And, critically, the complete orbit is inside the orbit of the smaller companion star. The gravitational forces of a decent binary ought to forestall any planets from forming inside this house early within the system’s historical past. So, how did the planet find yourself in such an uncommon configuration?
A confused previous
The truth that one of many stars current in ν Octantis is a white dwarf suggests some doable explanations. White dwarfs are shaped by Solar-like stars which have superior by a late helium-burning interval that causes them to swell significantly, leaving the outer floor of the star weakly certain to the remainder of its mass. On the distances inside ν Octantis, that may permit appreciable materials to be drawn off the outer companion and pulled onto the floor of what is now the central star. The online result’s a substantial mass switch.
This might have finished one in all two issues to put a planet within the inside of the system. One is that the transferred materials is not prone to make a right away dive onto the floor of the close by star. If the method is gradual sufficient, it may have produced a planet-forming disk for a quick interval—lengthy sufficient to supply a planet on the inside of the system.
Alternatively, if there have been planets orbiting exterior to each stars, the change within the mass distribution of the system may have doubtlessly destabilized their orbits. That is likely to be sufficient to trigger interactions among the many planets to ship one in all them spiraling inward, the place it was finally captured within the secure retrograde orbit we now discover it.
Both case, the authors emphasize, needs to be fairly uncommon, that means we’re unlikely to have imaged many different techniques like this at this stage of our research of exoplanets. They do level to a different tight binary, HD 59686, that seems to have a planet in a retrograde orbit. However, as with ν Octantis, the info is not clear sufficient to rule out different configurations but. So, as soon as once more, extra knowledge is required.
Nature, 2025. DOI: 10.1038/s41586-025-09006-x (About DOIs).
