18D/Perrine–Mrkos
A periodic comet lost after 1909, rediscovered in 1955.
18D/Perrine–Mrkos is a periodic comet that was first spotted on December 9, 1896, by Charles Dillon Perrine, an American-Argentine astronomer working at Lick Observatory in California. For a while, astronomers suspected it might be a piece of Biela's Comet. After its 1909 visit, the comet vanished from view and was considered lost. It was rediscovered on October 19, 1955, by Czech astronomer Antonín Mrkos at Skalnate Pleso Observatory in Slovakia, using only ordinary binoculars. Leland E. Cunningham at Leuschner Observatory (University of California, Berkeley) later confirmed that the object was indeed 18D.
The comet was last seen during its 1968 perihelion passage, when it came within 0.3144 AU (about 47 million kilometers, or 29 million miles) of Earth. It has not been observed at any of its subsequent predicted returns, which include perihelion dates in 1975, 1982, 1989, 1995, 2002, 2009, and 2017. Estimates for the next possible perihelion range from 2026 to 2032, but the comet is currently classified as lost, having gone unseen since January 1969—a gap of 57 years.
Quick Facts
- Discoverer
- Charles Dillon Perrine / Antonín Mrkos
- Discovery Date
- 9 December 1896
- Mpc Name
- P/1896 X1, P/1909 P1, P/1955 U1
- Designations
- 1896 VII, 1909 III · 1955 VII, 1962 I · 1968 VIII · 1896g, 1909b, 1955i, 1961h, 1968h
- Epoch
- 1968-10-31 (JD 2440160.5)
- Observation Arc
- 7 years / (Not observed in 1969 · 01 · 13 years)MPC
- Semimajor
- 3.56 AU
- Perihelion
- 1.272 AU
- Aphelion
- 5.85 AU
- Eccentricity
- 0.6426
- Period
- 6.72 yr
- Inclination
- 17.7759°
Facts from the source article.
Lore & Background
18D/Perrine–Mrkos was first observed by Charles Dillon Perrine on December 9, 1896, at Lick Observatory in California. For a time it was believed to be a fragment of Biela's Comet. After its 1909 appearance, the comet was lost and not seen again for decades. It was rediscovered on October 19, 1955, by Antonín Mrkos at Skalnate Pleso Observatory in Slovakia, using ordinary binoculars. Leland E. Cunningham later confirmed the rediscovery at Leuschner Observatory. The comet was last observed during its 1968 perihelion passage, when it passed 0.3144 AU from Earth. It has not been observed during subsequent predicted perihelion passages, with a series of estimated dates and apparent magnitudes recorded for 1975, 1982, 1989, 1995, 2002, 2009, 2017, and 2025. The difference in perihelion estimates for the 2025/2026 passage is 533 days. The next predicted perihelion could be in 2026 or 2032, but the comet is currently considered lost, having not been seen since January 1969.
Reader's Guide
18D/Perrine–Mrkos holds significance as a periodic comet that was lost and then rediscovered after nearly half a century. Its initial discovery by Charles Dillon Perrine in 1896 and the early speculation that it might be a fragment of Biela's Comet placed it within a historical context of comet fragmentation studies. The comet's disappearance after 1909 and its eventual rediscovery in 1955 by Antonín Mrkos using ordinary binoculars highlight the challenges of tracking small, faint periodic objects. The confirmation by Leland E. Cunningham at Leuschner Observatory solidified its identity. The comet's last observed perihelion in 1968, during which it passed relatively close to Earth at 0.3144 AU, provided the final direct observations. Since then, multiple predicted perihelion passages have gone unobserved, with estimated apparent magnitudes ranging from 19 to 24, indicating the comet has become extremely faint or has disintegrated. The uncertainty in its orbit is reflected in the 533-day difference between two perihelion estimates for the 2025/2026 window, and the possibility of a 2032 return. As of 57 years since its last sighting, the comet is considered lost, serving as a case study in the difficulties of maintaining long-term observations of periodic comets with uncertain orbital evolution.
Did You Know?
- For some time it was thought to be a fragment of Biela's Comet.
- The comet has not been observed since January 1969, a span of 57 years.
More in Named Comets, Part 5 1-24
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