Matthew Knight

We have tried to avoid putting it in one of those boxes and prefer to call it more generically an 'object,' in simple terms, asteroids are rocky and devoid of ices, while comets are a mixture of rock and ice, so-called 'dirty snowballs,'.

We have never seen anything like' Oumuamua in our solar system. It's really a mystery still, but our preference is to stick with analogs we know, unless or until we find something unique. The alien spacecraft hypothesis is a fun idea, but our analysis suggests there is a whole host of natural phenomena that could explain it.

The motion of' Oumuamua didn't simply follow gravity along a parabolic orbit as we would expect from an asteroid, but visually, it hasn't ever displayed any of the cometlike characteristics we'd expect. There is no discernable coma -- the cloud of ice, dust and gas that surrounds active comets -- nor a dust tail or gas jets.

We tend to assume that the physical processes we observe here, close to home, are universal, and we haven't yet seen anything like' Oumuamua in our solar system. This thing is weird and admittedly hard to explain, but that doesn't exclude other natural phenomena that could explain it.

In the next 10 years, we expect to begin seeing more objects like' Oumuamua. The LSST will be leaps and bounds beyond any other survey we have in terms of capability to find small interstellar visitors, we may start seeing a new object every year. That's when we'll start to know whether' Oumuamua is weird, or common. If we find 10-20 of these things and' Oumuamua still looks unusual, we'll have to reexamine our explanations.