Given how close the star HD 7977 was 2.8 million years ago, many times closer than any star today, it is pretty much certain that its passage has perturbed the

Given how close the star HD 7977 was 2.8 million years ago, many times closer than any star today, it is pretty much certain that its passage has perturbed the orbits of the planets. What is uncertain is only which were the changes, i.e. which were the orbits of the planets prior to the star passing. The changes must have been very small, but they must have existed. The point of the paper is that this stellar passing and others like it increase by a non-negligible amount the uncertainty of the simulations that attempt to determine accurately the planetary movements in the distant past of the Solar System, at scales of tens of millions of years. The star HD 7977 is slightly bigger and brighter than the Sun, so when it has passed at the minimum distance there are chances that it was noticeably brighter than Venus.