When a Star Flew Too Close: Could HD 7977 Have Sparked an Ancient Comet Shower?
Cao et al. investigate whether the star HD 7977 passed close enough to the Sun about 2.5 million years ago to disturb the Inner Oort Cloud and trigger a long-lasting comet shower. Their simulations show that such a flyby could sharply increase the number of kilometer-scale comets entering the inner Solar System, raising Earth’s impact rate by up to an order of magnitude. They compare these predictions with known craters to suggest the event may align with impacts near the Pliocene-Pleistocene transition.
A Lonely Ice Giant: Discovering 2017 OF201 in the Outer Reaches of Our Solar System
Astronomers discovered 2017 OF201, a distant dwarf planet candidate with a highly elongated orbit reaching the inner Oort Cloud. Its unusual path and large size suggest a hidden population of similar objects. The discovery challenges the Planet X hypothesis, as 2017 OF201's orbit does not fit the expected clustering pattern and would be unstable if such a planet existed.
Exploring the Oort Cloud: How Long Do Comets Stay Near Planets?
The study explores how comets from the Oort Cloud interact with planets, using models to simulate their evolution under galactic tides, stellar encounters, and planetary forces. It finds that comets typically stay in the planetary region for about 100 million years before being ejected or transitioning into other populations like Centaurs. These findings reveal how dynamic forces shape the solar system's structure and history.