Interstellar objects outnumber Solar system objects in the Oort cloud

Here, we show that the detection of Borisov implies that interstellar objects outnumber Solar system objects in the Oort cloud, whereas the reverse is true near the Sun due to the stronger gravitational focusing of bound objects. This hypothesis can be tested with stellar occultation surveys of the Oort cloud. Furthermore, we demonstrate that similar to 1 per cent of carbon and oxygen in the Milky Way Galaxy may be locked in interstellar objects, implying a heavy element budget for interstellar objects comparable to the heavy element budget of the minimum mass Solar nebula model. There is still considerable uncertainty regarding the size distribution of the interstellar objects.

Automated summary

The detection of Borisov suggests that there are more interstellar objects than Solar system objects in the Oort cloud, but the opposite is true near the Sun due to stronger gravitational focusing of bound objects. It is hypothesized that about 1% of carbon and oxygen in the Milky Way Galaxy may be locked in interstellar objects, implying a comparable heavy element budget to the minimum mass Solar nebula model. However, there is still considerable uncertainty regarding the size distribution of interstellar objects.