Avi Loeb

Yeah, as I say, even planets five times larger, this is planet X, five times larger than the mass of Earth out there are very difficult to detect

And so- So our cloud is still theoretical except for the few objects, yes?

Well, what we see are long period comets that originate from icebergs being sent closer to the sun.

And as a result, we recognize there is a whole population out there.

But we have never seen them at those distances because they don't reflect much sunlight.

They move very slowly at a speed that is a thousand times slower than the speed of the earth around the sun.

So a thousand years.

No, because the orbital time is not just the speed.

If they move on a circle, they are also farther away, 100,000 times farther away.

Oh, wow.

So you take 100,000,

times a thousand, that gives you a very long period if there is a circular orbit at the edge of your cloud of 100 million years or so.

These are old objects, and some of them are being exchanged with passing stars, presumably, so some of these objects might have been interstellar, came from another star that passed by, because the distance to the nearest star is twice.

the outer edge of the Oort cloud.

So it means that if the nearest star has an Oort cloud around it, these are just like billiard balls that are touching each other, and space is packed with those.

You would expect most of interstellar objects to originate

from the edge of the Oort clouds because they can easily be dislodged, they're not bound, they're not deep in the potential well of a star, they're loosely bound and they can easily get kicked out.

That's why it was a surprise.

So you would expect all of the interstellar objects to be comets, the way that the long period comets are.

Yet, we saw Oumuamua without a cometary tail, the first recognized interstellar object.