When a rocky interstellar object now known as 'Oumuamua was first detected in our solar system in October, it was thought to be an asteroid. Now, astronomers say it could be a comet whose core has withstood intense heat from the Sun thanks to a thick crust that insulated it, Science News reports.

Why it matters: Most objects that move between solar systems are thought to be comets so there was excitement that the presumed asteroid 'Oumuamua could help researchers to better understand how other solar systems formed. "Everybody's been assuming that this is just a lump of rock," study author Alan Fitzsimmons of Queen's University Belfast in Northern Ireland told Science News. "This may not be the case."