1:45 PM - 3:15 PM
[O11-P111] Inferring the Past Return Periods of Comet 122P/de Vico from Japanese Historical Records
Keywords:Comet, Return Periods, 122P/de Vico
1. Background and Purpose
The orbital motion of comets is highly susceptible to gravitational perturbations and non-gravitational effects, making their orbital periods unstable (Yeomans & Kiang, 1981). Consequently, estimating a comet’s past appearances is challenging, and most comet entries in Japanese historical records remain unidentified.
Traditionally, two methods estimate past comet returns: (1) calculating accurate orbits and comparing them with historical records, and (2) deriving orbital elements from records to find similar comets (Carusi et al., 1991). However, method (1) is ineffective with insufficient data, and method (2) is limited by the scarcity of detailed ancient records.
In this study, we propose an alternative approach: estimating prior returns by roughly computing return dates, defining an error range, and eliminating inconsistent records under the assumption they might be 122P.
We applied this to comet 122P/de Vico, which has appeared brighter than 6th magnitude but lacks confirmed past returns and has limited data (Table 1). The goal was to estimate its historical appearances using Japanese records.
2. Methodology
2.1 Orbital Calculations
We used the Solex software, which accounts for planetary perturbations, to calculate 122P’s orbit. We traced its position back to 600 CE and identified perihelion passage dates (“calculated dates”) to estimate potential past returns.
2.2 Setting the Error Range
We defined error ranges around each calculated date, increasing the range width by one year per return going back in time (Figure 1).
2.3 Elimination of Inconsistent Records
Records within error ranges were evaluated using sources such as Kanda (1935) and Osaki (1994). Those identified as other known celestial events were excluded. Further exclusions were based on inconsistencies with 122P’s expected position, direction, or visibility near perihelion.
For example, if 122P was near perihelion in September, it should have been seen in the eastern sky before sunrise; records not matching this were deemed inconsistent.
3. Results
3.1 Potential Records
After exclusions, we identified 33 potential sightings of 122P in Japanese historical records (Table 2).
3.2 Highly Probable Records
To assess likelihood, we evaluated three factors: motion across the sky, tail shape, and brightness (Table 3), with assigned weights (Table 4). Three records emerged as highly probable sightings of 122P.
3.3 Return Pattern Combinations
Assuming the orbit remained relatively stable, we considered three trends:
(i) returns earlier than calculated dates,
(ii) later returns, or
(iii) a mix of both.
Based on the three strong candidate records, we identified six potential return combinations (Table 5), allowing deviations of one year per return.
4. Discussion
Combination 1 includes the most consistent records (Figure 1, Table 5). Others contain only one pre-1300 record, despite 122P being historically bright.
Lunar phase and viewing direction support visibility in Combination 1’s records. Even a relatively faint comet like 122P (now about 5th magnitude) could have been observed.
Recent data suggest non-gravitational forces have shortened 122P’s orbit, meaning calculations using the current orbit may diverge further in the past.
5. Conclusion
Considering plausibility, record count, and orbital evolution, Trend (i) and Combination 1 provide the most reasonable interpretation. This aligns with studies of Chinese and Korean records identifying a 1391 sighting as 122P (Hasegawa, 1979; Figure 1).
The orbital motion of comets is highly susceptible to gravitational perturbations and non-gravitational effects, making their orbital periods unstable (Yeomans & Kiang, 1981). Consequently, estimating a comet’s past appearances is challenging, and most comet entries in Japanese historical records remain unidentified.
Traditionally, two methods estimate past comet returns: (1) calculating accurate orbits and comparing them with historical records, and (2) deriving orbital elements from records to find similar comets (Carusi et al., 1991). However, method (1) is ineffective with insufficient data, and method (2) is limited by the scarcity of detailed ancient records.
In this study, we propose an alternative approach: estimating prior returns by roughly computing return dates, defining an error range, and eliminating inconsistent records under the assumption they might be 122P.
We applied this to comet 122P/de Vico, which has appeared brighter than 6th magnitude but lacks confirmed past returns and has limited data (Table 1). The goal was to estimate its historical appearances using Japanese records.
2. Methodology
2.1 Orbital Calculations
We used the Solex software, which accounts for planetary perturbations, to calculate 122P’s orbit. We traced its position back to 600 CE and identified perihelion passage dates (“calculated dates”) to estimate potential past returns.
2.2 Setting the Error Range
We defined error ranges around each calculated date, increasing the range width by one year per return going back in time (Figure 1).
2.3 Elimination of Inconsistent Records
Records within error ranges were evaluated using sources such as Kanda (1935) and Osaki (1994). Those identified as other known celestial events were excluded. Further exclusions were based on inconsistencies with 122P’s expected position, direction, or visibility near perihelion.
For example, if 122P was near perihelion in September, it should have been seen in the eastern sky before sunrise; records not matching this were deemed inconsistent.
3. Results
3.1 Potential Records
After exclusions, we identified 33 potential sightings of 122P in Japanese historical records (Table 2).
3.2 Highly Probable Records
To assess likelihood, we evaluated three factors: motion across the sky, tail shape, and brightness (Table 3), with assigned weights (Table 4). Three records emerged as highly probable sightings of 122P.
3.3 Return Pattern Combinations
Assuming the orbit remained relatively stable, we considered three trends:
(i) returns earlier than calculated dates,
(ii) later returns, or
(iii) a mix of both.
Based on the three strong candidate records, we identified six potential return combinations (Table 5), allowing deviations of one year per return.
4. Discussion
Combination 1 includes the most consistent records (Figure 1, Table 5). Others contain only one pre-1300 record, despite 122P being historically bright.
Lunar phase and viewing direction support visibility in Combination 1’s records. Even a relatively faint comet like 122P (now about 5th magnitude) could have been observed.
Recent data suggest non-gravitational forces have shortened 122P’s orbit, meaning calculations using the current orbit may diverge further in the past.
5. Conclusion
Considering plausibility, record count, and orbital evolution, Trend (i) and Combination 1 provide the most reasonable interpretation. This aligns with studies of Chinese and Korean records identifying a 1391 sighting as 122P (Hasegawa, 1979; Figure 1).