Pedro J. Amado
For me, the most interesting thing about this finding is that it provides another example of just how different other planetary systems can be from our own. For many years, the Solar System was the only point of reference we had, and we used to think that it represented, more or less, the typical way in which stars form planets and moons. We now know that this is not the case. In this instance, we may be looking at a star orbited by a brown dwarf, and this brown dwarf, in turn, is orbited by an object with a mass similar to that of Jupiter. We have nothing comparable in the Solar System. Whether we ultimately call this object an ‘exomoon’, an ‘exosatellite’ or even a ‘planet’ is perhaps less important than the fact that nature forms complex objects and systems that do not easily fit into the categories we have created based on our own Solar System.
Of course, we must still proceed with some caution. The periodic signal is convincing and consistent with the presence of an orbiting object, but further observations will be needed to confirm its nature. The work is also very interesting from an observational point of view, as it demonstrates that radial velocities can be measured directly in an imaged brown dwarf and used to search for objects orbiting it. This opens up a new avenue for discovering more exomoons in the future, including objects with smaller masses, and for finding out whether systems like this are actually rare or whether we simply hadn’t been able to detect them until now.