丁香园AV

Synopsis

In 2017, the first asteroid to enter our Solar System from interstellar space was discovered at the PanSTARRS telescope in Hawaii, and has now been named 'Oumuamua, a Hawaiian term which signifies 'Messenger from Afar'. In 2019 a second interstellar visitor, comet Borisov (named after its discoverer) appeared.  Adding to the mystery of their origins are their contrasting properties: 'Oumuamua was rocky (unexpected), relatively slow (unexpected) and small (expected); while Borisov is the reverse: icy, fast and large. I'll briefly summarize what we know about these puzzling visitors, and outline the efforts being made at Western to back-track them to their points of origin, somewhere within our Milky Way galaxy.