“For a realistic flux of interstellar material, does capture happen often enough to make the discovery of such an object plausible?
” In terms of probability, an interstellar origin for BZ509 could be exceedingly special in comparison to other rare but likelier alternatives, Tremaine says.
An interstellar origin for the Oort cloud could only have occurred prior to 4.5 billion years ago, when our newborn sun was still embedded in its stellar nursery—a decidedly non-standard scenario, but one consistent with Namouni and Morais’s dating of BZ509 to the dawn of the solar system.
“So do you need to draw [BZ509] from the interstellar medium?
Such a star would likely have been a sibling of our sun born alongside us in a “stellar nursery”—a nebula filled with star-forming gas and dust.
Galactic motions long ago scattered this progeny far and wide, but it seems remnants may linger on our doorstep today.
Each time astronomers find a space rock that could be an interstellar immigrant, the need grows to take such far-out ideas seriously.
Discovered in late 2014 via the Pan-STARRS telescope in Hawaii, the object was provisionally dubbed 2015 BZ509.