2017, David A. J. Seargent identified that asteroid 2017 DW108 has a very similar orbit, but the link is not yet definitely confirmed.
Reader's Guide
The significance of D/1766 G1 (Helfenzrieder) lies in its status as a lost Jupiter-family comet with a high impact probability, despite uncertainties about its current existence. Its orbital history, marked by early parabolic calculations by Pingré and the first elliptical orbit determination by Burckhardt, illustrates the challenges of 18th- and 19th-century cometary astronomy. The close encounter with Jupiter in 1763, noted by Wirtz in 1915, likely perturbed its orbit, contributing to its loss. Its membership in the Hephaistos group links it to other notable comets and the Taurid complex, suggesting a shared origin. The highest Earth impact probability among near-Earth comets, though based on uncertain orbital data, underscores its potential hazard. The possible connection to asteroid 2017 DW108, identified by Seargent in 2017, offers a modern avenue for recovery, but remains unconfirmed. The comet's legacy is one of unresolved orbital puzzles and ongoing search efforts, reflecting the broader challenges of tracking small solar system bodies.
Did You Know?
- Comet Helfenzrieder was first observed between April and May 1766 and never recovered on later apparitions.
- Alexandre Guy Pingré made the first parabolic orbit calculations for the comet between 1766 and 1773.
- Johann Karl Burckhardt determined in 1821 that the comet has a short-period elliptical orbit of 5.02 years.
- In March 2017, David A. J. Seargent identified asteroid 2017 DW108 as having a very similar orbit, but the link is not confirmed.
Frequently Asked Questions
What is D/1766 G1 (Helfenzrieder)?
It is a Jupiter-family comet first sighted during April–May 1766 and named for its discoverer, Helfenzrieder. The object was never detected again on any predicted return, so it carries the 'D/' prefix that marks a lost comet.
Why is D/1766 G1 (Helfenzrieder) considered the most dangerous near-Earth comet?
Among all known near-Earth comets, it holds the highest calculated probability of eventually colliding with Earth. Because it was never recovered after 1766, however, astronomers cannot confirm whether it still exists as an intact body.
What happened to D/1766 G1 (Helfenzrieder) after its 1766 apparition?
No observer ever located it on a subsequent return, and it was officially classified as lost. Its perihelion distance was later revised downward from 0.637 AU to 0.33 AU, but that refinement did not help anyone find it.
What is D/1766 G1 (Helfenzrieder)'s orbital period?
Johann Karl Burckhardt calculated the period to be roughly 5.02 years in 1821, which places the comet squarely in the Jupiter-family category.
Did D/1766 G1 (Helfenzrieder) pass close to Jupiter?
Yes—Carl Wilhelm Wirtz identified in 1915 that the comet made an extremely tight fly-by of Jupiter on November 11, 1763, at a distance of only 0.03 AU (about 4.5 million km). That encounter likely sculpted the comet's later orbital path.
More in Periodic Comets 1-24
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