Docent Lecture by Jens Hoeijmakers

Interstellar visitors: strange objects from outside the solar system?

By Jens Hoeijmakers, Division of Astrophysics, the Department of Physics.

Abstract
The discovery of ʻOumuamua in 2017 marked the first detection of an object originating from beyond the Solar System. Its unexpected properties—including an unusual light curve and apparent non-gravitational acceleration—challenged our existing models of small astrophysical bodies, and led to wild speculations that we might be visited by extra-terrestrial technology. 

Up to today, we have observed two additional interstellar visitors, and these have provided striking counterpoints to ‘Oumuamua: chemically and morphologically similar to solar system comets yet originating from outside the solar system. Together, these three objects have provided the first direct samples of material from another planetary systems and inaugurated a completely new observational window into the formation and evolution of planetary systems.

In this talk, I will use interstellar objects as a framework to introduce key concepts in celestial mechanics, planetary sciences, and Galactic dynamics. I will show how observations—ranging from astrometry and light curves to spectroscopy—allow us to infer the properties and origins of these objects despite limited data. Placing them in a broader astrophysical context, I will discuss the mechanisms by which planetary systems eject debris, the expected Galactic population of interstellar objects, and what these bodies reveal about the diversity of planet formation beyond the Solar System. I will conclude by addressing ongoing uncertainties, recent controversies, and the prospects for future detections and study.

Jens Hoeijmakers´profile in the Lund University Research Portal.