HD 7977 and its possible influence on Solar System bodies

¹ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
e-mail: dybol@amu.edu.pl
² Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN), Bartycka 18A, 00-716 Warszawa, Poland
³ Instituto Universitario de Física Aplicada a las Ciencias y las Tecnologías (IUFACyT), Universidad de Alicante, Ctra. San Vicente del Raspeig s/n, 03690 San Vicente del Raspeig, Alicante, Spain
⁴ Istituto di Fisica Applicata “Nello Carrara” (IFAC-CNR), Sesto Fiorentino 50019, Italy
⁵ European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
⁶ Dipartimento di Fisica, Università di Padova, Via Marzolo 8, 35131 Padova, Italy

Received: 18 December 2023
Accepted: 28 February 2024

Abstract

Context. In the latest Gaia third data release, one can find extremely small proper motion components for the star HD 7977. This, together with the radial velocity measurement lead to the conclusion that this star passed very close to the Sun in the recent past.

Aims. Such a very close approach of a one solar mass star must have resulted in noticeable changes in the motion of all Solar System bodies, especially those on less tight orbits, namely long-period comets (LPCs) and transneptunian objects (TNOs). We estimate and discuss these effects.

Methods. Our current knowledge on the solar neighbourhood found in the latest Gaia catalogues allowed us to perform numerical integrations and prepare a list of potential stellar perturbers of LPCs. We used this list, made available in the StePPeD database. To study the past motion of LPCs under the simultaneous action of the Galactic potential and passing stars, we used precise original cometary orbits taken from the current CODE catalogue.

Results. We examined the reliability of the extremely small proper motion of HD 7977 and conclude that this star can be an unresolved binary; however, according to the astrometry covering more than a century, the current Gaia data cannot be ruled out. We present the parameters of a very close passage of this star near the Sun. We also show examples of the strong influence of this passage on the past motion of some LPCs. We also discuss the possible influence of this perturber on other Solar System bodies.

Conclusions. It is possible that 2.47 Myr ago the one solar mass star HD 7977 passed as close as 1000 au from the Sun. Such an event constitutes a kind of dynamical horizon for all studies of the past Solar System bodies’ dynamics.