The Gaia mission has allowed researchers to understand the motions of stars like never before, even revealing possible interactions between our solar system and nearby stars. Planetary Science Institute Senior Scientist Nathan Kaib and collaborator Sean Raymond (Universite de Bordeaux) have found that a recent stellar passage likely triggered a huge increase in comet formation as the star’s gravity altered Oort cloud objects’ orbits, sending them cascading into the inner solar system. We may even still be feeling the effects of this passage today. This work is being presented at the American Astronomical Society Division on Dynamical Astronomy.
HD 7,977 is a nearby sun-like star in the constellation Cassiopeia whose close passage was discovered by the Gaia mission. Approximately 2.5 million years ago, the orbits of the sun and HD 7,977 brought the two stars close together, but exactly how close is still an open question. Gaia data suggest they passed within 4,000–25,000 astronomical units of one another. Now, Kaib and Raymond have shown that the orbits of long-period comets suggest HD 7,977 came within 6,000–10,000 AU of our sun, setting off a major shower of new comets into the inner solar system.









