A Potential Signature of HD 7977’s Passage among Observed Long-period Comet Orbits
Abstract
It is generally presumed that the tidal field of the Milky Way’s disk is the main perturbation that has driven observed long-period comets (LPCs) from the Oort cloud into the inner solar system. The tide’s influence on the Oort cloud should produce a distinct anisotropy in the arguments of perihelion ( ω ) of dynamically new LPCs with semimajor axes ( a ) over 10 4 au. Simulating LPC production dominated by the Galactic tide, we find that observed dynamically new LPCs are more isotropic than expected. Meanwhile, our simulation exhibits much better agreement between simulated and observed “returning” LPCs that have made a handful of passages through the inner solar system prior to discovery. The isotropy of new LPCs can be explained if the Oort cloud is much less centrally concentrated than the conventional Oort cloud formation model predicts. However, a second possibility also exists. Additional simulations we perform show that the observed ω distributions of new and returning LPCs can both be well replicated if the star HD 7977 passed within ∼6000–10,000 au of the Sun ∼2.5 Myr ago. In such a scenario, our solar system is still undergoing the later stages of a comet shower. These simulations imply that the modern observed LPC flux is approximately twice as high as the longer-term (tide-dominated) rate. This also implies that estimates of the Oort cloud’s population should be revised downward by a factor of ∼2. Our LPC analysis predicts that the upcoming Gaia data release will favor an HD 7977 impact parameter of ∼6000–10,000 au.
Related
- Short-period pulsating hot-subdwarf stars observed by TESS in Sectors 61–97
- Physical characteristics of the Galaxy defining the oscillation period of librating orbits near the OLR of the bar
- Signature of exocomet transits observed with Ariel
- Rattling Resonant Chains with Dynamical Tides and Parametric Resonance Passage
- The JWST/PASSAGE Survey: Metallicity Radial Gradients in Emission-Line Galaxy Pairs at Cosmic Noon with NIRISS
BibTeX
@article{kaib2026potential,
title = {{A Potential Signature of HD 7977’s Passage among Observed Long-period Comet Orbits}},
author = {Nathan Kaib and Sean N. Raymond},
journal = {The Planetary Science Journal},
year = {2026},
month = jul,
doi = {10.3847/psj/ae7a65},
eprint = {2606.25069},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05760830v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - A Potential Signature of HD 7977’s Passage among Observed Long-period Comet Orbits
AU - Nathan Kaib
AU - Sean N. Raymond
PY - 2026
DA - 2026/07/02
JO - The Planetary Science Journal
DO - 10.3847/psj/ae7a65
UR - https://hal.science/hal-05760830v1
AB - It is generally presumed that the tidal field of the Milky Way’s disk is the main perturbation that has driven observed long-period comets (LPCs) from the Oort cloud into the inner solar system. The tide’s influence on the Oort cloud should produce a distinct anisotropy in the arguments of perihelion ( ω ) of dynamically new LPCs with semimajor axes ( a ) over 10 4 au. Simulating LPC production dominated by the Galactic tide, we find that observed dynamically new LPCs are more isotropic than expected. Meanwhile, our simulation exhibits much better agreement between simulated and observed “returning” LPCs that have made a handful of passages through the inner solar system prior to discovery. The isotropy of new LPCs can be explained if the Oort cloud is much less centrally concentrated than the conventional Oort cloud formation model predicts. However, a second possibility also exists. Additional simulations we perform show that the observed ω distributions of new and returning LPCs can both be well replicated if the star HD 7977 passed within ∼6000–10,000 au of the Sun ∼2.5 Myr ago. In such a scenario, our solar system is still undergoing the later stages of a comet shower. These simulations imply that the modern observed LPC flux is approximately twice as high as the longer-term (tide-dominated) rate. This also implies that estimates of the Oort cloud’s population should be revised downward by a factor of ∼2. Our LPC analysis predicts that the upcoming Gaia data release will favor an HD 7977 impact parameter of ∼6000–10,000 au.
SN - 2632-3338
ER -